Heat Pump Water Heater - Coil in Tube

[vwhead77]

Ok - second experiment - external coil / discharge from HP - (it's actually a lot more wraps than the internal coil) I managed to wrap 30' of 1/4" copper around a 2" copper pipe. I'm going to insert it into a 4" PVC jacket and fill it with 'fire rated' foam insulation. I'm thinking that a smaller water tube diameter with flow metered by ball valves, will actually give me a decent HX rate. I will have to transition from 2" to 3/4" and use my installed unions (previous pics) to interchange all these gizmos I'm making - (hey I'm semi-retired so I get to play with stuff).

Update : 10/30/14 - INstalled the hp water heater with the coil wrapped around the outside of a 2" pipe/insulated/ and throttled with BVs. Using R209, I have managed a 20 degree differential across the jacket at 4.5 amps. My electric 208V only gets 10 degrees at 12 /14 amps. Definitely gaining ground - my only issue now is the best placement for the outlet side. so far so good

[Mikesolar]

Try it out but you won't need to reduce anything. It needs very low resistance and the flow rate is self limiting so no need to restrict it.

BTW, I assume you are a VW nut (?). Check out my avatar. Very few in North America.

[vwhead77]

Thanks for the input - and yes, I have had over 60 VWs in my 55 years- including '72 Ghia 'Vert, '68 Ghia 'Vert, 2X'67 Vans, 2 Synchros, 1 Thing, 1 Fastback, 3 Squarebacks, a few Bugs (oldest was 63) , a few Rabbits, a few Jettas, two diesel pick-ups, a couple of Golfs - etc. - Plus, I used to find them for cheap- fix 'em up, drive them a while and then sell them. I love your Pick up man - had ONE chance to buy one and the guy backed out - I'm jealous

[jeff5may]

Why insulate the center? The copper pipe will have a positive effect on the heat transfer. If you want to restrict the flow, just stuff the pipe with copper or stainless steel pot scrubbers.

[Mikesolar]

The pipe needs to be somewhat clear bottom to top. LOW RESISTANCE to natural flow. It won't go fast anyway.

The LT is beast of a truck. Full 8'+ x almost 6' wide bed. It is now getting the a M-TDi from an 02 Jetta in it and then turned into a plug in hybrid.

[vwhead77]

I'm insulating the PVC 'jacket'- the HW is still in the 2" pipe with the discharge from the compressor on the outside - but I like the advice about restricting the flow with SS

[vwhead77]

Originally Posted by Mikesolar

The pipe needs to be somewhat clear bottom to top. LOW RESISTANCE to natural flow. It won't go fast anyway.

The LT is beast of a truck. Full 8'+ x almost 6' wide bed. It is now getting the a M-TDi from an 02 Jetta in it and then turned into a plug in hybrid.

OOhhhhh...I'm really jealous
now .. man .. thas so cool

[Ron342]

First congratulations!
I'm dying to know how you did such nicely wound coils!
I tried salt filled 3/8 copper around the outside of 1 1/2 copper but had only marginal luck with it.
Nice thing about that 2" copper is that you can run some 3/4 copper up the center of it and connect it to a solar panel if you want to expand this to a 2 heat source system.

[simenad]

what if you tapped into a nearby refrigerator. it would make the fridge much more efficient and direct the heat that would be released into the house into helping heat domestic hot water.

[theoldwizard1]

Originally Posted by stevehull

I am concerned about the material used to plug the holes where the copper tubing comes out. Time will tell.

I agree. I have never had good luck with epoxies long term, especially in warm environments. Perhaps I have not used the correct one.

What you need is a "bulkhead" type fitting. The only kind I have seen are for flared copper (not sure if they are rated for R410A pressure) and usually they "assume" that you have a flat (or at least somewhat flexible) wall that you are going through.