220.82 - Dwelling Unit Calc ( Optional )

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Npstewart

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Just want to make sure im not crazy..


In a dwelling unt, If you have a pool panel with a few large pool pumps, heaters, etc, is it permissible to categorize this under "general loads" where you take 40% after the first 10kW? This would be ofcourse after you figure 125% for everything continuous.

Thanks!
 
Yes, the pool pumps and heaters would be included under the general loads in 220.82(B).

I'm not sure what you would consider continuous load in a dwelling, though.
 
Thanks!

I always consider the pool pumps to be continuous because they typically have to run for over 3 hours. Most around here run for 3-6 hours per day.
 
Npstewart said:
Thanks!

I always consider the pool pumps to be continuous because they typically have to run for over 3 hours. Most around here run for 3-6 hours per day.
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Well motors are neither continuous or noncontinuous as far applying the noncontinuous plus 125% of continuous loads... and you only have to put in an extra 25% for the largest motor supplied by the conductors under consideration. When it comes to service or feeder conductor size and OCPD determination, put motors (and motor-operated appliances) in the with noncontinuous loads at their FLA rating, then a line for the extra 25% of the largest.
 
Smart $ said:
Well motors are neither continuous or noncontinuous as far applying the noncontinuous plus 125% of continuous loads... and you only have to put in an extra 25% for the largest motor supplied by the conductors under consideration. When it comes to service or feeder conductor size and OCPD determination, put motors (and motor-operated appliances) in the with noncontinuous loads at their FLA rating, then a line for the extra 25% of the largest.
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That's correct and I am assuming in most homes that the pool pump is the largest motor.

I am surprised with all the differentiated loads in a home that 25% of the largest is even necessary for a load calculation especially when it is probably the only item in the house calculated that way. Water heaters are continuous in most cases but not for service calc.
 
Dennis Alwon said:
I am surprised with all the differentiated loads in a home that 25% of the largest is even necessary for a load calculation especially when it is probably the only item in the house calculated that way. Water heaters are continuous in most cases but not for service calc.
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25% of the largest motor is not included in the Optional Method of 220.82. It would be included in the standard method, however.

Npstewart said:
I always consider the pool pumps to be continuous because they typically have to run for over 3 hours. Most around here run for 3-6 hours per day.
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The pump will only run 3-6 hours a day, but is expected to run for more than 3 hours continuously?

Regardless, the 125% factor for continuous load is applied AFTER the load calculation, not before.
 
Yes. Most pools use a time clock. Mine runs for 6 hours minimum each day and I may make it go longer when there is heavy use. The intent is to run all the the pool volume through the filter each day. At 50 GPM for the pump and 16,000 gallons of pool, that is a bit over 5 hours. Most people have no idea what their pump does for installed GPM, but I have a flow meter on my pipes so I know.

The pump has only 2 modes -- on and off. So I think it is one of the few residential things that is continuous. Whether a pump motor gets a 125% continuous factor, I've never been able to answer...
 
suemarkp said:
... Whether a pump motor gets a 125% continuous factor, I've never been able to answer...
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Under standard calc' it does not... it is only 430.24 specifies that an extra 25% is added for the largest motor.

Also, a motor can easily be run longer than three hours, but it also has to draw the max current for that period of time. Do we include service factor in that determination?
 
suemarkp said:
The pump has only 2 modes -- on and off. So I think it is one of the few residential things that is continuous.
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Actually, these days there are now two-speed pool pumps available. They can run at different speeds for just filtering and cleaning than when the heater is active.
This allows the pump to be more easily powered by solar PV and can also reduce the demand load if they have to run during the peak rate hours.
Typically low speed is enough for efficient action with a solar thermal heat source, but high speed may be needed for efficient use of a high temperature source like a gas heater. Such a pump might be continuous, but not continuous at full power. :)
 
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