Suction pipe explosion!!

[Martin Davies]

Hi Al - I mentioned in earlier post that I've recovered a lot of oil from the pack so far I estimate about 15L that was not needed and this was due to the ICM closing during off cycle. However if what Glenn is saying was implemented and the EKC361 was getting its temp input from the S3 then theoretically it would be open during off cycle as the temp would be above 4 degrees - BUT the way it has been wired means both the EKC controllers are getting there on signal from a digital input off of the CC210 and so when the CC210 is in off cycle the relay to both EKC's is powered down and when that happens they both close shut even if a minimum opening degree is set.

[Martin Davies]

Hi Al - I mentioned in earlier post that I've recovered a lot of oil from the pack so far I estimate about 15L that was not needed and this was due to the ICM closing during off cycle. However if what Glenn is saying was implemented and the EKC361 was getting its temp input from the S3 and was set to 4 degrees then theoretically it would be open during off cycle as the temp would be above 4 degrees - BUT the way it has been wired means both the EKC controllers are getting there on signal from a digital input off of the CC210 and so when the CC210 is in off cycle the relay to both EKC's is powered down and when that happens they both close shut even if a minimum opening degree is set.

Glenn I can't stop thinking about what you said about the ICM having no relevance to the superheat control.... Surely the opening degree of the valve which is controlled via the air off probe is maintaining the superheat in the evap? The 316 uses the S2 pipe probe and transducer on the suction line between the evap and ICM to calculate the superheat so this means the two controllers are working together?? I'm really sorry if I have this wrong but if the ICM isn't controlling the superheat then what is?

It's my understanding that the 361 is set 5 degrees lower than room set point as this is the optimum air off temperature to achieve target superheat? Thus allowing all refrigerant to be boiled off before heading back to comp and flooding it. The 361 controlling the superheat like this allows the 316A to calculate the superheat and allow in as much refrigerant as required. They have to work together like this because they are only getting an on signal from the cc210 they are not directly controlling the room temp. Again sorry if my refrigeration theory is incorrect but I'm sure this is the way it's working. Can anyone else say if they think this sounds correct?

[al]

Martin

Not sure how many evaps are off the pack, but if the suction valve was closing on defrost, unless the coolers are all defrosting at same time then room temps must be all over the place?
From a super heat perspective, the suction transducer would be S2 with S1 being a probe strapped after the EEV, but am open to correction on that as it's a good while since i worked on danfoss aKV's.

Have there been many compressor failures?

[Martin Davies]

There are 6 evaps off the pack but each has its own ICM and each are separately controllable so 1 can be in defrost at a time. The EEV is calculating the superheat from S2 pipe probe and transducer both located on the suction line between the evap and ICM

[Glenn Moore]

Hi Martin
The idea of the control was similar to the older plant on this site. If you ignore the CC210 controls and concentrate on the Pack controllers, the EKC316A 's and the EKC 361's and the ambient temperatures around the stores summer and winter.
The pack controllers control the systems minimum evaporator pressure/temperature say at -4 Deg C by switching compressors on or off to match the desired system capacity requirements to maintain the suction condition at -4.
The EKC316A controllers driving the ETS valves with information from the S2 Sensor and the suction pressure transducer control the liquid injection into the evaporators and control the Superheat in the evaps at around the design set point of between 4 and 7 Deg K superheat. These controls try to operate the evaporators with maximum efficiency and lowest stable superheat.
The EKC 361 with the ICM/ICAD motor simply modulates the suction(evaporator) condition inside the evaporator. The pack is running at -4 Deg C so the EKC 361 modulates the evaporator pressure/temperature so that the air OFF the coil cannot drop below 4 Deg C (EKS 361 setpoint). At this time the EKC 316A is still controlling the S/heat between 4-7 Deg K.

During the warm months with the ambient higher than 4 degrees , the cold store will absorb heat through the fabric of the store , and the product respiration load etc, so the pack still runs some compressors keeping the suction at -4 C , the EKC 361's are running holding the evaporator condition up at 4 Deg C .

During the cold winter months the cold store temperature will fall below the desired 4 Deg C .At this point the EKC 361 controls will force the ICM valves to close trying to raise the store temp up to the design 4 DegC. But the ambient outside the store is still very cold dragging the in store temperature below the 4 Deg. The pack now switches the compressors Off. At this point the CC210 thermostats come into play , as the in store temperature plummets below 1 Deg C the EKC 316A controller is switched OFF and the Defrost heaters are now energised with the Evap fans still running.
As the temperature rises above the CC210 differential setting the heaters switch OFF , the EKC 316A is restarted and the EKC 361 starts to open the ICM valves. The suction pressure starts to rise above the set point of the pack controller and the compressors now start to cycle in, and so on.

The EKC 361 when it starts to throttle to close the ICM, this changes the pressure and the temperature of the evaporator the temperature S2 and the pressure converted to temperature (S1) of the EKC 316A begin to equalise to 0 superheat or slightly negative -1 superheat. This causes the ETS valve to be driven closed (No more liquid injected.)
Sounds complicated but is easy when you understand the demands of the system. As I said only myself and one other understood how it was designed to work but like the design for a racehorse its lost in translation and you get a donkey . Send me your Mobile and Ill text you my contact details Glenn

[Martin Davies]

If the 361 was set at 4 and was reading the air on, all of what you just said would make sense and I believe that's how it should be but as I said earlier whoever installed the probes has put them infront of the air off and so the 361 cannot be set to 4 as it would shut the ICM as soon as the evap started cooling as the evaporating temp is about 0. This must be why it is set to -1?? I really need you, the commissioning engineer and the electrician in a room together to sort all this out! My number is (phone number removed to stop the spammer, sent to Glenn via PM, Brian_UK)