Pressure on water cooled condensing units

[oneofthesedays]

Just went to Copelands website and got the data sheet for the compressor I'm working on. Under performance data for a 20 degree evap and 120 degree condensing temp the data sheet states that compressor is rated for 6.20 amps. The RLA is 5 amps.
This may be my issue. Should I be looking at 6.2 amps for running amperage at a satisfied box based on the data sheet? Or am I misunderstanding the ratings? I now know for the past twenty years I was interpreting RLA incorrectly. Whoops! Compressor model is KWTA-0150-TAC

[VTP99]

Wow............how many words can you type per minute ? That would have taken me all day Mp39 is a good refrigerant to stay with, although it is getting very pricey. How many pounds you talking ? How many compressors ?

[jdwendling]

Ice am I on the wrong page? I just got a jug of R438A--MO99. A R22 replacement.

[VTP99]

Ice am I on the wrong page? I just got a jug of R438A--MO99. A R22 replacement.

R 437a

[icemeister]

Ice am I on the wrong page? I just got a jug of R438A--MO99. A R22 replacement.

Oops! You're right.

R 437a

Thanks

[VTP99]

Oops! You're right.

Thanks

So many numbers it's getting out of hand
Bring back 12 & 502

[oneofthesedays]

Thanks again to all who have responded,
I've edited an earlier post but probably should have posted the info seperately.

As Ice asked, the model number on the compressor is KWTA-0150-TAC. Equipped now with a better understanding of RLA (everyone I've asked thought that RLA was run amps as well)

I have a new question. On the performance sheet on Copelands web site for this compressor, it lists RLA as 5 amps. But under the 20/120 performance data, it lists amperage draw at 6.2 amps. ? I thought RLA was a rating you wouldn't want to exceed. Should I be o.k. seeing that compressor running at 6.2 amps? If thats the case I should be able to get my head pressure up and still stay within the amperage listed as 6.2. Does the performance data relate to a warm or a satisfied box? Thanks

[VTP99]

Just fellow the performance sheet as per your conditions. A warm pull down will generally pull higher amps.

[icemeister]

...I have a new question. On the performance sheet on Copelands web site for this compressor, it lists RLA as 5 amps. But under the 20/120 performance data, it lists amperage draw at 6.2 amps. ? I thought RLA was a rating you wouldn't want to exceed. Should I be o.k. seeing that compressor running at 6.2 amps? If thats the case I should be able to get my head pressure up and still stay within the amperage listed as 6.2. Does the performance data relate to a warm or a satisfied box? Thanks

The listed RLA of 5.0 Amps is based on a formula of the maximum continuous current (MCC), which is listed as 7.0 Amps, divided by 1.4 and is used for sizing the contactor. You'll note there's a second RLA of 4.5 Amps for this compressor. That one is MCC/1.56 and is used for wire and breaker sizing.

The 6.2 amps at 20/120 is still safe, but since this water cooled compressor is designed to run at 105ºF SCT, the normal amp draw would be lower. The MCC is 7.0 Amps, so yes, you're high, but still OK. The trip point will be somewhat higher than 7.0 amps.

If you raise the head higher than 120, then the amps will go up according to the performance chart. It's the same thing whether you have a warm box or a cold box. Whatever the pressures rebalance to, you need to move to a new spot on the chart corresponding to those pressures to get your new expected amp draw.

[crymtide]

At some point you're beating a dead horse. Cut your losses, pull the charge, (if I didn't put it in myself I don't know what's there) and start from scratch. Then you know what refrig. you have and how much. Not to mention that with the cost of water/sewer it wouldn't take long to recover the cost of an air cooled system. R-12 is a dinosaur and you need to get it out and switch to something that is available, and will continue to be available. I am no fan of 408, or 409, but if you can't change to air cooled; then the whole idea is to get it running. Also by pulling the charge and starting from scratch you will know that you are not under or over charged.You have mentioned quite a few possible issues and it's time to start taking control by getting a fresh start by chopping out the variables and controlling the situation.

[Russ57]

Personally I love water cooled condensers. I run my off cooling tower water. Keeps everything self contained and my head pressure a constant.

One thing I'd caution. Get your superheat under control. Think hot gas discharge temperature rather than just head pressure. I like MP39 a little better but likely I'm in a warmer climate.

I don't know what you have for a condenser. Mine are big old shell and tube types and I do have liquid line solenoids. I can pump down the unit and replace a water valve with ease. I then install one of those tees with shrader valves in them on the head for the water valve and pressure switch. It makes future replacement a breeze.

Set the head pressure for 105 SCT (110 will work and save a ""little" water). SST should be about 10 degrees colder than the box. Temperature of the suction line at the compressor ideally should be about ten degrees higher than box temperature. Check your oil. With the superheat as high as it is it could be cooked and your TXV screen could be plugged. I run 100% alkyl benzene oil in mine. 1970's vintage and still going strong

[oneofthesedays]

Thank you to all who have responded. Your input is greatly appreciated. I've decided to get out of the business and buy an ice cream truck. Kidding. Does Copeland offer any type of factory training on their compressor line, or are there other resources available? I have a few chillers I work on and would like to increase my knowledge in respect to the proper operation and diagnosis of their compressors in those units as well as the smaller splits I'm working on such as the one described in this post. Thanks.

[wildtech]

I've had goof luck with mo49 On old racks that used to be r 12 then got converted to mp39 then by us to mo49 after mid night salvage removed the cond and we replaced it although one thing we had going was Pluged tx strainers and ll filters but that may have just been from sh&t breaking loose on an old system which is commOn when all the gas went bye bye and it was started up again 1000 pound system ah prob a little more