The Homemade Heat Pump Manifesto - Page 193

AC_Hacker · 08-01-16, 11:11 AM

Quote:

Originally Posted by jdom

Hi AC_Hacker, I have been reading your awesome thread ....my heat-pump, which was mostly inspired by what you have accomplished.

Jdom,

Welcome aboard!

I'dd have to say I'm inspired by what you are doing!

Since you read the thread, you know how much help it can be for us when we have as many diagrams, photos, etc. so we can visualize and offer useful help.

Sounds like you are asking specifically for expertise on charging, superheat and subcool.

EcoRenovator member jeff5may has demonstrated the best understanding of precisely the problem you are facing. He has been able to give real, practical guidance to others who were wrestling with exactly your problem. I'm sure he will join the discussion soon...

Best,

-AC_Hacker

jeff5may · 08-02-16, 09:42 AM

Sorry I haven't been lurking or posting as much as usual lately. The flood gates have opened at work, and I'm on a 7 day schedule. Last day off was the 4th of July, next day off will be Labor Day. Good for the wallet, not so good for hobbies. Projects are deadlocked and just keep piling up...

Jdom,

That rig you have built looks like it should dominate and save you money on your power bills. Using the thing just like it is should work well for either heating or cooling. Setting your system charge should be done at high condenser temperature conditions. If you don't want to mess with cap tube length, make sure you have at least a few degrees of subcooling, and that the evaporator is not flooding.

I have a question: what is the silver bell-shaped thing in parallel with the cap tube? I'm envisioning it being a CPEV. If so, it can prevent freezing your evaporator BPHE, but you will need a suction line (slobber box) accumulator to keep from flooding your compressor.

Your 270V compressor should run just fine off 240V line current, but starting torque will be somewhat limited. A 2 or 3 minute short cycle timer box should be used to let pressure equalized between run cycles. That way, you won't have problems with the compressor stalling and drawing LRA current due to insufficient starting torque. In any case, a hard start kit will smooth the starting spike and provide a big jolt to kickstart the compressor if you need it.

As for reversing the cycle, I myself would accomplish this on the water side of the two heat exchangers, rather than reversing the flow of refrigerant. Those HX's run much more efficiently, with higher delta T, when they are plumbed in counterflow. Reversing the refrigerant flow means that unless you also reverse the water flow, the unit will run less efficiently in one mode than the other. Also, reversing the water flow requires less robust methods and components.

Whatever you do, make certain the evaporator HX can never freeze! Brazed plate HX's are very intolerant of Freezing conditions: they will split open like a tuna can in no time and spew their contents. Be sure to use antifreeze, and include some sort of frost sensing thermostat with flow sensing and compressor cutout control to eliminate all doubt. Other ecorenovators have been unpleasantly surprised by this event.

jdom · 08-02-16, 01:42 PM

Thanks AC_Hacker and jeff5may for this great info.

I know the feeling of working nonstop and no time for hobbies... with house remodel and my day job, I am pretty much working non-stop 16 hour days. Only time I have to play is when I put something else on hold...

The compressor is actually not a 270v hotel unit but from a large residential window unit that the fan motor went out on. I haven't been using the hotel unit compressors for anything, right now I have 18 of them, different makes and models but all around 12k btu. Each unit yields about 1.5lbs of r22. Hate to say it but they will all probably end up at the scrap yard.

To be completely honest, I don't know what the "bell shaped thing" is called. Maybe an AEV (see picture)? It came from an older hotel unit. The label has completely faded to white because it sat in the sun for a year in my backyard before I reclaimed the refrigerant and started stealing its parts. This was the only unit with such a device and when I tested it the unit, I noticed how it kept the low pressure right around 57 psi. Turn it out and the pressure would drop to 50 psi or less and turn it in and it would raise to 60+ psi (or vice versa…can’t remember? ). I kind of took a chance at using it because I didn't want to only use CAP tube without knowing how this unit was react and didn't want spend a bunch of money on this thing until I proven it can work.

Here is what I noticed at first with it being with water HX instead of air. If the HIGH side HX water is "cold", below 60 degrees F or gauge reads less than 100 psi, the low side will drop below 50 psi. At first I shut the unit down when this happened because I didn't want to break my new toy, and even though the HX looks cool, I don't really need a $135 paper weight. After gathering my thought, I plugged it back in and adjusted the bell shaped valve so the LOW side was just above 57 psi. It wasn't freezing at this point because the dew droplets on the copper were not frozen. As the high HX temp rises the CAP tube is forced to send more refrigerant and bell shaped valve seems to do less work. At around 250 psi on the High side the low side has risen to over 60 psi. I see the danfoss units use an electronic expansion valve (see picture)

I need to get my raspberry pi setup to get some real numbers here. So I can determine what is actually going on.

There also seems to be a discrepancy with the numbers the turbonics people have on the PDF and the temps I’m seeing.

They say: at 45f in water temp. Exiting air temp should be 52.9f. They also don’t list entering air temp. There unit has 4 4” duct ports, I modified mine.

I get: at 34f in water temp. Exiting air temp is around 65f. My entering air temp is around 75f and my return water temp is 50f. I modified my unit giving it 2 6” duct ports instead of the 4 4”. Although it seems to be able to cool the 2 rooms it is connected to, it takes quite a while to do so… and that’s not even close to the numbers they have.

I was planning on running my second unit off the same heat pump which I think I can because the low side HX has no problem keeping up with the 1. The problem will be, what to do with all the heat?

I’ll do some more testing tonight after work. It’s supposed to be 96f today.

as far as reversing valves go. I have 5 of them, I was thinking, could use 2 of them, swapping all 4 ports on the HXers. Wouldn't need a fancy reversing expansion valve either. Just a thought, got all these parts and I'm dying to use them!!!

jeff5may · 08-03-16, 12:15 AM

Yep, that's a CPEV aka flow-rator valve. Just like a TXV without a sensing bulb. It works just like an air compressor regulator. Plumbed in parallel with a cap tube, it will set the low pressure limit on the evaporator and try to maintain that low pressure. Eventually, the cap tube will pass enough mass to fully close the CPEV and cause low side pressure to rise.

AC_Hacker · 09-26-16, 01:06 PM

The Homemade Heat Pump Manifesto has just passed the one million page-views milestone!

Never in my wildest dreams did I think that there would be this much interest in converting discarded air conditioners, de-humidifiers, and refrigerators into other useful and amazingly efficient devices.

My initial hope was that possibly 4,000 hits would be very satisfying to me. Little did I know!

Readers of the ‘Manifesto’ will remember that the reason I started this on-line project thread, was that HVAC Trade groups, that are on the Internet, completely shut me out because I wanted to do something unusual. Rebel that I am, I was not to be shut out, I was not to be shut down.

I first tried to publish the work I was doing, on Build It Solar, but Gary was not interested. So, under the banner of EcoRenovator, I started my own thread, “The Homemade Heat Pump Manifesto”. I wanted to show people what I was doing, and that, YES you can actually work with vapor-change process, and you can do it for little money using discarded parts and assemblies.

Projects have since spun off from the Manifesto, with fascinating variation. DIY Heat Pump water heaters have had major success, and very quick return$ on the effort involved. Other projects like active (heat pump assisted) HRVs, heat pump hydronic water heaters, heat pump spa heaters, heat pump swimming pool heaters, heat pump clothes dryers, DX water heaters, heat pump food and crop dryers, heat & cool from air, heat & cool from: river water, stream water, pond water, and more!

The variety of discussions have grown to 483 project and discussion threads, regarding many different aspects of heat pumps, homemade or otherwise.

The EcoRenovator pages will be a lasting archive of detailed and illustrated projects that have achieved success. Even though some of the projects may have tripped and stumbled along the way (mistakes are every bit as important as wins), success was achieved through persistence, often patiently assisted by our informed core members.

Mega-Thanks to EcoRenovators who have undertaken projects and have gone the extra mile, with detailed descriptions and photographs, their projects. You folks are the real stars of the show. Everyone else is just standing on the sidelines.

Thanks of course to Daox and any other technical folks who keep EcoRenovator up and running. The fact that we don’t see what you are doing, is a testimony to your effort and success.

Thanks to the people with experienced, hands-on knowledge, who are too numerous to name but you certainly know who you are. You don’t need to proclaim expertise, because the depth of your knowledge and quality of advise speaks for you. You have shared the best of your knowledge with beginners and seasoned experimenters equally. And the fact that your advice was given straight, honestly and with no expectation of any financial reward gives me hope for a better world.

I would also like to thank members of EcoRenovator who have recognized and respect the fact that ‘The Manifesto’ is a Project Thread, and have agreed to refrain from turning it into JAOT (Just Another Opinion Thread).

A completely unexpected aspect of the ‘Manifesto’ and the many projects and the community that has formed, is that some enduring friendships have resulted from all this. Some in the cyber realm and others that are in the actual world. Icing on the amazing cake!

The ‘Homemade Heat Pump Manifesto’ stands alone on the Internet, and serves as a beacon to folks out in the vast reaches of the World Wide Web, who are searching for a way to actually make a Homemade Heat Pump. It sends it’s welcome to the rebels, pirates and hackers who are not content with the way things are, and want to do it better, cheaper, more efficiently, or any way they want.

Thanks to everyone who helped make this happen. You are the champs!

Sincerely,

-AC_Hacker

b420ady · 12-08-16, 09:17 PM

What remains to be done is a book and some video tutorials starting from brazing and ending to how to make a boring machine for well or geothermal heat pump, personally I feed my mind with images so please post a lot of photos of your achievements , I like so much to watch photos with your water to water units

Congratulations for this huge topic and for all the projects people made and post here and thanks because you are my inspiration and the reason I got so deep inside this domain.

AC_Hacker · 12-09-16, 04:23 PM

Quote:

Originally Posted by b420ady

What remains to be done is a book and some video tutorials starting from brazing and ending to how to make a boring machine for well or geothermal heat pump, personally I feed my mind with images so please post a lot of photos of your achievements , I like so much to watch photos with your water to water units

Congratulations for this huge topic and for all the projects people made and post here and thanks because you are my inspiration and the reason I got so deep inside this domain.

b420ady,

Welcome to the Homemade Heat Pump Manifesto!

Thank you for your appreciation.

As you work your way through the 'Manifesto', please feel free to make recommendations for improvements.

Because I can't actually interpose new posts in the series of posts, I can edit posts that I have made, and include improvements that you see lacking.

The way to do this is to record the URL of the post in question ( the uppermost right hand hyperlink of each post), and supply suggested text, photographs and video, as would most benefit the improvement you suggest.

You will certainly receive recognition for your suggestions.

It has been a huge undertaking, and will probably never be completely finished.

As regards a 'book', I think that is a splendid idea and I don't know why nobody has not already done it.

There is nothing in the Manifesto that is "New Technology", so nothing here can be patented. It is all in the public domain.

The only thing that is new is that I found that scrap HVAC equipment can be gotten for cheap or free, and reconfigured in something very useful.

Enjoy your reading, if there is anything I can help you with, you only need to ask!

Sincerely,

AC_Hacker

slippy · 02-15-17, 01:43 AM

It has taken a little more than a solid week at about 6 hours a day to make it through the entire Manifesto. I swear, some of you I feel like I know already. I look forward to working with some of you, if you are still around after these many years! AC, I promise to remain on-topic, and I hope your arm is better. Without further ado, let's begin.

Plan: either modify existing 5T ASHP and 2T/3T AC/gaspack units to become GSHP, or replace them with home-made, or modified surplus GSHPs. Indoors will be refrigerant-to-air, not radiant floor.

Building: 2-story, 2500sf per floor offices in a 10,000sf metal building located in Matthews NC, zip 28104. Good insulation, with improvements on the way. 40kWac solar array, grid-tied

We have had difficulties in the past keeping the building cool on peak heat days, and keeping it warm (without using tons of propane) in the coldest winter days.

The 5T HP is SEER 10, though I honestly doubt if it is performing that well. We do seem to have some air flow problems, perhaps (that is hard to measure). We have a small leak in the evaporator coil, which is inaccessible without it being a major project. It was installed in 2000. The 2T gas pack was installed in 1993. It seems to run like a top, despite being built in 1988!

My plan is to go open-loop. While AC_Hacker is clearly a fan of brazed-plates, I believe I will be going with coaxial heat exchangers, from Edwards or Doucette.

I have planned to water-flow two shallow supply wells (one on either side of the building, beside the 2 units) and 2 return wells. I believe I will hit fair water at about 20 feet, but hope to make it to 30. I spoke with a drilling contractor today, who seemed to think that this would be a very tough proposition without heavy machinery; apparently the ground can be very rocky here in the foothills of NC. The drilling technique I intend to try will be the one at drillyourownwell.com, which primarily uses pumped water or a bentonite mud drilling fluid through 1-1/4" to 3" PVC, with a modified-to-have-teeth pipe nipple on the end.

If I fail to be able to drill with this method, I may try another, but I'm no Vlad!

I have LOTS of questions, despite having read every last post thus far.

First question: Is efficiency realized with lower compressor draw, or by hotter indoor coils (in heating mode)? I did a simple test, pouring 10 gallons of hot water onto the outdoor coils while monitoring current. There was no noticeable change to the current. (Before you say Kill-A-Watt, it is hardwired 208V; I DO have a real power logger I just bought, but haven't installed yet, to better monitor.) I'm not sure if the efficiency will be gained by decreasing run time, or by decreasing current draw.

Second question: Assuming a "more than ample" heat exchanger outside, how will I prevent the indoor coil from freezing up? We have had this problem, possibly due to air flow, but more probably resulting from low refrigerant charge. I do not believe there is a TXV inside or out. Outside I can clearly see a distributor and many cap tubes. Inside, I really can't see squat, as the unit is basically inaccessible. The manual for the air handler makes no mention of a TXV, and I suspect it is cap tubes as well. I would like to add a TXV since that is something that should add efficiency, which is something I'm really wanting.

Third question: On the subject of TXVs, on the outside unit, do you simply attach the bulb to the return side of the coaxial heat exchanger?

Fourth question: On TXV sizing, I understand this is a "system." But, with a very good heat exchanger outside, how might that change the overall system size? That is, should I stick with a 5T TXV, or step it up (or down)?

Fifth question: If I am going to be gaining a lot of efficiency (no doubt, going from 30°F air to 63° water will make a huge difference), should I give thought to reducing the size of the compressor? I have a hard time understanding how a compressor really works; is it like a motor, where it is rated at a CAPACITY, but will only draw the power it needs, up to its rating? For instance, a 5hp motor won't use much energy at all unloaded. But, it'll use 745W of power per HP of load you put on it. So, will a largely unloaded 5T compressor draw the power of a 1T compressor, if the condenser is huge and the evaporator is small?

I have done my best to TRY to figure out our heat load and cooling load, looking at degree-days and the like, which indicate that 7T of cooling and 8T of heating are way more than enough. In reality, though, that hasn't been the case for us, but then again, we use programmable thermostats and set the units back significantly at night.

One last thing to add for now (and there WILL be more questions as things progress) is that we are really trying to limit our power consumption during poor solar hours. I would like to design our GSHPs with this in mind. We buy power for 3 times what we sell it for, so it is advantageous to us to heat/cool in the middle of the day, when there's lots of sun. I try to cheat a little by heating (or cooling) more during the day, to give us a bit more of a buffer through the night. It isn't enough, though, to keep the units from having to come on at, say, 5am to prepare the building for occupancy. I'm interested in heat (or cold) storage for this reason.

Thanks to all of the folks who have contributed to this mountain of info.

jeff5may · 02-16-17, 01:12 PM

Slippy,

Ok, here comes a bunch of hodgepodge quick answers to get you started in the right direction:

1. Cooler supply air and longer run times beat warmer supply air and short cycle times. Heat pumps take some time to "ramp up" at the start of each cycle. This is opposite from gas burners, which preheat pretty quickly.

2. In cooling mode, air handler hx freezing is caused by load mismatch. Usually it is a shortage of airflow, but if the evaporator is not sized correctly, the same thing happens. If a cap tube system is low on charge, the air handler freezing is usually the first thing that casual users notice going wrong.

3 and 4. A TXV should be matched to the capacity of the compressor. The sensing bulb should be attached to the suction line close to where it leaves the heat exchanger. Load matching needs to be done on the water side of the hx to prevent freeze up, and many systems employ thermometers and/or flow sensing to detect possible freezing conditions.

5. An unloaded a/c compressor draws less current than when it is fully loaded, but not THAT much less. Most constant-speed scroll and rotary hermetics use about 1/2 to 2/3 of full power when they are unloaded. They are designed for maximum performance within a fairly narrow range of operation. Due to their constant displacement, BTU throughput (mass flow) varies directly with suction pressure and inversely with compression ratio. That being said, even at very low compression ratios, the compressor can only move a certain amount of gas with every revolution. Performance doesn't magically skyrocket when the delta P decreases.

Another thing to consider here is that heat pump systems are not particularly well suited for temperature setbacks. Where a gas burner blasts out many times its "normal" load while gas is burning and then "coasts" for a while before the blower shuts off, a heat pump moves only its rated load (more or less) when the compressor is running. When the thermostat is set back, both types act the same: they don't run. When set "forward", the gas unit quickly heats up the space, where the heat pump recovers much more slowly. This can cause big time comfort problems.

AC_Hacker · 02-23-17, 01:05 PM

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