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Originally Posted by Trumpy
Originally Posted by gfretwell
The scary thing here is in a time when we are supposed to be conserving, there are more people getting 320 and 400 amp services.

Surely that isn't Residential with a load like that, Greg?



Not Greg, but it is still residential.

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The minimum service is 240v 100a (single phase) by code. 200a is becoming the standard and 320/400a is not unusual in these 3500 sq/ft and up McMansions they build. The only time I see much under 200a is if they have a significant use of natural gas. My house is 200a and I had to use the optional calculation to come up with that number when I pulled the permits for my addition. I suppose LED lighting should reduce that a little but lighting is really a pretty small part of the load on an "all electric" house. The heavy hitters are the water heater, range, spa and toaster wire heat. The last is really only practical in southern climates where the heat is not used enough to justify a heat pump. That is probably changing now since the heat pump option is becoming a lot cheaper on A/C systems, almost standard. I actually haven't had my toaster wire heat on in the 5+ years I have had this system. I know that because the installer screwed up and didn't connect the heat call from the thermostat. I tried it right before Christmas because my 92 year old FIL was over and he gets cold. We still got along without it using the 1.44kw heater in the electric fireplace. I since fixed the problem but I am thinking I should have left it alone, just so it doesn't get turned on by accident wink


Greg Fretwell
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Originally Posted by Trumpy
Originally Posted by gfretwell
The scary thing here is in a time when we are supposed to be conserving, there are more people getting 320 and 400 amp services.

Surely that isn't Residential with a load like that, Greg?


I think the first mention of a 400-amp domestic mains I came across was almost 20 years ago when some bloggers (before the term even existed) built an extension to their Virginia farm house and installed several electric on-demand water heaters. Those beasts can go up to 27 kW in Europe and I think US models are even larger because US showers require considerably higher flow rates than European ones. Of course ours are three-phase and the UK/Ireland single-phase ones only go up to 9 KW.

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Requirements start adding up fast in big houses with 5 ton A/C units, electric kitchens, spas and electric water heaters, even tank style. I had to use the optional calculation to get in under 200a when I put on my addition. The reality is I doubt I use much more than 100 at any given time but I suppose there are peaks. It is better to have it and not need it than to need it and not have it. I just didn't want to go through the hassle of a 320a upgrade.
The PoCo was probably going to leave my 2ga drop up there anyway even if I had to snake in a 350 MCM SE conductor set.


Greg Fretwell
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320/400 single phase, 120/240 are common for the McMansions here also. A few come in with the 320/400 meter pan and 2x150 amp MCB panels (300 amp connected).

Lately, the SFDs are rolling in with 200 amp services with ALL LED lighting. Natural gas heat/hot water, and cooking.

Most are now 2 HVAC only, no jacuzzi.


John
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Originally Posted by HotLine1
320/400 single phase

Ohh, you're talking amps, I was sort of frightened by that for a minute..... grin

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Originally Posted by gfretwell
. I had to use the optional calculation to get in under 200a when I put on my addition.
Greg,
Is that like the diversity (demand at any point in time) calculations that we use here to size mains conductors?
It is the idea that not everything is all turned on at the same time, is what I'm trying to say.

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I know of a family compound of 3 homes, most were built in the 1970's all supplied from a 400A, 1Ø Zinsco switchboard, family was doctors, & a lawyer.

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Originally Posted by Trumpy
Originally Posted by gfretwell
. I had to use the optional calculation to get in under 200a when I put on my addition.
Greg,
Is that like the diversity (demand at any point in time) calculations that we use here to size mains conductors?
It is the idea that not everything is all turned on at the same time, is what I'm trying to say.

Yes, NFPA has 2 different was to compute diversity in the load calcs. Basically the primary method deals with each load separately and the optional method applies the diversity to the total computed load. It is a little more complex than that but that is the basic idea. I think NFPA errs on the safe side anyway. I doubt I ever even see 60% of capacity with the spa running. I have looked with my clamp and it usually runs well below that. According to FPL (the PoCo) my average usage is about 14a on a 200a service. I understand there are peaks and valleys in there and we really care about maximum instantaneous draw. One of the cool things about the smart meter is they can give you statistics hourly, daily or monthly.


Greg Fretwell
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Originally Posted by gfretwell
I actually haven't had my toaster wire heat on in the 5+ years I have had this system.

What is "toaster wire heat"?

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