.............

Not 100% sure
New dryers are 4 prong
Older dryers were 3
Same for stoves

Most of the appliances that use 220 also have 110 circuits for the clock, and controls. In the past you would get the 110 off one leg and the ground, now with 4 prong you have a neutral and ground.

So 3 prong outlet was correct, but should be changed to 4, if possible, may only have 3 wires.
It does not HAVE be be changed to 4. but would be better as 4.

__________________
Rick Cantrell
Columbus GA

Ask electrician why they are now required to be 4-wire, if 3-wire is ok.

The four prong outlets with four wires are electrically safer. As Rcik points out though, you have to have four wires present if you want to upgrade to the 4 prong outlet (or be willing to run a new wire).

The reasons that the four prong outlets are safer is the same reason you need a four wire feeder to electrical panels downstream of the service equipment. The only interconnection between the ground and neutral you want in your electrical system is at the service equipment.

I believe the change from three to four wires started with the 1996 NEC.

In the three-wire system there are (at least) two possible problems.

1. There is relatively high resistance in the neutral line. To the extent that the neutral is carrying significant current (think the 115V drum motor in a dryer) there will be a voltage on the appliance frame equal to the voltage drop in the neutral line.

2. There is an open in the neutral line. If one of the 115V devices is turned on you could have close to 115V on the appliance frame. This situation is why the neutrals on receptacle outlets in split circuits are required to be pigtailed and not just daisy-chained through the device.

That said, the NEC folks took their sweet time to finally disallow 3-wire circuits, I guess there were few problems in real life.

If the circuit were run before the 1996 NEC took effect I would make a comment, but say that upgrading is not required. If the circuit war run when the new rule was in force I would have a problem with that.

- BOB

That answer (to some extent), as some have already pointed out, is that of timing.

The answer (to the rest of the extent) is that the electrician is wrong, and, depending on what you said and your wording, you may also be wrong.

First, let's take what the electrician said: "The electrician said it was okay and not a safety hazard."

"The electrician said it was okay ... "

It was, for eons.

" ... and not a safety hazard." I was always a safety hazard. Always was, and, until those old ones are changed, always will be.

No "upgrade", as Bob called it, is *ever* required. If the circuit 'should have been' run with 4 wires, then it 'shall' be replaced, meaning it is wrong, dead wrong.

If the circuit 'was not required to have been' run with 4 wires, then it 'should' be replaced, meaning it is safer to replace it, however, *IF* it is a 3 prong plug for the range or dryer, *IT IS* most likely only wired with 3 wires, meaning that correcting it may not be real easy - all depends on where the dryer is located in relation to the panel.

So, depending on 'how' you write them up, you could be right, or just partially right.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

I don't have an issue with it, nor do I report if it is a 3 or 4 wire equipped receptacle. I don't consider a 3 wire system a safety issue either. But this is me, and your opinions may differ.

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Scott Patterson
Spring Hill, TN
http://www.traceinspections.com

That brings up a question.
You buy a house with the 3 prong outlets, and your stove and dryer are the newer 4 prong style. Is it allowed ( by code and/or manufacture) to install a 3 prong cord on the stove, dryer?

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Rick Cantrell
Columbus GA

I do not know, but I believe that the answer is yes. Buying a new appliance does not require running a new cable from the panel to the receptacle outlet.

- BOB

Bob,

Rich said this:

Which means those circuits already 'have' the four prong receptacle, and, presumably, four wires.

You said:
In answer to Rick's questions, if the receptacles are already four prong, then a four conductor cord and plug would be needed to install the range or dryer.

I'm guessing that is what the manufacturer's installation instructions will say, and the code does not say that you may change the receptacle out to a three prong type from a four prong type. (But I could be wrong, I've been wrong before.)

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Jerry
Thanks for answering, but you misread my question.
3 prong receptacles
4 prong cord

__________________
Rick Cantrell
Columbus GA

Man I sure did. I must be losing my mind??? Can't seem to read anymore.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

One of the reason that dryers and stoves don't come with the connecting wire and plug.

__________________
Scott Patterson
Spring Hill, TN
http://www.traceinspections.com

A few years ago I bought a new dryer. The appliance company came out and installed the dryer. The dryer did not have a cord on it already. I noticed they brought with them both cords, 3 and 4 prong to use accordingly.

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Tim Moreira
Suncoast Home Inspections
Suncoasthomeinspections@yahoo.com

What difference does it make if you have a 3 or 4 wire dryer if both of the wires go back to the *Service Equipment* panel and are bonded together there anyway.

Now if the go back to a panel that is not *Service* then I would agree.

Am I looking at this correctly or not???

__________________
Tim Moreira
Suncoast Home Inspections
Suncoasthomeinspections@yahoo.com

There are two possible problems, which I mentioned in an earlier post.

In case 1. the problem is that the "ground" is also the neutral, there is current flowing through it, and the voltage at the "ground" point on the appliance frame is not the ground potential at the service because of voltage drop. With four conductors this is not a problem, because there is no current flowing through the ground conductor. The voltage here would probably be small, but real.

In case 2. we violate your assumption "if both of the wires go back to the *Service Equipment* panel". If there is a break in the neutral circuit, There could be almost 115V on the appliance frame. This is a similar problem to losing the neutral on a split circuit or on the service except here the neutral, with the far from zero voltage, is on the appliance frame. (A friend called me out for an electrical problem last autumn, weird voltages all over. The neutral was open at the transformer.)

- BOB

"Now if the go back to a panel that is not *Service* then I would agree."

The only difference that makes is that the resistance in the neutral may be higher (case1.) and there are more points of failure for the neutral (case2.) In a properly (other than being 3-wire instead of 4-wire) operating system, it does not matter if the panel to which the circuit is connected is the service or not.

- BOB

It's not really an "either/or' issue.

The old style ... neutral bonded to the appliance, three wire plug ... was, for the most part, safe enough. There was, nonetheless, a drive to change from this to the four wire plug, and with the neutral isolated from the case of the dryer.

Earlier dryers had no need for a neutral ... everything was 240v- switches, timers, and all. For reasons on economy, manufacturers were able to use 120v timers, etc .... by simply using the appliance case as a neutral, as well as ground.

Sure, the code says 'no objectionable current on the ground." Care to define 'objectionable?'

For reasons that had absolutely nothing to do with dryers, the electrical trade began to recognize the need to connect the ground to the neutral at only one place- and that place was the service entrance. Many problems, many dangers, were corrected once this was done. Yet, we still had those three-prong plugs on the dryers and ranges.

Still, for the typical romex-wired home, the "parallel path" created with this second neutral / ground connection was pretty much a non-issue. Make that a house wired in pipe, add a loose connection, have the dryer 'on' ... and you now have a section of the pipe that's "hot." Not a good situation.

For the sake of consistency, it was decided to change over to four-prong plugs.

More important than the type of plug is that the appliance be wired correctly for the plug that is used. If a four prong plug is used, yet the case is still bonded to neutral, this situation can still develop.
The reverse situation is even more dangerous ... a three prong plug on an appliance whose case is not bonded. That could allow the case to become "hot."

I believe 4 wire plugs for dryers and ranges was the code for mobile homes years before it was for code for non-metal housing. The more grounding paths the safer it should be in theory...