Blast Freezer Temperature Can not come down.why?
We exported 5 units of cold rooms to South Africa. 2 cold room chiller with -5C to +5C, 2 cold room freezer with -18C,and one blast freezer.
The blast freezer cold room size is L5mxW4mxH2.5m, temperature is -30C, each time input capacity is 800kg to 1000kg, freezer time is 10 hours to 12 hours.
Our solutions: 150mm PU panels with a 800mmx1800mm door,23HP Bitzer(4GE-23Y) with R404A gas,Evaporator is DJ140 and water type defrost. Expansion valve is Danfoss brand.
When finished installation, the temperature can come down to -30C easy from +38C , the pressure is 0.1Mpa for low pressure and 1.7Mpa for high pressure. it works for 3 month later.one day, customer call us and told us the temperature can not come down from -17C, we they set -30C in temperature control. why? now high pressure is 1.9Mpa and low pressure is 0.1Mpa. high pressure is much more higher than before. so inform them to push some cool water on the condenser and check, after two hours, high pressure reach 1.7Mpa.but temperature still not come down. at this time, expansion valve no ice or frost cover it, head of compressor(low pressure) frost is not too much. our engineer inform them to check if any place leak freon and some air come to system.
So they are checking and find leak. but as you know. if leak R22 freon, we can charge more freon,but if leak R404A, we must leak all freon and make vacuum,final charge new R404A refrigerant.
Notice: (1)when cold room can not make cool air,please check high and low pressure gauge,if they are all lower than before, we are sure,the system leak gas.
(2)The pressure of R404A will be much higher than R22 system.