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BillyHvac
BillyHvac, Journeyman HVAC Tech
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Satisfied Customers: 22092
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I have a Trane XL90 model TUC100B960A0 Furnace. I was told

Customer Question

I have a Trane XL90 model TUC100B960A0 Furnace. I was told by "HVAC Guru" (justanswer.com HVAC Technician) in May that my board needed to be replaced due to non-start condition. I have purchased a White Rogers Model 50E47-843 to replace my White Rogers Model 50E47-060. I am having problems identifying the correct wire conversion from the old to new board.
Submitted: 2 months ago.
Category: HVAC
Expert:  BillyHvac replied 2 months ago.

Hello,

My name is ***** ***** I will do my best to assist you. I am looking over your question now and will respond shortly.

Expert:  BillyHvac replied 2 months ago.

what particular wires do you have an issue with?

Customer: replied 2 months ago.
On my old Board 50E47-060 I had the following blade connections;MV
MV
TR
TH
FP
GND
L
ING
Customer: replied 2 months ago.
On my new board 50E47-843 I have the following blade connections;MV2
TR
GND
TH
MV1
L2
HS2
FP
L1
HSI
Expert:  BillyHvac replied 2 months ago.

Thank you...now just to assist as go along.

Did you have this in with the new control?

See Here

Expert:  BillyHvac replied 2 months ago.

MV - mv 1
MV- mv2
TR -tr
TH- th
FP- fp
GND - grnd
L - L1

ING - hsi

are there others?

Expert:  BillyHvac replied 2 months ago.

does that help at all?

Customer: replied 2 months ago.
please. I need help knowing which wires go where.I currently have the following connected;MV2 - Red wire going to gas valve transformer
TR - White wiring going to pressure switch / induction fan and ties to W on 24v thermostat board
GND - Light green wire going to ground
TH - Light purple wire going to B/C on 24v thermostat board
MV1 - Light blue wire going to gas valve
L2 - Ground to frame via pigtail included in replacement board kit
HS2 - Not used
FP - White wire to flame Sensor
L1 - Large red wire going to limit control
HS1 - Large blue wire going to Igniter
Customer: replied 2 months ago.
I have the manual. With the wires connected as stated in my previous text it throughts the breaker on the main house panel.
Customer: replied 2 months ago.
Pretty sure I have something crossed somewhere.
Expert:  BillyHvac replied 2 months ago.

the terminals you have connected are all low voltage and would not trip the breaker except for L1 and L2

Your white wire from power...that needs to go to L2 on the board

Customer: replied 2 months ago.
Ok. Let me check.
Expert:  BillyHvac replied 2 months ago.

and Hs2 should have a wire from ignitor on it

Customer: replied 2 months ago.
L2 is green going to grounding on furnace cabinet based on note "e" listed at bottom of the table you sent me.
L1 is Large Red Wire going to black wire that goes to main power coming from on/off switch on side of the furnace.
Expert:  BillyHvac replied 2 months ago.

the note E is if there is NO l2 terminal available. But on this control board there is a L2 terminal.

Customer: replied 2 months ago.
Ok. I am removing the the green ground to furnace jumper wire I added.
Customer: replied 2 months ago.
Removed.
Expert:  BillyHvac replied 2 months ago.

You said hs2 was not used...where is the other wire from the ignitor?

Customer: replied 2 months ago.
Nothing attached to L2 and still throws the breaker.
Expert:  BillyHvac replied 2 months ago.

where is your white neutral wire that comes into furnace with the black power wire?

Customer: replied 2 months ago.
White wire from igniter goes to netral in juction box built into furnace.
Black wire from igniter goes to HS1
Customer: replied 2 months ago.
Power comes in from furnace juntion box to L1
Expert:  BillyHvac replied 2 months ago.

ok that is a problem

The white wire from ignitor goes to hsi2

The white wire from neutral box goes to L2

Customer: replied 2 months ago.
OK. Let me check.
Expert:  BillyHvac replied 2 months ago.

standing by

Customer: replied 2 months ago.
Purge fan is running. No hot ignitor. The ignitor is new. No flame. Purge fan is still running though. I have noting connected to HS2 or TR
Expert:  BillyHvac replied 2 months ago.

the white from ignitor that you had in neutral box...that goes in hsi2

And previously you said the white wire from pressure switch was on TR.

Did you move it off

Customer: replied 2 months ago.
Purge fan continues to run constant but no hot ignitor. Again. I do not have any wires to blades HS2 or TR
Expert:  BillyHvac replied 2 months ago.

the white from ignitor that you had in neutral box...that goes in hsi2

And previously you said the white wire from pressure switch was on TR.

Did you move it off

Expert:  BillyHvac replied 2 months ago.

Ok this was mentioned earlier but lets make sure.

White wire from ignitor goes to HSI2

White wire from neutral box goes to L2

White wire from pressure switch you said was on TR but is not now?

Customer: replied 2 months ago.
I only have two white wires;One from Ignitor that is currently on L2
One from Flame sensor that is on FP
Expert:  BillyHvac replied 2 months ago.

The furnace needs 2 main things from the home power system

a black 120v and a white neutral. Both of these have to be on the board...L2 has to have a wire from the incoming white neutral to furnace

Expert:  BillyHvac replied 2 months ago.

the ignitor goes on HSI 2

Before doing anything right now...

Put the white from ignitor on HSI2

we will go one wire at a time.

Once again put the white wire fromignitor on HSI2

Customer: replied 2 months ago.
OK. I am giving you exactly where the the white ignitor wire goes.1. From the ignitor itself it goes up into the funace juction box.
2. It pigtails to a 24V converter.
3. It pigtails and goes to the white wire on the purge motor
4. It pigtails and goes to the incoming white neutral white.
Expert:  BillyHvac replied 2 months ago.

We do not want the white ignitor going anywhere except HSI 2 on the board.

Before moving forward...move the white ignitor wire to HSI 2

Customer: replied 2 months ago.
Black wire from ignitor goes directly to HS1.
Black main power goes directly to L1
Expert:  BillyHvac replied 2 months ago.

the 2 blacks are fine.

Move ignitor white to HSI 2

Attach neutral to L2

Customer: replied 2 months ago.
Roger-
Moving ignitor white to HSI 2
Attach neutral to L2I have to go to the garage and get a new blade to put on the wire to attach it.
Expert:  BillyHvac replied 2 months ago.

no problem.

I have to leave for 15 minutes. If you have another question I will respond as soon as I can.

If you are all set after the switch just rate service at top of page.

Customer: replied 2 months ago.
I have wired everything as you stated. Purge fan runs but no ignition. No light comes on the new board either. This is exactly what it was doing in March. I went on justanswer in May and was told the board was bad. Now I replaced the board and nothing has changed. What else could be causing this do you think?
Expert:  BillyHvac replied 2 months ago.

if you turn thermostat off does purge fan stop?

Customer: replied 2 months ago.
Turned off the thermostat off completely and purge fan continues to run!
Expert:  BillyHvac replied 2 months ago.

ok, this is commonly a tripped safety or open safety.

When this happens is the main blower running?

Customer: replied 2 months ago.
OK here is the deal. Purge fan is not running the main furnace fan is running. The AC worked perfectly all through the summer and shut on and off including the furnace. Now I flip to heat and the damn thing has gremlins. If I which it back to AC it works perfectly again.
Expert:  BillyHvac replied 2 months ago.

Prior to this swap...did the exhaust fan run?

Customer: replied 2 months ago.
Scratch that. Now the furnace fan runs continuously regardless if the Cool / Off or Heat is picked at the thermostat. It did not do that before replacing the board.
Customer: replied 2 months ago.
Expert:  BillyHvac replied 2 months ago.

is there a fuse on the new board?

Customer: replied 2 months ago.
Not that I see. It is a sealed unit.
Customer: replied 2 months ago.
Shit. The manual switch for the fan was on. Pulled it out now it is on auto. Fan has stopped.
Expert:  BillyHvac replied 2 months ago.

ok,

so where are we at now as far as operation

Customer: replied 2 months ago.
Ok, I switched the thermostat to heat and nothing. No purge fan no light on the control board. Nothing. If I switch it to cool it kicks the furnace fan on and the condenser outside runs.
Customer: replied 2 months ago.
Do I need to check the thermostat for a jumper?
Expert:  BillyHvac replied 2 months ago.

Thank you. Do you mind removing the top section of thermostat?

Customer: replied 2 months ago.
sure. One minute.
Expert:  BillyHvac replied 2 months ago.

we want a jumper from r to rc........and then we want to cross 2 wires so let me know when you are ready

Customer: replied 2 months ago.
OK. There is no jumper. Just the red wire on R. Nothing jumped to R to RC. Should I add a jumper?
Expert:  BillyHvac replied 2 months ago.

before we do that...take the red wire and the white wire on W terminal and cross them together. Tell me if the exhaust fan starts

Customer: replied 2 months ago.
at the thermostat or on the furnace?
Expert:  BillyHvac replied 2 months ago.

thermostat

Customer: replied 2 months ago.
OK. One minute.
Customer: replied 2 months ago.
Nothing.
Expert:  BillyHvac replied 2 months ago.

ok,

now red to green...

tell me if blower starts, and then we will go to circuit board for more testing

Customer: replied 2 months ago.
Nothing. No blower or purge fan. Nothing turns on at the furnace.
Expert:  BillyHvac replied 2 months ago.

I thought with the fan setting in "ON" the blower ran?

Customer: replied 2 months ago.
There is a manual/auto button inside the furnace. When I was tracing wires I bumped it in to manual mode and it ran all the time. I have sense pulled it back out to auto mode so that it only operates when the AC or heat calls for it.
Expert:  BillyHvac replied 2 months ago.

the issue is..

touching red wire to green wire starts the blower even in ac mode.

but your saying the red wire touching the green wire does nothing, so I am at a bit of a loss.

Customer: replied 2 months ago.
sorry I didn't see red to green wire. Let me do that now.
Expert:  BillyHvac replied 2 months ago.

standing by

Customer: replied 2 months ago.
Red to green furnace fan starts!
Expert:  BillyHvac replied 2 months ago.

Ok good,

so we know power is right

transformer works

Now put thermostat back together.

We go to the furnace next.

Door off and pop out safety switch (if present) taped down.

Then with a U shaped wire....we want to put one end on r and other end on w on the board.

Customer: replied 2 months ago.
ok. need a minute to put the thermostat together.
Expert:  BillyHvac replied 2 months ago.

standing by

Customer: replied 2 months ago.
Ok. Done by the furnace. Ready to go
Customer: replied 2 months ago.
No safety switch on upper cabinet door. I will next jump the r and w
Expert:  BillyHvac replied 2 months ago.

Ok....

Customer: replied 2 months ago.
R to W = Nothing. R to G = fan runs. this is at the furnace. is the thermostat bad?
Expert:  BillyHvac replied 2 months ago.

R to W at board eliminates the thermostat.

Is there a chance you could take a pic of the furnace with doors off and post here so I can mark test spots

Customer: replied 2 months ago.
Will attach as soon as I finish taking them
Customer: replied 2 months ago.
Trying to add picture now. 1 of 2 texts
Customer: replied 2 months ago.
2 of 2. let me know if you need any more pictures
Expert:  BillyHvac replied 2 months ago.

Thank you.

Look at this picture

Take the 2 wires off the switch and connect the wires direct together metal to metal. Then try R to W jumper again

Customer: replied 2 months ago.
Doing now. one minute.
Expert:  BillyHvac replied 2 months ago.

If same with no operation see HERE

Customer: replied 2 months ago.
I attached a jumper between the two connectors for the limit switch and jumped the R and W. Nothing.
Expert:  BillyHvac replied 2 months ago.

put those back...and try the next switch I showed you...also it would be a good time to see if the exhaust motor gets power but does not run.

Customer: replied 2 months ago.
Nothing changed but there is 120v going through them.
Customer: replied 2 months ago.
I have a simple multi meter and voltage finder. let me know what you want to test.
Expert:  BillyHvac replied 2 months ago.

Excellent.

go back to the r,w,y,b/c termonals (furnace)

set thermostat to heat and turn up temp...

then test terminal B/C to W and tell me if 24v

Customer: replied 2 months ago.
OK. There is no power to the purge fan.. I will go back to the r,w,y,b/c termonals (furnace) DONEset thermostat to heat and turn up temp...DONEthen test terminal B/C to W and tell me if 24v 27.6 volts.
Customer: replied 2 months ago.
tested terminal B/C to W and mutimeter reads 27.6 volts.
Expert:  BillyHvac replied 2 months ago.

Attached is a close up of a relay in top section.

With an insulated handle screwdriver or a pencil I want you to move the points I hav an arrow at...by move I mean press until it makes contact with other points

See Here

Customer: replied 2 months ago.
Understood.
Customer: replied 2 months ago.
Ok. Main furnace fan comes on until I release it.
Expert:  BillyHvac replied 2 months ago.

please tell me where the purge fan wires come from

Expert:  BillyHvac replied 2 months ago.

and I apologize but I have to go offline for a while but will respond as soon as I can

Customer: replied 2 months ago.
I will take a picture to show you what they attach to.
Customer: replied 2 months ago.
Black wire (600V printed on it) on picture goes to black round relay? Power coming in but nothing coming out to the purge fan. White wire goes into furnace junction box and pigtails to white ground. Pictures won't go through but round relay? says;Potter & Brumfield
S87R1A2B1D1-24
20 Amps
9041Could this be a bad relay? It's the only thing that is attached to the fan other than the white to neutral.
Customer: replied 2 months ago.
OK I took the relay off and pushed the plunger up and the purge fan started. Still no ingnitor. There is a wiring gremlin in this furnace on the heat side. I am calling it quits. Thank you for all your help.

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