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How do you figure what ton unit (heat pump) to use. Is it based off the heated square footage of the home.
 

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Use HVAC CALC. Its advertised on this site.
 

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As a ball park estimate you can use the rule-of-thumb of sq ft per ton, but for a home run get a copy of Manual J from your local library, or as been has suggested buy HVAC-CALC. Once you see what variables Manual J considers you will understand why sq ft per ton is inadequate.
 

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For heating of single family homes, some heat loss values are

.....x......x.x..x.....x.x
0.....|.....|.....|.....|....|
..............................10

where the units are
BTU/sq. ft./HDD

The 1.7 on the left is probably the best that anyone can do. My leaky old house comes in at 8.0. If additional, future data that I collect follows the same pattern you can be reasonably assured that most houses fall between 1.7 and 9 BTU/sq. ft./HDD, with newer houses being tighter.

If anyone has similar data for single family homes for cooling (heat gain) normalized to house sq. footage and cooling degree days I'd like to see it. When I had the 1985 Manual J in my hands I should have used the house in their example.
The cooling datapoints will probably be scattered more than above because the COP varies with outside temp, but oil/gas appliances have a more or less constant efficiency.

There should be some (loose) connection between the heating and cooling load since they're both related to insulation value.
 

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There should be some (loose) connection between the heating and cooling load since they're both related to insulation value.
Nope.

Heating is calculated with no solar gain(middle of the night).

Cooling calculated with solar gain(hotest part of the day).

So no real correlation.
 

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Nope.

Heating is calculated with no solar gain(middle of the night).

Cooling calculated with solar gain(hotest part of the day).

So no real correlation.
Bit by bit I learn the hands-on of HVAC.
So some of the scatter in my data is due to solar heating and the Manual J calc. is pessimistic since it assumes no insolation?
 

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Manual J doesn't assume no insultation. It has HTM for multiple insulation values.

The new ver 8 also takes into consideration radiant barriers.
 
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