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Old 10-30-2011, 11:03 PM  
gerrycurl21
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Default Trane XR90 - Pressure Switch

Does the inducer create the pressure for the pressure switch to activate? How are they connected?



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Old 10-30-2011, 11:59 PM  
paul52446m
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Default Pressure Switch

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Originally Posted by gerrycurl21 View Post
Does the inducer create the pressure for the pressure switch to activate? How are they connected?
The pressure switch is checking the pressure across the heat ex changer.
One line goes on the drain side under the heat ex=changer, and the other go after the inducer in the top side of the secondary heat ex-changer.
Paul


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Old 10-31-2011, 09:35 AM  
gerrycurl21
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My furnace stop working a day ago and being completely new to hvac, everything is a new experience to me in regards to my heating. Upon taking covers off the first time, i found the 3 blinking red led which means a pressure switch error. the bottom blower works loud a well and im getting air circulation throughout my house through my registers.

Now after clearing out the rubber hose between the pressure switch, gas valve and burner chamber i found that I can fake the pressure to the switch by taking out the chamber end of the hose and lightly blowing into it, the ignitors starts to glow red and if i keep at it, the gas valve opens and i get ignition. Of course when I stop, the gas valve shuts, ignitors stops glowing.

I narrowed it down to gas valve (which i had to change out the honeywell valve in my hotwater tank last winter) so that wouldnt be too surprising but really unwanted. Or the inducer. When I run the furnace the inducer motor gets warm to the touch, but i cant tell if its actually running because the damn blower at the bottom of the furnace is so loud. I took off the inducer and reran everything with the inducer in my hand and the inducer is not doing anything, just getting warm in my hand. Now like i said before, i dont know anything about hvac, but shouldnt the inducer be creating air flow? either sucking or blowing through the top end? shouldnt parts be rotating as it does kinda look like a car turbo.

Does this inducer create the pressure it needs in the hose to open the pressure switch? How would it do that if the inducer is not even connected through the rubber hose? or is inducer connected to the burning chamber?
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Old 10-31-2011, 12:09 PM  
paul52446m
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Default Trane XR90 - Pressure Switch

Quote:
Originally Posted by gerrycurl21 View Post


My furnace stop working a day ago and being completely new to hvac, everything is a new experience to me in regards to my heating. Upon taking covers off the first time, i found the 3 blinking red led which means a pressure switch error. the bottom blower works loud a well and im getting air circulation throughout my house through my registers.

Now after clearing out the rubber hose between the pressure switch, gas valve and burner chamber i found that I can fake the pressure to the switch by taking out the chamber end of the hose and lightly blowing into it, the ignitors starts to glow red and if i keep at it, the gas valve opens and i get ignition. Of course when I stop, the gas valve shuts, ignitors stops glowing.

I narrowed it down to gas valve (which i had to change out the honeywell valve in my hotwater tank last winter) so that wouldnt be too surprising but really unwanted. Or the inducer. When I run the furnace the inducer motor gets warm to the touch, but i cant tell if its actually running because the damn blower at the bottom of the furnace is so loud. I took off the inducer and reran everything with the inducer in my hand and the inducer is not doing anything, just getting warm in my hand. Now like i said before, i dont know anything about hvac, but shouldnt the inducer be creating air flow? either sucking or blowing through the top end? shouldnt parts be rotating as it does kinda look like a car turbo.

Does this inducer create the pressure it needs in the hose to open the pressure switch? How would it do that if the inducer is not even connected through the rubber hose? or is inducer connected to the burning chamber?
It sounds like you have found the problem, Bad inducer. Your gas valve is good. The inducer makes the pressure switch by sucking through the heat ex-changer and blows out the stack. they call all these switches pressure switches, but some work on pressure , some work on vacuum, and some read pressure difference so they use both vacuum and pressure. Paul
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Old 10-31-2011, 01:29 PM  
gerrycurl21
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Yeah, i just picked up a new one for 250$, and the found the fins rotating on the backside of the new unit, something the old unit was not doing.

Hopefully its a easy disconnect. I have the inducer off but its just the wiring im trying to disconnect. It doesnt seem like a simple tug and pull. Its in a plastic housing and there doesnt seem to be any moving parts on the housing.

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Old 10-31-2011, 02:28 PM  
paul52446m
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Default Trane XR90 - Pressure Switch

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Originally Posted by gerrycurl21 View Post
Yeah, i just picked up a new one for 250$, and the found the fins rotating on the backside of the new unit, something the old unit was not doing.

Hopefully its a easy disconnect. I have the inducer off but its just the wiring im trying to disconnect. It doesnt seem like a simple tug and pull. Its in a plastic housing and there doesnt seem to be any moving parts on the housing.
Did the new unit come with wires coming out of it? Is it possible to just cut and splice the wires back together? Paul
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Old 10-31-2011, 02:28 PM  
gerrycurl21
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Now I just noticed on my new inducer that its missing this entire thing



Im at work now with the part so I cant mess around with it at home to see if it still will work.

I gave the guy at emco the part number of D342094P02 and he said that one is now superseded by a -P06 model now, which I have purchased and is in my possession.

The new unit has the 4 wires supplied.

3 coming from the motor on the inducer,

-green being the ground im guessing

-a black one with a connector i dunno how to connect

-and a white one with a plastic connector.

Also included is a black wire not connected to anything. One end being with the same unknown connector and at the other end being another plastic connector that fits perfectly into the other end of the white wire coming from the motor.


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Old 10-31-2011, 02:49 PM  
paul52446m
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Default Trane XR90 - Pressure Switch

Quote:
Originally Posted by gerrycurl21 View Post
Now I just noticed on my new inducer that its missing this entire thing



Im at work now with the part so I cant mess around with it at home to see if it still will work.

I gave the guy at emco the part number of D342094P02 and he said that one is now superseded by a -P06 model now, which I have purchased and is in my possession.

The new unit has the 4 wires supplied.

3 coming from the motor on the inducer,

-green being the ground im guessing

-a black one with a connector i dunno how to connect

-and a white one with a plastic connector.

Also included is a black wire not connected to anything. One end being with the same unknown connector and at the other end being another plastic connector that fits perfectly into the other end of the white wire coming from the motor.


OK. your old unit had a capasator, the new one does't. So white to white,
green to cabinet ground. cut the black that is going under the motor and tie it to the black on the new motor. You might just have to splice them together
Paul
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Old 10-31-2011, 03:11 PM  
gerrycurl21
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Thanks for the reply, Ill try it out in a hour or so when I get home from work.

So the spare black wire with the new inducer doesnt get used at all?

I will take some more detailed pics once at home of the old unit.

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Old 10-31-2011, 04:26 PM  
paul52446m
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Default Trane XR90 - Pressure Switch

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Originally Posted by gerrycurl21 View Post
Thanks for the reply, Ill try it out in a hour or so when I get home from work.

So the spare black wire with the new inducer doesnt get used at all?

I will take some more detailed pics once at home of the old unit.
If you look at your pic. of the old inducer , you have a circle around the capasitor where the black wire is going. see if that unplugs from there, if so you might be able to use that new short black wire to run to the black wire on the new motor. Paul Ps use caution when trying to unplug this wire because those capasitor hold a charge even when power is off. Also make sure you have a gasket seal on the inducer if there was on before. Don]t want any air leaks Paul PS It was brought to my attention,
that i was wrong about the part you have circled in your pic. of the old inducer.
That is a limit switch. Leave the wires on it and install it on the new inducer.
You have a black and white coming out of the old motor, so use those to go to you black and white on your new motor.


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