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Old 12-23-15, 09:13 PM   #9
jeff5may
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Join Date: Jan 2010
Location: elizabethtown, ky, USA
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Ok, I finally got a little free time to have a life. Naturally, I used it to play with this unit. Here are some details that didn't stay on my phone last time I took pics.

I hadn't realized the unit is only rated at 9 EER until today.


Typical economy compressor. I'll have to make sure to feed it an ample supply of cool gas to keep from burning it up. These babies don't like to be starved for long.

Since I re-plumbed the unit with the reversing valve, both my buddy and his neighbor got tired of looking at it in the driveway. Buddy bought a couple of 1500 watt space heaters, which are the best thing ever this year... if you've been christmas shopping, you've probably seen them. Remote control, server tower looking things. I believe he paid 200 dollars or more for them. He has this idea that since the strip heater elements are hidden in the unit, the unit doesn't work on the same principle as the old "toaster" style space heaters. His reasoning for why the rigged window shaker beat the two boxes was "it runs off 240 volts, mine run off 120." Oh well, at least his garage is insulated now.

The unit got moved to the barn and now sits atop a small deep-freezer. I rigged up a 220 cord to plug it in where my arc welder usually does. Plugged it in, turned it on, and ran it with the 12 ounce bottle of worthington I put in it weeks ago. After maybe 20 minutes of ramping up, I got these pressure readings:



Reading in heating mode looks rather low on charge. The rather low suction pressure is also somewhat disappointing. I was hoping for a little closer split in pressures. We will see how this changes as I add charge.

A warm front came through yesterday and remained today, as a result, it was unseasonably warm. Outdoor temperature was almost exactly 60 degF at about 90% relative humidity. This lies right at the border between heating and cooling as far as outdoor temperatures go, so with this window unit, I should be able to get both heat exchangers to not frost up in both modes of operation with the right charge.

Over the course of about an hour, I added about 10 more ounces of propane to get the outdoor hx to a point where it did not frost up. IMHO, this unit is seriously overcharged, but I ran the unit this way to see how the cap tubes split the pressure during best-case conditions. I rigged a 24VAC doorbell transformer to the reversing valve solenoid to check pressures and temperatures in both heating and cooling, and to check for frost conditions.



Yep, it's a low-seer unit alright. This reading was in heating mode on medium fan setting. I am pretty confident of the manifold gauges and IR thermometer / heat leak finder I am using. So unless the reversing valve is dropping some pressure, something don't add up. A 40-ish psig suction pressure translates to a saturation temperature in the 20's, so I should still have some frost where the propane is still in a liquid state. A discharge pressure of 275 psig translates to a condensing point around 135 degF, so if my gauges are correct, I have 50 degrees F of superheat at the compressor shell! If the BBQ had some butane or methane in it, I would be getting these lower pressure readings in the evaporator also. It would take a decent amount of contamination to do it, more than an ounce or two.

I took some temperature readings to get a better idea of what's going on elsewhere in the circuit:

Leaving the cap tubes, the refrigerant is right at freezing.


3/4 the way up the evaporator, the heat transfer has stopped. 30 degF of superheat gained... harrumph! Still, not bad for the 9 EER design.


At the entry point, the gas looks to have lost most of its superheat on its way through the reversing valve. Also in this pic, a cap tube can be seen exiting the crimped end of the hx tubing at the bottom. This is going to be an issue if I end up running a txv in this beast to improve performance.


Further down the pipe, we have already entered subcooling territory.

Close to the condenser exit point, we have over 50 degrees of subcooling!


I believe this would qualify as nice hot air coming out of the unit. As the indoor temperature climbs, the outlet temperature follows. As small as the indoor hx is, it needs a high dT across it to move its rated btu's.

Like I said, I ran the unit in heating and cooling modes and charged it until neither mode produced frost on the evaporator hx. In cooling mode, this unit was obviously well below its design outdoor conditions, because it produced frost even with this overcharge when left alone. To get it not to freeze up, I had to completely block off the outdoor hx with a piece of drywall and a cinder block, plus run the fan on high speed. Even then, it still tried to frost up until the outdoor hx heated up and built up pressure above 250-260 psig.

Whirlpool obviously sized the cap tubes in this unit to handle some serious torture. During normal conditions, indoor and outdoor temperatures would be way above 60 degF, and head pressure would be close to where it was set by overcharge. There would not be such sky-high superheat and subcooling in the circuit, especially when outdoor temperatures were above 90. I am confident that with the proper charge, the thing could endure a hot life in Phoenix, running at head pressures approaching 300 psig.

The unit looks to be wired like this diagram:

The only thing missing is the electric strip heater. I won't be adding one.
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Last edited by jeff5may; 02-18-18 at 10:44 AM.. Reason: Getting rid of photos buckets
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