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Problem child

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Harvey Ramer
Harvey Ramer Member Posts: 2,239
in Geothermal
I went on a service call to a new customer with a Geo unit. Sometime this winter the unit tripped on high pressure and then remained on emergency heat the remainder of the winter, due to the lockout relay. His latest tech told him he needs a new txv, but he really needs a new unit. The previous tech hacked and butchered at it till he finally admitted he doesn't really understand geo.

The unit is only 15 years old. I would like to fix it, as i believe it is worth saving.

It is an open loop pump and dump.

Here are the symptons.
Heating mode;
50° subcooling
High side pressure way to high.
Compressor discharge temps reaching 210-220.
Low side pressure to low.
No superheat.
30° temp rise air side.
6° temp drop water side.

I played around with water flow and that is not the issue. Neither does it appear to have an airflow problem.

I believe the water to refrigerant hx is badly scaled.
System is way overcharged.
May have some sludging issues in copper spun filter driers and txv, due to compressor's inhospitable running environment.

Thoughts?

Comments

  • JUGHNE
    JUGHNE Member Posts: 11,061
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    The pump and dump HP's I used to do had a flow meter on the water discharge line. Looked like a rain gauge maybe 10" tall with a bobber that would indicate GPM. Was handy for annual check up's and adjustments.
    Later ones used a flow control orifice set to fixed GPM. Has a small rubber orifice that is supposed to pass set GPM at any pressure.
    Apparently the rubber flexes in reverse proportion to the pressure and is supposed to regulate rated GPM. Looks almost like a check valve. Always passed too much water for the cooling mode.
    Maybe that control device is partially plugged or sized wrongly.
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
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    If flow were the issue I would expect to see more than a 6 degree temp drop.

    I will be installing a flow meter.
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    How about the reversing valve? Supposedly they can be stuck mid way causing cross over for refg circuit. I would exercise it several times. Maybe overcharging and/or bad techniques could have messed with the original charge.
    I have some of these running near 20 years and surprised that they are still working. One did die at 16 years. We have excellent well water here for these units.
    Looking inside the units, there are a lot of components stuffed inside. 2 TXV's BTY. As they age I secretly hope for a compressor failure rather than trying to change TXV, revs valve or clean/change water coil. Also some of these are crowbarred into closets that I can not almost fit inside myself anymore. :'(
    15 years might be the limit for HP's, depending upon water quality. IMO
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,525
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    overcharged for sure. 50 deg sub cooling , high discharge causing txv to overfeed, no superheat flooding back to compressor
  • njtommy
    njtommy Member Posts: 1,105
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    I would definitely pull the charge and see how much gas is in it.

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