Need some advise Please! There's a 6750 sq ft house being built (nearly complete)and now they find out there there short of circuit breakers. Here is the breakdown---320 amps from Comm-Ed to the meter enclosure, 2) 200 amp 40 space panels completely full, contractor wants to add another 200 amp 40 space panel off the existing 320 amp, I told him NO. Does anyone AGREE or DISAGREE? Can you site NEC articles either way? There were no calculations done by anyone. Alot of add-ons. Thanks Denny
Panels
- Thread starter gunny7
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charlie
Senior Member
- Location
- Indianapolis
Re: Panels
Without calculations, you are flying blind. I am wondering how you know the service equipment that you have already installed is large enough?
Go to Article 220 and do the calculations. At that point, you will answer your own question. Our host even has a free spread sheet available to do the calculations for you.
Without calculations, you are flying blind. I am wondering how you know the service equipment that you have already installed is large enough?
Go to Article 220 and do the calculations. At that point, you will answer your own question. Our host even has a free spread sheet available to do the calculations for you.
- Location
- Massachusetts
Re: Panels
The number of breakers makes no difference, all that matters is the calculated load.
Say a customer wanted the ordinary number of outlets in their house but each one on a dedicated circuit, you would need a lot of panel spaces but no more current then if you had wired 7 - 12 outlets per circuit.
The number of breakers makes no difference, all that matters is the calculated load.
Say a customer wanted the ordinary number of outlets in their house but each one on a dedicated circuit, you would need a lot of panel spaces but no more current then if you had wired 7 - 12 outlets per circuit.
charlie
Senior Member
- Location
- Indianapolis
Re: Panels
Sorry Gunny, I gotta go with Bob. Do the calculations and if it works, install it. If you have a problem with an inspector, show him the calculations. By the way, it is not the inspectors job to do the calculations but it is his job to review them if he has a doubt about what you have done.
Sorry Gunny, I gotta go with Bob. Do the calculations and if it works, install it. If you have a problem with an inspector, show him the calculations. By the way, it is not the inspectors job to do the calculations but it is his job to review them if he has a doubt about what you have done.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Panels
You have to do your own calculation, based on the equipment that the house will contain. But I did a general ?sanity check,? just to get an idea of whether you were well below, below, near, above, or well above the 320 amp service.
I added 100% of the Small Appliance load (3000 VA), then took 35% of the combined total of the laundry circuit (1500 VA) and the lighting load (3 times 6750), and threw in a range (8000 VA), an electric dryer (5000 VA), and some space heating (15000 VA). That gave me a total (for this hypothetical house, not for your house!) of just over 38,600 VA. This equates to 160 amps at 240 volts, or just about half of the available 320 amps of service capacity.
I conclude that it would not be unreasonable to discover that you can add a third 200 amp panel. But let me stress, as the others have already done, you have to do your own calculation.
You have to do your own calculation, based on the equipment that the house will contain. But I did a general ?sanity check,? just to get an idea of whether you were well below, below, near, above, or well above the 320 amp service.
I added 100% of the Small Appliance load (3000 VA), then took 35% of the combined total of the laundry circuit (1500 VA) and the lighting load (3 times 6750), and threw in a range (8000 VA), an electric dryer (5000 VA), and some space heating (15000 VA). That gave me a total (for this hypothetical house, not for your house!) of just over 38,600 VA. This equates to 160 amps at 240 volts, or just about half of the available 320 amps of service capacity.
I conclude that it would not be unreasonable to discover that you can add a third 200 amp panel. But let me stress, as the others have already done, you have to do your own calculation.
charlie
Senior Member
- Location
- Indianapolis
Re: Panels
Gunny, you need to do them. If you need help, we will help. I don't think anyone will do them for you.
Did you check out the link I gave you on my first response? The spreadsheet is free and easy to use.
Gunny, you need to do them. If you need help, we will help. I don't think anyone will do them for you.
Did you check out the link I gave you on my first response? The spreadsheet is free and easy to use.
Re: Panels
We do houses like this all the time. Look out for the steam heat units in the showers. Some of those we do are 30KW by themselves. If you already know all the stuff that needs to be on the service it is a pretty simple calc. Getting the information of what actually is getting installed is the hard part for me.
The question we wrestle with is:
Is the steam unit a fixed in place appliance and can it be taken at 75%? It is not on hte list of things that cannot be taken at 75% but is similar in nature to them.
We do a lot of condos in downtown chicago. They all seem to be in existing buildings with old electrical services. They all are radiator heat buildings with no a/c, gas stoves and gas dryers. The owners always want to put in electric heat, A/C, electric oven, electric dryer, and electric steam units. The service coming into the unit is 100amps 208v, 1 phase. The steam unit by itself is over 100amps. Then you go look at the building service to see where you can get more power from, and you find out that they probably don't have enough to feed the existing units that have been retrofitted based on the NEC demand calcs. Luckily for these people the NEC is very conservative for residential loads. So we tell the condo owner, that the building will most likely have to upgrade the building service in order to supply the amount of power you need. Sometimes the owner of the condo has to sell the condo and find a different place because the building will not accomodate them. Others the service is large enough to add more service.
But you never know until you do the calculations. So the point of my rant is, Make sure you have all the electrical loads accounted for. Also, remember that electric heat and a/c may be redundant of each other. Also, the large humidifiers loads are intended to run only when you are heating generally, so those are sometimes redundant also.
We do houses like this all the time. Look out for the steam heat units in the showers. Some of those we do are 30KW by themselves. If you already know all the stuff that needs to be on the service it is a pretty simple calc. Getting the information of what actually is getting installed is the hard part for me.
The question we wrestle with is:
Is the steam unit a fixed in place appliance and can it be taken at 75%? It is not on hte list of things that cannot be taken at 75% but is similar in nature to them.
We do a lot of condos in downtown chicago. They all seem to be in existing buildings with old electrical services. They all are radiator heat buildings with no a/c, gas stoves and gas dryers. The owners always want to put in electric heat, A/C, electric oven, electric dryer, and electric steam units. The service coming into the unit is 100amps 208v, 1 phase. The steam unit by itself is over 100amps. Then you go look at the building service to see where you can get more power from, and you find out that they probably don't have enough to feed the existing units that have been retrofitted based on the NEC demand calcs. Luckily for these people the NEC is very conservative for residential loads. So we tell the condo owner, that the building will most likely have to upgrade the building service in order to supply the amount of power you need. Sometimes the owner of the condo has to sell the condo and find a different place because the building will not accomodate them. Others the service is large enough to add more service.
But you never know until you do the calculations. So the point of my rant is, Make sure you have all the electrical loads accounted for. Also, remember that electric heat and a/c may be redundant of each other. Also, the large humidifiers loads are intended to run only when you are heating generally, so those are sometimes redundant also.
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