The Homemade Heat Pump Manifesto

[Xringer]

Originally Posted by AC_Hacker

Seth,

The problem is that the leak is really small, about 2% a day, so I'm afraid I'll need to use extreme methods.

Regards,

-AC_Hacker

It's common to use a plastic tube held up to the ear or a stethoscope with an open tube on the end to listen for hissing leaks.

Maybe a small microphone on a stick, plugged into a amplified headset would work too..

Or, maybe some FJC (FJC4910) Universal A/C Fluorescnet Leak Detection Dye - 1 oz.

[Jay-Cee]

North Pole Guy,

It is interesting that you mention Warm Board. I have never used it nor do I personally know anyone who has. I did have a discussion about it with a friend of mine who works for a lumber wholesaler. He said he has not sold any of it, but is aware that the price is steep. Somewhere around $180 a sheet! I did some searching about it awhile back and there is a forum that has gotten plenty of feedback regarding that product, none of which is very positive.

contractortalk.com/f11/warmboard-radiant-heat-48360/

[North_Pole_Guy]

AC_Hacker,
I have a kit similar to this that I have had good luck with. Inject a little dye, let the system run for a while then look with the UV light and tinted glasses, the leak stands out pretty good.
.google.com/products/catalog?q=a+c+leak+detection+kits&oe=utf-8&rls=org.mozilla:en-USfficial&client=firefox-a&um=1&ie=UTF-8&cid=17138758188705153578&ei=_R4UTf3EM4H-8AaB4Mj-DQ&sa=X&oi=product_catalog_result&ct=result&resnum =3&ved=0CDkQ8wIwAg#

[North_Pole_Guy]

Jay-Cee,
Well that is not good news about the warm board, I know one guy that said he used it on a house in Anchorage that he built to sell so no feed back on that install.
I believe that it is like 1 1/8" plywood base so it should make one heck of a solid floor.
well I will have to read that link you sent.

I am guessing a guy could compare the price of that against one of the home built ideas and see how the numbers work out. Just some quick math, if my house is 1,800 sq feet and each sheet is 32 sq feet that equals about 56 sheets at $180/sheet equals $10,000 just in flooring.....wow
I am sure you could easily add 25% for shipping to my location also

[RobertSmalls]

Originally Posted by North_Pole_Guy

AC_Hacker,
I have a kit similar to this that I have had good luck with. Inject a little dye, let the system run for a while then look with the UV light and tinted glasses, the leak stands out pretty good.
.google.com/products/catalog?q=a+c+leak+detection+kits&oe=utf-8&rls=org.mozilla:en-USfficial&client=firefox-a&um=1&ie=UTF-8&cid=17138758188705153578&ei=_R4UTf3EM4H-8AaB4Mj-DQ&sa=X&oi=product_catalog_result&ct=result&resnum =3&ved=0CDkQ8wIwAg#

Tracerline TP8621 Complete A/C and Fluid Leak Detection Starter Kit

One of the privileges of a high post count is permission to post links.

Kits like this are available at any auto parts store, in the air conditioning aisle.

North Pole Guy, I'm curious. What is your location, and where is "the interior"? Maybe you should make an Introduction thread.

[North_Pole_Guy]

Robert,
Introduction post has been made, look forward to answering any of your questions
joe

[AC_Hacker]

Originally Posted by North_Pole_Guy

Part of the idea of adding the insulation on the outside to to build a continuous pure insulation to provide 100% free thermal bridging.

Excellent! Just wanted to make sure.

Originally Posted by North_Pole_Guy

AC_Hacker
I will try to insert a picture of my donor de-humidifier below, it has the capillary tube split into two parallel runs instead of one capillary tube coiled up...

Well, this is a very interesting set-up...

If it were me, I'd keep the cap tubes as they are. I'd exploit the fact that you have split cap tubes, and use two separate heat exchangers as evaporators...if you follow your evaporators tubes down to the end, you'll likely come across a "Y" that you can use when you make the tubing to re-join the refrigerant line after the two evaporators. The brazed plate exchanger prices are roughly based on the number of plates, so the cost to you would be about the same, and I think that you'll pick up some extra efficiency.

I had an interesting email conversation with a fellow homemade heat pump geek, and he reminded me that when sizing heat exchangers (AKA: HX), the condenser size needs be able to move the heat from the evaporator, and still be big enough to move the waste heat from the compressor (it needs to go somewhere).

So with this in mind, lets say you're going for a COP of 4 (not unrealistic), you'd start with the size of your compressor, for instance 1000 BTU/hr. Then you'd size your evaporator HX to be at least 3000 BTU/hr. Then you'd size your condenser HX to be at least 3000 BTU/hr + 1000 BTU/hr = 4000 BTU/hr.

So, when you figure your COP:

COP = energy out / energy in = 4000 BTU/hr / 1000 BTU/hr = 4

So then you start searching ebay for HX possibilities.

So, to size your heat exchangers, if you use brazed plate, here is the formula I cobbled together, after spending many hours pouring over many many pages of brazed plate data:

Heat (in BTU/hr) = ((width) x (length) x (# of plates - 2)) x 5000

...where width & length are expressed in feet.

When I put this formula together, I was focusing on R-22 (which is close to R-22a and R-290). If you're going with R134a, make your exchangers 15% to 20% larger.

... you will not likely find an exchanger that is exactly the right size, so look for the size larger.

I'd probably look for something something around 50% larger, if it were me.

You never did say what kind of refrigerant your donor system is using?

* * *

You said that you wanted to use the heat pump to keep your chicken house warmed... Just a thought, but you could pump some warm (but not too warm!) water through concrete pads that were underneath the nesting area.

What do you think?

* * *

By the way, I came across a heat exchanger jacket on ebay, but it would be just too easy to make one... so why haven' I done it yet!!

Regards,

-AC_Hacker

[North_Pole_Guy]

AC,
I like the idea of two exchangers have to look at that and see if there is enough capillary to reach two exchangers mounted.
I am attaching a picture of the data plate off the donor unit, looks like R-12 for refrigerant. How would I tell how big this unit is? In other words how many BTU's?
I tried to google the model number and came up with nothing.

The fine details don't need to be exact, I am just interested in the mechanics of making a working proto-type unit. After making something work I can further the details to make a larger unit.

About the chicken house yes that would be cool to pour a pad with tubing in it. I thought about an open source GSHP, right out in from of their current house is a pond. the discharge water could serve two purposes, one to provide medium for the heat exchanger and second to provide fresh water through a trough that could discharge into the pond.

I keep getting hung up on the cost of moving the water, even if a guy was to use a low draw pump like what is used for circulating water in a heating system. the lift is not that much like eight feet maybe so a small pump should be able to move the water especially with low back pressure of just the short run of piping and heat exchangers.

[AC_Hacker]

Originally Posted by North_Pole_Guy

AC, I like the idea of two exchangers have to look at that and see if there is enough capillary to reach two exchangers mounted.

Try to not cut the cap tubes, since they are already the right length and diameter for R-12, instead, cut the larger copper tubes that the cap tubes are brazed onto. There's a lot of science that has already gone into the cap tube, so make it easy on yourself and keep the same or compatible refrigerant and compressor and associated cap tube.

R-12, huh? That refrigerant was the first one to go because it was such a powerful damager to the ozone. If you really trust your homemade freezer compressor > vacuum pump, you can probably use it to salvage and reuse your R-12.

The procedure would be

• arrange some tubing & valves so that you could connect to your storage bottle (I use old camping-size propane bottles, which I have pumped out to low-microns), then pump it and the connecting-line down.
• Next, find a good location for your piercing valve. I like to put mine on a high point, so I won't loose too much lubricant.
• Then connect your vac pump to the piercing valve
• pump your connecting line down,
• Then connect your still-vacuumized storage bottle to the output of your compressor.
• At this point, you will want your vacuum bottle to be as cold as possible. I do this stuff in the basement where my freezer is, so I put my storage bottle in the freezer for a while to get cold, and I leave it there until the transfer is complete.
• turn on your vacuum pump and very SLOWLY open your piercing valve (if you open it too quickly, you'll get too much lubricant out with your refrigerant).

I'm typing this in a noisy cafe, and I can hardly think, but that is the general outline. If you need a drawing of the valves, etc. to make it all work out, let me know.

The general idea is that you want your bottle and lines vacuumed down before you release refrigerant into them.

So R-12 is a different breed of cat than R-22 and R134a and R410a, etc.

I think the closest organic equivalent is Iso-Butane, which, along with Propane, is very dangerous to work with, especially so in an enclosed space.

The Enviro Safe outfit has an R-12 equivalent refrigerant, called ES-12a. This may actually be IsoButane, I dont' know, I haven't used it.

I would guess that the R-12 / ES-12a / Iso-Butane setup would get considerably colder than R-22 / R-22a / R-290 setup.

Originally Posted by North_Pole_Guy

I am attaching a picture of the data plate off the donor unit, looks like R-12 for refrigerant. How would I tell how big this unit is? In other words how many BTU's?

(* I didn't see an attachment... but if you can find a model number on the plate, you could google that and find out. *)

If no model number, if you have a Kill-a-Watt, you could plug in the de-humidifier, look at the initial watts reading (the watt readung climbs the longer the compressor is running), double that and multiply by 3.412.

For instance, my compressor pulls about 225 watts at power-up. Doubling that gives me 450 (which is pretty close to the rated watts), multiplying that by 3.412 gives me 1535.4 BTU/hr, which is pretty close to the rated output.

[EDITED NOTE: I looked up similar Dayton models, they no longer make a 37 Pt per day, but they do make a 30 pint(495 watts) , and a 50 pint (650 watts), so I would guess yours is about 550 watt (550 x 3.1412 = 1727.66 BTU/hr)]

If you're considering doing an open loop HP system, you may have some trouble with brazed-plate HX. The reason being that the passage ways are a bit small and particles could eventually block them up. I think tube-in-tube or tube-in-shell HX offer less chance of fouling.

Using PEX or polyethylene loops in your pond would cost you a little efficiency, but would eliminate the fouling problem.

If the R-12 issues are stopping your progress, I have noticed that lots of R134a units are beginning to drift into the used market.

Best Regards,

-AC_Hacker

[North_Pole_Guy]

AC,
The top cover says 37 pints cap. I have plugged it into a kill a watt and am getting a pretty steady 320watts X 2 X 3.412 gives me 2,183.68 BTU's/hr.
This is without the condensor fan running, I pulled the wire off for testing.
There is a low side tap on the unit as you were saying it must be pretty old, before walmart and the shaving of pennies off each device to make a few more dollars off us all.

I have two more window units and see them on craigslist fairly regularly. I think I would like to at least try to recover the refrigerant with a setup like what you showed. I have a friend that does heat and vent work for a living if I get into a bind I imagine that I could get him to help. There is no magic involved in any of this work just fancy math (I am not good at) and wanting to play with something to see what you can make happen. So I looked on granger.com last night and see you can buy all kinds of refrigerant (with proper paperwork) but no R12.