Rheem Criterion II-Insufficient Airflow

[BaldLoonie]

So before you had no A/C coil? That's a 24" furnace if I remember right. They likely put a narrow coil above it and really blocking airflow. What capacity A/C?

[BigFan123]

A/C coil was put in in May. It seems that the old blower was able to move air better somehow though. For the few cool mornings we had in May after installation, the heat was fine. So problems didn't crop up untl now.

It is a 4 ton Gibson.

[udarrell]

A new motor fan and control card has been installed in my Rheem Criterion II. The blower speed is much too low in all three modes (fan on, heat and cool). The contractor who did the repair tried many different settings in many different scenarios (Hi, Med High, Med Low, Low). High and medium high are barely there and low is almost no flow at all. The person doing the work was baffled. The contractor is coming back next week to try again to resolve the issue.

I want to be "literate" in this particular problem so that I can evaluate if the contractor is doing the right things to resolve the problem. If not, I'll have to go with someone else. In that case, I'd want to ask the right questions of the new candidate to know if they have any better chance of success.

I think I understand how things work pretty well. You would want to test if the right voltage is being supplied to the motor, you would want to check the run capacitor with the right diagnostic tool. Failing finding a root cause in either of those two things, what would be the logical next steps after that? Thanks

So they changed out the motor without determining what was causing the problem?

The blower wheel blades & the A-Coil are two of the first things you check when there is low airflow & blower motors overheating.

A lint blocked A-Coil will cause the blower wheel to unload & that plus the lack of airflow over the motor will cause it to overheat & quit running.

This situation appears to be a mismatched application...

[BaldLoonie]

Nordyne makes a 24" wide 4 ton coil. Just adding a coil to a system shouldn't cut airflow enough that you can't use it. Unless they used a 17" coil over the 24" furnace but if it is a matched coil, there isn't a 17" wide 4 ton from Nordyne.

There's still something fishy. 1/2 horse when it should be a 3/4 horse?

Can you take any pictures?

[BigFan123]

Yeah...likely a mismatched application.

So matching with a proper furnace is an answer?

I confirmed the motor is 3/4 horse. I can take pictures...you mean of the inside of the A/C plenum?

[catmanacman]

The contractor that installed the coil should fix it

[BaldLoonie]

Take a picture of the furnace and plenum above it.

[BigFan123]

[BigFan123]

Agree...I'll be trying to work it through with him. I think he's thinking the only way to fix it is to right size the furnace.

[gravity]

wow....ductwork looks like a problem. cant tell because im not there but i suspect it is. i also see a barometric damper on the furnace. there may be a chance that someone who was properly trained in combustion installed it and tuned that furnace.

[jtrammel]

Ductwork looks like a problem, can you post a pic of duct coming off of coil

[catmanacman]

I wonder if they landed the y wire on the terminal strip or just wire nuted the y wires together causing the blower to run in low speed

[BigFan123]