does the three phase reciprocating compressor has the phase requirment?

[comfortable air]

I rewired a rooftop and checked the operation. suction pressure :70 psig, discharge pressure:220 psig. one phase current of the compressor is only 5amp, but the tag is said 8.8amp. I don't know why there is so big difference. does the three phase compressor have phase requirment? the compressor rotate in a wrong rotation because the phase?

[NormChris]

This article is what you need. It seems to address your problem exactly.

http://www.bacharach-training.com/norm/protecting.htm

Norm

[igwt777]

You should verify rotation prior to start a 3 ph scroll compressor. It does not make a difference in the rotation of a 3 ph reciprocant hermetic compressor.

[airworx]

amp ratings are full load amps so if its not 95 degrees or more it will not draw full load amps. also pressures dont mean much. so 70 and 225 doesnt tell us anything.
if want to know if charge is correct and if theres a problem then subcooling and superheat is whats needed.

[NormChris]

His post is not clear. Does he have unequal currents in each winding? Or, just less than FLA?

[comfortable air]

I list the presure to prove it is not undercharge. the compressor should draw much more current than now. all three phase current is balance. actually, the rooftop has two stage. the other compressor is also draw 5 amp when it is started. it could not two system short gas at the same time. what I wonder is the electric phase affected . maybe it is norm in todays weather when the compressor is not working at full load.

[igwt777]

comfortable air

you said one phase is only 5 amp.

let us know how many amps did you read on the other two lines?

[comfortable air]

each of three phase is 5 amp more or less. I think they are balance.

[igwt777]

If the three lines are 5 amps each , then I dont understand your question.

[comfortable air]

the unit information is following:
York
model number: D3CG120N20058JSB
Serial :NCCM019984

[comfortable air]

Mr. igwt777, I am not talking the current unbalance. what I mean is the compressor draw too small current than it should be. I think it could be a problem somewhere.

[fixerup]

Phasing on a recip. does not matter.The crank can turn clockwise or counter clockwise and the pistons will still be going up and down.

[igwt777]

Please let us know if you find anything.

[hvac3901]

uh, the oil pump cares dos'nt it. other than that the pistons and valves don't give a damn.

[mdp]

The majority of semiherms don't care about rotation, oil pump or not. The oil pumps will pump regardless of rotation. If fla is 8A~ and actual under moderate load is 5A there isn't a problem. The compressor will rarely draw fla in normal operation.

[comfortable air]

thank you everybody. but why the compressor draw too small current than it should be

[mdp]

light load

[comfortable air]

thank you everybody. but why the compressor draw too small current than it should be

[acjourneyman]

FLA is at design conditions, your not at design.

[john dalton]

Dear Comfortable air,

Let me give you a couple pieces of information you probably don’t have and that might clear things up regarding your unit’s suggested problem(s).

One, the 8.8 amp rating on the unit’s nametag is the FLA(full load amps) or RLA(running load amps) of that particular compressor within that particular unit under the “highest normal” continually operated condition. This would most likely be when the outside temperature is at 115 degrees F and the indoor temperature is at 85 degrees F.

Two, a typical hermetic or semi hermetic three phase compressor can operate either direction because of the inherent design of the compressor’s oil pump assembly.

Obtaining and posting a system’s suction and discharge pressure WILL NOT confirm or support if a system is fully charges or not…period.

In order to determine if a system is operating correctly requires several measured readings; several observed observations, and the experience of a service technician who is familiar with the type of system he is working on, without those anyone is only guessing at best as to the operating condition of a system.

Lastly I would “guess” that unless you have measured or observered something else that you have not posted on this thread that this two stage system just might be operating correctly my friend.

Respectfully Submitted,
John J. Dalton

[comfortable air]

thank you mr. john dalton, what you said make me very comfortable. you see, I take the job very seriously and I keep on learning and trying to figure out any problem what I met. this forum really give me lots of help.

[john dalton]

Dear Comfortable air,

Given the fact that I was not born into wealth and must use my profession to feed my wife and children, put cloths on their backs, and house them, I too take my profession extremely seriously.

I too have learned from reading and posting at this forum and find it even sharpens the knowledge and skills I already have. Honing one’s knowledge and skills among ones own peers and colleagues can be enlightening to say the least.

Keep reading and posting friend.

Respectfully Submitted,
John J. Dalton