Amperage on new house

**Jim Robinson** · 01-05-2009, 04:43 PM

This was a weird house today. It has in floor electric radiant heat. I figured it would have a large service, and it did. I was thinking it was 400 amps, but then when I got home I started second guessing myself. The house is not completed, and has never been occupied. It was foreclosed, and has sat empty for a while. The heat was on, and seemed to be working okay where they had thermostats. There are a total of 15 or 16 thermostats in the house. I guess you can only run so much square footage through each t-stat or it will overload it. It's a pretty big house, and it gets pretty darn cold here. I think it was originally going to be hydronic in floor radiant, and someone changed the plans later.

Anyway, there was a meter set up outside, and two service disconnects. I know, it was pretty weird. Each disconnect went to a 200 amp sub panel inside the house that was properly wired. Inside each service panel was a knife switch, and two 100 amp fuses. My question is does the two 100 amp fuses equal a 200 amp for each disconnect (400 amps total) , or is it currently set up as a 200 amp service, with 100 amps to each panel inside?

I don't have an outside shot of the service disconnect set up, but this is the inside view of one of them. They are identical panels.

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**Jerry Peck** · 01-05-2009, 05:50 PM

Originally Posted by Jim Robinson

There are a total of 15 or 16 thermostats in the house. I guess you can only run so much square footage through each t-stat or it will overload it.

No, you could run the entire house on one thermostat.

Using 15 or 16 thermostats means you likely have one for each space, which gives precise control over each spaces temperature, that's a good thing.

Anyway, there was a meter set up outside, and two service disconnects. I know, it was pretty weird.

Actually, that is quite common.

Was the rating of each disconnect?

Each disconnect went to a 200 amp sub panel inside the house that was properly wired. Inside each service panel was a knife switch, and two 100 amp fuses.

You are mixing terms so much it is difficult to follow what you have.

My question is does the two 100 amp fuses equal a 200 amp for each disconnect (400 amps total)

.

No.

, or is it currently set up as a 200 amp service, with 100 amps to each panel inside?

Again, you are mixing and misusing terms, making it hard to follow.

**Jerry Peck** · 01-05-2009, 06:02 PM

Now, based on what I think you are asking and based on that photo.

The "service equipment" consists of those two main disconnects outside, each one has 2-100 amp fuses in them. We don't know the rating of the disconnects, but they appear to be far greater than the 100 amp fuses as the fuses look like they are too small for that disconnect, which could be a problem. There are 2-100 amp fuses, you said, making each one a 100 amp disconnect (the ratings of the fuses are not additive, the same current flows through each fuse). Thus, the service is 200 amps.

Now, though, there are 2-200 amp rated panels inside. These *are not "service panels"!

Okay, you have 100 amps supplying a 200 amp rated panel, nothing wrong with that.

What size were the feeder conductors (what was their rating)?

The feeder conductors must have *at least* a 100 amp rating, and if they have a 200 amp rating, then the fuses could be changed to 200 amps to provide for a larger service if needed, but the power company would need to be contacted to verify that the meter was rated for 400 amps along with the overhead service (or underground service, which ever it was).

My guess is that the feeders are not 200 amp rated, meaning that the owners are stuck with what is installed, unless they want to replace the feeders (which may, or may not, be an easy job).

If everything else is gas, 200 amp may be enough. If there is any doubt or concern, have an electrician come out and do a load calculation on the house "as built" and advise your client whether or not it is acceptable or not.

**Jim Robinson** · 01-05-2009, 07:45 PM

That's what I thought. I just wanted to verify. Meter, service disconnects and feeders are okay for 200 amps, no problem there. The service from the transformer to the meter is not visible, so I'm not sure what size that wire is.

The t-stats are supposedly only good for up to 300 square feet each at 240 volts.

http://www.suntouch.com/pdf/_brochur...N_20080507.pdf

**Jerry Peck** · 01-05-2009, 08:32 PM

Originally Posted by Jim Robinson

The t-stats are supposedly only good for up to 300 square feet each at 240 volts.

http://www.suntouch.com/pdf/_brochur...N_20080507.pdf

.

Actually, (see underlining) the sensors which are for up to 15 amp capacity, which is 150 sf @ 120 volts and up to 300 sf @ 240 volts.

SunStat — Programmable
The Programmable control is both elegant and intelligent. This control handles both 120 VAC and 240 VAC, it has four preset program schedules and one user program schedule for customized programming. Features include a floor sensor and/or air sensor that controls floor temperature; 15-amp capacity controlling up to 150 sq. ft. of 120-VAC mats or 300 sq. ft. of 240-VAC mats; built-in ground fault protection with no need for a separate GFCI (in most code areas); large, back-lit digital display; temperature range of 40° to 99°F; temperature display in °F or °C; on/off switch; 12 or 24-hr. clock.

Want a larger room, simply wire cables together:

Warm the floor of a powder room or large family room. There really is no limit. A single cable can heat a 240 sq.ft. area at 3” o.c. Larger rooms can be warmed with multiple cables wired together.

All you would do is control more sensors with the one thermostat, with each sensor being limited to 15 amps.

An example would be our living room, it is nearly 500 sf, with about a 150 sf dining area off it. If I were to use that system, it would make the most sense to include the dining area and the living room on one thermostat. Then again, maybe not, maybe separate the dining room as we rarely use that area. Either way, it far exceeds on 240 sf roll and would require at least two rolls of that wire.

Then I would do the kitchen on its own thermostat, the breakfast room on its own thermostat, each bedroom on it own, each bathroom on its own, etc. As our house is now, there is one system, a/c and heat pump with back up electric strip heating - one thermostat. Keeps the house fairly even in temperature, but offers no individual control for the various rooms.

I can imagine that heating up a slab floor takes a while, then the heat can shut off and the slab will radiate the stored heat for a while after the thermostat cycles off. May take a while to heat initially, but (with the right control settings) could give a long even heating cycle once "pre-heated" (so-to-speak).

Ron Bibler · 01-05-2009, 08:50 PM

Infrared Thermal Imaging can be a big help in inspecting this type of floor systems. some times you will find dead areas or areas that did not get the proper coverage. These images are from an inspection I did last month. These floor had a 14X14 Inch tiles over the heat grids. These floor are very cool to Image.

The heat in the floor as Jerry stated will be in that concrete for some time after the system is shut down.

Best

Ron

Jeff Remas · 01-05-2009, 10:08 PM

I am seeing more 320A continuous meter bases with two 200A panels inside. Very common these days in larger homes.

If you look at the meter there should be a number on it such as CL200 or CL320. This lets you know what the meter is rated for. This way you will know what the utility company is probably set up for at the transformer.

Most meters are standard CL200 even when placed on 100A services so a 200A meter does not mean that you have a 200A service but a CL320 certainly does mean that you have a 320A continuous service and two 200A panels is fine.

I am still a little confused by your post and description so if you can clarify Jerry's questions we can help you more.

Jeff Remas · 01-05-2009, 10:12 PM

Ron, I would love to megg out the floor system in question and do a resistance check to see if there is a problem.

The photo in the middle looks more like the system has not been on very long and the tiles were cold to start with. If there is a break or problem then the color change would start at one point of the looped wire and not continue or not continue as bright. In your photo it appears as though the change in color thermal line crosses the wires perpindicular to the loops.

Ron Bibler · 01-05-2009, 10:29 PM

Originally Posted by Jeff Remas

Ron, I would love to megg out the floor system in question and do a resistance check to see if there is a problem.

The photo in the middle looks more like the system has not been on very long and the tiles were cold to start with. If there is a break or problem then the color change would start at one point of the looped wire and not continue or not continue as bright. In your photo it appears as though the change in color thermal line crosses the wires perpindicular to the loops.

I'm not sure if a break in the system would stop at the break or if they have prep the wiring for things like that. kind of like Christmas tree lights. I have not Image any floors with problems...

You should check into renting a camera and offer to image the floors in that home. use the photos i post if you need to. I would charge if its a big home 3000SQ feet $ 400 or $ 500 to image the flooring. that way they have a point to start with. and can no if the have any problems they need to deal with today...

Best

Ron

**Jerry Peck** · 01-06-2009, 08:15 AM

Originally Posted by Jeff Remas

Ron, I would love to megg out the floor system in question and do a resistance check to see if there is a problem.

The photo in the middle looks more like the system has not been on very long and the tiles were cold to start with. If there is a break or problem then the color change would start at one point of the looped wire and not continue or not continue as bright. In your photo it appears as though the change in color thermal line crosses the wires perpindicular to the loops.

.

Jeff,

I suspect that is reflected heat.

When using an infrared camera one has to be very careful of reflected heat. All the brighter area to the right looks like reflected heat, so I'm guessing those two perpendicular lines are also reflected heat.

Attached is a photo showing reflected heat. I was looking for moisture under a tile floor and found this, after scratching my head a few seconds, I realized I was looking at the reflected heat from the leaves on the tree outside. I stood there and watched it a minute or so and I could see the pattern move with the wind blowing through the tree.