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  1. #1
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    Frankenstein monster help...

    Alright, I broke the cardinal rule and set up a friend of mine with a cheap setup consisting of a 2.5 ton HP that we took out under warranty, and an aspen coil with a TXV, it sits atop his electric furnace in a trailer. The other day he told me it was kicking the breaker, so I checked and it was shorted to ground. My question is, if I shoehorn in a 4 ton compressor I have laying around, how likely is it that I will be changing it again soon? Or is it even feasible? I'm not familiar with mis-matches since we always match our equipment. I'm just looking to get him up and running again before summer as cheap as possible. I appreciate any help.

  2. #2
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    My guess is you'll be changing the compressor with 48 hours, or as soon as your friend finds out it isn't working. How is the low voltage circuit wired?

  3. #3
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    Quote Originally Posted by bobb25 View Post
    My guess is you'll be changing the compressor with 48 hours, or as soon as your friend finds out it isn't working. How is the low voltage circuit wired?
    Ummm. I dont understand the question. How is it wired?. My thought was that even though the compressor would move a higher volume, reducing the amount of freon, coupled with the TXV would allow it to operate at pressures pretty close to normal, I may be totally wrong, thats why I asked. But I dont understand why low voltage is an issue? Unless you mean high and low pressure switch which are absent from this model.

  4. #4
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    What kind of thermostat do you have? Did you install any extra controls on the furnace when you installed this?

  5. #5
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    Quote Originally Posted by bobb25 View Post
    What kind of thermostat do you have? Did you install any extra controls on the furnace when you installed this?
    Why would I need extra controls? I obviously changed the stat, there was a fan relay on the furnace, so I didnt need one. Do you understand my question?

  6. #6
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    I saw someone install a heatpump in a Coleman once, and in the heating mode, the fan would not come on unless the thermostat switch was in emergency heat.

  7. #7
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    Thumbs down Bad Idea.

    Quote Originally Posted by yelram View Post
    Ummm. I dont understand the question. How is it wired?. My thought was that even though the compressor would move a higher volume, reducing the amount of freon, coupled with the TXV would allow it to operate at pressures pretty close to normal, I may be totally wrong, thats why I asked. But I dont understand why low voltage is an issue? Unless you mean high and low pressure switch which are absent from this model.

    Totally wrong, If you put a 48,000 btu compressor on a 30,000 btu coil it won't last long maybe 24 hours.

    Tell the guy to break down and match the system, if he needs 4 tons of cooling and heating, then install a coil or air handler that will match the 4 ton heat pump condenser.
    "Everyday above ground, is a good day".
    "But everyday that you have made a difference in someones life, may insure you stay above ground a little longer".<aircooled>

  8. #8
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    Quote Originally Posted by aircooled53 View Post
    Totally wrong, If you put a 48,000 btu compressor on a 30,000 btu coil it won't last long maybe 24 hours.

    Tell the guy to break down and match the system, if he needs 4 tons of cooling and heating, then install a coil or air handler that will match the 4 ton heat pump condenser.
    Well its not matching the system at this point, it is matched, its finding a free compressor laying around, and currently I only have 1, and I know it will never get put in a job since we took it out of a job we were replacing. Noone has a 30000 btu compressor laying around somewhere out in western PA do they?

    Bobb25, thanx for your help, I understand how electric furnaces/heatpumps work well enough to know that the sequencer brings on the fan in most situations, and if there isnt a fan relay, you have to install one.

  9. #9
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    Quote Originally Posted by yelram View Post
    Ummm. I dont understand the question. How is it wired?. My thought was that even though the compressor would move a higher volume, reducing the amount of freon, coupled with the TXV would allow it to operate at pressures pretty close to normal, I may be totally wrong, thats why I asked. But I dont understand why low voltage is an issue? Unless you mean high and low pressure switch which are absent from this model.
    4 ton compressor on a 2.5 ton heat pump? First thing that'll happen when you slap that puppy in there is, if you fire it up in cooling mode and try to charge it, you'll see low suction pressure and you'll keep dumping gas in to get suction up. By the time you do, you have refrigerant screaming through that system, which likely ain't picking up much heat in the evap (cooling mode) and next thing you know there's liquid coming all the way back down the suction line and into the compressor. KABANG! She's done.

    So...you may not have a 2.5 ton compressor laying around, but at a bare minimum, that's what it needs. Better option is to get equipment in there with a warranty on it, and a clean installation. You want to be married to what's there now forever?

  10. #10
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    Quote Originally Posted by shophound View Post
    4 ton compressor on a 2.5 ton heat pump? First thing that'll happen when you slap that puppy in there is, if you fire it up in cooling mode and try to charge it, you'll see low suction pressure and you'll keep dumping gas in to get suction up. By the time you do, you have refrigerant screaming through that system, which likely ain't picking up much heat in the evap (cooling mode) and next thing you know there's liquid coming all the way back down the suction line and into the compressor. KABANG! She's done.

    So...you may not have a 2.5 ton compressor laying around, but at a bare minimum, that's what it needs. Better option is to get equipment in there with a warranty on it, and a clean installation. You want to be married to what's there now forever?
    Its really not a "married to" situation since I put it in for him cheaper than I could even buy the stuff. I appreciate the explanation though, as there is very little material to be found on the actual mechanics of mixmatching. What you are saying makes alot of sense, and is exactly the kind of answer I was looking for. What exactly would an undersized compressor do in that situation? I imagine it would obviously lessen the overall system capacity, but would it raise efficiency since it has a larger coil area?

  11. #11
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    1-Why are we discussing this in an open forum

    2- yelram you’ve got to be kidding with these questions

  12. #12
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    Quote Originally Posted by pecmsg View Post
    1-Why are we discussing this in an open forum

    2- yelram you’ve got to be kidding with these questions
    And why is that? Or are your posts ALL completely useless? Tell me how many times you've witnessed a mis-sized compressor? My dads been doing this 30 years, and his best answer was "it probably wont work". If you dont have anything useful to contribute, why even take the time?

  13. #13
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    Quote Originally Posted by yelram View Post
    Alright, I broke the cardinal rule and set up a friend of mine with a cheap setup consisting of a 2.5 ton HP that we took out under warranty, and an aspen coil with a TXV, it sits atop his electric furnace in a trailer.
    Atta Boy for trying to help.

    Was this coil matched to the condensing unit?


    The other day he told me it was kicking the breaker, so I checked and it was shorted to ground.
    Shorted to ground is usually caused by moisture. Either way something went really wrong.

    My question is, if I shoehorn in a 4 ton compressor I have laying around, how likely is it that I will be changing it again soon? Or is it even feasible?
    4-Ton compressor (48,000 btus) going through a 2 ˝-Ton condenser (30,000 btus) think about it.

    I'm not familiar with mis-matches since we always match our equipment. I'm just looking to get him up and running again before summer as cheap as possible. I appreciate any help.
    Sorry I can’t help with this one. The only thing I can say is you’ve wasted a lot of time, now you’re looking to make it worse. Rip that entire unit out. Line set included. Chalk it up to a Learning Experance

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