The Homemade Heat Pump Manifesto

[AC_Hacker]

Originally Posted by itjstagame

Yes, I think it makes sense to start small and cheap and hard braze it for heat and worry about reversing in a better model.

I think this is the best way to begin... You will learn quite a bit.

Originally Posted by itjstagame

I realize that this won't get me as hot a water as a furnace and not as good a cop as GSHP, but should be good learning.

Yes, even if it is only useful for the 'shoulder seasons' if you DIY, it will pay for itself many times over.

Originally Posted by itjstagame

I'm not sure with ASHP when it's 20F outside and I'm trying to get heat, but if I can stay above 1 cop (including the energy to run my baseboard circulating pump), I should still be saving money and not using natural gas.

A DIY ASHP will have a hard go of it, trying to make heat at 20F. That's when you should switch to gas... And, it doesn't stay 20F for long in Thomaston, CT does it?

Originally Posted by itjstagame

Obviously the hardest part will be the controller, but I think it could be a very cool system in the end.

The WebControl board that Xringer came across should really do the trick. It is cheap and has a lot of features built in. Have you ever done any programming at all?

Originally Posted by itjstagame

When you charged with R290, did you add oil first before charging? I was thinking of trying the R290 route but was wondering what you do about the lack of oil.

If the refrigerant was extracted very slowly, you shouldn't need to add oil. If the refrigerant was extracted quickly it might be likely you'll need to add oil.

Originally Posted by itjstagame

...did you use a small canister, like a mapp gas canister?

Far easier to handle... safer, too.

Originally Posted by itjstagame

I have pressure gauges from working on cars but need to get a vacuum pump first before I can charge anything.

Harbor Freight has some serviceable hobbyist-grade vac pumps for cheap. I have one and I like it just fine. The dual-stage is better than the single. They have good sales from time to time.

-AC_Hacker

[Thumper]

Has anyone fiddled around with marine heat pumps for the DIY geothermal application?

They run at around $1500 for a 16000BTU unit.

Thumper

[Thumper]

There are Flagship Marine units and |Marineair also has some.

Thumper

[Thumper]

They all seem to have co-axial (coil in coil types) of heat exchangers.

[Thumper]

I am currently working on a project for a shared lakehouse and the soil is 35-40 ft of pure sand (we use a sand point for our water year round). Water temp runs at a 48-50 deg F.

[Thumper]

We are considering an open loop system as our water supply is inexhaustible and the soil drainage is excellent for return water.

[Thumper]

Check out these units.

Self Contained Marine Air Conditioning Systems - Prices & Specifications

[MN Renovator]

Those looks like air conditioners only and not heat pumps. The heat output kw is the same as heat input amps*volts. Not bad for an air conditioning setup I suppose but I'd figure water sourced cooling would give better than a 10-12 EER range(based on their amperage draw to BTU ratings). Considering they need to run off of a generator or outlet power when docked, it seems that the benefit is the small size of the unit.

[AC_Hacker]

Originally Posted by Thumper

Has anyone fiddled around with marine heat pumps for the DIY geothermal application?

They run at around $1500 for a 16000BTU unit.

Thumper

This thread aims at building and re-purposing existing units to be functioning heat pumps. With this in mind, these units look somewhat interesting.

Originally Posted by MN Renovator

...The heat output kw is the same as heat input amps*volts...

MN Renovator's comment is not correct.

The web site you pointed us to states this:

With a reverse cycle heating system, a reversing valve reverses the flow of refrigerant, making the condenser an evaporator and the evaporator a condenser. We will outline the benefits of each system for your consideration.

BENEFITS OF REVERSE CYCLE HEAT:

Reverse cycle systems are a more efficient means of producing heat when compared to resistive electric heat.

In domestic applications these systems can save homeowners thousands of dollars/year in electric bills when compared to electric heat...

...additionally, if you look at the performance chart at the bottom of this page you see these specs for the 18,500 BTU system you are interested in:

Output = 18,500 BTU (cooling)
Amps = 16.2 (cooling)
Volts = 115
Amps * Volts = 1863 Watts (this is not exactly correct, but close)
1863 Watts = (1863 x 3.412) = 6357 BTU
COP = (output / input) = (18500 / 6357) = 2.91

So this unit will give you almost 3 times the power advantage, not 1 to 1 as MN Renovator stated.

The same table does not give a value for heat output, but because the heat from the compressor ultimately is part of the output, the COP in heating mode will be higher than the COP for cooling mode.

Curiously the same web site also says this:

Reverse cycle heat will not work with a raw water temperature below about 45-50°F and the compressor is stressed near these temperatures.

It is curious that they would say this, because I heated my basement last winter when the loop field temperature went significantly below 45F... In fact, I was still bringing in heat at 37F, when I finally shut the system down, fearing freezing in the heat exchanger.

So, while a unit like this would be useful. I have seen ready-made commercial units intended for use in terrestrial homes at a lower price, and because space is not such an issue as it would be aboard a boat, the parts are placed such that servicing would be easier.

But in regards to hacking a unit, why would you want to buy one of these systems when you could build one from parts avail from discarded air conditioner and de-humidifiers at a much lower price?

I think the only thing thing that could justify one of these systems is that you can get one for cheap or free.

Another advantage to hacking your own unit is that in addition to saving money, you will learn more and have fun.

And of course, bragging rights come with the territory...

Regards,

-AC_Hacker

[MN Renovator]

"MN Renovator's comment is not correct."

Model FM12R
KW of elec. heat 1.7kw
8.9amps*230v=2047 watts

Are you sure? The numbers don't seem to add up but they aren't putting in the BTUs of heating either but 1700watts of heat output would be 5800BTU. If it produced the same amount of heat as it would cold, it would be a COP of a little over 2 but they aren't claiming that anywhere.