The Homemade Heat Pump Manifesto

[randen]

A/C hacker

I did take into account the vibration. The HX themselves float in foam and the small 3/8 line has a liberal amount to flex. The one of small concern is the 3/4 Dia tube off the side of the compressor. The vibration has a lot of mass in the shear length of tube to be dampened. I used some styrofoam to support the spiral HX to clean it up. Next a cover, utilizing a stainless drum from a washing machine. I'll get some more photos soon.

Thanks Randen

[Geo NR Gee]

AC how old are you??? Your'e dating yourself.

[AC_Hacker]

Originally Posted by Geo NR Gee

AC how old are you??? Your'e dating yourself.

I never said I got it new!

On the other hand, I have a 'newer' refrigerator that was built in the 1930's (didn't get it new either) that still runs!

It's just like this one...

...you don't find many refrigerators made today that will last almost 80 years.

And because of the incredibly thick insulation, it consumes about as much power as a modern energy star refrigerator, of similar size.

The later refrigerators, the 'Round Tops' were the real energy hogs.

That's when electricity was essentially subsidized, to get more people to use it, so power costs were not seen to be such a problem.

-AC_Hacker

[AC_Hacker]

Originally Posted by randen

Next a cover, utilizing a stainless drum from a washing machine. I'll get some more photos soon.

This, I gotta see!

I really like your approach, I really do... re-purposing plus style... that's the way to do it.

-AC_Hacker

[sparkchaser]

Hmm, that just got me thinking! I'll have to look into that down hole hammer thing. And the Harbor Freight tool.... Then there's the air compressor required to run one of those- it would require pretty significant CFM. I have seen several air compressors built from car engines- one was a ford v8 with one head replaced so 4 cylinders power, other 4 cylinders compressor, and there is a kit available for a VW air-colled engine where 2 heads are replaced. The v8 I used for a 100 Lb jack hammer, and the other one was being used for a tire field service truck. I don't think it would be terribly hard to build your own high volume air compressor for the job... I am sure they typical home air compressor is not up to the task however...

[randen]

AC hacker

Can you check my calculations. The compressor running for about 30 min producing stable pressures is drawing 6.02A at 212 V ac. The heating out-put is 18,000 BTUs/H I get 4.391 COP Using 1kw= 3412. Is this right??

BTU/H 25 F deg rise in 15 min 180 Lbs of water = 4500/15 min = 18000BTU/Hr

Thanks Randen

[AC_Hacker]

Originally Posted by randen

I get 4.391 COP Using 1kw= 3412. Is this right??

You seem surprised?

Power conversion is kind of a problem for me, so whenever possible, I use a power meter that I feel reasonably sure can read in true RMS, power factor being what it is. But I'd say that you're very close to what you'd get with a proper meter.

However, to really get the full picture, you need to include pump power consumed and fan power consumed... I assume you're going to use a fan. Also, there will be some loss due to your water-to-air heat exchanger.

But for what you're measuring right now, it sounds like you're right on the money.

This is really pretty exciting isn't it, that it is possible to use junk that is on it's way to the scrap heap and get such good performance.

(* propane helps too *)

You have earned bragging rights!

Regards,

-AC_Hacker

P.S: I know that is was not in the scope of your plan, but if you had a radiant floor, optimized for Heat Pump radiant heating (I'm sure you've seen my many rants on that), you would push your COP higher, because you would be able to keep your heat pump's heating water-out temperature lower.

* * *

[randen]

A/C Hacker

The meter was a pretty good one and I would trust its close. The only down side I see is in my testing. The one 20 gal pail is loosing heat while the other is going up. As the one pails temp drops from say 17 Deg C to 2 Deg C The effiency also drops. If the GSHP has a steady supply of of constant loop water temp, wow. As far as the shop, the office area (600 sq ft) already has infloor heat and the shop area may get it next (next summer). For now I have the air handler. I hope it can keep up.
The two Grundfos circ. pumps are rated at 85 watts ea and the air handler is 5.6 A 120 V however it will be used at its lowest speed maybe 3 amp (360W) I'm not sure if the comercial GSHP include the circ. pumps usage in their calculations. If the system runs 24/7 the cost of electricity will be a joke compared to the cost of furnace oil.

So far the buget is: excavating $1900.00 HDPE tubing $750.00 tube welding $200.00 circ pumps (Ebay) with shipping $160.00 Components for heat-pump $300.00 Componets for installation approx $300.00 Total $3610.00 Projected cost of furnace oil for the winter 2.5 tanks @ about $1000.00 per fill $2500.00 maybe $3000.00 if its really cold.

Based on the preliminary figures GSHP operation 1.2 Kw/h x 24 hrs x 30 days. $130.00 for the cost of electricity if it runs 24/7 per month NOT BAD.!!



Randen

I'm glad to see my hording has paid off.

[AC_Hacker]

Originally Posted by randen

The only down side I see is in my testing. The one 20 gal pail is loosing heat while the other is going up. As the one pails temp drops from say 17 Deg C to 2 Deg C The effiency also drops. If the GSHP has a steady supply of of constant loop water temp, wow.

You are quite right with respect to temps and efficiency. The key measure is Delta-T, the difference between your loop temp in and your hot water temp out.

But the loop temp will drop, but since you have so many tons of heat holding earth, the drop will be very much slower.

There are two kinds of loop temp drop to keep your eye on...

• One is seasonal drop, so you will see a drop in the winter heating season, and then a return to the beginning temp during the summer, as sunshine gradually warms the earth.
• The other is a long term drop, that may be in tenths of a degree per year, if your ground mass doesn't completely recover it's heat-store during the summer.

You should carefully monitor your loop temp at the beginning of each heating season, with the same high quality instrument. If you see a long term decline, you may want to use the ground loop with your heat pump for summer cooling. This would put heat back into the ground, and give you cheaper A/C at the same time.

Some folks are also using solar panels to warm the earth during the summer months.

But you may not have to fiddle with solar panels at all.

* * *

As an aside, one of the things I found interesting is that because the efficiency of my heat pump was based on ground temp, seeing the relationship has given me what I call "ground consciousness"... something I just never thought about before.

Originally Posted by randen

I'm glad to see my hording has paid off.

Maybe some TV channel will do a show called, "My Hording Paid Off", with you in the pilot episode.

Great going,

-AC_Hacker

[AC_Hacker]

Originally Posted by randen

The heat-exchangers are home made copper shell and tube... The total cost was about $300.00 for fittings and tube insulation. ...The coils of copper where donations from a friend cleaning out the garage. Condensor is 3/8 tube surrounded by 7/8 tube about 25ft Lg while the evaporator is 5/8 tube surrounded by 1" PVC tube used for hot tubs. The counter flow shell & tube exchangers work very well. Refrigerant temps leaving the exchangers are only 2-3 deg. of the exitting glycol. The refrigerant used is propane and seems to work well. The pressures are comparitively lower than the R22.

randen,

This is very useful information for other folks who might be put off by the cost of Brazed Plate or other commercially made heat exchangers. Being able to DIY heat exchangers opens up a lot of possibilities.

So, as I gather from what you said, you made two heat exchangers, one was 3/8" copper tube inside 7/8" copper tube by 25 feet long (refrigerant inside water, right?), and the other was 5/8" copper inside 1" PVC. In both cases, they were counterflow.

It would be helpful if we also knew:

• what the BTU rating of your compressor was?
• what is the water flow rate in each loop?
• how long the copper/PVC HX was?
• what was the temp of water in and out of each HX?
• what was the temp of refrigerant in and out of each HX?
• what do the details of the ends of each HX look like? In other words, how do you take the water from the HX and how do you take the refrigerant from the HX?

If we had enough examples of homemade HX performance, then we could begin to build them with more confidence.

So any additional information you can share will be very valuable for future builders.

Thanks,

-AC_Hacker