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Viper677
Certified Home Inspector
join:2012-03-22
Toronto

Viper677 to mackey

Member

to mackey

Re: Another a/c issue.

said by mackey:

said by Viper677:

Ok - my question is:

Why "on the hottest days of the year, a properly sized system will never reach the set point and thus not shut off/cycle or barely hit it and only cycle minimally"?

A properly sized system is supposed to cycle unless you are constantly leaking air to the outdoors from your house as shown in my attached pictures above.

said by mackey:

This is because if the system was big enough to cycle normally on the hottest days of the year, it would short cycle on the milder days and not dehumidify properly.

/M

Ok then you should upgrade your system to one of those system where the stat controls the unit based on the humidity in the house and not 'entirely' based on the ambient temperature of the house.
aroberti
Sarcastic? Me? Never
Premium Member
join:2000-12-21
Norwalk, CT

aroberti

Premium Member

said by Viper677:

Ok then you should upgrade your system to one of those system where the stat controls the unit based on the humidity in the house and not 'entirely' based on the ambient temperature of the house.

But then you'll just end up over-shooting your temperature setpoint. Why would you want a system so oversized that it couldn't control the humidity correctly to begin with?

Your argument seems to be that outside temperature shouldn't affect how well the system cools? I've never seen a house that was 100% air-tight -- and even if it were, that would present a whole new set of challenges...
XXXXXXXXXXX1
Premium Member
join:2006-01-11
Beverly Hills, CA

XXXXXXXXXXX1

Premium Member

said by aroberti:

I've never seen a house that was 100% air-tight -- and even if it were, that would present a whole new set of challenges...

When building his house, a neighbor down the street went with Icynene insulation, and it's about as air tight as you can get without going closed cell. The downside is that it's expensive (about 3.5X the cost of fiberglass) and you are supposed to install air handlers to exchange the outside air because the home is sealed so well (or so said the salesman when quoting me a price).

I decided to go with traditional fiberglass with 2x6 exterior walls and a higher total R-value over the second floor. I just didn't want to get into additional equipment and I had heard of some buildings with interior problems because the house was sealed too well (mold, sickness, etc.) And I just thought it was simply too expensive. I don't think my heating and cooling bills are ridiculous either... 2x6 with vapor barrier has been great at maintaining interior heat and cooling.

My neighbor does like Icynene though... he recommended it and said he would use it again if he built again.