Rheem Heat Pump High Limit Switch

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  #1  
Old 01-06-05, 11:31 AM
Trob
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Rheem Heat Pump High Limit Switch

I have lost the high limit switch reset button for my Rheem XI heat pump. The little rubber cover came off, and the small plastic reset button got lost. I sure hate to replace the whole limit switch just because I don't have a reset button. Anybody got an idea where I can get one?
Thanks...

Troy
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Last edited by Ed Imeduc; 01-06-05 at 01:02 PM.
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  #2  
Old 01-09-05, 06:31 AM
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I doubt you're gong to be able to repair it, a new one shouldn't be more than about 20 bucks.
 
  #3  
Old 01-09-05, 10:44 AM
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If it wasn't tied into the freon system, I could replace it myself. But to replace, you have to dump the freon system and recharge, which I can't do. That would be the bulk of the cost, labor plus freon.
 
  #4  
Old 01-09-05, 11:36 AM
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If the filters are clean and the inside coil and the outside coil clean. Why would you hit high head. The only other would be if you lost the condensser fan.?

ED
 
  #5  
Old 01-09-05, 12:46 PM
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Change the filter once a month. In talking to some other users, some have to reset, some don't. It wouldn't be a problem, as it only trips 2 or 3 times a year. The problem is, I don't have a reset button (lost) to reset it. I know one thing: If I have to spend $250 plus to get it replaced, I bet I don't hit it with the weedeater again....
 
  #6  
Old 01-09-05, 12:51 PM
Trob
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When the heat pump was first installed, tripped more often. The installer came back out and reset the defrost timer where it would defrost the outdoor condenser coil more often, and the tripping frequency went way down. Down here in the south where I live, we don't get a lot of freezing days, but we do get some. But, we do have extremely high humidity. My theory is that on freezing days, coupled with high humidity, the condenser coils may ice up, causing high head pressure and a trip. Like I said, it doesn't happen maybe two or three times per year, and it wouldn't be a problem now if I had not lost the reset button.
 
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Old 01-09-05, 01:16 PM
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Dont just sound right. When your on heat pump its the inside coil that has to cool down to keep the head down. not the ice outside. You ducts big enough for the unit , cold air returns the right size? You have a lot of ifs to what makes it go off on high head. Does it go off on AC in the summer?


ED
 
  #8  
Old 01-10-05, 11:16 AM
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It hardly ever trips in the summer AC mode. This was a new installation in a new house we had built. Three ton for a 1500 sq ft house. It works fine as far as heating and cooling needs, very efficient.
 
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Old 01-10-05, 02:22 PM
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It should not be tripping at all.

In heat pump mode low air flow through the indoor unit or overcharged refrigerant will cause it to trip. In cooling mode low air flow through the outdoor unit, or overcharge of refrigerant will cause it to trip. There are a few other mechanical problems that will trip the head pressure switch but these are the most common.

It's not still under warranty is it??
 
  #10  
Old 01-10-05, 03:34 PM
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Ah Rheem
Check to see if the contactor is sticking.
Check the refrigerant level is correct.
Check the air flow thru the indoor unit by the temp. rise method.
If all else fails install a resetable pressure switch and a tee flare fitting on the liquid line and a time delay if the circuit doesn't already have one.
 
  #11  
Old 01-11-05, 11:25 AM
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The refrigerant has never been re-charged etc. since new installation in 1996. Again, it is not a bad problem if I had not lost the reset button. Another person I heard about, their dog had chewed the small reset button cover off, and when the unit tripped, they lost the reset button.
 
  #12  
Old 01-11-05, 12:09 PM
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Scott has a good idea and that is get a T for the access port and put it on and put a new pressure switch on the t and abandon the old one.
 
  #13  
Old 01-11-05, 12:51 PM
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Which side does the 'T' hook to? The suction or discharge? Will the 'T' have a Schrader valve connection to access later? Will the connection to the new pressure switch be a soldered connection? (I can't solder worth a flip). I guess I could get someone to solder the new switch to the tee, then install if it is only a twist fitting connection, but I afraid of leaks from twist fitted connections.

One repairman told me that it would be okay to jumper out the high limit switch, that he had been doing it for years. (I have a Rheem scroll compressor). My theory is that the switch is there for a reason, and I sure don't want to tear up my compressor. What do you think?
 
  #14  
Old 01-12-05, 04:26 AM
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It would go on the discharge fitting. It's called a refrigeration T, so it will screw onto the existing access port for the liquid line and will then give you 2 access ports with schraders. The new head pressure switch will just screw onto one of the 2 access ports. No soldering at all. Just leak check it with a mixture of dish soap and water when you're done.

http://www.grainger.com/Grainger/searchresults.jsp

Not sure if you can buy from grainger but this is what I'm talking about. Whoever local to you that will sell hvac parts to the public will have these and a head pressure switch to go on it.

*note: if that link don't take you there just go to www.grainger.com and do a search by grainger part number. The # is 3GD02.
 
  #15  
Old 01-15-05, 12:03 PM
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High limit switch

Is there a generic high head pressure cut out switch that will screw on to the discharge line? Or will I have to get one to coincide with the discharge pressure specific to my Rheem? (I can't buy from Grainger, they are wholesale only).

Thanks so much for all the info.

Troy
 
  #16  
Old 01-17-05, 12:14 PM
Trob
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Okay---got the high limit switch to reset, found a round file in my tool shed that was a perfect fit to reset the switch. Have continuity through the switch. Bad news, the unit still will not come on, contactors are not pulling in (will run if you manually push down on the contactors). I checked the low voltage side of the control circuit transformer, all voltages at all points are reading 5 volts, all voltages on defrost circuit board are 5 volts, all points on another relay are 5 volts (I did not disconnect any wiring). Should they not read 24 volts? Voltage is good on the high side of the transformer (115 volts).
 
  #17  
Old 01-17-05, 01:15 PM
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Did I miss something here. You said heatpump I would think that the transformer would be 220V in 24 out what do you read right on the low side of the transformer there 24V?????

ED
 
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Old 01-18-05, 02:41 AM
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There were 2 110 volt lines going to the transformer. All low side voltages read 5 volts, should they not have read 24 volts?
 
  #19  
Old 01-18-05, 04:31 AM
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If you have the correct primary voltage and don't have 24 volts on the secondary side you need a new transformer.
 
  #20  
Old 01-18-05, 12:04 PM
Trob
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I changed the transformer out, still reading 5 volts on the low side, unit won't come on. The guy at the store I bought it from said it should read 24 volts on the low side. The new transformer I changed out says: Mars switching relay, coil voltage: 24 volts. That is why I thought it should read 24 volts on the low side. Is there any reason I should be reading only 5 volts on the low side terminals? Is there something perhaps tied in that could cause a voltage drain? If I take all the low side wires off, should I read 24 volts on the low side terminals? The only other thing I see in the control panel is the defrost control board (card with plugins) and another switching relay with two brown (one comes from the high limit switch) and two yellow wires.

I also did the thermostat jumpering r, y, g, seen on another post. The outside unit still will not come on.

Only out $17 so far for the transformer, so not too bad. I took a basic refrigeration course about 20 years ago, forgot most of it. I have been working, for the most part, 12 hour night shifts without a day off since Dec 20. It has also been pretty mild days here in north Louisiana, we have even had the windows open some days. Supposed to be in the 60's tomorrow and on. Have been using the fireplace and strip heating, so haven't been without heat.

Is there a way to test the defrost control circuit board or the other relay? Also, is there a low freon pressure cut out switch, and where would it be attatched? Down where the reversing valve is, there looks to be a plug in of some sort. Is this the low pressure switch, or just the reversing valve?

Thanks so much for the info.
 
  #21  
Old 01-18-05, 12:23 PM
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It sounds like you changed the contactor not the transformer. The transformer will have just 2 wires going in and 2 wires coming out. No relay to it at all it's just a square maybe 2X2 with mounting feet and it's totaly enclosed. It could be located inside the airhandler. Check voltage at the low voltage terminal strip at "R" and ground.
 
  #22  
Old 01-18-05, 04:22 PM
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With Matt here lets go back and test the transformer there in the blower unit and see if its goodand we have 24V off it right there first-------------- then start to check out other things. 220V in 24V out


ED
 
  #23  
Old 01-19-05, 08:55 AM
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Checked the transformer in the air handler. 110 each leg in. Here's the weird part. Sometimes the reading was 24 volts on the red wire out, sometimes 19-20. I went to the Rheem dealer today, and he told me the transformer was probably not bad. Since I have no readings above 5 volts anywhere in the outside unit, he seems to think something is draining voltage, perhaps the thermostat. Another service man I talked to at another parts house suggested the transformer might not be putting up enough voltage. However, I checked the red thermostat wire to ground at the thermostat, and I have a good 24 volts there. Is there anyway I can jumper the thermostat, or check resistance across the thermostat terminals to see if the thermostat is bad?

Thanks
 
  #24  
Old 01-19-05, 04:13 PM
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Since found out g on the thermostat does not mean ground, even though there is a green wire going to it. It goes to the inside blower. Read 24 volts across it. Going to follow the wire off the y terminal to the airhandler with the thermostat calling for heat and see if I have 24 volts to ground at the wire nut. Then, if I do, see if I have 24 volts to outside unit.
 
  #25  
Old 01-19-05, 04:32 PM
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G on a tstat is always for the blower green or what ever color. You dont want to try and test to ground the transformer has a + thats R red to the tstat the other leg goes to all the controls as a - So like if you turn the fan to fan on at the fan relay you should read 24V on the low v side.

ED
 
  #26  
Old 01-19-05, 10:24 PM
Trob
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So if I turn the tstat to heat, raise the lever to call for heat, should I be able to read 24 volts across the r to y terminals? I guess something else could keep me from completing the circuit from the y terminal on, namely a break somewhere or another part of the control circuit not closed. Or, does the y terminal go directly to the 24 volt part of the contactor? I also may not be reading the voltage right at the contactor (talked to an electrician at work today). He said I need to read from one side of the contactor coil to the other, I had been reading one side to ground.

I am still on straight 12 hour night shifts with about 2 weeks to go , about to give up and call a repairman. I would like to know what the problem is though. May wait another two or three days, it is still mild down here in Louisiana, in the 60's. I have learned quite a bit about how the control circuit works in talking to you and others. Thanks so much for your time. I am still probably going to try it myself a little longer, just so hard working 12 hour shifts.
 
  #27  
Old 01-20-05, 12:15 PM
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I know I have been all over the place on this thread, but believe I am finally understanding part of the 24 volt control circuit. The latest:

I got back in the attic today and tested the 24 volt control circuit up there again.

Transformer: Red tstat wire disconnected, two 110 leads hooked up, brown wire hooked up - 14 volts. (This was red transformer lead to ground)

With heat on and heat lever pushed up, reading from terminal to ground in the attic:
Yellow tstat to outside yellow - 6-8 volts.
Blue tstat to blue outside - 6-8 volts
Pink tstat to pink outside - 6-8 volts

Then I went outside and tested the yellow wire coming into the outside unit to ground (everything hooked up outside) and read about 6-8 volts there.

Everything (to me) does point to the transformer being the culprit, but as you can tell, I don't claim, even one little bit, to be an electrician. What do you think? Yesterday I was getting readings on the transformer from 18 to 20? If the voltage on the red transformer lead was reading 14, shouldn't the yellow/yellow terminal in the attic approximate 14 volts also with the unit on and the heat lever pushed up?

Thanks again...
 
  #28  
Old 01-21-05, 12:38 PM
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Success

Success, I called the repairman today, and since he was local and had a slow week, was able to come right out in about 30 minutes. Found the problem was the defrost time delay relay (not the control circuit board), with 2 brown wires and 2 yellow wires going to it. He jumpered from one brown wire (the high pressure limit switch connection) to the bottom of the contactor and the contactor pulled in.
He didn't have a relay on his truck, so will come back and replace and then bill me. I will post next week after the cost to let everyone know how much.

Thanks so much for all the info, especially the moderators. I have learned a lot about the 24 volt control circuit, even though I didn't repair the problem myself.

Thanks again...
 
  #29  
Old 01-21-05, 06:40 PM
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We aim to please. Glad to see you got it figured out.
 
  #30  
Old 01-23-05, 08:51 AM
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Hey sorry to leave you in the dark.
It sounds like you are taking your readings to ground and working with AC voltages you dont read to ground.
Read high voltages go from L1 to L2 and on low voltages read from Com to .....
Com to Y
Com to G
Com to R
Com to W2
Com to B

Get it.
 
  #31  
Old 01-26-05, 10:05 AM
Trob
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Final Cost

This is the cost for getting my heat pump repaired:
Service call: $65
Time Delay Relay: 31

TOTAL: $96

Also, I spent $16 on a part I didn't need in trying to repair it myself. Not too bad all in all.


Thanks for all the help. I may not be able to repair it next time, but I definitely know a lot more about the 24 volt control circuit than I did before.

Thanks, Troy
 
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