PDA

View Full Version : Blast Chill







Big Frank
08-06-2016, 10:43 PM
Hi... I was running up a new blast chill today. It was an existing cold room. I just put in Blast chill kit to transform it. J&E hall condenser, frrigo bohn stand alone cooler. All really big kit. All sized by tech chap at suppliers. Anyway charged up up with 9kg of R404.. Ran system... Sight glass flashing away. Flashed in another 8kg. Compressor icing up but not too bad but sight glass still flashing.. If I opened the door in the room the sight glass would go clear but as soon as I closed the door the sight glass would flash again. Anyway long story short it eventually went clear. 18kg of R404a inside... Room seemed to be pulling temp really well. Had room set for -4 when charging but had to keep the door open to charge it as I didn't want it to cut out. Then set the room to -2 and it cut out in no time with door closed. Went back out to see condenser cut back in but wouldn't cut back in.. Checked and was out on head pressure. reset switch again. Unit would go out on head pressure in 4 seconds every time. 24bar.... No restriction on discharge, nothing front seated.. Put a coil on the solenoid which was lifting perfectly prior to that and it wouldn't lift. I kept at it and eventually the coil lifted with magnet plunger. Put back on the coil and it would run away until it cut out again on temp, Then out on head pressure as soon as the coil de- energises. I want to pump it down and see if there is any dirt in the solenoid body but with the J&E hall unit if you front seat the service valve after the sight glass the head pressure goes in the opposite direction as in reduces just like when I front seat the valve on the receiver tank. They don't seem to be like a normal condenser where the back pressure drops when you front seat the receiver. Can anyway point me the right direction here/ Thanks

frank
15-06-2016, 09:18 PM
Hi Big Frank and welcome to the forum

You haven't posted any running pressures or temperatures so it is difficult to picture what is happening, but, as you seem to be charging to 'a clear sight glass' you may have over charged it.

With an excess of refrigerant in the system, the excess can settle in the bottom of the condenser, thereby reducing the effective area of the coil. This is a classic symptom as you say it now goes out on HP.

High pressure faults relate to the system not being able to reject the heat of compression and absorbed heat. As your system goes out on HP really quickly we can disregard the absorbed heat, and I would say that your condenser is mostly filled with liquid, i.e. it is acting like a receiver. If you can get the system running long enough, you can check this with a 'touch' thermometer by measuring the temps on the coil returns.

I would suggest that you recover most of your charge, restart the charging process and measure superheats to determine the correct charge amount, rather than relying on a clear sight glass.