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Old 08-28-15, 11:13 AM   #1
mechanic
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Default Loop sizing question

My house has two geothermal systems, a 6 ton for the 1800sq ft house plus basement and a 2 ton for a 600 sq ft workshop. There is a 300' header trench branching into 4 300' x 4' wide trenches 8-9' deep. The house has a 1.5" line which someone on here had said was a little shy. The garage follows the same trenches with a 3/4" line. My question is would the smaller line have enough capacity to also run a water to water heat pump to handle my hot water needs? Thinking about modifying a 2 ton geo pump I have access to and just plumbing in to the same lines/pump. My hot water is all electric now.

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Old 08-29-15, 09:12 AM   #2
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Quote:
Originally Posted by mechanic View Post
My house has two geothermal systems, a 6 ton for the 1800sq ft house plus basement and a 2 ton for a 600 sq ft workshop. There is a 300' header trench branching into 4 300' x 4' wide trenches 8-9' deep. The house has a 1.5" line which someone on here had said was a little shy. The garage follows the same trenches with a 3/4" line. My question is would the smaller line have enough capacity to also run a water to water heat pump to handle my hot water needs? Thinking about modifying a 2 ton geo pump I have access to and just plumbing in to the same lines/pump. My hot water is all electric now.
If I'm reading you correctly, you have a trench system that already has two separate closed water loops in the trench. Is this correct?

And it sounds like you want to plumb an additional 2 Ton heat pump off of the smaller of the two water loops.

On first blush, dedicating a 2-Ton heat pump to handle hot water needs could be a great idea if you were running something like a commercial car wash, or a village laundromat, or had an over-sized tribe of teen-age girls living in your house.

The heat pump hot water heating projects so far at EcoRenovator, have been successfully run with compressor capacities in the range of 1/4-Ton to 1/3-Ton. To be clear these were being used for small to modest sized families. One of them had the advantage of drawing heat directly from warm, moist Mississippi earth, and another was an ASHP, which took advantage of heated house air, to supply the needs of an elderly couple.

There is a technique called de-super heater, which other EcoRenovators will surely detail in subsequent posts.

My intuition is that 2-Ton would be seriously over-sized, and could rob a significant amount of heat from your earth heat reservoir.

The fact that you live in Saskatchewan will have a huge impact on your system. If you tell us what town we can pull up some weather data that will assist both you and us in making better decisions.

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Old 08-29-15, 01:22 PM   #3
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You understood correctly yes, two separate loops spaced evenly across the 4' wide trenches. The reason for the 2 ton pump is a fellow near me has two water to air 2 ton pumps, still in they're boxes for sale for a very low price. The liquid side could easily be hooked into my loop as its sized the same then I'd only have to worry about fabricating the condenser side for the hot water. This loop is 3000' of 3/4" line. The small console pump on this loop now seems to have a pretty easy time keeping the shop warm enough, not sure if it could handle the hot water as well though. If the pump's too big I can start from scratch with a smaller one, just thought this might work out with a lot less labor...
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Old 08-29-15, 01:22 PM   #4
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Oh and the closest city to me would be Saskatoon
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Old 08-29-15, 01:29 PM   #5
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Right now my household geo unit has a desuperheater preheating a water tank with no elements which feeds an electric water heater. Unless we are in the depths of winter the preheat tank never gets very warm and in the summer it does nothing.
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Old 08-29-15, 04:05 PM   #6
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Just under 1/2 ton is what I used and even that's way oversized for just hot water. As in a run time of only 3 hours every day. It's just that there's virtually no good reason to go below that as 1/2 ton is about the smallest window A/Cs you'll commonly come across.

2 tons will work fine but tend to short cycle. With a flow sensor and smart controller, you can have it try to start it when hot water is actually in use, making the cycling not so short.
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Old 08-29-15, 07:23 PM   #7
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Right now my household geo unit has a desuperheater preheating a water tank with no elements which feeds an electric water heater. Unless we are in the depths of winter the preheat tank never gets very warm and in the summer it does nothing.

Mechanic - I don't understand the above. My desuperheaters provide LOTS of hot water in the summer, but almost nothing in the winter.

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Old 08-29-15, 08:17 PM   #8
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Well that's how it thought they were supposed to work, use the waste heat when in cooling mode.... Mine does nothing in cooling mode though, only works in heating mode. It's a climate master tranquility series.
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Old 08-29-15, 09:36 PM   #9
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If it's an especially efficient design, there might not be enough superheat for the thermal recovery to operate.
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Old 08-30-15, 07:24 AM   #10
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Mechanic - check your DIP switch settings. There is LOTS of superheat when in AC mode. I bet the pump (desuperheat water) is turned off.

Or something is amis . . . .

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