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-   -   Heat pump hot water heaters (https://ecorenovator.org/forum/showthread.php?t=5422)

oil pan 4 09-23-17 06:04 AM

I have my first heat pump water heater unit up and running.
It's just hot wired to run on a switch and water being fed by supplied by a 5 gallon container at the moment.
The compressor is very quiet even with the cover compressor cover plate off. With the cover installed it's even better. The fan is kind of noisy but not bad.
For a 6,000btu unit it's not bad. Running on 1.8 amps of 240v power with cool water, it's cooling the air off about 10F per pass and warming the water about 0.2F per pass, the water is being circulated at a few gallons per minute by the pump.
I don't think it would make a good ground source go thermal unit unless it's doing a lot better than 6,000btu.
What I have found when you cool the condensers on fixed speed air conditioners like this by say spraying water on them is they don't draw much less power but they do provide slightly cooler air.

With 122F water I am getting 2.6 amps of draw and 5 degree temp drop on the air.
I am using a flir to measure the air discharge and process thermometer totally immersed in the water to track it's temp.

I think I want to take 2 of these, put them on a 50 to 80 gallon tank for use during the A/C season which here runs from about March to as late as November.
Even then 1 ton of heat pump water heater is only about like using about a 4000w heating element. That should be plenty.

What my plan would be is take 2 of these put each on its own thermostat. Have one wired and plumbed as a line circulater. Have a DPST count down timer switch that can be manually turned on to get the water flowing in the morning and give the water heater a head start of the incoming demand. By the time the switch turns off the thermostat should be closed.

I also have a hot water heater timer I bought from lowes on clearance for $13. I would like to do most of the heat pump water heating during the day to help the air conditioners and that is when the house should be warmest.

I would probably add in a safety thermostat incase some one turns the timer to the max (30 minutes) with the water heater at max temperature and doesn't use any hot water or incase the timer switch breaks and fails closed.

ecomodded 09-23-17 09:26 PM

Ive been reading about the Helical coils being used in Water heaters , seems like a easy DIY project thought I would add a link to one paper on it in case its worthy of hacking


My thought is it can be used to scavenge heat from the heat pumps compressor or other parts or any heat source

This is a pdf file on it
https://www.google.ca/url?sa=t&rct=j...zUeGr5TuRuJgug

oil pan 4 09-25-17 10:57 PM

To go from a 50 gallon electric hot water heater to an 80 gallon electric the price just about doubles.

ecomodded 09-28-17 01:22 PM

Was going to swap in a 30 gallon tank instead of the original 60 gal tank at the time 2 months ago they wanted $200 MORE for the 30 gal tank so put a 60 in as Im moving anyways.

Today looked at prices at home hardware once more and the 30 and 40 gallon tanks are $200 cheaper.
It was either a typo a few months ago or they realigned the prices to match reality.
Had thought they reversed the prices as a way to milk people who wanted to conserve.

Oddly the 60 gal has a reported 57 watts standby loss the 30 and 40 gal a 54w and 57w loss.
Makes little sense to me or I don't understand standby losses correctly giving surface area differences.

oil pan 4 09-28-17 02:13 PM

My guess is the bigger tank is insulated better.

ecomodded 09-28-17 04:14 PM

Makes sense.
Next place I'll likely use a 40 gallon wrapped with R50 insulation and a plywood box with removable lid or some such thing.

Be nice to cut the losses down to 20 watts or less being it will be off grid

oil pan 4 09-28-17 07:12 PM

Any insulation will be an improvement.
Just start with wrapping with foil coated bubble wrap and putting 2 inches of foam on top.

TechShop 09-28-17 07:29 PM

Quote:

Originally Posted by ecomodded (Post 55798)
Makes sense.
Next place I'll likely use a 40 gallon wrapped with R50 insulation and a plywood box with removable lid or some such thing.

Be nice to cut the losses down to 20 watts or less being it will be off grid

I use a 28 gallon electric unit in my shop. The slab is heated, but I put it on 2" R-10 foam. My only hot water requirements are showers each day and a load of laundry once or twice a week.

If you have a spouse or other roommate, the 40 would be a good choice.

ecomodded 09-28-17 07:29 PM

Could also leave it in the box it came in and add some insulation to the voids.

It was right after I recycled the box that thought of using it for the tank now I wish I kept the box to use to make the portable ac heaters vent system.

Next house I think I may well keep the tank in the box now that I think about it and fill it with scrap insulation as its first layer and do a 2nd plywood case over it and keep it in a warmer part of the house.

That would smarten it up past Eco standards

ecomodded 09-28-17 07:44 PM

Quote:

Originally Posted by TechShop (Post 55800)
I use a 28 gallon electric unit in my shop. The slab is heated, but I put it on 2" R-10 foam. My only hot water requirements are showers each day and a load of laundry once or twice a week.

If you have a spouse or other roommate, the 40 would be a good choice.

Nice , my tank is in the cold part of the basement with cement floor. I slid a 3/4 inch piece of plywood under it to help. Thought to myself sleeping on a sheet of plywood on a cement floor sure would beat sleeping directly on it

Cement is a hell of a heat sink it keeps sucking and sucking

The foam base is a great hack.
I was thinking a 40 would be better for a hot bath which I prefer to showers atm , the 30 may work or be border line. I did the math and 30 sounded like it might work for a tub but it would be close and may have to kept hotter to make it work , the 40 would seal the deal


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