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Old 06-10-17, 08:57 AM   #21
jeff5may
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Originally Posted by Fordguy64 View Post
So this ice bank idea is kind of awesome. Although it seems for most cases it pays back faster if you have lower electric rates at night. I don't believe I have that. But I have almost enough solar to run a 12kbtu unit. So my first test rig might be two tanks of water for hot and cold. Hook up the solar and see if a can freeze a tank of water! Sounds easy
Solar thermal is a LOT more efficient than solar PV. In heating season, trying to freeze your cistern with the heat pump and thawing it out with a smallish ground loop and/or solar thermal would be ultimately effective. There are panels being made now, today, that do both.


dualsun wave panel (rated at 250W pv plus 900W thermal)

Solar angel is another brand that is available.

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Old 06-13-17, 07:56 AM   #22
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So another question.. Since I have access to the equipment to dig and also the yard to dig. Should I skip the extra pump and just go with a dx type system? I guess the nice thing about the water to water on both sides is in the summer time I can use the heat generated for cooling to hear my domestic hot water. I feel like the dx type system could be much more efficient with less pumps and heat exchangers..
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Old 06-13-17, 01:32 PM   #23
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After more thinking.. I think I'm going to stay with the original idea of water buffer tanks on both sides. Maybe I'll make a dedicated heat pump for the water heater that is dx.

I feel the water on both sides gives me so much more freedom to do things with the heat pump..
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Old 06-13-17, 05:49 PM   #24
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After more thinking.. I think I'm going to stay with the original idea of water buffer tanks on both sides. Maybe I'll make a dedicated heat pump for the water heater that is dx.

I feel the water on both sides gives me so much more freedom to do things with the heat pump..
Yes unless the capacity of the heat pump is small, the DX exchange pipes will use more refrigerant than a plate heat exchanger. The surface area of the piping isn't very large either. A plate heat exchanger is very compact and will use hardly any refrigerant compared to other types. Less refrigerant is pretty much always better.

I am a fan of matching heat exchangers to compressor capacity, plus extra. Once the rig is plumbed, it's done. The water side can be rigged to whatever, however, whenever. Having multiple rigs gives flexibility. The upsize lets you pump more water without losing heat transfer. With variable speed pumps, the exit water temps can be regulated at each unit if desired. This works on both sides of the rig to get you where you want to go quickly.

Last edited by jeff5may; 06-15-17 at 09:58 AM.. Reason: Spelling
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Old 06-14-17, 08:45 AM   #25
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We have officially closed on the new house. I'm going to take a side panel off of th ac unit as its so old it doesn't have a label on it. I'm going to see if I can figure out how many btu it is. The propane furnace has a sticker in it that says it's a 1992 model. I'm assuming the ac unit is the same age. It still works well but it's just a matter of time I feel. My quick estimation says that I'll need 2 tons for cooling. So it will be interesting to see what size is on the house now.

I haven't decided if I want to put this home made heat pump thing in the basement or in the barn out back. I'm leaning towards the barn just for home owners insurance reasons. The only downfall to this is that I'll have to do a lot of digging and a lot of insulated piping.. But we will worry about that in the next year or so. This winter I'll be working on insulating the barn and the oil burner. If I'm lucky I'll be able to play with the heat pump to.

If the house ends up being a 2 ton unit I'll start looking for heat exchangers in the 3 ton size range. That way I can use them for my 1 ton experiments and then use them when I go to the larger unit. The heat pump will be primarily used for cooling and only heating in the spring and fall when it gets cool at night. My main heat source wil e the oils burner. At least that's the plan for now
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Old 06-14-17, 09:02 AM   #26
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FordGuy,

Re putting the heat pump in the barn and piping the hot (or cold) water to the house.

Whoa, whoa . . . .!!!!!!!!

You will loose every advantage of having the high efficiency heat pump. Here is why.

A typical R value for pipe insulation is maybe 3-4. Unless you go 4 feet underground, your winter ground temps will be in the low 30's (in your area) or less. If you pump water at 100 F, then you have a 70 degree differential. Even 4 feet underground, your winter ground temp will likely only be in the 40F range.

Imagine trying to heat a house to 70 F when it is 0 F outside (same 70 degree difference). And imagine just how inneffective an R value in the walls and ceiling of 3-4 R would be! This differential would take about R30 or more to be effective.

Even some 30-40 feet of underground pipe will just result in heating the ground even with R10 insulation.

Put the heat pump in the enclosed house and preferably in the controlled air space.

Lastly, what is the deal with home insurance and the heat pump?


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Old 06-14-17, 11:35 AM   #27
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I was planning spray foam and pex for the run from the barn to the house.. Outdoor wood boiler guys use it very often and usually only have 1-2 degree temp drop.

As far as home insurance goes it's a non ul listed appliance full of propane.. There wasn't an option for that in my policy..
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Old 06-14-17, 02:13 PM   #28
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FordGuy,

The amount of heat a wood boiler puts out is HUGE. And the temp is a lot hotter too. The reason for the small temp drop you quote (1-2 F) is because the wood boiler pipes heat up the ground.

You have a much smaller capacity and temperature with the heat pump.

Now you know, do what you think is best. But you need pipes about 4 feet down.

Lastly, the risk of a propane issue is very, very small. Yes, it is a "risk", but one that many on this forum would not worry about. Remember the very small amount of propane that is in a heat pump - tiny.

Caveat emptor!


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Old 06-14-17, 06:19 PM   #29
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Hmm I suppose that's a valid point.. We shall see what happens.. Either way the test rig will be in the garage. Easy to dig by the garage also. Less sidewalks and plants and things
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Old 06-23-17, 08:16 AM   #30
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So I guess I really need to get in and so some real heat load calculations. Everything is driven off of that lol who knew? But going off of my hypothetical cooling of 24kbtu I've started to look into sizing buffer tanks. I've come up with 75 gallons on the cooling side and 50 gallons for the heating side. The cooling side was based on a minimum of 45 min run time. That way the compressor has time to run like it needs to. Since I have two 12k btu compressors I'm going to try and do a multi stage system. Being both compressors will be tied into the same heat exchangers. This will give me a really cheap system since I already have them and load control. On the not so hot days just one compressor will run and when it gets really hot and humid both can run.

Is 45 min run time long enough? Should I make the run time longer? From what I understand it takes about 10 min for a refrigeration system to get up to full efficiency?

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