Results 1 to 6 of 6
-
19-08-2014, 12:01 AM #1
HP cutout on chiller - every 3 or 4 days? Operating readings posted
Hello,
I attended a call out today which was because one circuit on an R407C chiller cut out on HP. The landlords said it cuts out every 2 or 3 days on the same fault, and it's always the same compressor circuit (there are two circuits in the chiller). I recorded all the operating data for circuit 2 and there was nothing there that greatly concerned me; however the evaporating temperature seems low, but it's the same temp as circuit 1 which never cuts out - and the chiller provides the correct water temp. The evap superheat is bigger then I would like, but I can't see how that would directly lead to a high pressure cut out after a few days of running. I recorded the other circuit to compare and the results are near enough identical. I'm thinking there could be an issue with the HP switch, possibly cutting out at a lower pressure then intended. I wasn't able to test this during the visit as the HP switch isn't connected via a schraeder connection.
All three fan motors are working fine and are spinning the correct way, and the condenser coil is not dirty as we carried out a full maintenance on the chiller a few months back and the coil is fine.
My readings are:
Compressor 2 (The circuit that cuts out)
Condensing pressure - 16 BarG
Condensing temperature - 44degC
Discharge pipe temp - 87degC
Discharge Superheat - 43K
Liquid line temp - 38degC
Sub cooling - 49K
Evaporating pressure - 2.4 BarG
Evaporator outlet pipe temp - 1degC
Suction inlet at compressor - 2degC
Superheat at evap outlet - 15K
Superheat at compressor inlet - 16K
Evaporator temperature - -14degC
Water flow temp - 8 degC
Water return temp - 11 degC
AHU Supply air temp - 16 degC
Compressor 1 (The circuit that works fine)
Condensing pressure - 16 BarG
Condensing temperature - 44degC
Discharge pipe temp - 89degC
Discharge Superheat - 45K
Liquid line temp - 38degC
Sub cooling - 51K
Evaporating pressure - 2.55
Evaporator outlet pipe temp - 2degC
Suction inlet at compressor - 3degC
Superheat at evap outlet - 16K
Superheat at compressor inlet - 17K
Evaporator temperature - -14degC
What do you guys think of the above readings? Anything jump out?
Like I say the low evap temp and large superheat is slightly concerning, but with a return water temp of 11degC, the pressure would be low anyway in order to remove heat from the water.
cheers chaps
-
19-08-2014, 12:18 AM #2
Re: HP cutout on chiller - every 3 or 4 days? Operating readings posted
Dammit. Just read through, my liquid line sub cooling is 6K....not 49/51K as I put..... Very tired!
-
19-08-2014, 12:23 AM #3
-
19-08-2014, 05:16 AM #4
Re: HP cutout on chiller - every 3 or 4 days? Operating readings posted
Hi
first look at client load profiles and changes in production, lead lag on chiller as well. compressor load rates etc., client could be doing something different every 3 or 4 days and load responses are being effected that creates HP fault.
regards magoo
-
19-08-2014, 09:32 AM #5
Re: HP cutout on chiller - every 3 or 4 days? Operating readings posted
Just check HP cut out, it's the first easy thing to check.
Raise the discharge pressure by whatever means if it hard example turn off condenser canes or restrict air/water flow.
Set it to 10-15% below relief valve setting or pressure vessel max rating design pressure.
Compare it to unit that runs ok.
-
19-08-2014, 07:53 PM #6
Re: HP cutout on chiller - every 3 or 4 days? Operating readings posted
I would also be looking at the condenser fans, contactors, loose wire etc.
Without the condenser fans staging in as expected, a HP trip is likely.