"Greg Johnson" wrote in message
...
I hired an established 20 year American Standard authorized "Customer
Care" Dealer size and install an AUY080 variable speed 2 stage high
efficiency natural gas furnace in my house last fall. It replaced a 30+
year furnace. Over the past two months we've had a number of nights
that fell to around -8 to -11 F, about as low as it ever gets for this
area. During this time, the furnace has never needed the second stage
at all. In fact, the only time the second stage goes on is when the 2
stage thermostat is manually increased more than 2 degrees.

There are return ducts in almost every room upstairs. The return air
flow is very noisy (to my taste), even in the rooms farthest from the
middle of the house, where the furnace is located. The supply ducts are
not noisy at all. When the second stage is on, the increased airflow is
very loud in my opinion. This wouldn't be a problem for the heating
season, but full fan is used for cooling.

I'm ready to give the contractor a call and ask him about this. But I'd
like to get more informed first. How much (if ever) should second stage
be needed? Is it normal to put up with a constant rumbling of air in
return ducts? The opening in the (upflow) furnace side between the side
return duct and the furnace is smaller than the blower, leaving me to
wonder if this is at least part of the return noise problem. How long
should the on cycle times be, for a 30F degree day, for example?

My house is a split level, about 1700 sq ft, 1350 "livable" and is in
eastern Massachusetts.

Thanks!

This is Turtle.

Most HVAC contractor will set the btu rating of the heat run time at about 90%
at Maxium Temperature outside as you say -8ºF to -11ºF . The reason of the long
run time here is you have the two stage gas furnace and first stage will tend to
run a long time for the second stage is if it gets in trouble and falls behind.

TURTLE