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Home > Forums > Electrical / Electronic Engineers > Activities > Electrical/Electronic engineering other topics Forum

when is your service maxed?Helpful Member!(2) 

thread248-327109
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syarn (Structural)
1 Aug 12 16:31
if an engineer says
"...The electrical panel is 400amp/240v/1 ph
We currently have 335 amps connected to the panel before the addition of the dishwasher
The dishwasher will overload the panel..."
the dishwasher looks to have 50 rated amps, 60 amp minimum supply circuit conductor ampacity & 60 amp maximum overcurrent protective device per the spec sheet.
when I add 50 amps to 335 amps I get 385 amps how does that over load the panel?

steve yarnall

http://svyarchitect.blogspot.com/

Helpful Member!  itsmoked (Electrical)
2 Aug 12 4:52
In the future ask the engineer your question. He should be happy to explain it. If he won't or seems bothered find a new one.

But to answer your question most authorities consider an installed load exceeding 80% of the equipment rating to be the maximum allowed. 80% of 400A = 320A

Keith Cress
kcress - http://www.flaminsystems.com

ScottyUK (Electrical)
2 Aug 12 8:11
Of course you will probably have diversity which helps to take into account real-world conditions where it is unlikely that all loads will simultaneously draw rated power. It is not unusual to see boards with a total connected load of perhaps double the feeder capability in instances where diversity is low.
djlozzi (Electrical)
23 Aug 12 21:00
Did you do an actual load test on your electric panel or did you simply count the breakers and amperage on the breakers? 335 Amps is a huge load for a home. To really obtain the actual load on your 400 amp service, someone would need to do an actual load test with an amp probe on each phase.
syarn (Structural)
24 Aug 12 8:57
djlozzi it is a commercial project (restaurant). the electrical engineer insisted the existing service had to be made larger and the client finally acknowledged...so the dishwasher was removed from the scope. thx u.

steve yarnall

http://svyarchitect.blogspot.com/

Helpful Member!  dpc (Electrical)
24 Aug 12 11:37
For commercial kitchens, the NEC has very explicit load calculation requirements that need to be followed. Historically, restaurant kitchens have been a leading cause of fires, so the NEC developed some pretty strict requirements.

MiketheEngineer (Structural)
24 Aug 12 13:40
And what are the odds all breakers will be maxed out at any given time?? About ZERO. Or run the dishwasher at night.....

If in doubt - try it - you will find out soon enough!!
nicole10g (Electrical)
27 Aug 12 20:19
385A per phase consumption for an installation is considered huge.

What size of copper wiring that you are using at the moment?
dpc (Electrical)
28 Aug 12 13:08

Quote:

385A per phase consumption for an installation is considered huge

Based on what? Everything is relative.
nicole10g (Electrical)
28 Aug 12 20:15
For a single phase installation of 400A panel, the incoming cable will be at least 240mm2. A normal practice will be using a 3 phase supply to balance out the load.
davidbeach (Electrical)
29 Aug 12 0:54
Normal practice where? 400A single phase is not at all uncommon.
nicole10g (Electrical)
29 Aug 12 4:24
At least in my part of the world in Asia
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