shop hvac assist?

[69.5CUDA]

ive got an OLD modine PA250AC, it runs like a swiss watch, however im wondering if theres a way to trigger "fan/blower
only" for times when i want to evac the air in the shop without running the heat...say right now when im trying to blow out all the dust

the unit on shut down kills the heat supply and runs the fan for a few mins to cool the unit down..so im sure the function is there i just dont know enough about hvac stuff to know the how/what/why for or parts i may or may not need to do it

and yes i have a t-stat that can trigger fan only
and yes 250,000 btu of overkill

i did some googling but everything came up as if i was trying to fix a "no heat" issue...and not an actual intentional running of fan only

 

[thrashingcows]

I have very little understanding of HVAC stuff but I think your heater might be to old to have this function.

You might have to put in a gas line shut off valve, either manual or electric then wire it through the T-stat so when you select the Fan function it will shut off the igniter and gas?

 

[69.5CUDA]

I have very little understanding of HVAC stuff but I think your heater might be to old to have this function.

You might have to put in a gas line shut off valve, either manual or electric then wire it through the T-stat so when you select the Fan function it will shut off the igniter and gas?

im not entirely sold on that, mostly due to its "shut down" function of running the fan for a cooling period at which time the pilot stays lit but has shut down primary gas flow...admitedly an electric pilot would be less wastefull on gas for sure

at the end of the day a new unit and an old unit are identical save for the control board to which is a 120$ part in which some control boards have electic ignition...all of the other components are actualy the same parts ....a good old unchanged design

i figure there probably something i can simply trigger to kick the fan on...even if i need to ad a 12/24v relay to do it wired off of its transformer

 

[b-body-bob]

ive got an OLD modine PA250AC, it runs like a swiss watch, however im wondering if theres a way to trigger "fan/blower
only" for times when i want to evac the air in the shop without running the heat...say right now when im trying to blow out all the dust

Most (maybe all) HVACs are a closed system - they don't vent air, they recirculate it, so it might be less helpful than you think. I guess it would work until you plugged the filter, and if you run it without one it will just suck that mess into the system. TBH it seems like you would want to turn it OFF, not ON, under dirty conditions.