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Originally Posted by crossthread

10-4, I agree. The original post was for some explanation on charging or rules of thumb. (not sure how to repost with my reply) So I gave a few. This not being a diy site, Didn't want to give to too much info. Just enough so anyone in the trade could find a few key points helpful. If we want to go crazy...I want pressures, sh, sc, amp draw, sight glass, were going see this box satisfy and make sure she pumps down. In the mean time if this isn't our account were checking the other equipment and working up a maintenance contract. Who was the last company out here?

Good point about no diy, I agree that its impossible to make a good diagnosis will out a full set of readings. sorry if it seemed like I was jumpin down your throat! Welcome to the forum BTW

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?

10-4, I agree. The original post was for some explanation on charging or rules of thumb. (not sure how to repost with my reply) So I gave a few. This not being a diy site, Didn't want to give to too much info. Just enough so anyone in the trade could find a few key points helpful. If we want to go crazy...I want pressures, sh, sc, amp draw, sight glass, were going see this box satisfy and make sure she pumps down. In the mean time if this isn't our account were checking the other equipment and working up a maintenance contract. Who was the last company out here?

We protect it by keeping it cool and ensuring that no liquid returns, I'm just saying with a reefer system charging it by checking compressor sh is a poor practice. I'm not saying it shouldn't be checked but sh should be checked and set at the evap. If its set 10* at evap but running 45* at compressor then there needs to be secondary means of cooling the compressor.

I think they call 404a a "near azeotrope" and so its fine.....However not the case for 414b.

ABSORBTION........too funny.

Copeland cares about compressor cooling. and recommends 30 dg sh, @ the comp. 1dg sh would be fine for protection.

Originally Posted by 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.

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.

Originally Posted by 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.

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

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.

Does it have a headmaster for head pressure control?

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

oh ok

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

Originally Posted by 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??

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!

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.

Ken11,

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

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

Originally Posted by 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??

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.

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??

Originally Posted by 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.

^^
Ya that....