Using small Window A/C for DHW Heater

[Xringer]

The project goal is to heat water using a 5000 BTUh window A/C unit.

I've started collecting parts. The heart of the unit is the HX. It came in today.


Spec from Ebay


I think the water should flow counter to the ref flow..?.


It's 8" long, 3.2" wide, abt 4" top-to-bottom, counting connections etc.


It's heavy and feels very solid! Looks like a good quality part.

~~~
Found a Bronze water pump down in the basement..

I wonder if this pump is too big for this project..?. Comments?

[Daox]

Cool project!

Is this going to preheat water to your boiler or try to be the main supplier of hot water? What kind of water temperatures are you hoping to hit?

I would think you would want cross flow through the heat exchanger as well... odd.

[Xringer]

Originally Posted by Daox

Cool project!

Is this going to preheat water to your boiler or try to be the main supplier of hot water? What kind of water temperatures are you hoping to hit?

I would think you would want cross flow through the heat exchanger as well... odd.

Currently, the boiler is heating up(140-150F) each morning for 1/2 hour, using oil ($2).
During the sunny part of the day, Solar PV adds 2,000 to 2,500 BTU/h.

This summer, I want to try shutting off the oil completely and see if it's
possible to maintain the boiler (76 gallons) above 120-130F using just the ASHP & Solar PV.

If the ASHP ran 6 hours @ 500w, that's about $0.50 in power cost.
Even a 12 hour run would still be a considerable savings over heating oil.

Edit:
I'm really not sure which way the water should flow, relative to the refrigerant.
I seem to recall that it should run in the opposite direction..?. Not sure.

[Daox]

From the pictures I've seen of your boiler, it doesn't appear that the water tank is insulated. Is this true? I would think you could achieve this if you had it insulated well.

[Xringer]

Originally Posted by Daox

From the pictures I've seen of your boiler, it doesn't appear that the water tank is insulated. Is this true? I would think you could achieve this if you had it insulated well.

It might work.. It does have some insulation. 1980s insulation.
I've added a few layers under the top cover, foam underneath and done some work on the in/out pipes.
It still needs more done, and I plan to finish it up after the plumbing changes have been done.

The losses aren't real bad. With the PV working to maintain the temperature
from the morning oil burn, there's enough warm water for showers in the evening.

We did one warm water laundry wash today and the water temp is still over 130F.
Which is enough for warm showers.

~~~
After completing the insulation work and ASHP install, if the ASHP can't meet our needs,
or runs more that 12 hours a day, I'll look at plan B and C.
I'll buy an insulated water heater tank, or upgrade the HP to 18,000 BTUh and install the Evap coil outdoors.
Which will likely mean only using the system during the warm season.

[BradC]

I wonder about the efficiency of using a small furnace just to keep the evaporator temperature in the efficient zone during the cold months? You would not need anywhere near as much oil as for directly heating the water as your waste heat should exit at or about the evaporator temperature, rather than the temperature of the hot water.

[Xringer]

What kind of fuel would that small furnace burn?

I have a web-buddy who lives locally (same weather) and uses a Geyser hot water heater.

Geyser HPWH links:
www.coler.com/pdf/GeyserManualV1.5.pdf

Thriving On Low Carbon: November 2011

His basement is about the same size as mine, and he seemed to be getting
pretty good hot water, even when it's cold out..

But, I think he still has a fossil fuel gismo running in his basement..
He does use modern mini-splits, so I'm not sure how much waste heat his Geyser HPWH is scavenging.
(Might be a lot)! I hope to cut the heat loss from my boiler to a minimum.

Anyways, my project goal is to built a cheap copy of the Geyser and use it during the warm months..
If it works into December, even better.

Since the water table is a few feet under my basement floor, I do need to
run a dehumidifier during the hot summer months.
If I am successful, I can sell that noisy dehumidifier..


Basic idea:
http://i46.photobucket.com/albums/f1...5000BTUdhw.jpg

Boiler:
http://i46.photobucket.com/albums/f1...HSTARMOT35.jpg
http://www.woodboilers.com/admin/upl...sssection2.jpg

[AC_Hacker]

Xringer,

How is your HPWH coming?

Looks like you have all the parts.

-AC_Hacker

[Xringer]

I got called back to work last week.. So my home projects time has been cut down.

I picked up some iron pump flanges for my bronze pump today..

But I still need to spent some time on some water connections for the HX..


And I would like to braze 1/4" SAE flare fittings onto the refer ports..
(Gotta go back and watch your youtube video again)..


I may have repair my little lathe, so I can mod some parts to fit..
I think maybe a MOSFET is gone..

[AC_Hacker]

Originally Posted by Xringer

I may have repair my little lathe, so I can mod some parts to fit... I think maybe a MOSFET is gone..

Maybe your router speed controller?

-AC