Mini-split hot water heater

[morphector]

I've been lurking a long time on here reading a couple of it water tank modification, I've decided to take to go for it.

Found a nice 10 years old Fujitsu rebranded as Friedrich ductless unit for 100$cad on FB marketplace.

I want to keep the electronics of the indoor unit and just replace the coil for a homemade coil inside the tank.

I measured the evaporator and there's around 75 feet of 1/4 copper tube in it.

Unit is "quite permissive" in terms of length of line set from 6 feet to 49 feet without having to mess with refrigerant charge.

I calculated the minimum and maximum cubic in of total volume for the line set+evaporator allowed, a 50 feet line set from an install kit is right in the middle so I'll make my evaporator from that line set and use a 1/4-3/8 flare adapter.

We are pretty heavy on hot water usage, installed an energy meter on our hot water heater and it's consuming between 10-15kwh per day

What do you guys think about this?

[morphector]

Yesterday I had an hour of "free time" and received the parts I needed to start up the project

I removed the stock evaporator from the indoor unit and I'll heat 55gal of water to test the cop of the stock evaporator.

Didn't have time to start up on the vacuum part before getting to bed.

I have a couple of free days in the next couple of days so I should have some data in the near future.

While I wanted at first to use a 50ft 1/4-3/8 lineset from eBay at 100$ they are unobtainium either from eBay or Amazon, I'll use a 3/8 50' copper coil from the hardware store.

[morphector]

Managed to get a bit of time to do some further testing, vaccumed the lines and filled up a 55gal bucket with 50gal of cold water from the hose.

After 15 mins I saw that I had way too much stratification so I restarted and installed a small fountain pump in the bottom of the bucket, now theres only 1-2 degrees between bottom-top.

Temp here is the output of the garden pump from the bottom to the top


Here's what my results are on a sheet of paper, test were done on ''auto mode''


Had a COP of 3.12 going from 56f to 130f with an uninsulated tank and lineset.

Unit didn't give my any error code of anything, just had to connect midpipe sensor to the return line.

Will try to ''tame'' the beast by playing with the temp sensors, I would like to get it to run on a slower rpm and achieve a better cop.

[morphector]

Yesterday I installed my 50' copper coil of copper instead of the stock coil


Ran the same cop test and got the same results.
Coil has great heat output.


Next step is testing the tank I found on the side of the road to know if it's worth modifying or not.

[pinballlooking]

Interesting. I would haver thought the copper would have performed better than the stock coil. But I would rather have copper come in contact my cooking/dish washing water. Than the stock coil.

[morphector]

Originally Posted by pinballlooking

Interesting. I would haver thought the copper would have performed better than the stock coil. But I would rather have copper come in contact my drinking water thank stock coil.

Stock coil is around 80 feet of 3/16 copper with aluminum fins.My 50 foot 3/8 performs the same way ( at least I don't have enought precise stuff to come to another conclusion)

Are you serious you drink water from your hot water heater?

[pinballlooking]

Cooking/dish washing water.