Range Load Note 2
The calculation to determine service load for several household cooking
appliances is full of rules which make a significance difference in the result.
A careful reading of these rules in NEC220 will be necessary to correctly solve
for service loads of these appliances.
Now, I know no electrician is ever going to be called upon to make this sort
of calculation. Yet this calculation seems to be included on every Journeyman
and Master license exam I have ever seen. So let's get to it.
There are three columns in the table.
Column A id for small appliances. If all the appliances you are calculating are
less than 3.5kW then find the percentage which corresponds to number of
appliances and multiply this percentage times the total nameplate for all
appliances. The result is the demand.
Column B. If the appliances you are calculating are from 3.5kW to 8.75kW,
same deal. Find the total nameplate then multiply by the percentage you find for
the number of appliances on the service.
Column C. This is the difficult one. There are a few rules which guide you
through this column.
If there are several ranges which are over 12kW, and all
are the same, then increase column C by 5% for each kW or major fraction .5 they
exceed 12kW. The audio support explains this with examples. Listen as needed to
the audio support for these pages.
If there is a mixture of cooking appliances, with even
one less than 12kW, still use column C but enter any that are less then 12kW as
12kW and find the average. Then increase Column C by 5% for each kW or major
fraction .5 the average is above 12kW.
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