Multiple welder receptacles - overload - pass inspection?

[BMEP]

I've read the 2010 California Title 24 electrical sections (based on NEC), as well as relevant parts of the NEC and haven't been able to answer this question for myself.

Do multiple 50A welder receptacles have to be all added to the load calculation or can I only add the largest (one 50A in my case) becuase this is a case of "noncoincidental load"? I don't want to exceed my 100A panel capacity as far as NEC and an inspection is concerned.

In other words, are the multiple 50A welder circuits/receptacles added together or do I only need to factor one of them into the sizing calculation because they're noncoincidental loads?

Here's the setup:
New 100A sub panel with the following loads
- 120V 20A receptacle circuits
- 120V 20A lighting circuits
- HVAC (20A, 240V)
- Compressor (24A, 240V)
- Floor lift (30A, 240V)
- Welder (50A, 240V)

As far as I can see, the only continuous loads are the lights, 120V receptacles (at least part of the load), HVAC and compressor.

 

[Aceman]

It looks like you're calculating load by breaker size for the most part. That isn't the correct way to do it, you need to read through Article 220 and figure the calc based on ACTUAL LOAD and square footage(for lighting).

In any case for a simple garage, I'll tell you most folks probably don't even do a real genuine load calc. They'll look at all the equipment, lighting, etc(not breaker size!) and knowing everything won't run at once is how they'll come up with a figure.

Looking at what you have, you should be fine with a 100 amp sub. I don't know if California is different, but up here in OR an inspector would check your wiring, etc and not even look think about a load calc when inspecting a sub panel.

 

[BMEP]

Yeah, sorry - some of those are breaker sizes since I don't know the actual loads yet.

The lights I still have to calcualate (haven't decided how many fixtures but I'll be well above the NEC standard for a garage). Also the lift is probably a 2-3 HP motor so it's probably 12-17 amps.

Still, I know I'm fine with all that stuff plus a single 50A welder circuit. I'm just worried that the inspector will see a 100A sub panel with 2 x 50A breakers, a 40A, a couple 30A and then start to ask questions about a load calc.

BTW, I've got 3 arc welders, one of which really does draw 50A.

 

[theoldwizard1]

My son's house has a fairly new panel and has had more than 1 inspector look at in in the past 3 years. The mains are a pair of 100A, and I know that all of the breakers add up to way more than that. The electric dryer and feed to the garage are a both 240V, 30A and we just put in 2 120V, 20A circuits for the kitchen and 2 more 20A circuits for the bathrooms.

Now what I thought was odd and the first inspector did not say anything, was that many of the circuits were wired with 14 gauge and connected to 20A breakers. I fixed that by switching to 15A breakers.

 

[Steevo]

My 100A load center in the shop has three 50A/240v breakers, three 30A/240v breakers, and eleven 20A/120v breakers in it, for a total of 460A in breaker capacity.
It passed electrical inspection with no problems. And some of those 50A and 30A circuits have two receptacles on them.

 

[BMEP]

My 100A load center in the shop has three 50A/240v breakers, three 30A/240v breakers, and eleven 20A/120v breakers in it, for a total of 460A in breaker capacity.
It passed electrical inspection with no problems. And some of those 50A and 30A circuits have two receptacles on them.

That's good to hear. I thought I read that a 50A circuit could only have one device on it but I could be mistaken.