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Old 01-06-2020, 10:32 AM   #16
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Re: Trane XB80 runs intermittently


Just installed the new main board. Before doing so I called White Rodgers tech support to review what I've already done and planned to do. They confirm that the low level hum from the main board is most likely a relay problem on the board and to just call back if there are still issues. Much more helpful than I anticipated to tell you the truth. Pleasantly surprised.

Everything fired right up. As some comments on the vendor websites noted for the updated replacement board, there are extra features and care had to be taken when transferring wires given the extra posts on the newer model.

We'll let it go a few days and see what transpires. Going to be warm during the day this week so it wont get much of a work out.

All's well for now!
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Old 01-07-2020, 08:47 AM   #17
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Re: Trane XB80 runs intermittently


After an evening of run time the profile from the thermostat looks more like it has historically. There are no full "60/min per hour" run time spikes indicating a call for heat and no change in room temperature.

Right now I'm going to declare victory with the new board. My first instinct when I heard the hum was bad relay but I didn't want to discount other possible causes. Looks like I spent $40-45 on a pressure switch I didn't need but the total of about $130 with taxes was still less than buying the main board locally and certainly less than calling a tech. I'll probably purchase a manometer as linked previously just to have in my tool chest

Will pop back in if not. THANKS TO ALL!
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Old 01-07-2020, 09:40 AM   #18
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Re: Trane XB80 runs intermittently


Good luck with your fully functional system and congratulations on your victory.
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Old 01-07-2020, 10:30 AM   #19
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Re: Trane XB80 runs intermittently


You can fix that board and have a spare for next time. The relay is replaceable if you or a friend are handy soldering on PC boards. You'd want to verify that the relay is bad by applying voltage directly to it and watching for the failure mode to appear by monitoring the contact resistances. It's possible that the power supply on the board has a failed filter capacitor... that will cause erratic operation of a DC relay. Those are easy replaceable components.

Or, you can take a hammer to it for all the grief it has given you.
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Old 01-07-2020, 10:36 AM   #20
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Re: Trane XB80 runs intermittently


For $80-85 I'll pass I'm capable of the repair and I'll probably put it in the box with the similarly failed double oven board and others for "just in case" but I won't sweat it for now!!!!!

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Originally Posted by surferdude2 View Post
You can fix that board and have a spare for next time. The relay is replaceable if you or a friend are handy soldering on PC boards. You'd want to verify that the relay is bad by applying voltage directly to it and watching for the failure mode to appear by monitoring the contact resistances. It's possible that the power supply on the board has a failed filter capacitor... that will cause erratic operation of a DC relay. Those are easy replaceable components.

Or, you can take a hammer to it for all the grief it has given you.
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Old 01-07-2020, 03:06 PM   #21
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Re: Trane XB80 runs intermittently


For what it is worth, I have a Trane XE80 (not sure how similar it is to yours), and I had to replace the control board a couple of times over the last 10 years. The symptoms were the same in both cases: no heat, just blowing cold air, plus 3 or 4 blinks of the red diagnostics LED. Tripping the breaker would help for a short period of time, but then it would go back to no heat.

The board is easy to replace, just pay attention to the installation manual, as in my case I had to attach a jumper wire to the board connector for this specific furnace model, and I missed that information originally.
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Old 01-07-2020, 03:19 PM   #22
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Re: Trane XB80 runs intermittently


I was able to get a drop in replacement. Everything seems to be working.
Haven't tested the AC though! It'll be in the 70's here Thu/Fri so I'll test it then!.

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For what it is worth, I have a Trane XE80 (not sure how similar it is to yours), and I had to replace the control board a couple of times over the last 10 years. The symptoms were the same in both cases: no heat, just blowing cold air, plus 3 or 4 blinks of the red diagnostics LED. Tripping the breaker would help for a short period of time, but then it would go back to no heat.

The board is easy to replace, just pay attention to the installation manual, as in my case I had to attach a jumper wire to the board connector for this specific furnace model, and I missed that information originally.
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Old 01-08-2020, 08:09 AM   #23
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Re: Trane XB80 runs intermittently


EDUCATION QUESTION -

I've often wondered if the difference in most of the equipment models isn't just the main board and its capabilities. In the industry I retired from that is mostly true

The replacement board I purchased is the recommended drop in from the manufacturer but with "extra features". For instance, it has both a HI and and LO Heat Fan spade whereas the original board had the LO "clipped" on the board.

Again, for education only, would this in theory give me a two speed fan control for the heat? The current setup is Black (HI) on cool HI and Blue (M-HI) on heat HI. Could either the red (L) or the yellow (M-LO) be moved from PARK to the heat LO spade and would the board sense the connection and provide 2 speed fan control?

JUST ASKING - At this point I have no desire to change anything about a furnace that's been doing its job for 18 years

BOARD - 50A55-3797 replacing 50A55-571

https://climate.emerson.com/document...us-3583530.pdf
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Old 01-08-2020, 09:30 AM   #24
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Re: Trane XB80 runs intermittently


I think you'd need a different furnace and a different thermostat to use that function. A 2-stage would likely use that board and the manufacturer has consolidated their design to accommodate both types of systems to reduce manufacturing costs and inventory.

I have seen things progress to the point where a product evolves into an all purpose item that doesn't exactly fit anything properly.

edit, After looking at the board diagram and reading all the specs, I see no way this board would be used for a 2-stage heat system so perhaps the spade terminal you see is merely a parking position. Is that possible?
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Old 01-08-2020, 09:39 AM   #25
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Re: Trane XB80 runs intermittently


I get the multi-stage thermostat part and the SKU consolidation.

I was just musing on a what if. I started this "dream" when I replaced the other 2 units (complete replace) over the past couple years and went with single stage again. The economics, at least in this part of the country, don't warrant the extra expense.

Listening to the techs as the new systems were installed it seemed the newer units (again SKU consolidation) really were only differentiated by the main board.

Again, just "thinking out loud" about all of this as we enjoy the once again toasty warm bedroom at night

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I think you'd need a different furnace and a different thermostat to use that function. A 2-stage would likely use that board and the manufacturer has consolidated their design to accommodate both types of systems to reduce manufacturing costs and inventory.

I have seen things progress to the point where a product evolves into an all purpose item that doesn't exactly fit anything properly.
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Old 01-08-2020, 11:10 AM   #26
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Re: Trane XB80 runs intermittently


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The economics, at least in this part of the country, don't warrant the extra expense.
Actually in texas it makes a lot of sense to get a 2-stage furnace - just not a 90%+. Extra expense isn't that great.

I don't think you have real winters but the blower needs to be sized for a large a/c. So furnaces get oversized.

2-stage can be locked on low fire to better match heat output with needs.

There are differences beyond the board - gas valve, inducer, pressure switch setup, sometimes blower motor type/connections if you compare constant torque ecm with variable speed ecm.
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Old 01-08-2020, 12:02 PM   #27
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Re: Trane XB80 runs intermittently


They price themselves out of the economic benefits around the DFW area.

I understand what you're saying but the actual pricing to the consumer doesn't align! Also, they've learned to go with more and smaller units these days for the A/C. Plus nat gas is still quite cheap.

Remember too that mechanicals are up in the attics here.

I converted to a tankless hot water but it wasn't for economy, it was to eliminate the 2 X 50 gallon water bombs in the attic I collapsed the two into a single zone and then installed loop circulation pumps in each zone (boy are those expensive for tankless because of the flow requirements the tankless used to have to trigger the burner)! OK, endless hot water is nice too!

Sad reality. Besides, we don't run the furnaces all that much

But your point is still sound.....

PS - We have gas H2O, gas dryer, gas heat, gas cooktop, gas grill and still don't use a lot. Sometimes we don't even break minimum charge in the summers. The January spikes are from using the gas fireplaces on Christmas (usually while the A/C is running



Quote:
Originally Posted by user_12345a View Post
Actually in texas it makes a lot of sense to get a 2-stage furnace - just not a 90%+. Extra expense isn't that great.

I don't think you have real winters but the blower needs to be sized for a large a/c. So furnaces get oversized.

2-stage can be locked on low fire to better match heat output with needs.

There are differences beyond the board - gas valve, inducer, pressure switch setup, sometimes blower motor type/connections if you compare constant torque ecm with variable speed ecm.
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Old 01-21-2020, 12:42 PM   #28
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Re: Trane XB80 runs intermittently


I am officially declaring the problem to be the main board and being fixed. I now have a spare vacuum switch but the total cost is still "a bargain" as compared to what it might have been!

THANKS TO ALL WHO HELPED!
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