[veesubotee]

my furnace has an ECM blower motor which has worked flawlessly for five years. Recently, in cooling, it has displayed an error message (over amping) in second stage (4 tons).

Nothing has changed--using Aprilaire 201 filters. Even changing to a fresh filter hasn't changed anything. I'm thinking that this is NOT due to a failure of the motor's control module since reducing cooling CFM by 200 deletes the error state.

This leads me to believe that somehow, static pressure has increased. The only possibility might be that insulation (cased coil) has come loose and is blocking part of the coil.

Has anyone come across this situation? Any other suggestions? Thanks.

V

 

[beenthere]

Could be the secondary heat exchanger(if a condensing furnace) is dirty, and or the A/C coil.

 

[veesubotee]

Could be the secondary heat exchanger(if a condensing furnace) is dirty, and or the A/C coil.

Yes, it is a condensing furnace (Rheem modulating).
Are there any overt symptoms of a dirty secondary heat exchanger? I doubt that the coil is dirty, as the Aprilaire filters where changed twice a year.

V

 

[beenthere]

Increased temp rise across the heat exchanger.

I would still check the A/C coil.

 

[supers05]

I would expect lower amps when reducing air flow. (usually those control boards only calculate cfm, they don't actually measure cfm directly. The expensive versions measure static pressure and try to maintain a certain value, where the cheaper ones just run to a specific rpm.

Is this an attic unit? Any ducts loose / disconnected / broken / etc?

Cheers!

 

[veesubotee]

I would expect lower amps when reducing air flow. (usually those control boards only calculate cfm, they don't actually measure cfm directly. The expensive versions measure static pressure and try to maintain a certain value, where the cheaper ones just run to a specific rpm.

Is this an attic unit? Any ducts loose / disconnected / broken / etc?

Cheers!

I physically reduced CFM on the control board. Enjoying the increased dehumidification, but miss the CFM.

Unit is in basement. Wouldn't loose/disconnected ducts reduce static?

V

 

[veesubotee]

Increased temp rise across the heat exchanger.

I would still check the A/C coil.

Temperature rise is within spec.

V

 

[beenthere]

Temperature rise is within spec.

V

Within spec for the units rated temp rise. Or correct for CFM and BTU output?