Heat Pump Water Heater - Coil in Tube

vwhead77 · 10-05-14, 11:13 AM

So here's what I have so far. A copeland scroll compressor 115V (hopefully find 208v eventually). Made a coil of 20' of 3/8" soft copper by winding around a 2" PVC pipe. Inserted into a 4" PVC tube - capped sealed and ready to pipe in high side compressor. pic:

NiHaoMike · 10-05-14, 12:25 PM

A pretty small 5000BTU/hr compressor will probably be plenty if it's only for DHW.

Mikesolar · 10-05-14, 03:50 PM

Quote:

Originally Posted by vwhead77

So here's what I have so far. A copeland scroll compressor 115V (hopefully find 208v eventually). Made a coil of 20' of 3/8" soft copper by winding around a 2" PVC pipe. Inserted into a 4" PVC tube - capped sealed and ready to pipe in high side compressor. pic:

Ummm, how did you seal around the 3/8 tubing?

vwhead77 · 10-06-14, 07:59 AM

Sealed using a high temp automotive epoxy - 600 deg.tolerance.

Mikesolar · 10-06-14, 08:02 AM

Just wondering about dissimilar materials and the liquid pressure. I guess we will see.

berniebenz · 10-06-14, 10:28 AM

Could be improved. Will have poor heat transfer because of very low water velocity in contact with cu tube. Water will flow straight thru the center.

jeff5may · 10-06-14, 01:14 PM

That is known as a "high density" exchanger and if you mount it vertically it may not need a water pump. If you run a pump the water is going to need to do multiple passes to get hot.

Now, on to the hard part: the refrigerant circuit!

I'm riveted and wish you the best of luck.

Mikesolar · 10-06-14, 05:34 PM

Quote:

Originally Posted by jeff5may

That is known as a "high density" exchanger and if you mount it vertically it may not need a water pump. If you run a pump the water is going to need to do multiple passes to get hot.

It is the same as the thermosyphon HX I was talking about in another thread. I will work fine.

AC_Hacker · 10-07-14, 02:40 AM

Quote:

Originally Posted by Mikesolar

It is the same as the thermosyphon HX I was talking about in another thread. I will work fine.

Acquario did a very similar HX for heating a swimming pool.

Here is how he did his coils:

...abd here is how he implemented his plastic shell:

He ended up modifying his basic design a bit. Yours may work right the first time.

Good luck!

-AC

Mikesolar · 10-07-14, 06:22 AM

Quote:

Originally Posted by berniebenz

Could be improved. Will have poor heat transfer because of very low water velocity in contact with cu tube. Water will flow straight thru the center.

It is a "tube in shell" (official term, if there is such a thing). Assuming it is placed vertically at the bottom of the tank, it will heat the body of liquid within it which will simply rise to the top of the tank, drawing from the bottom. No pump necessary.

10-05-14, 11:13 AM	#1
vwhead77 Helper EcoRenovator Join Date: Jan 2013 Location: Watkins Glen, NY Posts: 48 Thanks: 19 Thanked 5 Times in 5 Posts	Heat Pump Water Heater - Coil in Tube So here's what I have so far. A copeland scroll compressor 115V (hopefully find 208v eventually). Made a coil of 20' of 3/8" soft copper by winding around a 2" PVC pipe. Inserted into a 4" PVC tube - capped sealed and ready to pipe in high side compressor. pic: Attached Thumbnails Last edited by Daox; 10-06-14 at 11:28 AM..

10-05-14, 12:25 PM	#2
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	A pretty small 5000BTU/hr compressor will probably be plenty if it's only for DHW. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

10-06-14, 01:14 PM	#7
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	That is known as a "high density" exchanger and if you mount it vertically it may not need a water pump. If you run a pump the water is going to need to do multiple passes to get hot. Now, on to the hard part: the refrigerant circuit! I'm riveted and wish you the best of luck. Last edited by jeff5may; 10-06-14 at 08:41 PM..

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10-06-14, 07:59 AM	#4
vwhead77 Helper EcoRenovator Join Date: Jan 2013 Location: Watkins Glen, NY Posts: 48 Thanks: 19 Thanked 5 Times in 5 Posts	Sealed using a high temp automotive epoxy - 600 deg.tolerance.

10-06-14, 08:02 AM	#5
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	Just wondering about dissimilar materials and the liquid pressure. I guess we will see.

10-06-14, 10:28 AM	#6
berniebenz Helper EcoRenovator Join Date: Apr 2012 Location: Gardnerville, NV Posts: 66 Thanks: 0 Thanked 3 Times in 3 Posts	Could be improved. Will have poor heat transfer because of very low water velocity in contact with cu tube. Water will flow straight thru the center.