Dxgshpwh (ground source heat pump water heater)

[MEMPHIS91]

Originally Posted by jeff5may

Your brass cap adapter is an awesome idea! Coupled with a common union it's ingenious. Common parts, simple construction methods, I love it!

This adapter idea would make it much easier for the average garage hacker to build one of these energy-savvy devices. I hope you start a trend with this piece of magic.

Thank you, the parts ran me about $30. So not the cheapest but should make that money back after the first month of running. I hope a trend is started as well. Way to many people live in a reality that society has created that tells them that doing things on their own is stupid, dangerous and impossible. A reality that that same society seeks to gain much income and power from.

AC
I found a formula online that should give me a exact cap tube size. But I do hope the original one is at least the right diameter.

I saw in another post how you said to calculate the COP. What would be best way to measure water temperature accurately?

Yes the drill bit is homemade I made it after trying to go past 30 feet with just teeth cut into the PVC pipe the first time a ever drilled a borehole. Its just a 2 inch double female with flat bar weld at slight angles on the side and a square piece in the center. It cuts through the wood and small spots of sand stone we have here.

[AC_Hacker]

Originally Posted by MEMPHIS91

...I saw in another post how you said to calculate the COP. What would be best way to measure water temperature accurately?...

[NOTE: After I wrote all this, I realized that you only wanted to know about water temperature. I answered a lot more, but I'll let it stand for other readers. As to your question, I would think that if you removed the sacrificial anode rod and made measurements through that, it would work well. You are likely to have temperature stratified water, so I suppose a measure at the top and at the bottom, and averaging them would be a fair approximation.]

Calculating COP with a water heater is fairly easy.

The general idea is: COP = (energy out) / (energy in)

One BTU is the amount of energy to raise one pound of water one degree F.

You will need to know what the weight of water is in your tank. If you know what the volumetric capacity of the tank is, you can convert volume of water to the weight of water.

The density of water is about 62.4 pounds/cubic foot.

The density of water is also 8.343 pounds/gallon.

So, I will guess that your tank is 50 gallons, so 50 x 8.343 = 417.15 pounds of water.

Next, you will need to know the initial temperature is in your tank. For this, you could just stick a thermometer in, maybe through the hole in the top for the sacrificial anode rod, and take a reading. I will just guess that the starting temperature is 50 degrees F. You will want to know how many degrees the water is heated to. So you will subtract your beginning temp (50 F) from your final temp.

Next you will need to be able to measure the amount of power used. A Kill-a-Watt meter is an accurate and cheap way to do this. It can tell you how much power (kW-h) is used, and it will also keep track of time, if you plug it in at the beginning off the test.

So now, you have the initial conditions.

I'm not sure what method you are going to use to stop the heat pump when the water reaches the desired temperature. Even if you don't have this arranged yet, if you run the system for an hour and a half or so, you'll get useful information.

Now, having written down the initial temp, you start the test...

Plug it in and marvel at your creation... but don't get too carried away, because you are conducting a scientific test.

Make sure that the Kill-a-Watt doesn't get interrupted during the test, or it will 'forget' the data.

After the run time (maybe 1.5 hours), record the power power that the Kill-a-Watt indicates (kW-h). Also record the run time from the Kill-a-watt. As I recall, the Kill-a-Watt measures watt hours, but when the count goes over 999 watts-h, it goes to kW-h. So, when you do your calcs you will want to make sure that you are in watts... so 1.234 kW-h will be the same as 1234 W-h.

Just guessing here... let's just say that at the end of the test, your water temp is 85 degrees. This may be a bit tricky because you will have stratification with hotter water on top and colder water on the bottom. So do an average of top and bottom temps.

POWER OUT (power produced by your heat pump)

Your power-out will be (1042.9 pounds) * (85-50 degree F)

... so power-out = 1042.9 * 35 = 14600.25 BTU

Converting this to the electrical energy equivalent you divide by 3.412

elec power = 14600.25 / 3.421 = 4279.1 watts.

POWER IN (power consumed by your heat pump)

Read the kW-h from the Kill-a-Watt.

let's just say that you read: .9 kW-h

This would be the same thing as 900 W-h

then you multiply by time (1.5 hour) to get watts

Watts = (900 W-h) * (1.5 h) = 1350 watts

CALCULATE COP

COP = (power-out) / (power-in)

COP = (4279.1 watts) / (1350 watts)

cop = 3.2

I think that your efficiency will be better.

Best,

-AC

[MEMPHIS91]

Gotcha, sorry I was thinking I would be measuring this under pressure, but that makes more sense. Just fill it to the top and pull the anode out. Perfect because I have a kill-a-watt meter and aquarium thermometer.
Thanks for all the useful info. I just copied that into a word document and printed it for save keeping.

[randen]

MEMPHIS91 & AC.

These are the most fantastic machines. All of use hot water every day and while the hot water tanks are just sitting, they are losing heat energy every minute. So from a DIY - energy efficient upgrade wow this is the one.!!

Yes the COP is a cool thing but remember that this heat-pump is going to be maintaining a temperature at the top of its heating capacity envelope.

The amount of energy required to heat the water from 50 Deg F to 90 Deg F its a walk in the park. But that stretch from 90 F. to 110 F. its going to need a longer run time to reach that temp.

With this you will see your COP may start out at 4.0 but ultimately in a domestic supply condition you may be somewhere 2.5 to 2.0 But even 2.0 is amazing!!

Imagine if you could Eco-renovate your Chevy for a few bucks and get 42 MPG instead of the 21 MPG

This particular build with the ground DX will be a star. AC just imagine MEMPHIS91 is doing this without circ. pumps, external heat exchangers and or fan motors. ONLY that little compressor (275 watts!!!!!). Heat sequestered directly from the source (ground) pumped directly to the Tank.!!!

OK I want to build one now!!!

WE SHOULD ALL BUILD ONE

Randen

[AC_Hacker]

Originally Posted by randen

...With this you will see your COP may start out at 4.0 but ultimately in a domestic supply condition you may be somewhere 2.5 to 2.0 But even 2.0 is amazing!!

Yeah, you're right. The COP will start high and gradually fall off as the delta-T decreases. And under normal working conditions, the 'start' cycle to 'stop' command will be working at the low delta-T end of the scale.

But, "You never outgrow your need for insulation", to paraphrase the milk ad.

And don't forget that he is in MS, and the yearly environmental temp is such that standing losses from the tank will be smaller, PLUS the ground temp in MS is about 24 F warmer than yours, so his little compressor will not have a very heavy lift.

I think MEMPHIS91 will have ample bragging rights!

-AC

[randen]

AC-Hacker

Right on all accounts. And don't forget his water supply temp. will be a lot higher than we experience in the great white north. During winter the water supply temp can be a teeth rattling 45 Deg F. infact in the depths of winter I must temper the cold with the addition of hot to rinse after brushing. BURRR.

But KOODOS to MEMPHIS91. Keep us informed.
I would like to report summer like conditions have arrived here in southwestern Ontario and for our domestic hot water is now heated with solar (DIY). The collection is via a 80 watt circ. pump from about 10:00 to 4:00pm. 120 gal of 140 Deg F. water for nearly FREE!!

Randen

[MEMPHIS91]

Yeah COP is something I understand just seems to vary a lot under different conditions. 42 MPG does sound nice.
AC
I wish I could take credit for all this, sure it was my idea to put it all together but I'm just pulling from hundreds of other peoples good ideas.

So today was BOREHOLE DAY.
Here is the 2 inch drill adapter I made. It has a compression tee, the 2 inch side is for the drill pipe, the 3/4 inch side is a valve to help the pump prime, also makes for a nice handle. Two 90 degree turns into a 2 inch female that connects directly to the output of the mud pump.

Here is the 2 inch pump line and drill pipe connected.


This is the mud pump that is pulling water from the near by pond and sending it about 75 feet away to the drill location. Water flows right back into the pond.


This is just a cool picture of the water flow coming through the drill head. I am rethinking a better drill idea. But this works fine for now.


The first 10 feet is SO easy, I stated at 3:30pm and the first 10 feet was done at 3:50pm.


Then comes the hard part. As you can see its solid clay. The idea is to slam the drill head into the bottom of the hole and then twist the clay loose and plunge it down again. The plunging action shoots the heavier solids up and out of the hole.


Then just keep adding pipe with glue on couplings. This is my second bore hole so I reused the first pipe, hence the 2 joints back to back. This is not a fast job, it takes time and TONS of energy.


I stopped at 6:45pm to have dinner with the parents and brother before he heads back to DC. I got to 28 feet and hit coal. I CAN get through it, but it will just take some time. It could be 3 inches or 30 inches thick. I'll probably give it one more run tomorrow just to try to get to 30 feet. But as you can see it really is very easy. 3 hours 15 minutes, plus I repainted a wood heater while waiting for glue to dry.

[jeff5may]

Well that was almost too easy. 28 feet in an afternoon. Wow. In my area, I would just call a drill truck. The whole area is on top of Mammoth Cave. Rocks the size if basketballs in clay or limestone. Good for you, bad for me.

Did you decide what size compressor to rob from its home? If you are not going to push your COP with a critical charge and high evap temp or use an expansion valve, I might just call it quits at 28 feet.

Propane is sort of the opposite property wise compared to r22. Low molecular weight, high heat capacity, less viscous. More will flow through the same cap tube vs r22, and the engineers say run a shorter cap tube. I never have, and everything worked out ok for me.

[MEMPHIS91]

Jeff
Basketball rock don't sound fun. The compressor is out of a 5,000 btu window unit. It was running R22 and says LRA 23.00.

AC you asked a long time ago about temperature control mechanism. I plan to just wire it off the existing bottom element thermostat.

I went ahead and chipped my way 12 inches through the coal (I know its coal because when it dries you can light it on fire), and so we are at 30 feet deep!

Bad place to drop something valuable. Water level was at 6 feet.

So on to coil making. I made 3 of these up the pipe as per the suggestion by Jeff5may.

This is a shot of the entire drill pipe out of the hole.

This is the coil in the hole. It went in much easier than I thought it would. I also ran in a permanent temperature probe. It will be interesting to see the change as I run the unit, and winter vs summer.

This is the 3 part mixture of peagravel, lime stone and powder lime. (1.75"x1.75")x3.14159x360" gave me the amount of material needed to fill up the hole. And it work out perfect. I love when math works, or should I say I like when I make math work right.

And this is the insulated lines running under the patio where the compressor will be.


I'm ready to start the compressor or work. Main 2 points to figure out are the oil, how much and what kind. And the cap tube, how long and what size. I do have one on the window unit right now that I can use but should I shorten it some? My current one is 33 inches long and measures at .11 inches OD.

[MEMPHIS91]

Update:
I got the service ports brazed on, compressor mounted, return line wrap around top of compress and brazed in. I talked with a HVAC tech today. His numbers said 31 inches would be about right for the cap tube. And I'm using mineral oil, not sure how much yet. Temperatures at bottom of borehole holding steady at 66.2-66.5F all day.