And remember, if this is a dwelling, once you have 3000VA covered at 100%, further general load has a 35% demand factor applied. Some circuits have no calculated value (e.g. bathroom receptacle circuits, outside circuits, HVAC servicing receptacles). Others have a specified load even though you already covered the square footage elsewhere (kitchen counter top circuits, laundry room circuit) but still get to be hit with the 35% demand factor if you've already hit the 3KVA threshold.
Convert Branch Ckt Into Sub Panel
- Thread starter euclid43
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Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
I think that demand factor applies to a 100 amp dwelling feeder not a sub feeder. Correct me if I am wrong. You would not be placing additional branch circuits from what was a Range outlet. Then put back the range and new circuits. You are looking for trouble I'd say dinner party on a holiday and poof goes the circuit. See it all the time.
kwired
Electron manager
- Location
- NE Nebraska
And yet we had for years had many services fed with only 60 amps with an electric range with little troubles blowing mains, until they started adding water heaters, clothes dryers, air conditioning ..... 8 kW really is a high demand from a range most of the time IMO. It may demand that when you first turn things on, but once things warm up, elements are going to cycle and you may even find times where little or no current is even being drawn, but NEC likes to calculate it a little on the heavy side just in case. How often do people use all the surface elements as well as the oven all at the same time anyway? I'm sure there are occasions but most of the time they only use one or two surface elements and sometimes maybe the oven is going at the same time.
kwired
Electron manager
- Location
- NE Nebraska
First I find your wording a little confusing but I have a feeling you meant a feeder that feeds the entire dwelling.
But even if that is what you meant, I have to disagree, until someone proves me wrong anyway.
Even if there is only two "general illumination" branch circuits I think it applies, which makes some sense as it will take two circuits to be able to handle 3000VA if you are limited to 15 and 20 amp 120 volt circuits for this purpose. Go beyond 3000 VA and you can start applying demand factors.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
What about this section.
220.82 Dwelling Unit.
(A) Feeder and Service Load. This section applies to a
dwelling unit having the total connected load served by a
single 120/240-volt or 20SY1120-volt set of 3-wire service
or feeder conductors with an ampacity of 100 or greater. It
shall be permissible to calculate the feeder and service
loads in accordance with this section instead of the method
specified in Part III of this article. The calculated load shall
be the result of adding the loads from 220.S2(B) and (C).
Feeder and service-entrance conductors whose calculated
load is determined by this optional calculation shall be
permitted to have the neutral load determined by 220.61.
or
220.83 Existing Dwelling Unit. This section shall be
permitted to be used to determine if the existing service or
feeder is of sufficient capacity to serve additional loads.
Where the dwelling unit is served by a 1201240-volt or
20SY/120-volt, 3-wire service, it shall be permissible to
calculate the total load in accordance with 220.S3(A) or (B).
(A) Where Additional Air-Conditioning Equipment or
Electric Space-Heating Equipment Is Not to Be
Installed. The following formula shall be used for existing
and additional new loads.
Load (kVA)
First S kV A of load at
Remainder of load at
Percent of Load
100
40
I don't think that you are allowed to apply the reductions unless the feeder carries the entire load to the home.
Also a 50 amp feeder is not the same as a 60 amp service. By the way who says you can add load to an old house with a 60 amp service without doing a calc and if it calcs out short how is that install compliant.
kwired
Electron manager
- Location
- NE Nebraska
Sections you quoted are in the optional calculations methods (part IV) and they do state they apply to feeders supplying the total connected load of the dwelling. I don't see any such wording in the general calculation methods in part III.
Plus the mentioned 3000VA limit before demand factors are allowed is in part III.
Basically the optional methods as applied to dwelling units apply to feeders supplying the entire dwelling unit, so a subpanel within a dwelling unit (not supplying entire unit) can not use the optional methods to determine the load. (I think)
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
I don't think you get to apply the demand factor twice.
Nor does the range get a 35% from table
The range as my understanding does not get added into the lighting /general use table 220.42.
Please correct me.
kwired
Electron manager
- Location
- NE Nebraska
No I wouldn't think you would get to apply the same demand factor twice to the same feeder, but you can calculate two different feeders with demand factors applied differently in each feeder With the optional calculations you use either the standard or optional calculations and not both. Each method has a different approach at applying demand factors, and you can't mix and match to fit your wants or needs, you can use both options and select the one with the lowest result if you wish.
When calculating for a multifamily application you are likely to have demand factors that apply to individual dwellings, but yet you will look at total numbers in all units when applying demand factors to the service or higher level feeders. A feeder to an individual dwelling likely has just one range, one dryer, one each of other possible fixed appliances. But a feeder or service to a multifamily dwelling can use the total number of ranges, dryers, other fixed appliances as a basis for certain demand factors. You are not really applying a demand factor twice, you are making two separate calculations.
Cavie
Senior Member
- Location
- SW Florida
I'll put my money on the fact that there is no neutral.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
That or no EGC. Choose one.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
That or no EGC. Choose one.
the OP's first post states that he has a 4 wire. you have reason not to belive
James S.
Senior Member
- Location
- Mesa, Arizona
You should have just bet them.
kwired
Electron manager
- Location
- NE Nebraska
Actually he doesn't confirm this until post #4
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Actually he doesn't confirm this until post #4
ooops
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