Need refrigeration advice

[roberttigar]

Havent touched my refrigeration unit in 10 years. Now it seems to have lost most of its charge. After checking for leaks and finding it secure, I attribute the loss of some pressure to less use this year because of other commitments and some really awful weather for the last 4 months.

I am prepared to vacuum it out and recharge. I also bought a can of oil and and a can of Stop leak. These are 3 oz cans mixed with 134a. These seem like a good preventive measure, just in case.

Should I add these before I add any 134a, in between or at the end?

System has 2 cold plates, a 12v reciprocal (or rotary?) York compressor and a water cooled condenser.

Thanks, Bob

[Bowdrie]

Originally Posted by roberttigar

a 12v reciprocal (or rotary?) York compressor and a water cooled condenser.

Just a bit more info would be nice.
A 12V York?
Do you mean that you have a York compressor that is driven with a belt from a 12V motor?
Two cold plates?
One for reefer, one for freezer?
Is the system using TXV or cap-tubes?

[SailingHarmonie]

The oil doesn’t normally leak out. Do you really KNOW you need more?

Adding any kind of stop leak to a capillary tube system will destroy it because a cap tube is basically a tiny, controlled leak put to good use.

It sounds to me like you are throwing stuff at the wall and hoping the right stuff sticks. With refrigeration this approach is far more likely to result in an expensive mess than actually fixing anything.

[roberttigar]

Bowdrie Both cold plates are in the refrig, not capilary tube but expansion valve. Yrst 12v motor belt drives the compressor.


Sailingharmonie-yea you are kind of right. thats why I asked about the oil and stop leak.


until the system lost pressure it worked fine for 9+ years. It holds pressure now. I guess I'll go on the asumption that the loss might be a little leak around the shaft as some of literature on old systems suggest. I'll just vac the system and charge with only 134a.


Bob

[Bowdrie]

Originally Posted by roberttigar

Havent touched my refrigeration unit in 10 years. Now it seems to have lost most of its charge. After checking for leaks and finding it secure, I attribute the loss of some pressure to less use this year because of other commitments and some really awful weather for the last 4 months.
I am prepared to vacuum it out and recharge. I also bought a can of oil and and a can of Stop leak. These are 3 oz cans mixed with 134a. These seem like a good preventive measure, just in case.

Addendum; If the compressor is a belt drive it probably uses a carbon ring seal where the crankshaft exits the compressor, (kinda like the one in your vehicle AC).
The surface those seals ride against are lapped within a few helium light bands, and they use and depend upon a film of oil to seal effectively.
Leaving the system unused for long periods of time allows the pressure to slowly leak past the seal.
You don't need "stop leak" added, and unless there has been some kind of catastrophic "blow-down" of the system resulting in oil being blown out of the compressor you won't need any oil either, (some compressor models have a sight-glass on the crankcase, if so, the oil level should be middle-of-glass when compressor is stopped).
However, the replaceable filter-driers do collect some oil, and as a portion of oil is always circulating along with/mixed with the refrigerant it is good practice to add a bit of oil when changing filters.
If your system is using the common C-062 or CH-062 it doesn't hurt to just squirt ~ounce into the new filter just before you change filters.
On big systems different methods are used for adding oil, but with the little fractional Hp units putting the oil into the new filter is sufficient unto the cause.
If your using the C-162 or CH-162 then add 1-1/2 ounces of oil.
Before putting a vacuum pump on the system crank the compressor over for a bit to pump some fresh oil up to the seal.
As those seals are designed to keep high pressure in rather than keep the atmosphere out, they will allow outside air to leak in if a very high vacuum is maintained for a long period.
If system has a replaceable filter-drier it should be changed before the vacuum pump does its work.
After vacuuming is done it helps to "sweep" the system with a small bit of refrigerant and then vacuum for a little bit more.
You just bleed a very small amount of refrigerant into the high side while the pump is still pulling on the low side.
It helps to get whatever residuals are in the system to "move along" to get picked-up and discharged by the pump, (as pressure goes down, "more vacuum", the motion of residuals/non-condensables slows down).
You'll not recharge by pressure; the high side pressure is dependent on the water temp in the condenser.
Unlike cap-tube systems which are always "kinda full" a TXV system needs room to store refrigerant as the valves throttle and/or condensing temps increase.
At the end of the run cycle when the plates are frozen and the TXVs are throttled down the sight-glass should still show some "open space", not show 100% full.
This shows that when the water temp rises that there is still some room in the receiver to store refrigerant.

[Bowdrie]

Sorry, I misspoke, I said C/Ch-062, and I meant to say C/Ch-082.

[roberttigar]

Bowdrie...thanks very much. Just the information I needed. Bob

[RaymondR]

Good post Bowdrie.