Climatemaster w/ ground loop. Any pointers?

[southerntester]

Ok guys, I installed my Climatemaster 50ydv 064 about 6 years ago and it's been a great decision as my electric bills have gone down by 30% over that time. I installed it using a ground loop with Methanol for anti-freeze(jumper is clipped). Before I ask my question please understand that I haven't done a thorough investigation and I know that. I haven't checked superheat or sub-cooling and haven't checked water side pressure drop across the coil. Filter is new and coil is clean. Plenty of air moving.

Last year when the outside temperature got really low my unit tripped on low pressure a couple times. I threw a set of gauges on and it looked a little low on gas so I add a little. The rest of the winter it ran fine no matter how cold it got. Last week I started having issues with low pressure again with the extreme low temperatures here in Virginia. I put gauges on it last night and with the compressor running at full capacity my low side was 75 and high side was 350. Entering water from the field was 38ish. According to the chart my low side pressure is perfect and my high side is a little high. I watched the unit run for a solid 30 minutes and the pressures stayed consistent. I went upstairs for about 10 minutes and when I checked the gauges again the low side was down to 50 and the high side was well below 300. Shortly after that it tripped off on low pressure. I changed my thermostat setting so that it only used 1 stage of heating and it ran the rest of the night and all day today without issue.

Anyone ever seen this before? I could understand if the change in pressures happened as soon as it engaged the 2nd stage but not after more than 30 minutes. It almost seems like an intermittent TXV issue or a water flow issue. What would cause both high and low side pressures to drop like that? Thanks...

[Chuck]

You need to test the antifreeze. That's what happens when ice starts forming on the walls of the coaxial heat exchanger.

Is the refrigerant 410a?

[southerntester]

You need to test the antifreeze. That's what happens when ice starts forming on the walls of the coaxial heat exchanger.

Is the refrigerant 410a?

Yep, 410A. Freezing doesn't sound good at all. When I filled the loop I used a calculated total volume and figured about 15% Methanol. I did a little work on it last summer but shouldn't have changed that mixture much. Not aware of an easy way to test Methanol mixture. You?

[Chuck]

Hydrometer

[Earth Power AC]

We are in Texas and rarely use antifreeze. For this reason the few time my techs see frozen coax they diagnose wrong. Low freon, TXV valves, whatever. Trick is to run in cooling mode for a few minutes and see if things drastically change. If it does, you are building ice on coax as the previous post said. Running to cooling mode will thaw the coax, same as an air to air unit.

[CoolCatHeatPump]

Agreed - look at the source you will most likely find your problem - Your unit is now over charged (Need to Correct), and if problem continues recheck your geo loop sizing? And never assume.

[SkyHeating]

Agreed - look at the source you will most likely find your problem - Your unit is now over charged (Need to Correct), and if problem continues recheck your geo loop sizing? And never assume.

most geo manufactures that i know of do not want gauges on the unit unless authorized by the factory. Geo units rarely need charge adjusted if its a package unit so you probably need to recover your full charge and weigh it in.