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Old 08-06-2011, 08:58 PM   #16
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Refrigerant Problem


You guys wear out an AC in 12-15 yrs just like in Florida so all the old recips probably have been changed out. Unless you are an old school guy like myself who started in the trade with recips you don't have the experience with them. I have overhauled car engines, 2 stage 4 cylinder air compressors etc etc so the internals are familiar. ALL compressors have to have a compression ratio and will eventually lose it as they wear. If they cannot buildup enough discharge they cannot get rid of the heat /need to get the corresponding press/temp 20 deg higher than OAT. And if the suction is too high the coil temp goes up.

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Old 08-07-2011, 04:24 AM   #17
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Once you recover and recharge it by weight. You have a starting point, and can check it by SH and SC.

One of the things in this trade, not matter how technology changes. Is that going back to basics, often points us in the right direction to get the system to work right.
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Old 08-07-2011, 07:29 AM   #18
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I'll fess up now, I don't have a scale.
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Old 08-07-2011, 07:33 AM   #19
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I'll fess up now, I don't have a scale.

Buy one, its a basic tool. While not cheap, a good accurate digital scale, is an invaluable tool on many calls.
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Old 08-07-2011, 07:41 AM   #20
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Yuri, here's a two stage compressor that ended up being a high voltage electrical problem to the condenser. Not sure what the compressor is. I also have an old Trane condensing unit with the Roto-Loc compressor in the truck right now. I changed out the entire unit yesterday. I think it's reciprocating.?









Roto Loc unit.
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Old 08-07-2011, 07:42 AM   #21
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Buy one, its a basic tool. While not cheap, a good accurate digital scale, is an invaluable tool on many calls.
Will do. I guess I'm heading out now to try and figure things. Thanks for your help.
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Old 08-07-2011, 08:01 AM   #22
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hard to tell from here and Trane is less than 5% of our market here so I don't see many to know that one. Grind it open and post pics of the internals for us.

I have a Mastercool scale which has been from -40 to 110F in my truck for several yrs and works well.
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Old 08-07-2011, 11:44 AM   #23
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Good news, the home insurance company is footing the bill for a brand new Copeland Scroll compressor, piping modifications, recovery, new refrigerant, disposal, lineset flush, ll drier, and labor.

The homeowner is going to owe $30 total.

Now I can truely start from scratch, Tuesday or Wednesday morning.

I have pics of today I'll be posting in a bit. Suction pressure at 8:37 in the morning was 80, head was 200 with a supply air temp of 65.6 I think it was. Within two hours the supply air raised to 68.9 and the superheat was almost non existant, something like 3 or 4 degrees.

At that point I ws just not going to bother any more with having the evaporator coil cleaned and recovering the old refrigerant and adding new, I just called in for a new compressor so I can start then.

Thanks for all the help guys, I truely appreciate it. Enjoy the pics when I post them.
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Old 08-07-2011, 12:43 PM   #24
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Usually when a compressor is worn it will not draw its full load amps as all the NRG goes into compression. Should do that in your climate especially.

Once you get your charging scale and ONLY if you are careful and have done this B4 you can quickly liquid charge 3/4 of the charge into your system. Pull a deep vacuum and invert your jug and while weighing it charge as much liquid in as you can by flashing it thru your gauges which should have a sightglass. Do it not too fast or you may wash the oil out of the compressor. A charging scale can help a lot for filling an MT system. Beware the hose will add weight to the jug so I record that weight while setup on the scale B4 starting the process. After you are done you can re-weigh the jug to see what you used.
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Last edited by yuri; 08-07-2011 at 01:03 PM.
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Old 08-07-2011, 01:10 PM   #25
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Usually on an empty system I liquid charge through the high side with the system OFF until the gauges read 200-250 psig. Then I crank it on and watch the pressures stabilize which usually means close to freezing on the suction and slightly low head. Then I vapor charge the rest of the way to according superheat/subcool via my Fieldpiece ssx14 or whatever it is digital sh/sc meter.

For this job I'm going to purchase not a scale first but a new pshycrometer for wet bulb and figure out the target superheat by way of wet bulb x's 3 - 80 - ambient divided by 2. That is the correct formula, right?
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Old 08-07-2011, 01:16 PM   #26
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http://www.youtube.com/watch?v=HvXuh8MMIiE
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Old 08-07-2011, 01:35 PM   #27
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I have never used it but I seem to be able to find the charging chart on the back of the electrical box cover 90% of the time. I have a 10 SEER chart and for the rest of the time after 33 yrs of charging units I can do them by instinct/experience. There are other variables like a worn compressor/poor airflow etc etc which affect superheat so there is NO definitive way to do it. Also changes greatly with the higher SEER units. In your case if you can find the factory amount on the sticker then a scale would be a better way to do it.
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Old 08-07-2011, 02:38 PM   #28
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Refrigerant Problem



Before and after the drier. I re-checked at the condenser once more after I checked past the drier and the temp was the same, 94-ish.




Superheat. The clamp is on the suction line.


Backside of the evaporator. Usually it's the front side I'm used to seeing filthy. It's a straight slab coil but mounted diagonally, an old Carrier.


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Old 08-07-2011, 02:44 PM   #29
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Supply air temp, first thing in the morning.
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Old 08-07-2011, 02:59 PM   #30
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That is an OLD Carrier. Compressor is worn and has lost some capacity. Do you have the serial # and I can get the age off it. Like I said earlier B4 you change it just for giggles check the RLA full load amps to see how hard it is working.

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