What Am I Missing?

[Jeff P]

Two Luxaire Furnaces- Model #PBFMD12F08501A and Model#PBFMD12F05501A.Both Furnaces Use The Same Blower Motor And Wheel With Different Airflow Ratings.Something Has To Regulating Flow On The Smaller Output Furnace.

[Jeff P]

No,All unit dimensions,filter & duct openings are identical.It almost has to be electrical.

[Jeff P]

No,All unit dimensions,filter & duct openings are identical.It almost has to be electrical.

Here is wiring diagram:

[cartercrew]

Smaller furnace has higher pressure drop across furnace section?

[hearthman]

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[beenthere]

Probably has baffles in the smaller one to make sure air flow goes over the heat exchanger. And not bypass it.

[Jeff P]

Thanks beenthere.I have seen low firing rate baffles mentioned after searching it.This is the only PDF I have found:http://www.hamiltonhomeproducts.com/...s/Pfm-tech.pdf

[genduct]

means 2 different pressures with this twinned unit SO the unit with the higher pressure is stopping the air delivery from the smaller unit. Not good since winter operations could see high limit trips and cooling will have frozen coils.

The units need to be balanced airflow regardless of dischagre temp. The air will mix so no need to worry.

[Jeff P]

I take it this is a bad design.Adding baffles to reduce airflow to save manufacturing costs.I am looking into natural gas.(line is appx.350' away) and hopefully get rid this fuel hog furnace.

[t527ed]

Probably has baffles in the smaller one to make sure air flow goes over the heat exchanger. And not bypass it.

if the cabinets are the same size it would make sense to have baffles and a smaller heat exchanger.