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Old 04-08-17, 03:35 PM   #1
Ron342
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Default Help in hooking up geowater water heater?

So thanks to you guys i can braze & purge hvac plumbing (Jeff, your detailed explanation from your 2010 post was great) and have a 100 ft geo hole done, with 3/4" hdpe poly ubend pipe -mostly saturated with water and sand in the hole from about 25' on down, leads into the basement where the water heater lives. Plan on tapping a small bladder expansion tank, 1/25 hp grundfos pump and air extractor from my old baseboard hot water system into the geo line to the evaporator - am i missing anything in this circuit?
I have a 80 gal elec hot water heater with 25 ft of 1/4" coppper twirled thru the top of it thru a 3/4" threaded hole and out thru the bottom drain hole (see pics) for a condenser. There are furrel fittings that seal it off and thread into the tank. You can see the top in the pic. I'll probably put a galvanized T fitting at the drain hole to retain the drain valve.
Theres an evap that surrounds the top of the water heater made from 3/8 copper spiralled inside about 30 ft of 3/4 hdpe poly pipe. The copper enters and exits the poly pipe thru 3/4 copper T fittings and more of the furrel fittings. The 3/4 copper ppipe stubbed into the T fits well into the 3/4 popy if you heat the poly and round over the mating end of the copper pipe. Its an easy exchanger if it works - the copper and poly pipe are coiled about same diameter and the copper coil can be turned backwards into the slippery hdpe pipe.
Theres a 7500 btu r22 compressor and its mating cap tube from a window unit that i plan to sit on top of the water heater. I think its a scroll comp. since its relatively tall and skinny. I plan on putting the r22 back because its in my basement.
Locations of the comppressor & evap can easily be moved at this stage.
And i'm stopped with these questions:
1. Do i run the comp. discharge into the top hot end of the water heater or into the cold bottom end? Most of the hacks i've seen go in and out thru the same element hole but this could make a significant difference since theres so great a temp difference. Also, do i have enough condenser tubing in the tank?
2. Should i run the cap tube in at the bottom of the evap coil or the top? I am concerned about oil flow? I assume either way that counterflow with the geo water works best?
3. I have a liquid line filter dryer, sight glass and taps for the hi and low sides. Does the sequence of the liquid filter and sight glass make any difference? Should i also add a pressure tap for the condenser exit?,
4. The comp. has a receiver or filter already in its inlet close to the comp, see pic. Should i just leave it there? The unit worked well.
I am trying to put together an IOT controller for this from Actuario's posts - one of the worlds and this sites renaissance men, i think, & this is sort of a learner for a geo water heat pump system.
Thanks guys!

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Old 04-09-17, 09:22 AM   #2
jeff5may
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Here come some answers:

1. Compressor discharge to top of water heater tank. Liquid (and oil) falls to bottom. Superheat is gobbled up quickly at the top, refrigerant condenses slowly and should start to subcool down low. With the outlet at the bottom, the coolest water will be there to ensure adequate subcooling. Whether or not there is enough condenser tubing depends on your efficiency expectations.

2. Cap tube should connect between bottom of condenser and bottom of evaporator. Liquid enters bottom of evaporator and quickly expands, causing oily froth/foam to travel quickly through. By the time all liquid has evaporated, oil has been carried close to end of evap tube. With the configuration you are running, it makes more sense to put the cap tube up high on the vertical path, rather than down low. This ensures some subcooling in the bottom of the condenser, due to a standing liquid column in your liquid line. If left exposed to ambient air, the small amount of escaping heat would keep flash gas out of the liquid line (window air conditioners run the liquid line through the drain pan for added subcooling).

3. The sight glass should be installed directly upstream from the cap tube, then the filter dryer and liquid line tap (I use a SUPCO copper drier- SUD 111 and SUD 115 have charging valves attached) if installed. This will allow you to see if there is any gas making its way into the cap tube.

Plan on having to adjust the size of your cap tube to make this unit operate correctly... with a modified evaporator, the cap tube is no longer the correct length. Too long a cap tube, and the unit will take forever to heat water and try to freeze your evaporator. Too short a cap tube, and the evaporator will try to feed your compressor liquid. Either leave extra tubing in that can be cut and spliced or install some flare fittings on both sides of the cap tube assembly. I like the ball valves with flares on both sides for obvious reasons.

4. The muffler that is built into the compressor inlet also acts as a suction line accumulator. When the unit first starts, the bulk of the refrigerant lies in the evaporator as liquid. The accumulator catches this liquid before it has a chance to enter the compressor. Once sufficient vacuum is pulled, the refrigerant boils off and is pumped to the high side. The screen on the suction line in the muffler is not considered a filter, it is there just to catch any coarse particles that would cause damage to the compressor. Leave it as-is, let it do its job. If you are concerned about contamination, install a liquid line filter drier in the liquid line near the cap tube.

Since you are using a digital controller, why not add some extra sensors to the unit when you build it? Thermistors and digital thermometer sensors are cheap, and will enable you to log whatever data you want.

Looks good so far! I wish you luck in your build.
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Old 04-09-17, 10:23 PM   #3
Ron342
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Thanks Jeff, i'll hook it up that way and report how it works.
The geo water path sounded ok?
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Old 04-10-17, 12:45 PM   #4
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You will never know how well the geo loop will actually perform until it is tested. For best results, use antifreeze and employ some kind of low temperature or pressure cutout. proving fluid flow through the loop is also highly advised.

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