The Homemade Heat Pump Manifesto

[Xringer]

Some Maxim DS18S20 units or thermistors would be an excellent way to know
what's going on down there..

[jroode32]

AC,

Yesterday after a hard day of paintball, I couldn't wait to get home and start playing with my hacked AC, anyway I had left my gauges connected while I was gone and when I got home the gauges showed that I lost a little more gas but still showing over 150-PSI on the HS and 40-PSI on the LS so i fired it up and let it run for about 15 minutes and within a minute or so I saw the magical frost, what got me is as time went on the LS eventually reached 70-PSI and the HS reached 250-PSI, but as soon as I turned it off the LS gauge pegged out at 250-PSI and the HS went down to 150-PSI I used soapy water on all of the connections and when I didn't see any apparent leaks I used just pure dish soap to see if I could find a bubble forming on any of the connections, but nothing happened. This time I used my two temp sensors (they both have probes) to monitor sub-cooling and super-heat and at one point I had a 14 degree difference (as I understand, optimum would be about a 20 degree difference) the air coming from the evaporator coil was reading 52 degrees, everything seemed as if it was working properly so I shut it off and in the now complete silence I heard what sounded like a leak I put my ear up to it and I couldn't tell if it was coming from the gas inside just settling or if it truly was a leak, I waited several minutes and kept listening I finally determined that it was a leak and it was coming from where the HS gauge connected to the HS shrader valve was, so there is a leak and although barely a hissing sound I disconnected the HS gauge and put the cap on the valve, I then noticed the same thing on the LS connection.

I did end up using this gas that only crazy people would use called "Maxi Fridge" that will definitely ignite if it ever saw a 3-9% gas to air ratio and had an ignition source. after putting on my bomb suite and paintball mask for protection I went to town without incident, whew!! close one

Oh btw I have read to page 59 so far so if I do ask a lazy question it's not too lazy, I read all the stuff on sub-cooling and super-heat and man AC you had some nice high res photos on there (thank You!) they helped a lot, I had to chop my pics down a lot to meet the resolution requirements?

My questions today are
1. I'm thinking I need to open the system again and redesign my heat exchanger (condensing side) I realized your heat exchangers are way! better than mine, considering the gas I used how would you go about it safely?

2. I will be upgrading my vacuum pump to the same HF 2 stage that you have as well as getting a yellow jacket micron gauge (because I definitely want to do it right) as soon as the funds become available, but considering how many systems there are out there that are running "good" using the same methods I used how bad or inefficient are they running, really?

3. If I sent you the money via paypal or check or money order could you or would you sell me a set of those fine heat exchangers you have, I would happily pay extra for your time and inconvenience of getting them for me and of course I would send you the money first?

And as always I'm grateful for all your help AC
Thank You!
JRoode32

[AC_Hacker]

Originally Posted by jroode32

AC,

Yesterday after a hard day of paintball, I couldn't wait to get home and start playing with my hacked AC, anyway I had left my gauges connected while I was gone and when I got home the gauges showed that I lost a little more gas but still showing over 150-PSI on the HS and 40-PSI on the LS so i fired it up and let it run for about 15 minutes and within a minute or so I saw the magical frost, what got me is as time went on the LS eventually reached 70-PSI and the HS reached 250-PSI, but as soon as I turned it off the LS gauge pegged out at 250-PSI and the HS went down to 150-PSI I used soapy water on all of the connections and when I didn't see any apparent leaks I used just pure dish soap to see if I could find a bubble forming on any of the connections, but nothing happened. This time I used my two temp sensors (they both have probes) to monitor sub-cooling and super-heat and at one point I had a 14 degree difference (as I understand, optimum would be about a 20 degree difference) the air coming from the evaporator coil was reading 52 degrees, everything seemed as if it was working properly so I shut it off and in the now complete silence I heard what sounded like a leak I put my ear up to it and I couldn't tell if it was coming from the gas inside just settling or if it truly was a leak, I waited several minutes and kept listening I finally determined that it was a leak and it was coming from where the HS gauge connected to the HS shrader valve was, so there is a leak and although barely a hissing sound I disconnected the HS gauge and put the cap on the valve, I then noticed the same thing on the LS connection.

There is a possibility that you have no leak at all...

I don't know what the temperature swings are where you are, but ambient temperature change can make a change in system pressure... not a huge change, but a change.

Originally Posted by jroode32

I did end up using this gas that only crazy people would use called "Maxi Fridge" that will definitely ignite if it ever saw a 3-9% gas to air ratio and had an ignition source. after putting on my bomb suite and paintball mask for protection I went to town without incident, whew!! close one

Stay alert & aware when you are working with hazardous materials... We really don't want to lose any HVAC hackers.

Originally Posted by jroode32

1. I'm thinking I need to open the system again and redesign my heat exchanger (condensing side) I realized your heat exchangers are way! better than mine, considering the gas I used how would you go about it safely?

The rules and regulations applying to releasing refrigerant into the atmosphere are based on the fact that proprietary refrigerant gases are either going to destroy the ozone layer or contribute in a profound and long-lasting way to global warming.

The gas you have in your system is a hydrocarbon gas and has none of the planet destroying characteristics found in the proprietary gases.

Your problem is that the gases are flammable, and heavier than air, so you don't want to release the gas inside a building, or in an area where they might "puddle" (I actually saw this happen). Obviously, you don't want to do this where there might be a spark or flame. and you want to disperse the gas quickly so that it does not reach a critical ignition level.

Also, your gas is mixed into your oil, kind of like fizz gas in pepsi cola. If you release the gas too quickly, you'll lose oil also.

So, I'd set up a fan (with an induction motor) a few meters away, blowing on the unit in question, and release the gas really slowly... if it takes a half hour, that's just fine...

When you're done, you still have gas in your system, and it should be vacuumed down as deep as you can.

* * *

The worse thing you can do is to braze an enclosed system that has a mix of air and hydrocarbon gas... very bad news.

* * *

Originally Posted by jroode32

2. I will be upgrading my vacuum pump to the same HF 2 stage that you have as well as getting a yellow jacket micron gauge (because I definitely want to do it right) as soon as the funds become available, but considering how many systems there are out there that are running "good" using the same methods I used how bad or inefficient are they running, really?

If a really sloppy job of vacuuming down was done and very little water was removed, there can be a situation of intermittent cooling surges, as ice crystals alternately form in the orifice and then melt and then form and then melt, etc.

Otherwise there is the issue of acid formation inside the system which would take longer to manifest, but shortened service life of the equipment would be the result. A properly set up vapor compression system should have a service life of 20 years or more... that's what you are shooting for.

Originally Posted by jroode32

3. If I sent you the money via paypal or check or money order could you or would you sell me a set of those fine heat exchangers you have, I would happily pay extra for your time and inconvenience of getting them for me and of course I would send you the money first?

Here is the place where I got mine from. The DudaDiesel people really are very fast shippers.

Here is the model I should have gotten for my first unit, I wouldn't have had the refrigerant leakage problem that I had. Note that it has brazable fittings on one side and water fittings on the other. I think that this particular model has an actual refrigerant-to-water heat transfer capacity of around 6,000 to 9,000 BTU. I was seeing performance like this when I did tests.

If you write to the DudaDiesel people, they can order any of their standard sizes, with the fittings you desire.

I'm hoping to hear back from Ko_deZ in Norway, he said he found a direct line to a supplier, at a considerable saving.

In the AirSource Heat Pumps Hacks and Mods thread there was a guy named Acuario who had developed a very interesting method of building copper & plastic heat exchangers. He went into a fair amount of detail in describing his efforts.

Regards,

-AC_Hacker

[Xringer]

So, a threaded refrigerant fitting is no-no..
I wonder if anyone makes this kind of exchanger with a flare fitting?

[jroode32]

AC,
I went and looked at the heat exchangers you lead me to and I thought they were priced quite reasonable, I did notice the ratings of up 17,000 Btu/hr. the design pressure was 145-PSI and test pressure was 290-PSI, obviously they are working great for you but I was wondering about it because when I had gotten the unit stabilized the HS was holding steady @ 250-PSI while the LS was a steady 70-PSI they look like very high quality exchangers and I really only need one for my HS since I'm focused on cooling only and am using the original evaporator coil and fan. As far as the heating goes I plan on building a solar air heater and have gathered most of the materials for that project and plan on building it this fall.

I wanted to ask about scroll compressors, I understand they are used in the larger systems but I have read of them being as low as 1 ton, I currently run a 10,000Btu and a 5,200Btu window units and it does a good enough job at keeping most of my (smaller 1,000 Sq') house cool so I was thinking once I get good at all this I would like to find a 1.5 ton scroll compressor, I have read they are the most efficient and very reliable, any Ideas on that?

Xringer, I want to thank you as well for your help, I can't send PM's yet (I'm still a newb)

Thank again you all, you have all been so helpful, I just cant thank you enough!

Best Regards
JRoode32

[AC_Hacker]

Originally Posted by jroode32

AC,
I went and looked at the heat exchangers you lead me to and I thought they were priced quite reasonable, I did notice the ratings of up 17,000 Btu/hr.

I think that 17,000 is much more than you will get if you run refrigerant through that HX. A lot of the brazed plate HXs on ebay are being used for solar or wood-heated boilers, or chilling beer wort. Water has a very high ability to transfer heat, refrigeration gasses are less.

If you want to get a better handle on brazed plate heat transfer, get some brazed plate selection software or selection charts from companies that are making identical or similar products. You'll probably find something that is very close, so give it your best guess... just remember to only use information that pertains to refrigeration. When I looked this stuff over, it mattered which refrigerant you used, but even then the difference was small.

{BTW, Xringer spotted this HX looks pretty good, pretty much perfect if it had sweat fittings on one side.}

You can bet that most of the commercial units use the smallest (cheapest) heat exchangers they can. It wouldn't hurt you to oversize by 20% to 50%.

For starters, try this

Originally Posted by jroode32

the design pressure was 145-PSI and test pressure was 290-PSI, obviously they are working great for you but I was wondering about it because when I had gotten the unit stabilized the HS was holding steady @ 250-PSI while the LS was a steady 70-PSI

Yes, that is definitely a factor. They usually specify working pressure and peak pressure. You should design with the lowest of these, which would be working pressure.

Originally Posted by jroode32

I wanted to ask about scroll compressors, I understand they are used in the larger systems but I have read of them being as low as 1 ton, I currently run a 10,000Btu and a 5,200Btu window units and it does a good enough job at keeping most of my (smaller 1,000 Sq') house cool so I was thinking once I get good at all this I would like to find a 1.5 ton scroll compressor, I have read they are the most efficient and very reliable, any Ideas on that?

I think you are exactly right, and your approach is also very good. Scroll compressors are pretty expensive, though. You might want to look around and try to find out just what the efficiency increase is. I think it is maybe 4% to 6% better... look around, see what you can find out. If everything else was equal, and I had to choose between a scroll compressor and a rotary, I'd choose the scroll compressor. If I had to choose between a used rotary (low miles) for $15 and a new scroll compressor for $250... then the choice is not so easy. Over the service lifetime, the scroll would come out to be less expensive, but I'd really want to be confidant that I had my technical mojo working before I spent that kind of money.

Lastly, I have noticed that pretty much all of the current crop of minisplits are going to 'inverter technology', which means that they convert the line AC to DC, and then run the DC through a circuit that produces variable AC, for controlling the speed of the compressors and fans. This way they can match system performance to demand... very efficient.

It would be totally awsome if someone hacked an inverter technology unit to ground source application. That would be a real super win! What I have in mind would be a conversion from Air-in-air-out to air-in-water-out, for the purpose of heating. In a mild climate like mine, it would be a really good fit. I have seen mini-split outdoor units for sale at about half the price of a whole unit. What's holding me back is the electronics... I don't know how much of a role the inside unit plays in the functioning of the whole system.

There are currently some very high-end units that are being made with this technology. For instance, there's a unit called the Altherma that's very advanced, unfortunately for me, the price is also very advanced.

-AC_Hacker

[jroode32]

AC,

I have been looking at vacuum pumps and micron gauges, I came across this in an ad for a 4CFM Yellow Jacket superevac 2* I have never read anything like this anywhere on the web, I'm assuming it's just marketing trying to get you to buy more stuff. What do you think.

Evacuation Rates & the "CFM Wars": It's true! The capacity of a standard 1/4"ID hose is limited to 3/4 (0.75) CFM. And that's ONLY if you remove the valve core depressors from your hose ends AND Schrader valve cores from the system's high and low side access valves. Thus, evacuating from both high and low sides, you'll max out at approximately 1.5CFM. Standard 1/4" charging hoses are also not designed for vacuum applications, so much as charging & testing. Therefore, please consider and search our eBay store for Yellow Jacket brand PLUS II™ 3/8" & 1/2" Heavy Duty Combination Charging/Vacuum Hoses.

Thank You
JRoode32

[AC_Hacker]

Originally Posted by jroode32

...I'm assuming it's just marketing trying to get you to buy more stuff. What do you think...

Partly true, partly hype...

A lot of professional HVAC work is done on commercial equipment and the capacity of the systems may be very large compared to systems that you and I as experimenters might work on. Since for people in the trade, time is money, and the quicker you can pump down a system and complete the job, the more productive you are. In this scenario, having really good, high capacity equipment is very important. This is where the "CFM wars", and larger diameter tubing, etc. is relevant.

Regarding the hoses, I have heard that regular hose sets can be permeable to molecules in air (not moisture). So if you had good seals on all your fittings and drew a vacuum and left the setup overnight you might see a small drop in vacuum, even if the ambient temperature was the same... but the loss of vacuum would be small.

I was advised by my HVAC mentor (who has decades of experience in the industry), that because of this, some folks use a copper line for their center hose, with 1/4" flare fittings on both ends because it's a lot cheaper than high quality vacuum hose.

* * *

BTW#1, Since you are in the process of HX selection, I assume you read the section in the manifesto where I went through the steps involve in selecting a HX that matches the capacity of your compressor, right?

BTW#2, I sent an email to Dudadiesel to see if they can order sweat fittings on any of their HXs... not heard back yet.

Regards,

-AC_Hacker

[jroode32]

AC,

Yes I read your HX selection stuff I believe it was page 50 of the thread, anyway I have been brainstorming and brainstorming and all the sudden it hit me (you know those moments any DIY "scientist" has) a couple years ago I built a very nice foundry (I say that because for my first one it turned out great and I have done several successful melts in it) I also built a nice used car oil burning torch and have named the system BIG Bertha. I will post pics here in a minute (I need to go take some real quick, and I really wanted to get to 15 posts so I can reply to a couple of PM's I've received My thinking is this, I have tons of aluminum scrap (well over a 1,000LBs) I have been saving for years and with it I plan on making my own custom heat exchangers.
The "plan" after looking at what you have and reading about them on the ebay site you referred me to I thought I can make that. I know my design won't be as efficient as the ones you have but for just a few bucks I could fire up BIG Bertha and do some casting of my own. Now mine will definitely not be a series of plates but I think I have a plan to compensate for some of the high efficiency the plates (and added surface area) give you.
What if I poured a slightly bigger "block" of aluminum but in side of it I had "U" shaped copper tubing which protruded for connection points, since most metals are fairly good thermal conductors I was thinking I could use one "U" for the refrigerant and have it in the center of the aluminum block with the two ends protruding for connection points and then have from 2-4 more copper lines, 1-2 on each side of the center refrigerant line for the water from the GSL to run through and then tie them together just outside the aluminum block.
I have a picture of this in my head and I just tried to explain it, that is sometimes hard to do I hope you all see what I'm seeing I think by dividing the water flow from the GSL to flow close to but on the outsides of the refrigerant line it should extract the heat fairly well and since it will be outside (maybe outside, depending on the efficiency) I could cut some fancy grooves in the block to give it a small increase in surface to air ratio to maybe get a little air cooling assistance.
I thought about using brass for the water lines but since the two metals won't be fusing together due to there different melting temps it would be possible to have a leak within "the block" and since copper is easy to sweat a "line" with no connections inside the block seems like a better option. I can just sweat the low pressure water connections on the outside of the block, also the pressure rating should be as high as the weakest link which should be the refrigeration grade copper tubing rating and actually be stronger inside the block.
Let me know your thoughts???

Thank you all so much, I'm really loving this forum and this thread in particular, AC you have been a great help and I am grateful.

JRoode32

[AC_Hacker]

Originally Posted by jroode32

...all the sudden it hit me (you know those moments any DIY "scientist" has)...

Good luck with the HX!

Take lots of photos.

-AC_Hacker