Optional Dwelling Load Calculation

[Little Bill]

For the purposes of an optional load calculation, if you have heating & cooling with separate units for main level and upstairs, you would just take the larger of heating or cooling for each level, correct? IOW, the largest load of each level and add both to the calculation?

 

[wwhitney]

Do you anticipate heating one floor while cooling another?

If not, I would take the larger of (sum of both floors' heating) and (sum of both floors' cooling).

Cheers, Wayne

 

[Hv&Lv]

Do you anticipate heating one floor while cooling another?

You’ve never been in a house with my wife.…


we have the AC on for both floors. During the fall on those crisp mornings she will get up and turn the gas logs on. If she remembers to turn the AC downstairs off it’s a plus. She never remembers to turn the one upstairs off. By the afternoon the AC is needed up and down.

some of the time she has the fire going, both AC units are blowing, and she is wondering why the house is still cool…

 

[Little Bill]

Do you anticipate heating one floor while cooling another?

If not, I would take the larger of (sum of both floors' heating) and (sum of both floors' cooling).

Cheers, Wayne

It's for a new house I'm doing. I wouldn't think they would have heat and cool at the same time. I know that if you just have one unit, you take the largest of either heating or cooling for the calculation. But since this is two units, I figure I need to take the largest load from each floor and add them together.

 

[Dennis Alwon]

It's for a new house I'm doing. I wouldn't think they would have heat and cool at the same time. I know that if you just have one unit, you take the largest of either heating or cooling for the calculation. But since this is two units, I figure I need to take the largest load from each floor and add them together.

And that is no different then what we do when there is one unit. I agree that is the way to do it.

 

[wwhitney]

It's for a new house I'm doing. I wouldn't think they would have heat and cool at the same time.

In which case, the largest of the combined heating or the combined cooling would be appropriate, and gives a possibly lower number than your initial suggestion.

And that is how I read (2017) 220.82(C), in that each subsection says, e.g. "(1) 100 percent of the nameplate rating(s) of the air conditioning and cooling." Since rating(s) may be plural, that would mean add the ratings of each piece of cooling equipment when there is more than one. And then you take the largest of the each of the subsection computations.

Cheers, Wayne