Programmable thermostats burning out?

[John Kogel]

My clients bought a new condo unit with electric baseboard heat, 2xx volt on 20 Amp breakers. They replaced the basic round knob thermostat with an I-don't-know-the-brand programmable unit. One day, it caught fire and left a black streak up the wall. They replaced it with a Noma programmable thermostat. It worked for a while, then caught fire and shot burning plastic across the room. They are now back with the old manual unit and afraid to try a third time, and I don't blame them.

They have spoken with two electricians, but have not solved the problem. The melted Noma I saw, is rated for 240 v, but I wonder if the load is, say 3600 watts, too high for that model, maybe?

Are there cases where a programmable thermostat simply can't be installed? This is the message they got from at least one of the electricians.

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[Ken Rowe]

Copied from another site:

OK, if you're sure you have electric baseboard heaters, you probably have the wrong type of thermostat. You have a "4 pole" type unit, but need a "2 pole" type. A "2 pole" type is just going to have a single pair of wires (one red, one black) and you hook it up, like your old one.

But you should be aware that thermostats can be "line voltage" or "low voltage" types. Most simple electric baseboard systems use "line voltage" types, where the thermostat directly switches 120 VAC or 240 VAC to the heaters. The wires in the wall will be fairly thick (10 or 12 guage) because the current they are conducting will be up to 15 amps - the amount of power required to run about thirty (17) 100 watt light bulbs (for a 120 VAC 1750 watt system). "Low voltage" types only send a control current to a remote relay that maybe mounted in the baseboard units, so the wires in the wall can be very light guage, say 22 guage.

If the wires in the wall are pretty thick, your thermostat is switching line power, and you need to be careful dealing with it, since if you don't kill the circuit correctly before starting your installation, there is enough power in it to be dangerous. If the wires coming out of the wall are thick and stiff, you shouldn't try this if you aren't experienced in working with electricity, and have a meter to test the circuit .

[John Kogel]

Thanks, Ken. Yup, them wires was "thick and stiff", eh?

Somebody measured voltage and found 208 volts. They told my clients this was "legal", but the apartment needs to be rewired for them to use a programmable thermostat. Huh? Were they suggesting it's a 3-phase circuit??? I saw the 20 amp two-pole breakers for the heaters in the panel, and it's a normal 100 amp panel.

I want to email these clients and tell them that any decent electrician can install a good quality thermostat that will cause no more problems. Anyone seen this before?

[H.G. Watson, Sr.]

Is this a unit built to be a condo or one that was converted from former apartment dwelling? Is the building a mixed use (with commercial/retail, etc.), have a large "common element" electrical consumption (big common A/C chillers, pumping stations, etc.) or have a large number of units?

Sounds like their split phase is off of a three phase transformer supplying the building since voltage is 208. Current through the neutral is not zero with a resistive (heater) load.

120/208 Y not 120/240 split single phase AND if a neutral falls open yowza. If Y or delta & a neutral isn't falling open, could be they're using the wrong thermostat might also fry. What happened to the original thermostat when it was re-installed?

poly-phase 120/208 power: Three-phase power systems : POLYPHASE AC CIRCUITS

HTH

[Jerry Peck]

On another matter ... if they have 208 volts instead of 240 volts (which is seems they do) then I would advise them that resistance heating elements will not heat as much as they are used to. I.e., clothes dryers, ranges, ovens, water heaters, etc. will heat noticeably slower, clothes will take longer to dry, food longer to cook or raise setting, etc.

[John Kogel]

Is this a unit built to be a condo or one that was converted from former apartment dwelling? Is the building a mixed use (with commercial/retail, etc.), have a large "common element" electrical consumption (big common A/C chillers, pumping stations, etc.) or have a large number of units?

Yes it is a 30 unit condo, so sure the main service may very well be 3-phase. It is a brand new building, not converted anything.
I am posting a pic of the condo unit distribution panel, sorry, it's another Canadian Fed Pioneer. There are 3 20 amp breakers (obviously 240 volt) baseboard heating circuits in the upper right of the panel, color coded red for 20 amp.
The original manual thermostat is back on the wall and functioning. The clients are elderly and somewhat befuddled by the info they have been fed so far.

I think someone is feeding these people hogwash.

[Ed Garrett]

John,

You are dealing with a situation where the thermostat is providing the on/off switching for the heater(s) rather than engaging a solenoid in the heating unit to switch power on/off.

As Jerry said, 208V will provide less heat than 240V but that should not effect the use of a thermostat rated for 240V.

An electrician can install a switching solenoid for the heater(s) with a transformer to feed a low voltage thermostat....but 240 volt thermostats are available as well Honeywell T4700 Programmable Line Voltage Thermostat - 240 Volt Systems

The need is to match up the heater draw with the thermostat. Not sure if derating would be required for running @ 208V. Units would be expected to operate longer than @ 240V but the "new" construction may have better insulation so not need as much heat ...

My thoughts,

Ed

[H.G. Watson, Sr.]

First we just do not have enough information. We must have the panel information from the baseboard heaters at a minimum to find a compatible line voltage programable thermostat control.

Second, there ARE electric baseboard heating units (hard wired) which are SPECIFICALLY DESIGNED to work on 120/208V (usually designated by model number with 208 OR 200 in the sequence), just as there are those designed to use line voltage 240V and 120V.

120/208V the two legs are 120 degrees out of phase NOT 180 degrees, its apples and oranges on how you calculate. You need this confirmed.

Third, there are DIFFERENT TYPES OF LINE VOLTAGE THERMOSTATS, programmable. There are those designed for LINE VOLTAGE for Hydronic and those for LINE VOLTAGE Resistive/electric heat. There are those which are compatible to use 120/208/240 V (oft marked 1-240V) and those which are not so multi-compatible. Without the correct specifications being matched installing the wrong line voltage thermostat will be a problem/danger.

Fourth, we cannot assume 120/240/1, esp. with what has already been said by JK and has provided. Need more information. Common DIY mistake is to get an electronic line voltage thermostat for hydronic baseboard and to install for electric resistive baseboard.

I must admit I have forgotten Canadian Color Coding - but I do know for certain it often differs (electrical high leg delta, plastic pipe solvents/glues; etc.). IIRC you can find all you need regarding the panel and breakers on the canadian Schnieder website.

If I'm reading correctly the couple has talked to two electricians, but no actual electrician has been on sight - and from what has been said about the history I'm getting the impression someone less than qualified has been tinkering around, not good. Its not just the occupants of the particular condo unit but the entire building who might be in jepordy should this less than qualified activity continue. I'm not so sure just why a H.I. is in the middle of this situation.

[John Kogel]

First we just do not have enough information.
I'm not so sure just why a H.I. is in the middle of this situation.

Thanks, HG. I'm not involved but was informed of the kerfuffle while dealing with another issue, a foul smell which I hope has been resolved.
(I believe the 208 volts is baloney, so we should forget that part.) I am fishing for anyone who may have seen this type of thermostat go up in smoke, before I advise the people at all. Yes, they probably need a line voltage unit for up to 4000 watt resistive heaters. I agree, I should have more info about the 2 units which burned.

[Jerry Peck]

Second, there ARE electric baseboard heating units (hard wired) which are SPECIFICALLY DESIGNED to work on 120/208V (usually designated by model number with 208 OR 200 in the sequence), just as there are those designed to use line voltage 240V and 120V.

And many, possibly even most, are 240 volt / 208 volt, which simply means less current draw at 208 volts (even states that lesser amount on the nameplate data) which means less heat on 208 volts than on 240 volts.

[Vern Heiler]

[quote=H.G. Watson, Sr.;116486]First we just do not have enough information. We must have the panel information from the baseboard heaters at a minimum to find a compatible line voltage programable thermostat control.

120/208V the two legs are 120 degrees out of phase NOT 180 degrees, its apples and oranges on how you calculate. You need this confirmed.


H.G. Three phase power is distributed over the main trunk lines. We typically use one of the phases for residential power. It is a single phase. If we had two phase power 180 degrees from each other we would measure 0 volts between them.

[H.G. Watson, Sr.]

H.G. Three phase power is distributed over the main trunk lines. We typically use one of the phases for residential power. It is a single phase. If we had two phase power 180 degrees from each other we would measure 0 volts between them.

VH, No.

120/240VAC 60 Hz and 120/208VAC 60 Hz are both providing split phase power. 120/240 each half-phase tap is 180 degrees - 120/208 each half-phase tap is 120 degrees.

We use SPLIT single phase, low voltage power distribution for most residential, difference being if the step down transformer prior to service point is single phase (already tapped off of a singular tap winding upstream in the power distribution) it is split, each split half is 180 degrees from the other at 60 hz.

We have split single phase at 120/240V/1ph 60 Hz most residential. One conductor is carrying 120 volts half (plus) of the A/C "wave" for the single phase the other conductor 120 V the other half (negative) of the a/c "wave" of the single phase - each half is 180 degrees from each other, but both taps are sourced from a single phase transformer. Combined to provide a single phase 240 volt sinusodal wave, With a resistive load the neutral carries no current. This is why we can ADD the two halves.

Polyphase power at the last transformer in the distribution gives us something different - each "half leg" is sourced from a different split phase tap 120 degrees from the other - that's why we cannot ADD the two haves - the sq rt of Pi and the out of phase cycling of the sine wave gets involved - current flows on the neutral when FULL single phase power is being worked.

120/208/1ph is split polyphase power, each conductor is carrying 120 volts one + the other - of the "wave" but at 120 degrees out of phase, and are each sourced from different taps of a polyphase transformer. As one is therefore when combined to provide 208 v not 240v and the neutral carries current with a resistive load neutral must be sized correctly and be present in the circuit at line voltage unlike 120/240 which can safely function without a neutral at 240 v 60 Hz as the neutral carries no current and each half phase is precisely 180 degrees out of phase with its other half phase leg - having sourced off the same split tap with reference to ground.

[H.G. Watson, Sr.]

And many, possibly even most, are 240 volt / 208 volt, which simply means less current draw at 208 volts (even states that lesser amount on the nameplate data) which means less heat on 208 volts than on 240 volts.

Not quite. Less voltage worked, on the hots - current carried on the neutral out of phase. 208 must have a neutral throughout no two wire (pls grnd) needs a third wire (pls grnd) for a resistive load.

[H.G. Watson, Sr.]

Thanks, HG. I'm not involved but was informed of the kerfuffle while dealing with another issue, a foul smell which I hope has been resolved.
(I believe the 208 volts is baloney, so we should forget that part.) I am fishing for anyone who may have seen this type of thermostat go up in smoke, before I advise the people at all. Yes, they probably need a line voltage unit for up to 4000 watt resistive heaters. I agree, I should have more info about the 2 units which burned.

I'm thinking the 208 V is not baloney, and may well be the issue. It changes how things are wired for the unit (normally needing to wire/jumper the programable thermostat differently, and thus perhaps the need to pull new cable between to accomodate or correct the wiring/jumpers). No undersized neutrals - conductors may already have been "fried", wouldn't trust since there has already been two instances of known failures both involving malfunction, smoke, and unknown fire, and one with an apparent near explosive destruction of a themostat device (arc perhaps).

Safety and responsibility - makes SENSE that in either case - a responsible electricitian might have indicated work WOULD not be done by them unless replacing of the wiring or a portion thereof took place - too many things could have gone wrong - the "useful life" and integrity of the wiring after such a series of events - especially with a demand/continuous use resistive heating circuit(s) and "smoking" should be done, especially if any of it is not exposed/cannot be inspected/fully tested, etc.

[Joe Klampfer]

Typical voltages up here is 120/240 for residential and 120/208 for commercial, which also includes apartments and condos. The appliances purchased for these units are usually rated 120/208 but oftentimes the owners may upgrade and not knowing about the voltage differences, purchase a 120/240 volt range then wonder why it's performing slightly below par.

Not a problem, but it sure sounds like they've installed a low voltage thermostat onto a line voltage feed - dangerous! Another example why diy'ers should know their limitations and call in a professional. The $100 in thermostats they blew up would have covered the electrical service call

[Vern Heiler]

VH, No.

120/240VAC 60 Hz and 120/208VAC 60 Hz are both providing split phase power. 120/240 each half-phase tap is 180 degrees - 120/208 each half-phase tap is 120 degrees.

We use SPLIT single phase, low voltage power distribution for most residential, difference being if the step down transformer prior to service point is single phase (already tapped off of a singular tap winding upstream in the power distribution) it is split, each split half is 180 degrees from the other at 60 hz.

We have split single phase at 120/240V/1ph 60 Hz most residential. One conductor is carrying 120 volts half (plus) of the A/C "wave" for the single phase the other conductor 120 V the other half (negative) of the a/c "wave" of the single phase - each half is 180 degrees from each other, but both taps are sourced from a single phase transformer. Combined to provide a single phase 240 volt sinusoidal wave, With a resistive load the neutral carries no current. This is why we can ADD the two halves.

Polyphase power at the last transformer in the distribution gives us something different - each "half leg" is sourced from a different split phase tap 120 degrees from the other - that's why we cannot ADD the two haves - the sq rt of Pi and the out of phase cycling of the sine wave gets involved - current flows on the neutral when FULL single phase power is being worked.

120/208/1ph is split polyphase power, each conductor is carrying 120 volts one + the other - of the "wave" but at 120 degrees out of phase, and are each sourced from different taps of a polyphase transformer. As one is therefore when combined to provide 208 v not 240v and the neutral carries current with a resistive load neutral must be sized correctly and be present in the circuit at line voltage unlike 120/240 which can safely function without a neutral at 240 v 60 Hz as the neutral carries no current and each half phase is precisely 180 degrees out of phase with its other half phase leg - having sourced off the same split tap with reference to ground.

H.G. To have it the way you describe, the secondary winding would have to have the induced voltage as; +,-,-,+ with no difference in potential between the ends and all current flowing through the neutral. The way it works is; -,+,-,+ with full voltage potential across the ends and part of the totoal voltage tapped off between the ends. In our case the tap is centered, giving 120 from each end to the center and 240 across the full secondary. The sine wave you see in many diagrams are a representation of time, not the voltage/current on the winding at all times. Many of the xfmrs that are used in electronics have several taps along the secondary to give multiple voltages, all in phase. Without adding capacitance, how would you induce voltages out of phase onto the secondary? There is only one high voltage wire going to the xfmr primary. One phase.

[John Kogel]

I'm thinking the 208 V is not baloney, and may well be the issue.

HG, please look at the pic of the panel, post #6, and then tell me if you think that is 3-phase. The baseboards are supplied by the red breakers.

Safety and responsibility - makes SENSE that in either case - a responsible electricitian might have indicated work WOULD not be done by them unless replacing of the wiring or a portion thereof took place - too many things could have gone wrong - the "useful life" and integrity of the wiring after such a series of events - especially with a demand/continuous use resistive heating circuit(s) and "smoking" should be done, especially if any of it is not exposed/cannot be inspected/fully tested, etc.

Yes that's possible. Good point.

Joe, I think it is possible that the first thermostat was a 24 volt unit, fried that one, then they bought the Noma unit I saw, which was a line voltage unit. Just bad luck I suppose, or he got a couple of wires crossed.....

Let me see if I got this right. Each leg of a 3 phase supply is 120 volts. The three legs operate so that 2 are always energized but out of phase so the average voltage is, in our country, 208 volts. When you convert that to single phase, which is what you do for residential, you have two 120 volts legs, or 208 volts when you bridge both bus bars. Ok, I've corrected this to avoid further confusion. []

[Vern Heiler]

John, I'm not H.G., but I can tell you that is not a 3-phase panel. I think I still have one out in my shed and can send a pic if you like. You only have two hots entering the panel at the bottom. Three phase panels have 3 hots.

If you think the service is 3-phase, go out to the power pole. Three phase requires three xfmrs each supplied from individual high voltage line. If you have three phase power serving the neighborhood, I'll be surprised.

[John Kogel]

John, I'm not H.G., but I can tell you that is not a 3-phase panel. I think I still have one out in my shed and can send a pic if you like. You only have two hots entering the panel at the bottom. Three phase panels have 3 hots.

If you think the service is 3-phase, go out to the power pole. Three phase requires three xfmrs each supplied from individual high voltage line. If you have three phase power serving the neighborhood, I'll be surprised.

Thanks, Vern. No poles, it's all lateral service, new subdivision.

[Jerry Peck]

John, Vern,

You can service a large building such as a condo with 3-phase, then tap off at each condo with a single phase panel using 120 volts / 208 volts as the supply to each condo. It is done quite frequently.

This is a good depiction of it: (scroll down toward the bottom for the single-phase alternator and three-phase alternator drawings and explanation, then down further for the 'Y' configuration drawing and explanation)
Three-phase power systems : POLYPHASE AC CIRCUITS

Between hot and ground (neutral) you have 120 volts.

Between hot and hot you have 208 volts instead of 240 volts.

Thus a high rise could be wired with one unit on Phase A - Neutral - Phase B for 120 / 208, another Phase B - Neutral - Phase C for 120 /208, and another Phase C - Neutral - Phase A for 120 / 208.

[Joe Klampfer]

Wow! There is a lot of over-analyzing going on. It's really quite simple... Houses are fed from a single phase 120/240 volt transformer, commercial bldgs are fed from a three phase 120/208 volt transformer, to the main switchgear then it is broken down to 120/208 volt single phase panels in the individual units (although I have rarely seen 120/208 three phase panels in a few units)

Your picture in post # 6 is a single phase 120/208 volt panel (two hots and one neutral). It's really that simple, no need to drag out and discuss the possible phase angles etc.

Now back to the thermostat... if the 2nd thermostat was indeed a line-voltage stat, then it is possible that he connected accross the two hot legs so that when the thermostat called for heat, it created a direct short circuit across the 208 volts. The reason it blew up as bad as it did is that the internal components were never designed for and cannot take that amount of short-circuit current.

[Jerry Peck]

Wow! There is a lot of over-analyzing going on. It's really quite simple... Houses are fed from a single phase 120/240 volt transformer, ...

Not ALL houses ... it is sometimes more dangerous to under-analyze and unintentionally present incorrect information than it is to over-analyze things as present ... ... and this was presented as "My clients bought a new condo ... " which is not even a typical "house" as you are referring to in your reply, nor is it a "commercial" building either in the most often thought of sense of the word, and, in fact, it is not classed as a commercial building, but would be classified as an apartment house.

[Joe Klampfer]

You bring up a good point Jerry but I have worked up here for a lot of years, both as an electrician and now as a home inspector and that's how 95 to 98% of the bldgs are done here. It just does not make sense to bring in a 120/240 volt single phase service to a building with 10 or more units, I don't even think our hydro Co. would allow it

[Vern Heiler]

Thanks Jerry, good site. I don't see where the phase angle of -30 comes from, but that part is way beyond need to know!

[Jerry Peck]

It just does not make sense to bring in a 120/240 volt single phase service to a building with 10 or more units, I don't even think our hydro Co. would allow it

How about the opposite?

Running 3-phase to a residence?

That is also what I was pointing out as another possibility. Typically, when I've seen that done, the 3-phase only went to run the a/c systems. I say "typically" as I have seen 3-phase to some of the larger homes (talking quite large here ... 20,000 sf and more).

[Joe Klampfer]

Yes, that's another good point. It all comes down to load / demand and what makes sense. On a residence THAT size it wouldn't make sense to feed it with a 120/240 single phase service, and again, our hydro Co. would likely insist on a 3-phase service.

I've not inspected a home that large yet and am not looking forward to it either. They're likely within that 3 to 5% I referred to earlier.

I think we're both on the same page so I'm done with this topic

[John Kogel]

Thank you Jerry, Joe, Vern and HG. I get it! I've seen single phase coming from 3 phase lots of times but never had occasion to measure the voltage across the hot legs, just assumed it was 240. I feel smarter now!

Here's some pics of a 600 amp 3 phase? (I think) fused service from about 1937 apartment building. The custodian was guarding the place pretty close so I just grabbed a couple of quick pics. No chance to open up the big fuse panel.

[Vern Heiler]

Thank you Jerry, Joe, Vern and HG. I get it! I've seen single phase coming from 3 phase lots of times but never had occasion to measure the voltage across the hot legs, just assumed it was 240. I feel smarter now!

Here's some pics of a 600 amp 3 phase (I think) fused service from about 1937 apartment building. The custodian was guarding the place pretty close so I just grabbed a couple of quick pics. No chance to open up the big fuse panel.

John, I don't see anything that would indicate 3-phase in your pic's. It could be two phases off of a 3-phase xfmr, but I doubt it. Three phase power would have 4 wire service drop. (3 hot, 1 neutral) With the pic's of over head service you should be able to see the xfmr it comes from. If single phase, there will be one high voltage line into the top. If three phase there will be three wires into the top or three serperate cans.

[Jerry Peck]

Here's some pics of a 600 amp 3 phase (I think) fused service from about 1937 apartment building. The custodian was guarding the place pretty close so I just grabbed a couple of quick pics. No chance to open up the big fuse panel.

As Vern indicated, that is "most likely" a simple 120 volt / 240 volt service.

The service drop outside, as Vern pointed out, only has two ungrounded (hot) conductors and one grounded (neutral/ground) conductor.

The photo showing the switch with the cover open is showing two fused ungrounded (hot) conductors and one unfused grounded (neutral) conductor.

I don't like the routing and connection of the neutral conductor, I'm guessing the schematic shows the service entrance neutral going up and around, then down to the neutral terminal (like the two hot service entrance conductors do), with the feeder neutral coming off the bottom of the neutral terminal. The reason for this is, as routed, one would need to work between two *hot* lugs (they will still be energized even with the switch 'OFF') to work with the neutral feeder conductor (replace it, whatever), whereas if routed as I described all of the bottom terminal would be 'dead' with the switch 'OFF'.

[John Kogel]

Three phase power would have 4 wire service drop. (3 hot, 1 neutral)

Great, thanks, Vern. I was wondering about the lack of a neutral at the weather head.

Jerry, I noticed that as well but didn't think of someone working in there like you say, between two hot leads. Good point. It's time now for an upgrade, eh?

[Jerry Peck]

Jerry, I noticed that as well but didn't think of someone working in there like you say, between two hot leads. Good point. It's time now for an upgrade, eh?

John,

That was designed to be top fed from an overhead service mast, which would have dropped in the service entrance conductors from the top, landing on all of the top terminals.

I'd have to read the instructions and schematic to see if it shows allowing for what is shown in your photo, but then the argument would be put forth that feeding from the bottom "would be allowed", which is when I would state "If you are going to feed from the bottom, you will need to do this ... " (what I did in my other post about the routing of the neutral).

[John Kogel]

OK. Here's some pics of what we normally would see in a more modern condo electrical room. I would expect this to be 3 phase, and it is usually lateral underground service.
Taking these covers off was beyond the scope of my inspection.
One thing I can say is that for most of these switches, "on" is "down".

[H.G. Watson, Sr.]

H.G. To have it the way you describe, the secondary winding would have to have the induced voltage as; +,-,-,+ with no difference in potential between the ends and all current flowing through the neutral. The way it works is; -,+,-,+ with full voltage potential across the ends and part of the totoal voltage tapped off between the ends. In our case the tap is centered, giving 120 from each end to the center and 240 across the full secondary. The sine wave you see in many diagrams are a representation of time, not the voltage/current on the winding at all times. Many of the xfmrs that are used in electronics have several taps along the secondary to give multiple voltages, all in phase. Without adding capacitance, how would you induce voltages out of phase onto the secondary? There is only one high voltage wire going to the xfmr primary. One phase.

No. I explained correctly. You're incorrect. We center tap in N.A.
You're discussion of AC electrical theory and power distribution is incorrect/incomplete and limited to limited application of DC to split single phase in the lucky applicaton of N.A. line voltage at 60 Hz in most small residential (120/240). You're all wet when it comes to polyphase power - proven by your limited description of a bank of three step down transformers and your other statements.

A sine wave representing alternating current represents MORE THAN TIME, it represents time (period for cycle), distance (wavelength - how far it moves in one cycle), frequency (cycles/sec) , amplitude (the value at the peak) and just how positive or negative the voltage is at a point in time and distance.

Stick with effective voltage (rms voltage), in John's case it is 120/208 VAC.

[Phillip Smith]

In the new condos I see around here I see banks of these. The service is 3 phase and I do not open them up.

[Jerry Peck]

One thing I can say is that for most of these switches, "on" is "down".

Actually ... ... "on" is "to the left" or "to the right", the switch handle is already "hanging down" but the switching action is "rotational".

If the breaker operates horizontally or rotationally, then "on" is not required to be down, that only applies to breakers which operated vertically:
- 240.81
- - Circuit breakers shall clearly indicate whether they are in the open “off” or closed “on” position.
- - Where circuit breaker handles are operated vertically rather than rotationally or horizontally, the “up” position of the handle shall be the “on” position.

[Vern Heiler]

No. I explained correctly. You're incorrect. We center tap in N.A.
You're discussion of AC electrical theory and power distribution is incorrect/incomplete and limited to limited application of DC to split single phase in the lucky applicaton of N.A. line voltage at 60 Hz in most small residential (120/240). You're all wet when it comes to polyphase power - proven by your limited description of a bank of three step down transformers and your other statements.

A sine wave representing alternating current represents MORE THAN TIME, it represents time (period for cycle), distance (wavelength - how far it moves in one cycle), frequency (cycles/sec) , amplitude (the value at the peak) and just how positive or negative the voltage is at a point in time and distance.

Stick with effective voltage (rms voltage), in John's case it is 120/208 VAC.

H.G. You would do well to go to the link Jerry posted: Three-phase power systems : POLYPHASE AC CIRCUITS

go to the bottom of that page and click on "Previous Page". Read about "Single-phase power systems". Pay special attention to the Review at the bottom of the page.

[H.G. Watson, Sr.]

H.G. You would do well to go to the link Jerry posted: Three-phase power systems : POLYPHASE AC CIRCUITS

go to the bottom of that page and click on "Previous Page". Read about "Single-phase power systems". Pay special attention to the Review at the bottom of the page.

Vern Heiler,

Hey GENIUS , I posted that link on post #3 long before Jerry Peck did.

You are obviously in over your head and just can't "get it".

John K's panel is rmsVAC 120/208 polyphase. The red "hot" is out of phase with the blue "hot"; unlike your basic residential split single phase rms VAC 120/240 which both hots are "in phase" . Both peak @ about 170V+ A to ground or B to ground.

[Vern Heiler]

Vern Heiler,

Hey GENIUS, I posted that link on post #3 long before Jerry Peck did.

You are obviously in over your head and just can't "get it".

Oh, I didn't know you had not read it! If you had you would have seen this part:
"Power systems in American households and light industry are most often of the split-phase variety, providing so-called 120/240 VAC power. The term “split-phase” merely refers to the split-voltage supply in such a system. In a more general sense, this kind of AC power supply is called single phase because both voltage waveforms are in phase, or in step, with each other.
The term “single phase” is a counterpoint to another kind of power system called “polyphase” which we are about to investigate in detail. Apologies for the long introduction leading up to the title-topic of this chapter. The advantages of polyphase power systems are more obvious if one first has a good understanding of single phase systems. "

[Jerry Peck]

Hey GENIUS , I posted that link on post #3 long before Jerry Peck did.

Vern,

And I thought you would point out that it was in post #4 and not in post #3.

I'm just sitting back watching the two of you dance around the mulberry bush.

[Vern Heiler]

Vern,

And I thought you would point out that it was in post #4 and not in post #3.

I'm just sitting back watching the two of you dance around the mulberry bush.

I thought that would be a bit of over kill . Besides whats one number off between friends?

[H.G. Watson, Sr.]

ARGGGGGH!!!!!!

What's your point VH? That you're dense? You obviously either didn't READ the first few posts, or they were over your head!!!!!

Split single phase 120/240 is center tapped - 180 degrees - polar opposite out of phase but mirror image supplied from the same phase from the distribution - get it? That's why a series 240 resistive load carries zero current on the neutral at your house supplied with split single phase 120/240 from the power company.

In JK's panel supply = You have overlapping wave forms for each 120 VAC source - out of phase in time - positive cancels out negative ------ thus the lack (120/208 compared to 120/240) of comparable voltage to DC power when the two rms VAC 120 circuits are combined for the heater circuit (resistive load) - BECAUSE THEY ARE OUT OF PHASE. (one 120V supply is on the way down or up in voltage out of sync with the other).

Do you even have a clue what "rms" is? I suspect the math from the link I PROVIDED (and Jerry Peck repeated) was too much for you: That's NOT a "greater than" sign. being used in the diagrams or equasions.

[Vern Heiler]

ARGGGGGH!!!!!!

What's your point VH? That you're dense? You obviously either didn't READ the first few posts, or they were over your head!!!!!

Split single phase 120/240 is center tapped - 180 degrees - polar opposite out of phase but mirror image - get it? That's why a 240 resistive load carries zero current on the neutral at your house supplied with split single phase 120/240 from the power company.

You have overlapping wave forms - out of phase in time - positive cancels out negative ------ thus the lack (120/208 compared to 120/240) of comparable voltage to DC power when the two rms VAC 120 circuits are combined - BECAUSE THEY ARE OUT OF PHASE. (one 120V supply is on the way down or up in voltage out of sync with the other).

Do you even have a clue what "rms" is? I suspect the math from the link I PROVIDED (and Jerry Peck repeated) was too much for you: That's NOT a "greater than" sign. being used in the diagrams or equasions.

H.G. I have a very good understanding of root-mean-square. No one but you has even thought about rms. No one has mentioned peak or peak to peak voltage. RMS is the only measurement we make with our meters.

If you would read the rest of the article, and start at Single-phase, you would see where you went wrong. You have done what my wife does so often. Only heard (read) part of the conversation. And then think you know everything.

[H.G. Watson, Sr.]

Vern,

And I thought you would point out that it was in post #4 and not in post #3.

I'm just sitting back watching the two of you dance around the mulberry bush.

3rd RESPONSE post - post number 4. Doesn't change the facts nor VH's nonsense throughout this entire topic thread.

Most stupendous was his 2-PH commentary.

BTW If there were common usage and all 30 units one building, your assumption Y transformer questionable (your a-b, b-c, c-a example) - likely wouldn't be centertap.

[Vern Heiler]

3rd RESPONSE post - post number 4. Doesn't change the facts nor VH's nonsense throughout this entire topic thread.

Most stupendous was his 2-PH commentary.

2-PH commentary? Could you get me within say 3 post of that?

[H.G. Watson, Sr.]

H.G. I have a very good understanding of root-mean-square. No one but you has even thought about rms. No one has mentioned peak or peak to peak voltage. RMS is the only measurement we make with our meters.

If you would read the rest of the article, and start at Single-phase, you would see where you went wrong. You have done what my wife does so often. Only heard (read) part of the conversation. And then think you know everything.

I know what it says, I didn't go wrong YOU MISS split SINGLE phase is accomplished with a step down pottransformer being center tapped (creating two 120 which are 180 out of phase - sourced from the same phase). Your thinking the CONDO Building is supplied with 120 V Single Phase, its NOT there are 30 individual units it wouldn't be. This has already been explained and evidenced by JK's second post wherein he shared the voltage was mesured at 208.

[Vern Heiler]

I know what it says, I didn't go wrong YOU MISS split SINGLE phase is accomplished with a step down pottransformer being center tapped (creating two 120 which are 180 out of phase - sourced from the same phase). Your thinking the CONDO Building is supplied with 120 V Single Phase, its NOT there are 30 individual units it wouldn't be. This has already been explained and evidenced by JK's second post wherein he shared the voltage was mesured at 208.

As I said you should have paid attention to the

REVIEW:
Single phase power systems are defined by having an AC source with only one voltage waveform.
A split-phase power system is one with multiple (in-phase) AC voltage sources connected in series, delivering power to loads at more than one voltage, with more than two wires. They are used primarily to achieve balance between system efficiency (low conductor currents) and safety (low load voltages).
Split-phase AC sources can be easily created by center-tapping the coil windings of transformers or alternators.

[H.G. Watson, Sr.]

First we just do not have enough information. We must have the panel information from the baseboard heaters at a minimum to find a compatible line voltage programable thermostat control.

120/208V the two legs are 120 degrees out of phase NOT 180 degrees, its apples and oranges on how you calculate. You need this confirmed.

H.G. Three phase power is distributed over the main trunk lines. We typically use one of the phases for residential power. It is a single phase. If we had two phase power 180 degrees from each other we would measure 0 volts between them.

2-PH commentary? Could you get me within say 3 post of that?

There you go jackass your badly quoting of MY post with your posted response 10, post count 11, follow the hyperlink.

You couldn't read what I said - you INJECTED your OWN MISUNDERSTANDING, then made a 2-PH reference - no one but YOU ASSumed ANYone was discussing 2-PH anything. Then you PREsumed to tell ME that regular residental power was a SINGLE PHASE, to which others further discussed during my absence. 120/240 is SPLIT from a single phase. 120/208 is POLYPHASE POWER as I said in the THIRD responsive post in this topic thread (post count number 4).


If we mark the two sources' common connection point (the neutral wire) with the same polarity mark (-), we must express their relative phase shifts as being 180o apart. Otherwise, we'd be denoting two voltage sources in direct opposition with each other, which would give 0 volts between the two “hot” conductors. Why am I taking the time to elaborate on polarity marks and phase angles? It will make more sense in the next section! I told you that wasn't a "greater than" sign!

[Vern Heiler]

Your post.

VH, No.

120/240VAC 60 Hz and 120/208VAC 60 Hz are both providing split phase power. 120/240 each half-phase tap is 180 degrees - 120/208 each half-phase tap is 120 degrees.

We use SPLIT single phase, low voltage power distribution for most residential, difference being if the step down transformer prior to service point is single phase (already tapped off of a singular tap winding upstream in the power distribution) it is split, each split half is 180 degrees from the other at 60 hz.

If you would have read the whole article you would see that the below statement was to help students understand how poly-phase works in the next section. I do not know of any power that is distributed this way. All single phase, center tapped xfmr that I have seen. (Other than 3-phase that is 120 deg. as we agree on.)

If we mark the two sources' common connection point (the neutral wire) with the same polarity mark (-), we must express their relative phase shifts as being 180o apart. Otherwise, we'd be denoting two voltage sources in direct opposition with each other, which would give 0 volts between the two “hot” conductors. Why am I taking the time to elaborate on polarity marks and phase angles? It will make more sense in the next section! I told you that wasn't a "greater than" sign!

[H.G. Watson, Sr.]

The outside pictures of a service drop that JK posted from a 1930s APARTMENT BUILDING have NOTHING TO DO with the NEW CONDO Unit panel WHICH IS POLYPHASE (meaning MORE THAN ONE PHASE) which JK originally pictured and inquired about.

THE POCO SUPPLY TO THE CONDO BUILDING would NOT be three stepdown transformers wired as a Y. THE 30-unit BUILDING with electric heat would need MORE POWER THAN THAT.

Try reading again. THE CONDO PANEL that JK FIRST PICTURED DOES NOT HAVE SINGLE PHASE OR SPLIT SINGLE PHASE SUPPLY: Each lug is being supplied with 120 V which is 120 degrees OUT OF PHASE from the other - i.e. POLYPHASE. (poly means more than one, not necessarily THREE)

Now take off your Peck Specks and read what was actually written. Perhaps THEN you can actually UNDERSTAND phase angles.

[H.G. Watson, Sr.]

If you would have read the whole article you would see that the below statement was to help students understand how poly-phase works in the next section. I do not know of any power that is distributed this way. All single phase, center tapped xfmr that I have seen. (Other than 3-phase that is 120 deg. as we agree on.)

Then you don't know and don't understand, have a sheltered experience and limited understanding of power distribution; and you don't want to know or understand. This explains why you don't and don't want to or won't "get it".

[Vern Heiler]

H.G. Watson, Sr.;116787]The outside pictures of a service drop that JK posted from a 1930s APARTMENT BUILDING have NOTHING TO DO with the NEW CONDO Unit panel WHICH IS POLYPHASE (meaning MORE THAN ONE PHASE) which JK originally pictured and inquired about.

So how did you identify the panel as polyphase by the picture? ( I agree that it could be.)

THE POCO SUPPLY TO THE CONDO BUILDING would NOT be three stepdown transformers wired as a Y. THE 30-unit BUILDING with electric heat would need MORE POWER THAN THAT.

Gee, I've never seen 40-60 thousand volts connected straight to the building!

Try reading again. THE CONDO PANEL that JK FIRST PICTURED DOES NOT HAVE SINGLE PHASE OR SPLIT SINGLE PHASE SUPPLY: Each lug is being supplied with 120 V which is 120 degrees OUT OF PHASE from the other - i.e. POLYPHASE. (poly means more than one, not necessarily THREE)

So why did you post this?


VH, No.

120/240VAC 60 Hz and 120/208VAC 60 Hz are both providing split phase power. 120/240 each half-phase tap is 180 degrees - 120/208 each half-phase tap is 120 degrees.

We use SPLIT single phase, low voltage power distribution for most residential, difference being if the step down transformer prior to service point is single phase (already tapped off of a singular tap winding upstream in the power distribution) it is split, each split half is 180 degrees from the other at 60 hz.

[H.G. Watson, Sr.]

So how did you identify the panel as polyphase by the picture? ( I agree that it could be.)


Gee, I've never seen 40-60 thousand volts connected straight to the building!


So why did you post this?


VH, No.

120/240VAC 60 Hz and 120/208VAC 60 Hz are both providing split phase power. 120/240 each half-phase tap is 180 degrees - 120/208 each half-phase tap is 120 degrees.

We use SPLIT single phase, low voltage power distribution for most residential, difference being if the step down transformer prior to service point is single phase (already tapped off of a singular tap winding upstream in the power distribution) it is split, each split half is 180 degrees from the other at 60 hz.

1. I didn't. John K made TWO posts by the time I formed my opinion, based upon his posts AND pictures. Experience suggested this, however, John told us himself in his second post on this string....err which post count number....perhaps number THREE, that the measured voltage was 208.....DING DING DING. He further told us after I inquired, that this was a NEWLY BUILT 30-unit Condo Building not a conversion or repurposing of an older SERVICE or BUILDING. Despite that JK didn't think the measured voltage was significant, or how he refers to the panel or breakers. Note the red and blue to the LUGS. I noted made reference to "color coding" and the Canadian Code but did not BOTHER to look it up and confirm my vague recollections nor to look up the schnieder/canadian breaker color coding.

2. How and why do you LEAP to 40-60 kV? Just curious if there is some kind of logic/reason/basis for this statement, or are you just pulling this out of your a$$.

3. Because. Perhaps you should keep reading/re-reading .

[John Kogel]

Actually ... ... "on" is "to the left" or "to the right",

I beg to differ, but not right now.
(Hint: zoom in on the wording)
Bit of Canadian ignorance there, eh?
The orientation of the handles, I mean.

On an inspection note, if I may ask a question of the bored.....

if I suspect a poly-phase electrical supply to a condo, I could measure current in amps on the neutral, if there is a load on that circuit. Is this correct?

For example, could I plug in a toothbrush and measure amps on the neutral?
I could build a tester adaptor that loads one side of a duplex receptacles with a big resistor, with a couple of leads to ground and the neutral to measure the amps.
This would keep me from "working", poking and measuring inside the distribution panel.
Is this feasible?

[Vern Heiler]

I beg to differ, but not right now.
(Hint: zoom in on the wording)
Bit of Canadian ignorance there, eh?
The orientation of the handles, I mean.

On an inspection note, if I may ask a question of the bored.....

if I suspect a poly-phase electrical supply to a condo, I could measure current in amps on the neutral, if there is a load on that circuit. Is this correct?

For example, could I plug in a toothbrush and measure amps on the neutral?
I could build a tester adapter that loads one side of a duplex receptacles with a big resistor, with a couple of leads to ground and the neutral to measure the amps.
This would keep me from "working", poking and measuring inside the distribution panel.
Is this feasible?

John, the neutral is to keep voltage constant with unbalanced loads, just like the single phase 120/240. Only amperage on the neutral is due to different loads on one or more phases. The tutorial was showing how there would be full amperage on the neutral with two phases 180 deg. Then went on to build the 3-phase xfmr we have all come to know and love. Short answer, no.

[John Kogel]

John, the neutral is to keep voltage constant with unbalanced loads, just like the single phase 120/240. Only amperage on the neutral is due to different loads on one or more phases. The tutorial was showing how there would be full amperage on the neutral with two phases 180 deg. Then went on to build the 3-phase xfmr we have all come to know and love. Short answer, no.

Thanks Vern. I tought it out some more and you are correct, in fact, I'd only be checking one 120 volt leg. The current through one leg is the same for either single phase or poly.
I would need to check the 208 volt outlets, so just measure voltage at the dryer plug if it's accessible. But it'll be a stacker, 99% of the time. Easy access is in the panel. but I'm supposed to stay out of there.

BTW, now that you mentioned it, I'm seeing clusters of 3 transformers on poles all over town. Thanks for that, now I can't keep my eyes on the road!

[Jerry Peck]

I beg to differ, but not right now.
(Hint: zoom in on the wording)
Bit of Canadian ignorance there, eh?
The orientation of the handles, I mean.

I tried zooming in on the wording but could not read it, otherwise I would not have had to allow for the 'either left or right' aspect.

What do the words say?

[Joe Driscoll]

Jerry and friends et al, you can have a 120 /240 volt 3 phase system with no bastard leg, it would be a wye - wye with a concentric neutral tap, instead of the typical edge or corner, really quite common here where residences are somehow popping up where industrial was planned by the liberal republicans. And unfortunately all manufacturers stopped making line voltage tstats for the resistive load that exceed 22 amps. and following 80% rule by design, (ole sparkys rule) load should be no greater than 17.6 amps, now another ole sparky rule is 250 watts per foot baseline on resistive loads, = no greater than 4200+/_ watts on 240v or 16 ft of baseboard, or 3660 watts at 208V or 14.6 ft of baseboard so the real question is how much load are we attempting, or would the reasonable fix be unit mounted tstats for each section.? We constantly run into homes that had 35A rated tstats that cooked, but they were installed during the reign of john revolta and the disco regime.

[John Kogel]

I beg to differ, but not right now.
(Hint: zoom in on the wording)
Bit of Canadian ignorance there, eh?
The orientation of the handles, I mean.

Off is up.

[Jerry Peck]

Off is up.

As I said, "but the switching action is "rotational" " .... and it is.

Which means there is no "down" per se, only rotated. Granted, though, the rotational direction does leave the handle "facing down" for "on", but ... the interior mechanism, which likely weighs more than the handle, may well be "rotated" "up" when the handle is "down", meaning that gravity could be working to keep it down "off" ... I just do not know.

Besides, you are in Canada, and you guys just do things strange up there.

[Richard Soundy]

Yes Sir,

To switch your computer OFF you go to the START Icon - it all makes perfect sense does it not!

VBR - Richard

[bob smit]

As was mentioned, Most switch gear is rotational, OK because it is the indicating type.
Just for yet even more fun; Just three (3) xfrms on a pole for 3 phase is somewhat of a misnomer. The (3) xfrms would be wired wye = 120/208.
Then there is the 120/240 arraignment where one would only observe two (2) xfrms, one larger than the other. This arraignment is wired delta which avails us the so-called High leg (208 v to ground)

I assume we've all had experiences with the high leg or (wild leg).
Once while wiring a machine shop, I heard the finish carpenters that had just arrived sawing away with their equipment screaming.
I ran over to the panel, pushed my help to the side, shut off the breaker and moved it down to the next buss slot. To my surprise, the termites started yelling that I did something to the electricity cause their stuff didn't run as fast now.
After that incident, I put orange tape next to each 208 tab in the back of the panel. Oh ya, and then there was the time a nacho machine smoked the chips and blew out the lamp inside.......
Bob Smit, County Electrical Inspector

[Vern Heiler]

As was mentioned, Most switch gear is rotational, OK because it is the indicating type.
Just for yet even more fun; Just three (3) xfrms on a pole for 3 phase is somewhat of a misnomer. The (3) xfrms would be wired wye = 120/208.
Then there is the 120/240 arraignment where one would only observe two (2) xfrms, one larger than the other. This arraignment is wired delta which avails us the so-called High leg (208 v to ground)

I assume we've all had experiences with the high leg or (wild leg).
Once while wiring a machine shop, I heard the finish carpenters that had just arrived sawing away with their equipment screaming.
I ran over to the panel, pushed my help to the side, shut off the breaker and moved it down to the next buss slot. To my surprise, the termites started yelling that I did something to the electricity cause their stuff didn't run as fast now.
After that incident, I put orange tape next to each 208 tab in the back of the panel. Oh ya, and then there was the time a nacho machine smoked the chips and blew out the lamp inside.......
Bob Smit, County Electrical Inspector

Thats not just any delta xfmr though. One of the windings is center tapped, correct?

[David J. Smith]

Just checked the installation instructions for my programmable thermostats, Aube TH104Plus, and it is stated that the max wattage is 3500.

Programmable thermostats should be able to replace any regular thermostats.

A qualified electrician should be able to sort this out pretty quick.

Another possibility is one of the heaters may be defective but is not tripping the breaker.

Are electricians on Vancouver Island familiar with electric heating?

Here in Quebec 80% of the heating is electric and many people have the programable thermostats including me.

[bob smit]

Tis true Vern.
The two xformer/3 phase arraignments are usually used on 4.8 kv primarys.
In the case where we have 3P 4W open delta we have one winding center tapped (grounded) as U mentioned, designated 'OD4' = Delta 120/240 208/G power L
Then there's the case of the corner grounded delta and a weird wye/open delta, also center tapped to ground.
I think it suffice to say that if a 120v to ground is produced in a delta secondary, it is due to center tapping one winding to ground, which necessarily creates a 208v to ground on one leg also.

When this is done on a pad mount xformer, the manufactures will usually mark them 'dual'.
The Utility in my jurisdiction has told me they can add an additional drop conductor to provide a 240v option (say for a specific piece of equipment) off a 3 bank wye service. I was playing around with this idea on paper...then my head exploded. More coffee please.
Bob Smit, County Electrical Inspector