Load calculations

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Have you tried to do it yourself using article 220?

Roger
 

kwired

Electron manager
Location
NE Nebraska
I got 7-208v 60a ovens and 17-120 12.5 warmers. Need help sizing panel
Some questions that will come up sooner or later:

Are they single or three phase?

Is the panel single or three phase?

Is the 60 amps the actual current rating or the recommended and/or required overcurrent protection?

17-120 12.5 warmers = you have 17 warmers rated 120 volts, 12.5 amps?

Again is that 12.5 actual rated current? (though it likely is)

Can we assume these are capable of all operating at full output all at same time?

Also assuming these are appliances in a commercial kitchen type of environment?


Add: maybe even answering some of these questions gets you past where you were stuck.
 

jph320

Member
Location
Cinnaminson nj
Occupation
Electrician
The current draws I posted are from info giving to me by the company bringing equipment in. I have no eyes on them til they arrive. From plug type listed on specs they are single phase appliances. I did calculations and came up with the kva, then times it by the number of the same unit but it seemed really high. I oven was 12480 kw times 7 unites. Then 87360kw ÷208 =420a. Am I correct?
 

kwired

Electron manager
Location
NE Nebraska
The current draws I posted are from info giving to me by the company bringing equipment in. I have no eyes on them til they arrive. From plug type listed on specs they are single phase appliances. I did calculations and came up with the kva, then times it by the number of the same unit but it seemed really high. I oven was 12480 kw times 7 unites. Then 87360kw ÷208 =420a. Am I correct?
If they do draw 60 amps that is correct, if 60 amps just means that size of branch circuit is needed they will be less - but likely not too significantly less. If they just went with next standard size of overcurrent device could be the units draw just over 50 amps, or if they are considered to be continuous load and have an adjusted rating they could even draw down near 40 amps and still call for a 60 amp breaker - that situation can cut your actual current by nearly one third. So you either design your supply for worst case or find out what the actual load is.

Don't forget if you are on a three phase supply you can balance the load across all three phases. If you put 6 units @ 12480kw evenly distributed across all three phases you have 74880/208/1.732= 208ish amps plus an additional 60 amps on two phase conductors for the seventh unit.

Depending on application which we haven't heard much details yet - there may be demand factors that can be applied to lessen the minimum supply requirements for this equipment.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
The current draws I posted are from info giving to me by the company bringing equipment in. I have no eyes on them til they arrive. From plug type listed on specs they are single phase appliances. I did calculations and came up with the kva, then times it by the number of the same unit but it seemed really high. I oven was 12480 kw times 7 unites. Then 87360kw ÷208 =420a. Am I correct?
Did you look at Table 220.56?

Roger
 
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