New Variable Speed Fan on Heat Pump - Leave it ON?

[Mike592]

So I'm watching the HVAC guys put in a new Air Handler for our electric Heat Pump. Merry Christmas to the savings account!

It includes a Variable Speed Fan and this will be the first one for me. They're telling me it's best to leave it in the ON position (instead of the AUTO) all the time. The little bit of energy it uses knowing how to push air around is less than if it were on AUTO and the heat pump had to kick on more.

They say with the wood stove it will especially help to keep it ON all the time? Is that the case? I'm trying to wrap my head around the "variable" part and how it is smart enough to know which fan speed to use? Especially with heat coming from my stove and not the Heat Pump.

Thoughts? Advice? Help me understand?

Thanks.

 

[begreen]

If you are trying to solve a heat distribution issue, then maybe. Our system comes on when the thermostat calls, but not otherwise. Unless your ductwork is well sealed and well insulated I wouldn't run the fan continuously, especially if the house is open and easy to heat. For us, it would be a needless use of power and more wear and tear.

 

[Mike592]

We have a 2700 sq ft ranch that's pretty sprawled out with all four bedrooms down a little hallway at one end of the house. So it would be great if the variable speed fan would help push hot stove air to those rooms.

I'm just surprised the HVAC guys say leave it in the ON position all the time, regardless of the wood stove. I guess I'm just not understanding exactly how the fan operates.

They say leave it ON all the time in every house, and having it push my woodstove air around is just icing on the cake.

 

[begreen]

Is the heating system connected to a whole house fresh air intake? If not, I see no reason for running up an electric bill. Normally duct losses negate the gains of moving around the heat. That's why I said the ductwork needs to be well insulated. Otherwise the air cools down too much.

For heat distribution, try this trick. It works quite well assuming that there is a line of sight path between the cooler area and the stove room. The idea is to blow the cooler air down at floor level, toward the stove. For more even heat in the house put a table or box fan at the far end of the hallway within sight of the stove room, placed on the floor, pointing toward the woodstove room. Run it on low speed. It will blow the cooler air down low, toward the woodstove. The denser cool air will be replaced with lighter warm air from the stove room. Running this way you should notice at least a 5F increase in the room temp after about 30 minutes running. And the stove room temp should drop by a corresponding 5+ degree

 

[Mike592]

Yep, I already run a small fan on the floor blowing cold air towards the stove and i have a ceiling fan in the stove room running the correct direction as recommended here on this great forum.

Just trying to understand the variable speed fan on the heat pump air handler better and why it's best to leave it ON all the time as recommended by the HVAC guys.

 

[CenterTree]

We have a variable speed air handler too. I would never leave the fan on all the time regardless of it being "variable". (our wood stove = basement). Now take into the equation of the wood stove (if on the main living floor) then yeah, maybe I can see the fan being on as a plus to move the already heat air around.

Our system fan is set to auto and works perfectly. However, maybe due to the fact that we also have a heat pump with variable speed compressor, maybe the auto setting is best for us.

If you run the fan full time, there would have to be times when your system is just pushing cooler air around (bar the wood stove).

I think you may just need to experiment with your fan setting to see if you notice a difference. (other than your electric bill)

 

[begreen]

This wouldn't be the first time an HVAC man was wrong. You might enjoy the discussion of this topic here:
http://homeenergypros.lbl.gov/group/hvac/forum/topics/furnace-blower-fan-on-100-of

 

[Mike592]

Interesting read there begreen.

I'd be curious to know the percentages of the fine folks on this forum that leave a HVAC fan on or not.

 

[Highbeam]

There is a reason that the manufacturer put the "auto" setting on there. He was probably a lot smarter than the HVAC installer.

 

[Hogwildz]

I would think start & stop would cause more wear then constant running. Not sure about the electrical savings, would have to weight the spikes in start up each time vs just constant run.
I would agree with the others, to set to auto though.
Guess it depends on your situation and if you need to constantly move air.
Definitely worth researching more about. Maybe hit some HVAC sites.

 

[mellow]

I turn mine from auto to on when the room where my insert is located gets up to around 73, return is in the same room as the insert and I have highly insulated ducts so it works well to transfer the heat to the other rooms on the same floor. The registers in the other rooms are at 72 within a couple minutes of running the fan. I do not have variable speed on my goodman air handler.

 

[begreen]

Interesting read there begreen.

I'd be curious to know the percentages of the fine folks on this forum that leave a HVAC fan on or not.

We do not.