Using HVAC Air Handler to move hot air

[farmwithjunk]

I've read a lot on here and elsewhere about using vents, HVAC and fans for moving hot air around with mixed results, usually poorly.

My house is a modular with a basement stove install at the very far end, not ideal for 56' long. It was built with small ducts on each side of the house that ran lengthwise but one was never utilized. I panned off a bay between the floor joists in the stove room, tapped into the trunk and brought the other end down to my air handler in another room with 30 foot of 8" flext duct.

It does work pretty well but maybe not as much as I was expecting but I may have just been unrealistic. Air at the ceiling above the stove can get to 90f. When I run the air handlers fan I can see the vents go up 2.5-5 degrees depending on temps. I can see the thermostat slowly climb when running the fan. Worth the effort and $150 in materials IMO.

 

[ericm979]

I've tried running the HVAC in fan mode and for us it appears to not do anything. It's great that you found a way to make it work though.

OTOH we're fortunate that the stove is right next to a 8'x16' opening to the second floor, and that lets just about the right amount of heat upstairs.

 

[begreen]

I've tried running the HVAC in fan mode and for us it appears to not do anything. It's great that you found a way to make it work though.

OTOH we're fortunate that the stove is right next to a 8'x16' opening to the second floor, and that lets just about the right amount of heat upstairs.

Most often heat loss in the ductwork negates the advantages. Oil and gas forced-air furnace systems are designed to move hot air at much higher temps (~135º) so the losses are considered acceptable (or they used to be with cheap fuel). This doesn't work well for moving 80º warm air. The exception can be a modern forced air system that is completely sealed and fully insulated, including the returns. This is typical for heat pump systems that are moving 100-110º air.

 

[begreen]

My house is a modular with a basement stove install at the very far end, not ideal for 56' long. It was built with small ducts on each side of the house that ran lengthwise but one was never utilized. I panned off a bay between the floor joists in the stove room, tapped into the trunk and brought the other end down to my air handler in another room with 30 foot of 8" flext duct.

If this is the supply air, I am fairly certain that panning the joist space against mechanical code and maybe fire code too. If you can post a sketch of the floor plans there may be a better way.

How many sq ft is the basement? Same for the main floor? What stove is this? Are the basement walls insulated?

 

[farmwithjunk]

If this is the supply air, I am fairly certain that panning the joist space against mechanical code and maybe fire code too. If you can post a sketch of the floor plans there may be a better way.

How many sq ft is the basement? Same for the main floor? What stove is this? Are the basement walls insulated?

I'm pulling na return from the same room as stove. I know code is 10'. Basement is 1600', same with upstairs but have an addition about 300'. All of the duct work is in a conditioned space in the basement ceiling so not much heat loss. Almost all of it is insulated as well. I do have a trunk that feed the addition (kitchen) in an unconditioned garage which I insulated with 2" EPS.

Basement walls have 2" EPS and the end by the stove on the outside has either 1/2 or 3/4 EPS.