View Full Version : freezer problems
01-26-2007, 05:49 PM
went on a call yesterday on a 15 door freezer not keeping temp. got there and found it was low on refrigerant. i locate and repair 3 different leaks. pull a deep vacuum and recharge unit everything seemed pretty easy and straitfoward,system temp is droping so i pick up and leave. now i go to check up on it today and it is short cycling off on high pressure switch. this is a 408A refrigerant and yesterday it was running at 210lbs high side and 15lbs low. now today the head pressure is cycling off at 310 lbs. i imediatley think i overcharged so i recoer until i see bubbles in the sight glass but it is still going off on hp switch. this is a split system with the cond on the roof and comp inside with a headmaster for head pressure control. so i climb up on the roof and find that neither cond fan is running and they are each controlled by there own t-stat that senses outdoor ambient temp. so i got thinking of how it was about 25degrees f. out yesterday and now today its 0 deg. f. so i get fan running like i assume it was yesterday. go back down stais and now system running real low head press. and headmaster bypassing so i add back into it the recovered ref. Seems to be working fine again. this is not a pumpdown system so im wondering if its a poorly designed system and the cond and receiver are not big enough to hold entire charge or if i just need to keep 1 fan on at all times regardless of temp outside and let the headmaster just control head pressure. just looking for any thoughts with what might be happening. thxs and hope it all makes sense lol
01-26-2007, 09:12 PM
try reversing the lead fan and run it continously. put the other fan on pressure overide. make sure to go back when the weather warms up and reverse the lead fan back.
01-26-2007, 09:36 PM
Since you have a headmaster, shouldn't both fans be running constantly? regardless of outside temp??
01-26-2007, 09:49 PM
One fan needs to run whenever the compressor is on. If the compressor is an air cooled semi-hermetic that fan that blows across the compressor should run continuously with the compressor. It's Ok to cycle the secondary fan on an ambient thermostat as long as it's set high enough to keep the head pressure in a reasonable range.
01-26-2007, 11:02 PM
Run header end fan 24/7 - cycle 2nd stage fan based on pressure if at all possible.
01-27-2007, 12:49 PM
thxs for the replies i will wire the header fan to run at all times and cycle the other on e
03-11-2007, 10:30 PM
markettech, and see what happens.....I do not beleive in that type of environment to run a fan based on ambient...pressure is the best. And like he said keep the end header 24/7
03-12-2007, 12:24 AM
Well my thought is did you get all the leaks fixed? If the system was low enough on gas that it was out, to which you had to pull a vacuum.....did you pull air into the system???? I was looking for you to say the liquid return was hot! Too hot to touch. That would tell you it's not air, if your running 310 psig and the ruturn is cool you have air! Why would you try to start tricking out the fan motors on a system thats been running the same for years??(I'm guessing it's not new) Just my thoughts.
03-12-2007, 02:48 AM
I don't know fellas. Kinda sounds like he's got a big ol' peice of air in the pipe.
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