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Bob F

wrote:
On Tuesday, October 29, 2013 12:20:11 PM UTC-4, Bob F wrote:
cln wrote:

My 18 year old house has a combination Wood and Electric pushed air

furnace.

I'll start a fire and eventually the fan starts... typical and

expected.

I question what follows. The fan will run for 1 to 2 minutes. In the

beginning the ducts barely have time to warm up so the air isn't hot

when it comes out.

After a few minutes, the fire is roaring and produces plenty of
heat.

I even added a tiny 4" fan on the flue pipe to propagate the heat in

my shop.

So if this 4" fan is enough to make a small difference in my shop,

why isn't the furnace running longer at times?

I had the furnace inspected last winter/spring time. A fuse had

popped. He checked it over and said there was nothing wrong with it.

Is there something I can do? I asked if the fan could be upgraded to

a two speed fan. I figured that it could run on a lower temperature.

Any advice appreciated.

Does heat come out the heat registers even when the fan is not
running? Maybe

this is a convection system, and the fan is only there to "prime"
the system

with warm air to start the convection. IF so, it should use very
little

electricity, and continue to work when the power is out.

Otherwise, I'd check the thermo-switch that turns the fan on when it
warms up

and replace or adjust it.

You have an example of a furnace where the fan is there
only to "prime" it?

Many really old furnaces were convection furnaces. No, I don't have an example.
I was just hypothesizing based on the symptoms. If the convection is strong
enough, it could keep the temp at the exchanger low enough to not need the fan.
Admittedly, it's not a likely possibility.

Then I suggested where the problem is more likely.