Jeff5may

The performance is looking promising using BBQ propane gas. R290. The compressor and fan draws about 220 watts. I've purchased a kill-o-watt meter to confirm our calculations on the cost of usage. The blue paint is left-over from a customer's machine color. All their equipment in the plant is this color. I was amazed it's still able to be used. After all this time I thought it would be trash.

The propane burning water heater that the DIY HPWH will be replacing is about 12 years in service. The parents had rented it all those years. The rental fees started at about $6.00/month and now $22.00/month. That's a pretty lucrative return for the propane man. It just plain luck that its being changed out when the propane has made such a huge leap in price.

Randen

another hot water tank heat pump
 

I can see the finish line clearly now. We drained and removed the Rented Propane fired Hot water tank. And in went the DIY heat-pump hot water tank. Not so smoothly. Old copper fittings are a little difficult to get soldered nicely, had a leaker when we turned the water on. Dam.:eek: And a second leak on the tank drain valve. Another trip to the hardware store remedied all that.

It fired up nicely. A lot quieter than the propane fired HWT. :thumbup: After 5 hrs. of run time it became quite apparent I wasn't getting enough air through the evaporator. The 4" tube on the side of the evaporator foam box restricted the volume of air enough that the evaporator blocked up with frost. With a sharp box knife I modified the foam box to maximize the amount of air passing through. NICE cured.

Still I'm very surprised at the amount of condensate that is produced. During the build I had operated the system a few times in the shop and in my dads garage with no where near the amount of condensate running out like that which occurs in the humid basement air.

In my prior posting I had indicated that the unit was running at 220 watts. I must have checked the wrong wire as the actual run current is 3.2 amp including the fan motor. That makes it more like 350 watts.

I've installed a Kill a Watt meter to see how the operational costs stack up.

The temps are 110F degree water temp.

After we let it run for a day or two we'll get the timers install. One timer to prevent a stalled compressor on a short cycle with a power interruption and the other for time of use favoring the better electric rate period. Then the cover for the finished unit.:cool:

After a month of run I'll post the savings of operation.

Randen


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Looks great as usual Randen! I'm interested to see a cost analysis and comparison.

The reduced power consumption of the unit running on propane is interesting. It was a 5000 btu unit to begin with, yes? If so, they usually draw around 500 watts.

The extra condensate is a bonus. You're grabbing latent heat out of the room, rather than cooling the room down. Water down the drain equals less energy wasted cooling the room. Hopefully it won't dry out the house too much.

another hot water tank heat pump
 

Thanks Daox & Jeff5may

There are a lot of advantages with this type of water heating. So far the parents seem to be happy with the creation after a couple of showers have been made. They had mentioned they didn't add much cold to the mix for the shower water temp. I had explained to them about the capabilities of a heat-pump water heater and they understood it. Basically, in one way you pay extra for the higher water temperature from losses in addition to more expensive type fuels only to add cold water to make it comfortable. Its wasteful.

We can install a timer to take advantage of the less expensive time of use costs.
The heat-pump will reduce the humidity of the basement.
The COP of about 2.5 means better efficiency compared to a electric water-heater. For $1.00 worth of electricity you get 2.5 time the heat.

The latent heat in humid air is another nice little advantage.:thumbup:

Randen

Pretty sanitary looking job.

I don't remember if you posted the capacity of the water heater tank? It would be useful to know.

So you're using a 5,000 BTU compressor, are you? That is just great, because that particular size is the most abundant on the used market, and therefore the cheapest. They are absolutely everywhere.

So if your project proves successful, it could well be the template for a tsunami of DIY heat pump water heaters just like yours.

My hunch is that a compressor of that size could have a slowish recovery... if it turns out to be the case, it wouldn't necessarily be a bad fit for your parents. In fact, if it is able to keep up with their normal use, it's probably going to prove more economical than a larger compressor.

And I really love the tank color, and know that it would be a crime to cover it up with insulation, but that would help your economy, also.

Good job!

And... if you were so inclined, your project could be easily turned into a nice PDF (like this one), and at that point, it could easily proliferate. If EcoRenovator doesn't have the storage capacity for such a PDF, I'm quite sure Build It Solar would have the capacity, and their traffic count is quite large, AND their stuff gets backed up on www.archive.org, so it would be eternal.

-AC

another hot water tank heat pump
 

AC_Hacker

So far so good. Yes the placard indicated a 5K Btu unit. I Don't remember the other data for wattage or other. Jeff5may is right 5Kbtu is about 500w after checking on-line so the BBQ gas refrigerant is a good gas for the application. The power reduction of 500watts to 350watts relates to a 30% increase in efficiency??

I had promised Gary Reysa upon finishing my Solar Hot Water space heating system that I would write up the information and get it over to him and Builditsolar but I've been dragging my feet.

The build of this HPWH was straight forward and anyone with a few hand tools could replicate it without too much difficulties.

The tank is a 40gal. and the temperature now is 45 Deg C at the top of the tank and 41 Deg C at the bottom. The condensing side is entering the tank at 55 Deg C. and out at 42 Deg. So that 22 ft. of 5/16 copper tube makes a nice immersion type heat exchanger. The evaporator shows to be quite effective as well being the original from the window shaker. Just need to be sure to have good air flow.

After a month of operation I'll post the data.

Randen

Thought I would offer an up-date. I'm visiting the parents and checked up on the DIY HPWH. Its been purring away in the basement for more than a year.

Some of the data I'm checking. These are real world numbers. The refrigerant is BBQ propane or R290 its suction side is 18 psi the kill-o-watt is indicating 415 watts and after a month running hot water for the parents works out to 118 KWH per month. Using the cost of energy here in Ontario Canada it works out to $23.00/ month.

Heck that's what they paid for rental on the propane fired unit they had. They are saving a pile of money. No propane being burned there.!!

Randen

Propane is dual use.. Heat Pumping or burning for heat.. :)

Not quite.

The formula is:

Efficiency = (Power Out) / (Power In)

To figure the power in you would need to do a test to see how much energy is required to heat a given amount of water from a beginning temperature to a final (set-point) temperature.

It's a bit complex on a system that is in daily use, but if your parents were going to be away for a few days, you could ask them to unplug the tank before they left. Wait a couple of days, then:

1. measure the starting 'hot water' output temperature of the tank, which should be pretty cold

2. connect the water heater compressor unit to power through a Kill-a-Watt

3. Run until the unit until it reached the set point and measure the hot water temperature

4. look at the total watt-hours used (energy in)

5. divide watt-hours by the run time to get total watts

6. convert the total volume of water to pounds

7. knowing that one pound of water requires one BTU to raise the temperature on degree F.

8. Multiply the total pounds of water by the total temperature rise

9. this gives you (energy out) which you will need to convert to watts

10. divide (energy out) by (energy in) to get efficiency

In my experience, and the experiences I have seen on this forum, your efficiency will not be a meager 30%. Rather it should calculate out to 250% to 375%.

This is where you get your well-earned bragging rights, and it is why you are saving so much money heating your shop.

Best,

-AC