Carrier 30GB075 Issue !help!

[_knight_]

Started having an issue with this chiller where the EXV was freezing up on circuit 'A', which is a tandem circuit, one of these 06Es was just replaced. Well, the EXV was freezing up then locking out on code '68', low superheat.(which from what I was told was doing that even before this compressor locked up). Since I knew I didn't have low superheat (pressures were 160/5), I checked all the thermistors, they all ohmed out properly with the corresponding temperatures that they were at, checking some tech docs on it, the only other things that it says could cause this code was a stuck EXV (stuck open) or misplaced thermistors. Verified thermistor location, ohmed them all out again, all checks out good. So, the EXV appears to be the culprit, it gets changed out. Same. Damn. Problem. There were new thermistors on-site, so I pulled both off of the board that served circuit 'A' on the refrigeration side, the one on the compressor, and the one on the chiller barrel, I hooked up the two new sensors but left them sensing outside temp, around 85deg (I did this for now because replacing the sensors is extensive since they don't have immersion wells, and they were ohming out fine). It still would not open the EXV. Now....circuit 'B'. this one only having one 06E, the compressor runs fine, good charge and on a semi warm day can pull the chilled water down by itself, however when we come back after leaving it running (while waiting for parts on circuit A) that circuit (B) is also down, locked out on a code 55. Now, at this point I want to lean towards it being the board, but I just don't know. A new board is on its way in the A.M. but I want to hear from you guys as other possible issues, carrier tech support was zero help, and told me they did not support, or could help with a chiller that old, please help. I want do well for this customer, they are a church and are in desperate need of getting this fixed, Thanks in advance.

[Six]

Last 30 GTN that did that to me was sensors.

Suction saturation below the EEV and suction temp thermistor at the back of the compressor.

Sometimes they even ohm out fine. You can test the EEV output from the board on those with a red led at the plug.



Pull it off the EEV and use the LED for a visual indication. Or if you have a meter with PWM option you can test the out put from the board.

EEVs on those chillers dont go out often and neither do the boards.

Verify minimum flow after also.

[R123]

I hooked up the two new sensors but left them sensing outside temp, around 85deg (I did this for now because replacing the sensors is extensive since they don't have immersion wells, and they were ohming out fine). It still would not open the EXV.

How would the EXV open if the sensors are just hanging......both reading the same ambient temp? The processor would be seeing the same temp on both sensors which means '0' degrees superheat and it would think the evap was flooding and trying to CLOSE the EXV.

[milkyway]

You said it starting freezing, just checking, is the charge right ,

[Dallas Duster]

What does 160/5 mean?

[_knight_]

How would the EXV open if the sensors are just hanging......both reading the same ambient temp? The processor would be seeing the same temp on both sensors which means '0' degrees superheat and it would think the evap was flooding and trying to CLOSE the EXV.

I tried it with a variation, I hooked up a new sensor, left the old connected which senses the saturated refrigerant temp in the chiller barrel, left the new one hanging sensing outside air which typically goes on the compressor, so it is now definitely sensing a high superheat difference, also tried it with both sensors and vice versa, none of those configurations made any change. I definitely agree with what your saying though, I was just trying anything at that point...

[_knight_]

What does 160/5 mean?

Pressures: 160 head....5 suction . It starts at around 200/60, then slowly drops due to the EXV not opening.

[_knight_]

You said it starting freezing, just checking, is the charge right ,

Yes, this is at factory charge at 122 lbs on that circuit of r-22 on that circuit.

[Dallas Duster]

Pressures: 160 head....5 suction . It starts at around 200/60, then slowly drops due to the EXV not opening.

You got a bad sensor somewhere.

[_knight_]

Last 30 GTN that did that to me was sensors.

Suction saturation below the EEV and suction temp thermistor at the back of the compressor.

Sometimes they even ohm out fine. You can test the EEV output from the board on those with a red led at the plug.



Pull it off the EEV and use the LED for a visual indication. Or if you have a meter with PWM option you can test the out put from the board.

EEVs on those chillers dont go out often and neither do the boards.

Verify minimum flow after also.

Do you happen to have a reference chart for the dcv drop that I can check the temps the thermistors are sensing while it is running?

[_knight_]

You got a bad sensor somewhere.

Are the only two sensors that would cause this the one sensing saturated temp on the barrel and the on on the compressor body?

[Dallas Duster]

Are the only two sensors that would cause this the one sensing saturated temp on the barrel and the on on the compressor body?

Yep what about your water flow?

[_knight_]

Yep what about your water flow?

Water flow is good, circuit b runs great until it eventually locks out on code 55, which is a variation of possible issues not pertaining to the refrigeration circuit. I'll start with the sensors, I'm on my way to the customer now, I'll update shortly upon changing sensors. Thanks for the advice.