Quote:
Originally Posted by MN Renovator
It looks like we've discovered why this unit was for sale on Craigslist, that dustcake made the thing next to useless for cooling the space of its previous owner.
|
That is very possible, although the guy said it worked fine when he used it in his apartment, but the house he moved into had central A/C so he didn't need it anymore.
AC, the coil I was referring to that I successfully bent, I ended up causing to rupture after I bent it back to "air conditioner position" and tried to bend it down again. I was able to bend this units coil down and out into a good position though, with no kinks or breaks.
I have now water tested the unit and can say that I do believe it will heat my hottub.
This is my test setup: The A/C is sitting on its shell and the coil is just sitting submerged in a 15 gallon tub. I filled it with 75* water because I wanted to avoid issues with low condensing temps( I know many refrigeration machines have low ambient fan controls to keep condensing temps up). The spatula is what I used to circulate the water.
I ran the test for one hour twenty minutes and went from 73* to 105* where I ended the test. The temp rise averaged about 4* every 10 minutes even as the water got hotter. These temps aren't the most accurate because I was using an IR thermometer unfortunately.
By my calculations:
15 * 8.34 = 125 lbs water
105 - 73 = 32* rise in water temp
125 * 32 = 4000 BTU(1)
4000 / 80 = 50 BTU/Min
50 * 60 = 3000 BTU/Hr(1)
*1 watt = 3.41 BTU per hour*
*800w * 3.41 = 2728 BTU @ COP of 1 (2)*
3000 / 2728 = COP of 1.1 (1)
(1)Actually higher because I used an uninsulated plastic tub sitting on wet concrete which was losing BTU's the whole time.
(2)I wasn't measuring, so I'm using the rated wattage, 800w.
I had to stop twice for 10 minutes to defrost(so actual testing time was 1:40, with 1:20 of it being running time. Defrost consisted of turning off the comp and leaving the fan running.
So I had a COP of 1.1 which could be higher, or maybe the same depending on the heat loss of the tub and the actual wattage being drawn, but with an outside temp of 34* I don't think that's too bad.
Things to improve efficiency:
Have good water circulation through coil. I only had what my stirring with a spatula created, and I wasn't consistently stirring.
Harvest heat,
Question can I steal heat from the compressor or is that a bad idea? During the test the compressor was around 110 on the bottom half and 135 on the top. The other thing I'm going to do is to steal heat from the jet pump on the hottub. It's 1HP and draws around 1300w. This should improve efficiency even in colder temps.
One last thing, after reading your post about fluid routing, I looked closer at my unit. The condensor is like you state most are, top in from comp, bottom out to evap. My evap is interesting though, its a dual layer coil with two runs. One entering at the top, and the other entering halfway down. The top one flows down the front layer halfway and back up where it exits. The bottom run does the same on the lower half of the evap. This pic below shows it better.
Adam