Proper/best way to to charge 60dg walk in cooler R-404a

[Ken11]

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

[crossthread]

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

[jpsmith1cm]

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.

[timebuilder]

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

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.

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.

[ruuufuhbock]

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.

[2sac]

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.

[ruuufuhbock]

This should be in the ARP forum.

Man can't believe I missed that! Maybe in the aop roe v wade section

[ryan1088]

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.

^^
Ya that....

[Ken11]

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??

[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??

If you've got a receiver, clear the glass.

Don't care what the refrigerant number is.

Systems without a receiver are a different animal entirely.


Typically, walk in equipment has a receiver, so clear the glass.

[jpsmith1cm]

Ken11,

They were joking a bit with you about a misspelling in your post.

Issues like Art, Religion and Politics belong in ARP...

[jpsmith1cm]

http://sporlanonline.com/90-30-1_072012.pdf


Here are Sporlan's charging recommendations.

Reading them carefully, I see NO mention of leaving bubbles in a sightglass for 400 series refrigerants.

[ryan1088]

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??

I guess you're telling me jp has lied to me this whole time!! Guess I have been doing it wrong this whole time and have every refrigeration system I have worked on charged incorrectly....

Love to see where you are basing your information from!

[Ken11]

like I said will find information and post when I get back to work. I was also surprised to see. Thanks for replies

[Ken11]

oh ok

[Ken11]

Funny but they keep dirt in this cooler for research purposes. Yes unit has reciever, rooftop condnser, yes it is a pump down system.

[ryan1088]

Does it have a headmaster for head pressure control?

[Ken11]

No head pressure control. This really isnt one of the most difficult pieces of equipment at all. I just wanted to make sure i was doing everything correct before I go back and charge. Its only about 2 years old if that, and im already replacing a comp. Not sure what tech. did before me. Old comp. LRA amped. Could have been coincidence but i doubt it. Im pretty sure it was a charging issue the first time.

[jpsmith1cm]

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.

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

[jpsmith1cm]

No head pressure control. This really isnt one of the most difficult pieces of equipment at all. I just wanted to make sure i was doing everything correct before I go back and charge. Its only about 2 years old if that, and im already replacing a comp. Not sure what tech. did before me. Old comp. LRA amped. Could have been coincidence but i doubt it. Im pretty sure it was a charging issue the first time.

A lot of times, that headmaster valve is stuck back in the back and isn't easy to see on a first inspection.

I don't know California's weather, but if your ambient drops much below 50F or so, you'll definitely need some sort of low ambient control to maintain a minimum liquid pressure.