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| Subject - When to opt for a 400 amp service. | |
| MONOLITH |
I'm currently bidding to wire a large custom home. I'm also designing the complete electrical system for it. I'm a little unsure of whether to push the limits of a 200 amp service, or install a 400. Here's what I'm looking at... Using the example from the back of the 2005 NEC...Annex D, Ex. D2(c). The 'worst' case scenario for a home the book examples provide. It has a calculated load of 145 amps, and says a 150 amp service is acceptable. First, I thought you could only load a breaker to 80%? (150 x .8 = 120) Starting with the D2(c) example, I'm adding 4000 more sq ft. The example uses 2000 sq ft, this home is 6000, which includes a 2000 sq ft unfinished basement. BUT, I want to allow for the possible finishing of the basement, so I'm including it's footage. So to the NEC's 145 amps, I add 20 more for the extra 4000 sq ft, as follows... 4000 sq ft x 3va = 12000va. 12000va @ 40% = 4800va. 4800va/240 = 20 amps Now I'm up to 165 amps. This is with just generic light outlets in each room. I have no doubt Recessed lighting will be added along the way, and with three floors at 2000 sq ft each, lets' say up to 30 recessed cans; 75 watt bulb = .62 amps. .62 amps x 30 = 19 amps. 19 amps @ 40% = 8 amps (assuming I can treat the extra lighting the same as additional General illumination (sq ftage) and reduce it to 40% ) Now I'm up to 165 + 8 = 173 Amps. Add to this, the probability of : A disposal Pool equipment Water Purifying system A jucuzzi/Spa tub Exterior landscape lighting Security floods at the corners of the house Seems like I could definately exceed 200 Amps, yes? Does it look like I had better put in the 400 Amp Service? I spent a lot of years building commercial buildings from already engineered drawings, designing homes from scratch is a little new to me. Any advice would be apreciated. Thanks. |
| kbsparky | What is the heating system? Gas, oil, or electric heat pumps? Sometimes, that is all that is needed to trip the scales here.... 
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| MONOLITH | Sorry I didn't mention it, but it was because it's already in the example I listed. 2 1/2 ton heat pump unit with 15 KW of backup heat is built into the original 145 amps from the example. |
| lctrc789 | Go ahead, and do not push it install a 400 amp service and two 200 amp panles for future use as well of peace of mind. Then try to balance each panel as best you can you will find that these folks will apppreciate the fact they will have room for future use..... |
| MONOLITH | That's what I was leaning towards, but just wanted to check with the more experienced. Thanks for the response. I'm a little surprised there are so few. *feels dissed*. 
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| WELLSEROUSKI | With my home builder I use I tell him it's a good selling point that they have a 400-amp service in case they add whatever..At this point 7 homes have sold before completion( in a row ). If the owners have to upgrade later that's no good. Unless it's obvious you don't need it according to estimated demand( electric heat ect. ). |
| MONOLITH | quote: Agreed. That's what I'm putting in my bid proposal (explaining the slight extra cost for a 400 amp service). The more I think about the potential for expansion with this type of house, the more I think trying to stick to a 200 would be a mistake. |
| Jason33 | looking at your specs it's border line. Any time it's even close you should opt to a 400 for future, and breaker space also. Depending on if gas is available or not the 2 poles eat up space in a hurry. I just finished a house where it started with a 200 amp service and ended with a 600 with a gen tran. The home owner didn't now what he wanted but my first day at the job I found out there was more than what we had bid. Drive way gates, fire systems, lanscape lighting, fountians, 100 amp future shop, and electric boiler for floor heat. The boiler alone was 180 amps. And in the long run there will be a little room for add ons. |