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Access to a sealed system
July 10, 2010
11:09 am
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Steve Pooler
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reefgeorge said:

Sounds like after leak detection, the next thing is service ports on both sides?


Simple Answer ?...Yep  Wink

Steve~

July 10, 2010
9:27 am
reefgeorge
Melbourne, Fl.
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Sounds like after leak detection, the next thing is service ports on both sides?

July 10, 2010
8:28 am
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Steve Pooler
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reefgeorge said:

Steve

Is the compressor OK as long as it is still running and not cutting out…No, and that's what I've been trying to say…Just because a compressor runs, does not mean it can pump the flow rate it was designed to pump…Just like a car that has leaky valves…It will have a loss of compression, and therefore a loss of power…It's also why both High & Low side service ports are important for troubleshooting…Low head & High suction could be indication of the compressor not pumping well…I have not started this unit in months but it was starting to smell hot so I shut it off. Now that I understand HVAC and refrigeration better and the refrigerant cooling the compressor, I would have shut it off at the first sign of cooling deficiency but I did not.

Obviously we cannot monitor pressures in a sealed system so I will start it up, check for leaks…First look for evaporator leaks with the compressor not running…The compressor running will likely pull the evap side into a vacuum (if it is good & enough freon has leaked out) thus a leak would not show to your sniffer as the compressor is only sucking in air (moisture too) thru that leak… and look at compressor temp, compressor amp draw, and signs of any cooling capacity but are there any other things to check before opening the system to determine my starting point?…Not really…You are blinded without gauge ports…It's all guessing…and by now enough freon may have leaked out that a leak will not show at all...

Thanks.


July 9, 2010
5:29 pm
reefgeorge
Melbourne, Fl.
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Steve

Is the compressor OK as long as it is still running and not cutting out. I have not started this unit in months but it was starting to smell hot so I shut it off. Now that I understand HVAC and refrigeration better and the refrigerant cooling the compressor, I would have shut it off at the first sign of cooling deficiency but I did not.

Obviously we cannot monitor pressures in a sealed system so I will start it up, check for leaks and look at compressor temp, compressor amp draw, and signs of any cooling capacity but are there any other things to check before opening the system to determine my starting point?

Thanks.

July 9, 2010
8:43 am
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Steve Pooler
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reefgeorge said:

This unit just started loosing cooling capacity/evap coil temp slowly. Sub zero told me that a leaking evap coil is common. Air circulation is good on this unit.

I am set on rehabilitating this unit. I have the evap coil and a compressor on hand but only want to replace what is needed.

I have a leak detector.

Is the process stub on the high or the low side?   Yes the process port is on the low side.

It sounds like any access needs to be on the high side since you can evacuate and vacuum on either side but you have to weigh in a critical charge on the high side?   Yes since you don't want to dump liquid on top of the valves or piston…Doing so will lock the compressor because you cannot compress a liquid.

this unit did run for a while with marginal cooling so the compressor may have been damaged.


If the compressor was overheated from lack of charge…It could have pumped any internal burnt junk out to the drier…be sure you replace the drier either way to avoid that junk from blocking the cap tube…Also when windings overheat/burn they create an acid that is also pumped throughout the system (with the oil) that will eat away at the new compressor windings…

There are products to neutralize that acid like "Acid Away" but always replace the drier….

It should be a fun learning experience for you…But usually not one that is economically feasible for us to do if the box can be replaced easily.

But then there are the boxes like one I worked on recently on a 106' Burger that getting the 26 cu ft Sub Zero out would have been a cut a hole in the cabin top type project to lift it out with a crane…Cry

Steve~

July 9, 2010
7:52 am
reefgeorge
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This unit just started loosing cooling capacity/evap coil temp slowly. Sub zero told me that a leaking evap coil is common. Air circulation is good on this unit.

I am set on rehabilitating this unit. I have the evap coil and a compressor on hand but only want to replace what is needed.

I have a leak detector.

Is the process stub on the high or the low side?

It sounds like any access needs to be on the high side since you can evacuate and vacuum on either side but you have to weigh in a critical charge on the high side?

this unit did run for a while with marginal cooling so the compressor may have been damaged.

July 9, 2010
7:26 am
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Steve Pooler
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reefgeorge said:

How do you access a sealed refrigeration system to reclaim, change out, evacuate, and weigh in the charge? My first "victim" is an 8 year old Sub Zero 700BR (134A) on a boat that most likely has a leaking evap coil....I would first verify if the coil is leaking...If that is the case then you may be wasting your time to go any further...Do you have a electronic leak detector ?

I see bolt on piercing valves, are these any good? If that's the starting point, do you go with a more permanent valve after the system is reclaimed? What do you do with the pierced hole?...In my experience, the bolt on valves usually end up leaking...A pierced hole can either be soldered up, or cut out later when you solder in a copper Tee for a standard access port. 

I see valves that solder/braze on. Is this safe on a charged system? I would imagine that Stay Brite #8 is safer than brazing...The solder on piercing valves are best, and yes there is a risk of melting the tubing and causing a blowout if you are not careful with the torch...

Do you guys pierce/attach on the main line or the process stub?...Doesn't matter much, but I would also put in a high side port...This is helpful for troubleshooting & balancing the charge later...It's also needed for weighing in a measured liquid charge...You don't want to dump in liquid on top of the valve plate/piston.

How about adding a site glass?...Site Glasses don't work well with cap tube systems...

I want to get in without an explosion or poison gas, have a leak free solution, and be able to re-access/monitor if needed. This is a real system that needs fixin' but is also a learning vehicle for me.


If the box was living in a hot location like inside a cabinet with a door that closes covering the kick plate breathing ports (very common on boats) Then the unit has most likely been re-cycling it's own hot air discharge back onto itself, and has weakened the compressor valves from high head pressure...The compressor then won't pump well enough to cool the box...

Steve~

July 7, 2010
12:35 pm
reefgeorge
Melbourne, Fl.
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How do you access a sealed refrigeration system to reclaim, change out, evacuate, and weigh in the charge? My first "victim" is an 8 year old Sub Zero 700BR (134A) on a boat that most likely has a leaking evap coil.

I see bolt on piercing valves, are these any good? If that's the starting point, do you go with a more permanent valve after the system is reclaimed? What do you do with the pierced hole?

I see valves that solder/braze on. Is this safe on a charged system? I would imagine that Stay Brite #8 is safer than brazing.

Do you guys pierce/attach on the main line or the process stub?

How about adding a site glass?

I want to get in without an explosion or poison gas, have a leak free solution, and be able to re-access/monitor if needed. This is a real system that needs fixin' but is also a learning vehicle for me.