High suction, normal head and a low TD???? - http://www.hvacmechanic.com/ Forums
Original message
| new tech
 |  "High suction, normal head and a low TD????"
, posted Wed 11 Jun 13:40  
Hey guys, Trying to determine whether or not I have a faulty compressor. Possiblly bad valves??
I have a 2.5 ton York condensing unit model (030) and matching indoor coil, 12 years old (estimated). R-22; metering device is an orfice. I think #63 (don't quote me) 25ft line set length at most from furance to outdoor unit
Ambient 95 degrees...
I have an 82 lb suction; 200 lb head; 59 degree suction line at compressor about (-4 superheat) and 98 liquid line about (-3 subcooling).
Compressor RLA= 13.8 Currently running at 10.3
I am only getting a 13 degree temp difference. (supply air-56) (return air -69)
I noticed that the liquid line is rather small. I think it is a 1/4 instead of 3/8tubing. Does this play a role in these readings?
Can't do any better than the 13 degree TD????
Thoughts.....
Comments/questions welcomed and encouraged
Thanks
E
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Replies:
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| allen1980
| "Re(1):High suction, normal head and a low TD?" , posted Thu 12 Jun 21:26
new tech i would say that the valves in the comp are weak just as you thought.the head should be higher and the suction should be lower the pressures are equalizing do to the valves.
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| theduke03
| "Re(1):High suction, normal head and a low TD?" , posted Wed 11 Jun 20:11
Those are some screwy readings. That head pressure seems low for 95 degrees but your evaporator is full. I'm suspecting an incorrect orifice but that is a stretch although I have seen stranger things. Could the orifice be backwards?(sorry I'm not familiar with york's orifices). I doubt that problem is the compressor valves or size of liquid line.
"My dad was the most feared furnace fighter in Northern Indiana."
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| geo fan
| "Re(1):High suction, normal head and a low TD?" , posted Wed 11 Jun 20:06
over charge reclaime some refrigernt the right way you probly will want a super heat 15+ i would tell you exactly if you stated the indoor wetbulb
ctd2b
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| 341
| "Re(1):High suction, normal head and a low TD?" , posted Wed 11 Jun 16:51
If you have 82psig on the suction side then the saturation temp is around 49F. If your suction line is 59F then your superheat is 10F... not -4F.
Your subcooling is 2F. That seems low, so does your head pressure. I would expect a head of 250 psig or higher with that ambient.
What's the wet bulb reading at the evaporator?
Normally you would slow down your indoor fan to increase the temperature drop. But I agree, the suction is high, the discharge is low, the subcooling is low. If the Amps on the compressor were low then I would say you have an inefficient compressor. They don't seem low though. You might just have alot of humidity. 13F TD isn't too bad.
www.hvactechgroup.com
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| | new tech
| "Re(2):High suction, normal head and a low TD?" , posted Wed 11 Jun 20:37
The wet bulb is 54.4, I believe. I have 68 degrees at the evap. I don't have a psychrometer. I am not sure how accurate this is.
The 2.5 ton coil is married to a york 80k btu furance so, the blower is adequate.
Would you conqer that a 13 TD is adequate. I normally see 18-20 TDs. Also, there is alot of old windows on the house. So there is a lot of excess load. This should not be a influencial factor when dealing with a high suction pressure. Right?
Also, the liquid line does not look like the required size. It is smaller. Would this matter?
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| | theduke03
| "Re(3):High suction, normal head and a low TD?" , posted Wed 11 Jun 20:49:
A 68 DB and 54 WB is not an excess load. Your TD is low because the suction pressure is high. Did you read my previous post or are you disreguarding it as nonsense?
"My dad was the most feared furnace fighter in Northern Indiana."
[this message was edited by theduke03 on Wed 11 Jun 20:50] |
| | new tech
| "Re(4):High suction, normal head and a low TD?" , posted Thu 12 Jun 10:51
Deff. not nonosense the orfice is labeled as a #67...not #63, I as stated previously. I would have to talk to a tech at york's service center as I dont have the proepr literature to confirm as to whether or not this is the correct orfice for this unit.
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| | Freon
| "Re(5):High suction, normal head and a low TD?" , posted Thu 12 Jun 13:47
Have you checked the evap coil to be sure it's clean? All filters clean? Have you checked the blower to be sure the motor is delivering it's stated hp. Before messing with the refrigerant, be sure the air flow through both the indoor and out door coils is nominal. Once you are certain the air flow is correct, then adjust refrigerant.
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| | new tech
| "Re(6):High suction, normal head and a low TD?" , posted Thu 12 Jun 18:32
from my experience a dirty or blocked evap would show low suction pressure and a frozen evap. i might just reclaim the gas and weigh it back in and then see what pressures i get before i jump to anymore conclusions.
ill let u guys know how i make out.
thanks for all the responces.
E
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| | Houston204
| "Re(7):High suction, normal head and a low TD?" , posted Sat 14 Jun 10:48
I would pump it down and install the correct piston before wasting refrigerant. It would also verify your compressor valves if your unit can pump down.
"Tip of the Day" Remember to remove power first.
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| | new tech
| "Re(8):High suction, normal head and a low TD?" , posted Sat 14 Jun 21:42
Great piece of literature, Houston! Thanks, I deff. was going to pump it down or at least try to. If I can get all the gas into the condenser I will then be able to watch and see if the compressor's valves actual hold the refigerant in. Thats the tell-tale sign of bad valves. I would put my money on the fact that the valves are worn. But why? Humm? It's only a 13 year old unit. haha!
Well see! According to your literature all my symptons point towards the compressor.
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| | Houston204
| "Re(9):High suction, normal head and a low TD?" , posted Sun 15 Jun 00:08:
With a 59 degree suction line my money is on your metering device as the problem.
If you have bad valves, it will not pump down. Your amp draw also looks good.
If you could only get 70 to 75 degrees at the suction line I might think it was your valves.
"Tip of the Day" Remember to remove power first.
[this message was edited by Houston204 on Sun 15 Jun 12:46] |
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