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swampwiz_gw

Need help in determining Q for appliances and infiltration factor

swampwiz
14 years ago

I am in the process of doing a Manual J calculation (or at least something very close to it), and there are two terms that I am having difficulty determining: Q for appliances and the infiltration factor.

I guess that for the Q for appliances, I should consider the worst case scenario to be a continual use of a number of lights on, a few televisions, and my big stereo system (presume I could crank it out to 800W power!) There could also be the use of the electric range and ovens, which in the case of a long cooking meal could be long enough to be considered continual, and unfortunately would tend to happen in the late afternoon, which of course is typically the hardest load for cooling. Besides the ovens, I could see having about 1200 W continual, which would result in a load of about 5000 BTU/hr. But how much should I add for the ovens?

Concerning the infiltration, I am just trying to figure out what value to use. And of course, infiltration has a huge effect on the load. I will be using open cell spray foam completely around the home. I have read that a very well sealed home could get the infiltration down to about .3, which is actually so low that the home should have an intake mechanism to bring in fresh air (which would need to be accounted for, of course).

In the long run, it may not really matter since even if I use generous values here, I am right at about 3.5 tons, and I would really need to squeeze these parameters down to get a result close enough to 3.0 tons.

So I am just trying to get an idea about what I should use for these parameters. What do you think?

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