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Thread: Walk-in freezer charging
08-06-2012, 01:13 PM #40
You've got alot of good info on this thread now go kill it and drag it home.
08-12-2012, 09:30 PM #41Regular Guest
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- Aug 2012
[QUOTE=Tommy knocker;13917851]You've got alot of good info on this thread now go kill it and drag it home.[/QUOTE
I did just that! Sorry for the delay in an update but the last week has been busy. The 100 degree + Month of July sure weeded out the weak ones.
My walk-in is up and running and has been for a week. I am notb entirely sure I have a complete full charge yet that will operate system @ -20 ambient. but it is working well in the 65-100 degree ambient we have been experiencing the last 10 days. I still do have a couple of questions though.
On determining a full charge to (-20) ambient this is the way I figured it based on the the Sporlan bulletin 90-30-1.
Condeser is 3/8" tubing, 28" long with a total of 42 tubes and 42 return bends.
42x28=1176/12=98lf of tubing 42x.200=8.4lf for the return elbows Total tubing =107lf
107x .050= 5.4 lbs additional refrigerant after inital fill to clear sight glass.
My initial charge was 6lbs 4 oz to clear sight glass. I added and additional 4 lbs beyond that. In my mind 5.4 lbs additional seemed like alot for the small system that this is. That would put the total charge at aprox 12lbs. Right now it has 10.5 lbs. I understand the problem may come as Winter gets here and the ambient drops. Did I figure the additional charge properly?
Is there a way to tell if a system is indeed charged for all ambient temps without dumping the charge and starting from scratch?
Next, Sub cool as I measure it is somewhere between 6 and 9 degrees. From what I read suction temp and pressure should be measured at the TXV bulb. Temp is not a problem but this system has no service valve at the evaporator. Service valve on suction line is located on condenser which is just outside the cooler with about 8' of insulated line in between.How accurate is my subcool temp? Seems to me you might have a slight rise in suction temp/pressure between the evap and the service valve.
Thanks again to all who have helped. I found out this week that I might just have a little more knowledge about this system than my boss who had this job before me. Great guy but when I began to explain the charging procedure to him I could see the lights go out and he just said "do whatever you think is right"!!!
08-12-2012, 09:52 PM #42Local 597 Service Fitter
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It was working when I left...
08-12-2012, 10:12 PM #43
08-12-2012, 10:33 PM #44
You misseded a step.....
Once you arrived at the 5.4# figure, you need to take that number to Table 2.
So, assuming (bad idea, I know) a -25F evaporator and a -20F minimum ambient, you need 88% of that 5.4# figure or 4.752#.
Since you've already put 4# in past a clear glass, add 12 ounces and call it DONE!
08-12-2012, 11:11 PM #45Regular Guest
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- Aug 2012
08-13-2012, 06:01 AM #46
08-13-2012, 09:30 PM #47
Good to see you got it and I would leave that charge right where it is for K,C.Never kick a lying dog.