Proper/best way to to charge 60dg walk in cooler R-404a
Working on a Copeland R404a 5x7 walk-in cooler maintaining 15C/59F. Have been getting mixed advice on charging techniques. I normally charge to subcooling specs and 20-40dg compressor SH. Am confused about the 10-20dg TD charging rule and how to use it. I understand all freezers have a 10dg TD and Medium to High temp use 15-20 TD Can someone please explaine? Thanks in advance
So many variables......I've really only seen the subcooling method applied to R410a, but thats another story. R404a......Charge with liquid to a full glass. No glass, 30dg over ambient. 10dg subcooling (optimal). As far as heat abortion "superheat"....freezer 7-9, cooler 10-12, a/c 12-15.
Copeland says 30dg......sounds high to me, but they're the engineers.
Hope that helps
This should be in the ARP forum.
Originally Posted by crossthread
Officially, Down for the count
YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET
I know enough to know, I don't know enough
Liberalism-Ideas so good they mandate them
Copeland recommends a minimum 20 to 40 degrees compressor superheat. Within this range you should be able to get the right evap SH. Compressor SH always trumps evap SH. Is this 59 degrees the temp you want or the temp you are getting before topping the charge off?
Tell me more about this unit...
A 5x7 box maintaining 60 degrees? What purpose?
Does it have a receiver? Is the condensing unit outdoors? Is it a pumpdown unit?
Now, ASSUMING that it has a receiver, I'll make the following suggestion.
Charge to a clear sightglass.
Taking it further.
IF the condensing unit is indoors, I'd add a small amount of refrigerant to handle temperature fluctuations.
IF the condensing unit is outdoors, there's a whole nother bit of calculations that are required to properly charge the unit.
Funny but they keep dirt in this cooler for research purposes. Yes unit has reciever, rooftop condnser, yes it is a pump down system.
Print out the document that I linked to earlier in this thread.
Originally Posted by Ken11
Read it and follow the instructions.
You will KNOW that the unit is charged properly.
If you want to get into WHY the compressor has failed in such a short time, you'll need to give us a full set of system operating conditions once you've got it back online
That is a great question, but I'd like to see you post it in the Pro forums. Get you post count up to 15 (only 12 posts to go) and we can answer that question.
Originally Posted by Ken11
Hint: in refrigeration, the "TD" value uses the evaporator suction saturation temp, and in air conditioning, we use delta T, or the return air temp versus the supply air temp. It's a different approach to the subject.
[Avatar photo from a Florida training accident. Everyone walked away.]
2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
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Crossthread- you are talking about sh taken at the evap, which is how it should be set on reefer system. Copeland cares about comp protection.
Copeland cares about compressor cooling. and recommends 30 dg sh, @ the comp. 1dg sh would be fine for protection.
Man can't believe I missed that! Maybe in the aop roe v wade section
Originally Posted by 2sac
Originally Posted by jpsmith1cm
Ok will post in ARP forum, sorry. As for crossthrreads response to charge to a full sight glass, hmmm.... not too sure bout that. R-404a series refrigerants should never be charged to full sight glass based on research from this exact same problem. The first time I did just that and unit was overcharged. I believe i read that in Danfoss refrigeration basics or something. I will find and post. But i never really got an answer as to why you shouldnt charge this series to full glass. Is it due to blend, fractionization capabilities, pressure drop??