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Wayne Whitney

On 2008-12-21, wrote:

Last night, the temp here in Iowa dipped down to around -10 with a -35
degree windchill. This morning I noticed the temp was about 4 degrees
off of where I had the thermostat set (It was set for 68, but the
heater was running continuously to keep it at 64). Right now, the
temp has risen to about -5 and the heater is running continuously to
keep the house at about 66-67 degrees.

When you look at the windchill, I think this is probably one of the
coldest days since I moved in 2 years ago.. Does this sound normal, or
could there be an air flow problem? The amount of hot air coming out
the vents seems to be normal compared to warmer days.

A heating system should not be designed to maintain the set point 100%
of the time. Instead it should maintain the set point, say, 99.5% of
the time. Otherwise, that extra capacity that you installed to get
from 99.5% to 100% would only be used 0.5% of the time, which is not
cost-effective.

So if your heater is only outpaced once every two years, there's no
problem with the sizing. Others have mentioned ways to reduce your
house's heat loss, which would decrease the frequency that your
current heater is outpaced by the cold weather.

Cheers, Wayne