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  1. #1
    Join Date
    May 2012
    Location
    Los Angeles
    Posts
    31

    outdoor thermostat

    I apologize in advance for being a light on the model numbers( im not in need of assistance at this point) But I was just curious if anyone has come across an outdoor thermostat used with a dual fuel kit and found that switch contacts were stuck open (because of cold weather). I checked the continuity for the switch and had nothing then after exercising the dial on the outdoor stat the furnace began to work properly. So the unit is working fine now I was just wondering if anyone else came across the same solution. And by cold weather I mean it has been 5-20 degrees the whole last week.

  2. #2
    Join Date
    Jun 2007
    Location
    Greenwood Indiana (Indianapolis)
    Posts
    420
    System needs upgraded to the new century. IAQ stat, I suggest.
    As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84

  3. #3
    Join Date
    May 2012
    Location
    Los Angeles
    Posts
    31
    Quote Originally Posted by Kevin Weaver View Post
    System needs upgraded to the new century. IAQ stat, I suggest.
    It's my mother's home and she is about to be moving out so no chance she will put money in to it but thanks for the advice it seems like it would be a huge upgrade from the MESS of wires she owns now.

  4. #4
    Join Date
    Oct 2002
    Posts
    1,252
    I assume this shifts gas heat to HP. Can you use a mechanical temperature control with remote bulb. SPDT for about $50. I use a lot on HP systems.

  5. #5
    Join Date
    Mar 2010
    Posts
    28
    what stat do you use?

  6. #6
    Join Date
    Oct 2002
    Posts
    1,252
    Remote bulb thermostat. Honeywell makesthem, as well as Robert shaw, Penn, Grainger, etc. SPDT with adj differential.

    They all look the same. Multi purpose. I use them on all HP installs, as well as commercial refrigeration and temporary repairs.

  7. #7
    Join Date
    Mar 2010
    Posts
    28
    tks. i know there are a few different stats. i just used a wr dual fuel stat that turns on 2nd stage wo locking out hp. makes me wonder sometimes if all the heat on coil is hard on compressor?????

  8. #8
    Join Date
    Jan 2013
    Posts
    45
    While we're on the topic of dual fuel units, I went to a 5 ton oil furnace/ 5 ton heat pump dual fuel call some time ago,complaint was the breaker would trip about once or twice during the day. Don't remember the make of the oil furnace, but the hp was Payne. While I was on site the breaker did trip once and I did reset to find the root of cause. I didn't trip again but did notice the rla's were a bit high while the compressor would run, I remember the breaker being compatible with what the hp called for. What I did notice was the furnace had a single return with a direct drive motor and a aprilaire 5000 filter cabinet with the proper filter and no return at the basement,would this have been the culprit putting strain on the compressor??

  9. #9
    Join Date
    Oct 2002
    Posts
    1,252
    Simply-high temperature at condenser(inside coil) is like an AC in summer time with a very dirty condenser coil. You would draw high amperage.

  10. #10
    Quote Originally Posted by jeremyg View Post
    tks. i know there are a few different stats. i just used a wr dual fuel stat that turns on 2nd stage wo locking out hp. makes me wonder sometimes if all the heat on coil is hard on compressor?????
    I am assuming that the indoor coil is downstream of the furnace and most likely on top of it. In that case, yes, this will be very hard on the compressor. The idea of a heat pump is to bring relatively cooler indoor air across the indoor coil to condense the compressed hot gas flowing through it into a liquid and in the process removing a lot of heat from said gas. By operating the furnace at the same time as the heat pump with the indoor coil being downstream of it, the air is so hot that the hot compressed gas does not condense down as it should and you jack the head pressure of the operating heat pump through the roof. Use a modern day digital stat coupled with the appropriate outdoor sensor to switch from stage on to axillary once outdoor temps drop below the appropriate level or use a SPDT outdoor thermostat to switch the Y signal to W2 on temperature fall below the appropriate level.

    -Brian

  11. #11
    Join Date
    May 2012
    Location
    Los Angeles
    Posts
    31
    Thanks for the info, this system could really use an updated thermostat. maybe the next people to buy the house will install one

  12. #12
    Join Date
    Mar 2010
    Posts
    28
    i agree it has to raise head pressure but this type of white rodgers stat is a dual fuel designed to turn 2nd stage on during defrost and when hp cant keep up. maybe its not as good as honeywell vision pro. that explains why its half the cost of honeywell??? tks for feedback

  13. #13
    Quote Originally Posted by jeremyg View Post
    i agree it has to raise head pressure but this type of white rodgers stat is a dual fuel designed to turn 2nd stage on during defrost and when hp cant keep up. maybe its not as good as honeywell vision pro. that explains why its half the cost of honeywell??? tks for feedback
    Energizing 2nd stage while in defrost should be a very desirable thing as it will speed up the defrost cycle and should have no negative effect on heating mode head pressure as long as it de-energizes once defrost is over.

    It's funny, I never even thought about the defrost cycle, but I bet that all properly designed duel-fuel systems energize the gas furnace during defrost. BTW, in most situations the 2nd stage is energized during the defrost cycle by the control board in the outdoor unit (split system setup), indoor thermostat has nothing to do with it.

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