[HandyGirlie]

Hello!

I appreciate any and all input I recieve here. Thank you in advance.

I was not sure how to word to title for the post. As I'm not exactly sure how to describe it to label it one specific thing.

We recently had to replace the circuit board on our furnace. We have used the heat regularly since the replacement. We just uncovered the a/c unit outside and used it yesterday for the first time this season. After turning it on the output flow of the central air is exceptionally powerful, while the heater maintained the same normal consistent flow. We replaced the motor on the outside unit last summer ourselves & ran it without incident all summer.. However I am sure this is not what is causing the problem, as it isn't connected to the furnace and I know it is irrlevant. Just thought it should be mentioned since I'm asking for help? Idek. It ran the same, perfectly fine, last year, after the installation of the new motor. This didn't present itself as an issue until the furnace was repaired. It is powerful and it does work fast, then shuts off, rather quickly., Is this normal? I do not want the fan on my furnace to burn out as it is extremely powerful and I have never experienced this before.

 

[raylo32]

The blower airflow for A/C is generally higher than in heat mode. The circuit board usually has jumpers to select blower speeds for the different modes... and stages if multi stage. Post the system size, brand, and model and the circuit board model # and someone here can probably tell you how to tweak the blower settings.

 

[beenthere]

Yep. probably just connected a higher speed tap for cooling then what was connected with the old board.

 

[HandyGirlie]

Hello, thank you for your replies. They are very informative and helpful for me. To obtain the number on the circuitboard I must unscrew it.. There are steps I need to take to accumulate all of this info for findings to give you a proper example to help me adjust it.

But before I do that, and take all those channels, I would like to know is this even safe for the furnace fan? is it OK to blow out at a higher rate? Or will it damage the motor in the furnace, the fan, the blower, or whatever it is running that mechanism.. Or can I just leave it like this? Since it does come out rapidly and produce quite a bit of air flow and then shuts off relatively quickly... I do not mind this aspect.. or should I lower it and adjust setting to match the output of the furnace fan?

Thanks again!

 

[raylo32]

You really should have the blower speed set to where it needs to be. Too high and it makes for noisy ducts and might not do the blower any good long term. Too low and the coil could freeze over. And you generally get more dehumidification, better efficiency, and better comfort with longer runtimes, but that depends on a rightsized system that is properly set up. So if yours runs only a few minutes under design outdoor conditions it might be oversized, which seems to be pretty common.

 

[user_12345a]

Having the fan on the highest speed won't burn the motor out, but can cause poor dehumidication.

normally high is the correct speed for a/c unless it's a smaller unit which needs lower airflow than what the fan is designed for.

 

[HandyGirlie]

it is a Ducane central air system and furnace. The circuit board is a 2008 Honeywell. I have some numbers on the board as follows, st9120u1011 1429j02475 I also removed the snapped a couple photographs..

We did inquire about this happening with the repairman. He said it would pose an issue. However, it is vastly different than it was prior to the replacement. The basement or the house doesn't seem to have a humidity issue. Possessing some knowledge I was able to locate the issue and pinpoint the problem. After researching some solutions I knew calling a professional was the best option, as it was cold, a weekend & needed to be done asap. He charged way more than he should've and made a weeks pay from 25 minutes on the job. It was a Sunday. He was a professional. So I paid him.. I realize now I should've paid him for the service call- 28$ and saved all of that money, doing it myself. I watched him diligently & will not need further services on this particular issue, if it arises in the future. I will be able to do it myself now.

Hopefully this info and attached photos are enough to help me out, along with my ramblings thanks again!

 

[HandyGirlie]

I resized the photos. It's no longer telling me that the files are too large. It's just continuously saying error.

 

[HandyGirlie]

The serial number (barcode) on the board itself is as follows, ST9120u1.2 4 the 4 is small in the top right corner. Not attached to the rest of the sequence of numbers.

 

[HandyGirlie]

He said it would not* pose a problem

 

[raylo32]

Easier to post them to Photobucket or your favorite photo sharing site and then copy the <img> code from there into the text of your post here.

I resized the photos. It's no longer telling me that the files are too large. It's just continuously saying error.

 

[user_12345a]

What size is your a/c or if u don't know, what's the model number?

What's the model number of the furnace itself?

I'm trying to see if it probably should be on high or not.

Generally if you have a 1.5 or 2 ton a/c on a furnace made for up to 3 tons of cooling, the fan speed will need to be lowered. (same goes for other sizes)

Otherwise high is fine provided that it's dehumidifying properly. The higher airflow actually improves the capacity and efficiency of the unit, at the expense of dehumidification. (you can probably exceed the unit's airflow requirements by 25% or by okay without any issues - have 50 to 100% excess airflow and i'm sure there would be issues)

 

[HandyGirlie]

Thank you for the info. We have called the repairman since there's a warranty. But he was a sourpus and if we can adjust if necessary ourselves, we would prefer it.

ACC30AA is the model number

450 psi max

 

[user_12345a]

Is that model from the unit outside or the indoor coil? is it the full model - usually the sizing info is after the first dash.

What's the full furnace model number?

it may not be a warranty issue if it's cooling. high may be okay and even when it's not a lot of furnaces prob still get left on high.

as stated b4, it's mostly an issue with smaller ac units, not 2.5+ ton models unless paired with a 4 or 5 ton drive furnace. if that's the full model number it's probably a 2.5 ton.

 

[HandyGirlie]

This is the model number on the furnace itself.

 

[user_12345a]

that's not a furnace model number or doesn't look like one, did it come from the coil above the furnace cabinet or where?

need the number of the outdoor unit and the full number found on the data plate inside the furnace.

Tells me the design cfm of the blower and tonnage.

 

[HandyGirlie]

 

[HandyGirlie]

Here is the photo of the model number on the furnace & the circuit board itself

 

[HandyGirlie]

 

[user_12345a]

Yes, that's your evaporator coil.


The coil appears to be a 2.5 ton norminal but a coil of one size can be matched to 2 to 3 different outdoor unit sizes.


Circuit board doesn't matter, it's the model of the actual furnace model that's needed as is the model of the outdoor unit. (not the coil)

Need sizes, airflow capacity.