Diakin RXYMQ36MVJU high pressure

[qcfish]

This is my first time with a Daikin but the customer has complained for 6 months it does not cool. I like these Diakin VRV BTW. Techs have tried different repairs by clearing drains, adding *****, removing *****, etc.

The drain pump was not working so I pulled power from the pump and piped drain to gravity which stopped the A3 alarms. Next problem is the compressor will not ramp above 90HZ before it goes back down to 52 HZ even when it's very hot in the space because suction saturation drops below 43 degrees F. Adding ***** causes high pressure to fault. Pressures are 400/125 psi @82 HZ (410a)measured at the line set. I was pressed for time due to evening arrival, I did not have time to check splits inside and I forgot to check the pressure at the service port. Pressures were taken at the line set only. There's only one 3 ton air handler.

Liquid line temp is approx. 87F out of condenser, 87F after check valves to the receiver. Liquid line cools down to 61F after the Y2E sub cooling TXV and an 70F suction line temp.. I shut it down for 10 minutes and static was 260psi or 87F. It's 82F outside and 78F inside so it appears to be non condensable gasses based upon static and press/temps.

I don't know the history of past work beyond 6 months but they've had issues with HP failure alarms 6 months ago. These systems are complicated for most people. You need to go into setting mode 2 and scroll to energize valves to evacuate properly. Just connecting your gauges to the line set and evacuating won't work.

So aside from me not obtaining splits and discharge pressure.......am I missing anything? Thanks for your help.

[install monkey]

gas charge is critical- weighed in, dumping gas in wont increase compressor freq
comp freq is reduced if discharge temp/pressure out of safety zone, also compressor current
http://www.icshvac.com/upload_files/...vicemanual.pdf
click on link above for service manual

[r.bartlett]

. I wonder how well the system has been installed given the drain issues?

as monkey say's gas charge is 'critical' within the guidelines. Remove the gas and vac out for several hours. Then weigh in a fresh charge. That was you eliminate a huge number of potential issues. Then monitor the system and you may find it comes back to you.

[qcfish]

gas charge is critical- weighed in, dumping gas in wont increase compressor freq
comp freq is reduced if discharge temp/pressure out of safety zone, also compressor current
http://www.icshvac.com/upload_files/...vicemanual.pdf
click on link above for service manual

Thanks for the reply. I have a book on this unit from my wholesaler. Amperage and discharge line will unload compressor but both are lower than maximum. When I added ***** the suction pressure rose and HZ went up to 120 but I had to remove ***** due to high pressure. An over charge will do that but it doesn't act like an over charge. My hunch is there are non condensibles and my office will quote the customer on recovery, evacuation, and weighing in refrigerant per OEM spec including line set. Especially since the charge has been removed partially and added to twice that we know of, I will verify pressure/ temperature of recovery bottle to see if it matches 410a table.

Air in a low pressure centrifugal is easy to spot. I've rarely come across a positive pressure machine with enough air in it to grossly effect pressures(40 years). However this machine with all the traps could hold air if it's not evacuated properly. I was curious if someone else has had non condensibles in this type of unit and what were their readings. I'll let you know if I get to return to the site and what were my findings. Thanks again.

[install monkey]

yep, if they didnt drive valves open to degas,pressure test and vac then its a major headache

[frank]

120hz on a Daikin VRV is not high or excessive. Certainly not something you should make an over or under charge decision on.