NEC 220.56

[rebelecdgn]

In setting up panel schedules for a large laboratory area, I used a Kitchen Equipment demand factor (because I have over 40 freezers and refrigerators) in my panel schedules in the overall load calculation. Since when is a refrigerator or freezer not a piece of Kitchen Equipment? The city plan reviewer said that, since they were used in a laboratory instead of a kitchen, that demand factor could not be used. These pieces of equipment are probably subject to less use (opening and closing) than in a commercial kitchen and are thermostatically controlled. Why can't NEC 220.56 be applied in this situation?

 

[petersonra]

In setting up panel schedules for a large laboratory area, I used a Kitchen Equipment demand factor (because I have over 40 freezers and refrigerators) in my panel schedules in the overall load calculation. Since when is a refrigerator or freezer not a piece of Kitchen Equipment? The city plan reviewer said that, since they were used in a laboratory instead of a kitchen, that demand factor could not be used. These pieces of equipment are probably subject to less use (opening and closing) than in a commercial kitchen and are thermostatically controlled. Why can't NEC 220.56 be applied in this situation?

I agree it is not kitchen equipment.

I know that it sounds silly not to be able to reduce your calculated load based on what you know with certainty will be, but it appears that is the way it is.

 

[brother]

I agree it is not kitchen equipment.

I know that it sounds silly not to be able to reduce your calculated load based on what you know with certainty will be, but it appears that is the way it is.

Can you please explain your answer? I'm tending to side with the OP, I believe kitchen equipment is still kitchen equipment regardless of where it is located at. What if they were coffee pots, and toasters that some poeple put in labs even though they probably shouldn't. I know the plans examiner is probably the AHJ for that area, and they have the final word. But please elaborate on your opinion in case Im missing something.

 

[Gregg Harris]

220.56 Kitchen Equipment ? Other Than Dwelling Unit(s). It shall be permissible to calculate the load for commercial electric cooking equipment, dishwasher booster heaters, water heaters, and other kitchen equipment in accordance with Table 220.56. These demand factors shall be applied to all equipment that has either thermostatic control or intermittent use as kitchen equipment. These demand factors shall not apply to space-heating, ventilating, or air-conditioning equipment.
However, in no case shall the feeder or service calculated load be less than the sum of the largest two kitchen equipment loads.

I would ask the same question.

 

[G._S._Ohm]

Seems like it is permissible, not obligatory, to use the demand for kitchen equip. and the OP wants to.


To be completely thorough, I'd ask, "If and when is it permissible for the AHJ to deny the EC the use of the demand factor?"


How much time and money and material rides on going either way?

 

[petersonra]

220.56 Kitchen Equipment — Other Than Dwelling Unit(s). It shall be permissible to calculate the load for commercial electric cooking equipment, dishwasher booster heaters, water heaters, and other kitchen equipment in accordance with Table 220.56. These demand factors shall be applied to all equipment that has either thermostatic control or intermittent use as kitchen equipment. These demand factors shall not apply to space-heating, ventilating, or air-conditioning equipment.
However, in no case shall the feeder or service calculated load be less than the sum of the largest two kitchen equipment loads.

I would ask the same question.

The part I put in red would seem to be the answer. It is kitchen equipment not being used as kitchen equipment. I would say it is kitchen equipment used as kitchen equipment if it was used to store people's lunches, but not to store lab samples.

 

[north star]

= =>

This application sounds like Kitchen equipment being used in
a non-Kitchen environment......Also, if you do not use Table 220.56,
do you then use the nameplate rating, of each appliance, for the
calculation of the loads [ RE: Article 422.10, `08 NEC ]?
<= =

 

[Gregg Harris]

The part I put in red would seem to be the answer. It is kitchen equipment not being used as kitchen equipment. I would say it is kitchen equipment used as kitchen equipment if it was used to store people's lunches, but not to store lab samples.

I cannot conceive the thought that members of the CMP took the time to deleniat between the different uses of a refrigerator other than dwelling or other than.

 

[marti smith]

The equipment has thermostatic control, and I would ask the question as well, pointing out the either/or section. IMO the demand factor should be allowed as I think the point is the limiting factors being thermostatic control or intermittent use, not necessarliy where the appliances are. You should ask.

 

[G._S._Ohm]

Using Excel to reverse engineer demand factor

Using Excel to reverse engineer demand factor

Please pardon the formatting.
Using the magic of Excel. . .

For the case of fridges pulling 1 kw while the compressor is running,

1/3 duty cycle, 1 fridge
0.33	=avg pwr
1	=1/3 of the time
0	=2/3 of the time
1/2 duty cycle, 1 fridge
	0.5	=avg
	1	=1/2 of the time
	0	=1/2 of the time
1/3 duty cycle, 2 fridges
		0.67	=avg
		2	=1/9 of the time
		1	=4/9 of the time
		0	=4/9 of the time
1/2 duty cycle, 2 fridges
		1	=avg
		2	=1/4 of the time
		1	=1/2 of the time
		0	=1/4 of the time
1/3 duty cycle, 3 fridges
			1	=avg
			0	=8/27 of the time
			1	=12/27 of the time
			2	=6/27 of the time
			3	=1/27 of the time
1/2 duty cycle, 3 fridges
			1.50	=avg
			0	=1/7 of the time
			1	=3/7 of the time
			2	=3/7 of the time
			3	1/7 of the time

What this all says is for 1/2 duty cycle for n fridges drawing 1 kw the avg. pwr is 0.5 x n x 1 kw and for a 1/3 duty cycle for n fridges drawing 1 kw the avg. pwr is 0.33 x n x 1 kw.

For 40 fridges I'd have to use formulas to come up with what kw what percent of the time.

If this doesn't correspond to the NEC's table they are taking into consideration other factors.

Also, the fridge "on time" relative to the thermal time constant of the cable is relevant. For #14 NMB it's about 3 minutes.