DIYbanter - View Single Post - High Efficiency gas furnace

M Q

wrote:

M Q wrote:

....
Of course, unless you bought the extended warranty, the heat exchanger
is likely to corrode through after your warranty expires.

I would also think that any concer over the return air temp being below
55 is likely predicated on it being under that temp for very long
periods do to some unusual furnace application not seen in residential
environments. It seems difficult to believe occassional operation
like that for say a vacation home, where it will only run below 55 for
short periods, followed by heating fully to normal temps, is going to
cause problems.

In a vacation home, you are likely to be operating it below 55 for
extended periods: as low as possible to keep the costs down,
but above 32 to keep the pipes from freezing.