Advice on nova kool lt201 recharge

[Josephcrawl]

I've recently installed an lt201 kit into my icebox. It has been used in a couple of previous fridge projects over the years. So it has been disconnected three times and each time has lost some refrigerant. It is still cooling but slower than I remember. I would like to recharge the unit. Nova kool recommends using a vacuum pump to empty it completely then recharging with the weight of refrigerant listed on the compressor label.

I've watched some utubes in the subject and understand the general idea. Wondering if anyone here has some tips, tricks or pitfalls to pass on.

Thanks!

[Turtle Blues]

In addition to the amount of refrigerant you loose you also introduce moisture which is worse.
Yeah, to do it right you need to recover what is inside the system, pull 30" vac for a good period of time to assure it is dry, and then weigh in the new oil and refrigerant charge.
Unless you have all the equipment necessary probably easiest and least expensive is to hook it up and then call a tech to do the evacuation and startup for you. Alternatively if you reconnect the lines, pull a vac on them, break that with refrigerant you can then add what is required by using the pressure / temperature method. Trouble is you are dealing with a relatively small amount of I'm guessing R134, and this method won't remove the moisture already held in the existing refrigerant.

[Josephcrawl]

I've found a used vacuum pump with the hoses and gauges for $75. Figured I would put the can of refrigerant on a scale to get the proper charge on the system. Not sure about the recovery but I guess I could find an empty can of refrigerant at the scrap yard but then what do I do with the can?

[Josephcrawl]

Another question I can't figure out is where I can obtain a small can of 134a. It is my understanding that the automotive type uses a different oil and should not be used.

[Josephcrawl]

Originally Posted by Josephcrawl

Another question I can't figure out is where I can obtain a small can of 134a. It is my understanding that the automotive type uses a different oil and should not be used.

After looking at the MSDS sheet for various r134a cans from the auto parts store some are just r134a.

Also has anyone paid to have a recharge? How much was it? Sounds like the procedure should be done in under an hour.

[Josephcrawl]

I have the vacuum pump and about to start this recharge process. Everything I've seen about vacuuming does the process on the high side of the system which on the nova lool would mean adding a piercing valve which I would rather not do. What are the alternatives? Can the low side be vacuumed using the existing Schrader valve? Will this pull the oil from the compressor? Is it possible to just attach the manifold here and vent the r134 to atmospheric pressure and then do a weighed recharge? I would imagine if it is under pressure it would not allow air back in.

[Bowdrie]

Originally Posted by Josephcrawl

I have the vacuum pump and about to start this recharge process. Everything I've seen about vacuuming does the process on the high side of the system which on the nova lool would mean adding a piercing valve which I would rather not do. What are the alternatives? Can the low side be vacuumed using the existing Schrader valve? Will this pull the oil from the compressor? Is it possible to just attach the manifold here and vent the r134 to atmospheric pressure and then do a weighed recharge? I would imagine if it is under pressure it would not allow air back in.

Yes, the system can be vacuumed from the low side, it will just take somewhat longer because of the tiny cap-tube.
You can leave the vacuum pump on as long as you wish, it will not pull oil out of the compressor.
A few grams of released refrigerant is pretty much un-avoidable, don't worry too much about it.
You'll need a good electronic scale to weigh-in a charge, we're talking grams/ounces, overcharges are easy to do.
No reason for air to get back in, you will use your refrigerant to purge the middle line on the gage set after first closing the manifold valve(s) before disconnecting the middle hose from the vacuum pump.
Perhaps this is a better explanation.
1, You're finished vacuuming the system.
2, Make sure both valves are closed on the manifold.
3, Now turn off pump and disconnect the middle hose from the pump.
4, Attach your "tapped" refrigerant can to the middle hose and open your valve on the can of refrigerant.
5, Unscrew the middle hose connection at the manifold just enough to hear/see/feel, (whatever,) some refrigerant escape that connection.
6, Re-tighten the connection.
7, Place your refrigerant cannister on the scale and then open the low side manifold valve to allow flow into the system.
8, Keep track of how much you're putting in.
Needless to say, things like flopping hoses can easily affect your scale readings, be patient, take it easy.
There are "workarounds" if "scale work" is too daunting or un-satisfactory.

[Josephcrawl]

Originally Posted by Bowdrie

Yes, the system can be vacuumed from the low side, it will just take somewhat longer because of the tiny cap-tube.
You can leave the vacuum pump on as long as you wish, it will not pull oil out of the compressor.
A few grams of released refrigerant is pretty much un-avoidable, don't worry too much about it.
You'll need a good electronic scale to weigh-in a charge, we're talking grams/ounces, overcharges are easy to do.
No reason for air to get back in, you will use your refrigerant to purge the middle line on the gage set after first closing the manifold valve(s) before disconnecting the middle hose from the vacuum pump.
Perhaps this is a better explanation.
1, You're finished vacuuming the system.
2, Make sure both valves are closed on the manifold.
3, Now turn off pump and disconnect the middle hose from the pump.
4, Attach your "tapped" refrigerant can to the middle hose and open your valve on the can of refrigerant.
5, Unscrew the middle hose connection at the manifold just enough to hear/see/feel, (whatever,) some refrigerant escape that connection.
6, Re-tighten the connection.
7, Place your refrigerant cannister on the scale and then open the low side manifold valve to allow flow into the system.
8, Keep track of how much you're putting in.
Needless to say, things like flopping hoses can easily affect your scale readings, be patient, take it easy.
There are "workarounds" if "scale work" is too daunting or un-satisfactory.

Thanks so much for this excellent explanation! Right after posting I called the HVAC teacher at my local tech school and he gave me this same info. He recommended running the vacuum for an hour or more because of the capillary tube restriction. He also said I should let the system take as much charge as it will before turning the system on to finish the recharge. And of course because it is the low side keep the can upright so that only vapor enters the system not liquid refrigerant.

[Bowdrie]

Yes, the HVAC teacher is right, I didn't give a specific time frame to run the pump, more is better.
On larger systems I've let pumps run all day, (and a few overnight).

[Josephcrawl]

Did the recharge as described above and the fridge is working great. Hope this helps someone else.