commercial garage service calculation

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gserve

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Have never done service calculations for a commercial garage before and need help. This is a 40' X 80' building. According to article 220 the lighting load would be 1/2 VA per square foot. and 180VA for receptacle load all with a 100% demand factor. What I need to know is how 2 welder outlets,air compressor and car lift would be factored in. I do not see any examples in annex D. I am trying to determine service size. Does anyone know of any good calculation examples on this type of calculation. Any help would be appreciated. Thanks
 
I don't know of any examples, but I believe the NEC would direct you to Article 630 for welders, Article 430 most likely for the air compressor, and possibly 430 for the lift also.

I question that 1/2va is enough for commercial garages. I usually put more than that in one. I also question 180 va for gp receptacles since many will have wheel balancers, tools, etc. These are minimum values and a good designer will use them carefully.

Jim T
 
Salesmanship is the biggest part of the install. If it is a garage, try and get who ever is charge of the ca$h to consider lights on the wall in front of where the hood is, per bay, so that the mechanics get decent lighting. Another good seller is cord reels, one by each lift. Only thing special that gets any major consideration at a Service station is the seal-offs and pump area(C1D1 and D2)....sign at remote in the lot, and the mushroom.
 
gserve said:
According to article 220 the lighting load would be 1/2 VA per square foot. and 180VA for receptacle load all with a 100% demand factor.
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That is the general lighting load and required recept.s load are MINIMUMS.

What I need to know is how 2 welder outlets,air compressor and car lift would be factored in. I do not see any examples in annex D. I am trying to determine service size. Does anyone know of any good calculation examples on this type of calculation. Any help would be appreciated.
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Could you imagine how big the NEC would be if every conceivable example was contained in it?

Sometimes you have to clear a few trees to see the forest....you could make the place brighter by using specific luminaries - that are greater than 1/2VA/ Sq.Ft.....you could add a few more recepts. at the work stations....all adding to that MINIMUM set forth by the NEC....you could also add 18 welders and 14 lifts....just do the extra math on what's NOT minimum, that the client is asking for (add the minimums) and you will arrive at an accurate figure for the service (with no room for expansion).
 
If the multiple welder receptacles will only be used one at a time, then you only count them once. If multiple people will be welding with multiple welders, then you count them however many times.
 
gserve said:
So if I don't know what welders they are going to use and I install 2 -240V 3 wire 50A receptacles how do I calculate this?
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The Power of Pray?

If you don't know what their plan is...ASK.
 
gserve said:
I did.All they could tell me is that they are the portable ones you plug in.
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Have them give it to in WRITING....then find the smallest one you can find (online) and wire it up to that spec. Then they can pay you to re-do it with the equipment they have in mind.

You can even tell them this is your plan - to light a fire under their butts and get in the game!
 
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