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Id say fouled heat exchanger. Did u ever record inlet and outlet refrigerant temps at hx?

If refrigerant delta is low at hx and water delta is good, you have scaled hx

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Hey guys, sorry I haven't been following this thread as it is a little over a year old. To make a long story short, the manufacturer replaced the unit with a brand new one. After a couple of trips to the install site by the manufacturer to "fix" the problem, the unit was showing the same symptoms as originally mentioned in original post. I didn't get paid for my time to swap units, but I do have a happy customer to this day. I was out at the install this past week on a different call and the new unit is still going strong. Strange problem and they never did get back to me to tell me what the cause was. Thanks again for all the help guys!

My mistake , misread your tank temp as 185 , like other poster , 100 may be too warm , but confirm , 150 is definitely too warm too! This system has worked fine for two years Right? check controller sensors and tank sensor for accuracy. sorry for the confusion !

This is my best guess, Right now your expirienceing colder than usual outdoor temperatures? , your reset controller has ramped up the buffer tank temperature to compensate and the upper limit was set too high , reset controllers do not help efficiency , they simply keep cycle lengths the same regardless of outdoor temperature, with water source to hydronic systems this means that condenser temperature climbs , compression ratio suffers , (which is anything but efficient ), set a maximum of 150 buffer tank temperature and let the cycles run long in cold weather. a closer guess on the max temperature may be needed to ensure you will exceed the heat loss from the space during cold weather, but the lower the better . another thought would be to check the accuracy of the od temp sensor that it is not telling the controller that it is colder outside than it actually is?

Vikingsguy, i need more info if i am going to even try and answer. ive got some questions other than the brand/model.
1.what is the entering/leaving: load/source: temp/psig
2.what is the rate of flow through the source/load heat exchangers
2.at the above reading what is the refrigerant discharge/suction: temp/psig
3.what is the subcooling/superheat

im also wondering what the fluid mixture on the source/load is with percentages and where the fluid originated

Temps of 10 degree load side at the buffer tank looks good.Also the 7 degree temps at the water coil looks good as well.Maybe non condensable or someone added the wrong refrigerant to top it off.

I have a couple ww units .... problems have been with high head also . It does sound txv maybe, but I agree with other post about refig charge. Also I wont name either but I had a couple that have taken about .5 lbs less to keep head in 450 head max. You have to verify hydronic pump on load side gpm, at 1gpm per 10,000 btuh just like hydronics. On the source side 3gpm per ton equals 15 gpm from loopfield . EWT from load is the issue on high head ususally and it WILL BE HIGH, just try to operate high head in safer range otherwise youll lose a compressor sooon!

Originally Posted by Vikingsguy

Thanks for your reply. The main hydronic pump was my first thought even though my delta t tells me the pump is indeed moving water. I did replace pump with a new one I had on the truck and the issue remained the same. Id rather not name brand as ive really had nothing but great equipment and service in the past. Would bad compressor bearings or something cause high head like that.while maintaining low suction pressure? Officially stumped. Thanks guys.

i would love to help you out but i really need to know what brand and what model.

According to what you posted, you are only picking up 42000 btu on the open loop. IF that is correct you would only have about 9 GPM on the load side. On a 5 ton unit you should be running closer to 15 GPM on both sides. 3 gpm/ ton is normal water flow for the open loop side, not sure if they run the same on the load side or if they slow it down to raise the temp. All the Geo systems I have done have been water to air, no water-water. If the flow has not changed, I don't know why you would be having hte issue now. But it looks to me like low water flow on both sides.

What's the flow rate on the LOAD side? You need to know if the load side is absorbing the proper amount of Btu's.

Bergy

After re reading posts I have a ?
The 500 psi is that beeing found at discharge from compressor or is that liquid pressure?
I'm assuming it's discharge because of the 35 degrees of super heat it would help to see what the liquid pressure is and the amount of sub cooling is been obtained from the buffer tank coax. Just thinking out loud maybe some thing will help I noticed you said that the open loop was flowing at 12 GPM if the water is flowing through to quickly ( think it should be 1.5 to 2 GPM/ ton) the evap coax can not absorb enough heat causing low super heat causing TXV to try to slam shut which would increase liquid pressure and increases sub cooling intern increasing discharge pressure sort of like running over charged. The last thought would be just beeing overcharged this seams like a far fetched idea seeing how system is only 2 years old and you seem to be the only one to work on it. However it may not be a bad idea to recover the refrigerant check weight with unit info and at that time I would replace with fresh refrigerant ( contaminated refrigerant can do some weird stuff. Maybee thies thoughts are out there and not helpfull but I do hope they can ster some other thoughts to lead to an answer. Can't wait to find out what hapens, good luck.

Assuming this is 410a system 100 psi on low side is slightly lower than what it should be. Probably should be around 120 psi or so. You may want to investigate TXV by placing bulb in hot and cold water to see if you get a change in pressures you may have a stuck TXV. If its stuck Part way open it would raise discharge pressures and lower suction. If you see littlle to no change in pressures as you have bulb in hot and cold water there's your problem.

185 is the temp of the high side liquid line in the refrigeration cycle. Inlet water on hydronic side is 90 leaves Geo at 100.

Originally Posted by Vikingsguy

EWT temp is 50 degrees, leaving water temps 43. Checked low and high side temps today high side temp. at 500 psi was right around 185 degrees. Low side temps were around 41 degrees at 100 psi.

If you are saying the leaving water temp on the hydronic side is 185 you either have low circulation or the water is short circuiting the buffer tank and being returned directly to the inlet. 185 leaving is way to hot it's no wonder it trips the HP

What is the hydronic inlet temp when the outlet is 185, also what is the buffer tank temp under the same conditions

Yes in heating mode sorry I am in Minnesota. Tank temp is derived through outdoor sensor to improve efficiency.

Thanks for your reply. The main hydronic pump was my first thought even though my delta t tells me the pump is indeed moving water. I did replace pump with a new one I had on the truck and the issue remained the same. Id rather not name brand as ive really had nothing but great equipment and service in the past. Would bad compressor bearings or something cause high head like that.while maintaining low suction pressure? Officially stumped. Thanks guys.

Have you checked your Pump on hydronic side to make sure of circulation. It would be like a restriction in air coil with dirt build up
causing head pressure to do Like what you said. Also Can you name this Geo? I am assuming you are heating going by your temps

EWT temp is 50 degrees, leaving water temps 43. Checked low and high side temps today high side temp. at 500 psi was right around 185 degrees. Low side temps were around 41 degrees at 100 psi. On the phone with the engineer i know he was quite concerned with the superheat and subcool calculations, but was unable to come up with an answer for what might be causing the issue. As high side pressure climbs so too does the amp draw on the unit obviously near cutout it is drawing a tad over 25 amps. Im just baffled and I do believe they (manufacturer engineers) are as well. Anybody see anything that we could be missing?

Any more information such as what your EWT temps are from the well? What brand equipment is this incase there are known issues with a certain brand. I can't answer this question for you since I don't do refrigerant and all my techs are getting ready for the weekend, but the more info you post the more likely you are to get an answer.

Water to water heat pump going out on high pressure lockout

5 Ton water to water heat pump with buffer tank. Open loop. 12 GPM on source side. Been in operation for 2 years before any issues. Unit will run for about 25 minutes with high side pressure slowly creeping up until it hits 530 psi and trips the high limit switch. Low side pressure stays steady at 100 psi throughout the entire run time. Temp difference on source side of 7 degrees. Temp difference on hydronic side of 10 degrees. All radiant zones come off of buffer tank, buffer tank set at 100 set point, so temp going back into Geo is 90 degrees. Flow meter on source side shows no signs of scaling whatsoever as it is as clear as the day it was put in. Im not a refrigerant tech, but shouldnt that low side pressure climb along with the high side? Anybody have any thoughts?