# Sensor Fell off Trane XE1000. What is it?



## Krell (Jul 4, 2011)

I have a 1997 Trane XE1000 heat pump. I'm trying to find out what sensor this is, in the attached pics. It's the round silver thing, lying on the bottom of the unit, with the two blue wires coming out of it. Note that there is a concave groove on it which has some orange junk in it (glue?). There are all sorts of tubes within reach of it that it may have been glued to. I think I have shown all the tubes, in the pics, that it might have been attached to. 

What I have found out so far, on the internet, is that this round silver sensor is probably one of two things : 1) the sensor which turns off the crankcase heater when the compressor is on, and attaches to the discharge line / tube. 2) the sensor which controls the defrost cycle, and attaches to the coil. 

What / where is the "coil" in the pics, and what / where is the discharge line / tube ????

The model number from the actual plate on the unit is TWR024C100A2 .

The wire to the crankcase heater has broken off, you may have noted, in the pics, and is lying on the bottom of the left rear of the unit near the compressor electrical box. It's the black wire with the red cylinder on the end of it. Maybe it's related to the situation somehow. 

_The heat pump works fine._ It was putting out lots of heat this past winter, and was cooling well this summer. I never checked down inside the unit until this Spring, and noticed the sensor and the CCH wire lying there. They may have been off for a couple years already! This Winter I had a block of ice about 3 inches thick on the bottom of the unit, for several weeks in a row, but the heat worked fine, with hardly any need for the auxiliary heat to come on.

I don't recall a lot of defrosting going on last Winter (in which the big cloud of vapor comes out of the heat pump), but I wasn't looking for it. 



Can anyone tell me what this round silver sensor is, and where it supposed to attach? 

Thanks


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## JJboy (Oct 12, 2010)

This sensor is TDL - Discharge Line Thermostat. There is a clamp that goes in the back of this sensor and in the liquid line.


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## Master of Cold (Aug 7, 2011)

Just curious..your running a 25 year old heat pump..how is you electric bill?


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## Krell (Jul 4, 2011)

JJboy said:


> This sensor is TDL - Discharge Line Thermostat. There is a clamp that goes in the back of this sensor and in the liquid line.


Thanks! I guess I can clamp it back on. Can you point me to the Discharge Line and the Liquid Line in the pics? And does the DLT affect the defrost, or the CCH, or both?


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## JJboy (Oct 12, 2010)

This sensor is in series with the crankcase heater when liquid line reaches a specified temperature this sensor opens the circuit.

You have to connect this sensor in the small copper line just after the compressor


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## Krell (Jul 4, 2011)

Master of Cold said:


> Just curious..your running a 25 year old heat pump..how is you electric bill?


I was wrong!   It is only a 14 year old heat pump, from 1997.

I was thinking of the original pump, which would now be 25 years old. Thanks for mentioning that. I hope I can still edit my original post.

I need another vacation.


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## Krell (Jul 4, 2011)

JJboy said:


> This sensor is in series with the crankcase heater when liquid line reaches a specified temperature this sensor opens the circuit.
> 
> You have to connect this sensor in the small copper line just after the compressor


Do you mean I should connect it to one of those copper lines that look like an exhaust manifold, to the right of the compressor?


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## Master of Cold (Aug 7, 2011)

The sensor goes on the small line just after the compressor.
What is that other wire in the third picture? It is at the bottom of the compressor.


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## JJboy (Oct 12, 2010)

Krell said:


> Do you mean I should connect it to one of those copper lines that look like an exhaust manifold, to the right of the compressor?


Just after the compressor:thumbsup:


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## Master of Cold (Aug 7, 2011)

Krell said:


> I was wrong!   It is only a 14 year old heat pump, from 1997.
> 
> I was thinking of the original pump, which would now be 25 years old. Thanks for mentioning that. I hope I can still edit my original post.
> 
> I need another vacation.


I didn't catch that either..wong model # for 1986


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## bobelectric (Mar 3, 2007)

master of cold said:


> just curious..your running a 25 year old heat pump..how is you electric bill?


2011-1997=25


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## beenthere (Oct 11, 2008)

bobelectric said:


> 2011-1997=25


2011-1997=14


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## Krell (Jul 4, 2011)

Master of Cold said:


> The sensor goes on the small line just after the compressor.
> What is that other wire in the third picture? It is at the bottom of the compressor.


 The black wire that curls at the end, and has a red tip, is the wire to the Crankcase Heater, I believe. There is also a twig or a pine needle lying on the bottom, pointing to the vertical grey cylinder. Speaking of crankcase heater, even if I reattach the sensor to the liquid line, it won't change the operation of the heat pump until I fix or replace the crankcase heater, right? Assuming the only function of that sensor is for the CCH. Fortunately the hp works fine even with the sensor off and the cch wire broken.


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## Master of Cold (Aug 7, 2011)

You will want that working for the heating season.


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## Master of Cold (Aug 7, 2011)

bobelectric said:


> 2011-1997=25


Please read the whole thread before making fun of me.
OP originally said 1986 unit.


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## JJboy (Oct 12, 2010)

Krell said:


> The black wire that curls at the end, and has a red tip, is the wire to the Crankcase Heater, I believe. There is also a twig or a pine needle lying on the bottom, pointing to the vertical grey cylinder. Speaking of crankcase heater, even if I reattach the sensor to the liquid line, it won't change the operation of the heat pump until I fix or replace the crankcase heater, right? Assuming the only function of that sensor is for the CCH. Fortunately the hp works fine even with the sensor off and the cch wire broken.


AC unit is going to be needed in the cold season. One wire coming from the side of the contactor, goes to the Crankcase Heater, after that it goes to the sensor connected to liquid line, and finally it closes the circuit to the other side of the contactor. :thumbsup:


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## Krell (Jul 4, 2011)

Thanks for the replies!  How easy is it to replace the CCH, or fix the wire going to it? I guess I would remove the side panel, and lie on the ground next to the HP, and reach in sideways under the compressor. 

There are some wires like paperclips sticking out of the bottom of the compressor next to that black and red wire that goes to the CCH. Are they part of the CCH? Why would the wire just snap off like it did? 

The heat pump acted normal all Winter, and the heat bill was normal, so maybe I was just lucky so far. 

If I run the HP in Winter with the CCH not working, will it ruin the compressor, or just run less efficiently?


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## beenthere (Oct 11, 2008)

Could damage the compressor by allowing liquid refrigerant to wash out the oil.


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## Master of Cold (Aug 7, 2011)

Its not easily changed after this many years. I install a belly clamp heater, if it doesn't come out easily.


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