Reply1) Voltage?Originally Posted by Butch1234
Regular Guest
More on the saga of my ZR61 single phase R22 compressor problems with my geothermal system. In summary the compressor is drawing about 10 amps more than the table (curve) shows at every operating point on the curve.
Here is what we have done to trouble shoot the problem:
1) Replace Start and Run Capacitors
2) Replaces Start Relay
3) Replaced starter contactor
4) Replaced in line filter dryer
5) Made multiple measurements of the motor current with 3 different clamp on meters…all read about the same high current
6) Made multiple measurements of the suction and discharge pressure with 3 different gauge sets…all read the same suction and discharge pressures
7) Removed the compressor and installed a spare ZR61. Put brand new oil in it.
8) The spare compressor (only slightly used) had the same running characteristics as the unit it replaced. About 10 amp more current than the table for any suction/discharge pressure combination
9) We ran it in the Cooling mode (55 psi suction 170 psi discharge) measured about 25 amps…chart says we should measure about 16 amps) but the compressor has the best sound in this mode…sort of hummed …no rattle
10) Ran in the hot air heating mode (65 psi suction 220 psi discharge) measured 29-30 amps chart says should be about 19-20 amps*
11) Ran in hot water mode (like hot air but water heat exchanger instead of air heat exchanger) (65 psi suction and 320 discharge) measured 37 amps chart says about 27 amps.*
12) Pretty much nothing left to replace Our old notes show that when this unit was initially started with the first replacement compressor (we have replaced 6 so far) at 65 psi suction and 250 psi discharge we measured 23.9 amps which is close to your chart (22 +/-). So in theory the proper current was measured at one time
• * compressor runs with a slight rattle sound at these higher pressures.
In summary we are at our wits end. Assuming compressor table is accurate, and compressor/pump theory holds, then knowing the suction and discharge pressure should establish the point on the pump/compressor curve. The only items that might be impacting this and these are wild guesses at this point are the following:
1) There is too much oil entrained in the R22 causing ???
2) The mass flow rate through the compressor is much higher than we figure thus causing the compressor to draw more current?
3) The compressor is connected to a Crankcase Regulating Valve (CPR, which is tied to an accumulator). The CPR valve regulates the compressor suction pressure to keep it under 75 psi, maybe the flow is restricted somehow?
4) Maybe some sort of flood back...guess we can add a site glass??
None of this makes any sense at this point unless we are missing something????
Any ideas?
Professional Member
1) Voltage?
“If You Can Dodge A Wrench You Can Dodge A Ball”
Regular Guest
good question probably should have noted it was 237 Vac which is more or less the rated voltage for the single phase (240 v) compressor
Professional Member
What's the possibility of a restriction somewhere between the compressor discharge and the point of head pressure measurement? Muffler somewhere? You absolutely sure of the correct wiring connections and capacitor values?
Professional Member
Did you try adjusting the cpr? Did you try more than one amp meter?
Regular Guest
There is no restriction where the pressure (suction and discharge) is measured there is a high pressure switch (~400 psi) that has and will trip unit if we get to 400 psi...the pressure taps are within a few inches of the suction and discharge pipe connections
capacitors are new...and OK ..the wiring has been checked and rechecked thanks for the thoughts as I said we are at our wits end...?????????????????????
Regular Guest
that is a good idea...the CPR valve is set at 75 psi....since we were getting suction pressure below this (65 psi) and still high current it does not seem that this is the problem ...I have asked the compressor manufacturer for some suggestions but have not heard anything so far....one would think that the suction and discharge pressures would indicate where on the pump/compressor curve the unit was operating??????
Professional Member*
+1
Regular Guest
we are sure of the wiring and capacitors...one idea we have is that perhaps we have too much charge (R22) in the system. We are going to try taking some out and see if that makes a difference.....
Professional Member*
Was voltage measured at the compressor terminals?
Was amp reading taken away from motor and away from any interference?
What's the discharge superheat?
Regular Guest
voltage reading was taken at disconnect which has about 5 ft of lead before the motor...no voltage drop in this short run
amp reading at disconnect and at starter...no interference (we thought about that but used 3 different amp probes and got the same reading at different parts in the circuit
not sure about the amount of superheat
Professional Member*
Edit: Removed my reply becoming too DIY. Apply for a pro account.
Professional Member
So you never really did 1)
“If You Can Dodge A Wrench You Can Dodge A Ball”
Professional Member*
Yeah, this made me wonder DIY.
Professional Member*
Did you check voltage when it is running? If not, well????
But I will take a guess, on copeland scrolls, discharge pressure is the biggest single factor on power draw (presume voltage is good), because you have fit more than one, then i will say that you pressure port is being influenced by flow, like a venturi.
New pressure tapping required.
Regular Guest
not sure what that means....we did some more checking last night...the CPR valve may be an issue but too soon to say....also we probably do have too much R22 in the system and we are removing some...this may be part of the problem...more later...we need to check a few more things...thanks for all the suggestions so far nothing definite
Professional Member
And measuring at the disconnect doesn't eliminate a voltage problem.
Regular Guest
technically you are correct, however, the voltage at the disconnect is effectively the voltage at the motor in this case ,..there is 3 ft of copper wire from the disconnect to the starter, 2 feet from the starter to the motor and all wires are good....if we had a bad wire it would have shown up...in this case we do not have a voltage problem..thanks for your input
Regular Guest
we can actually measure the discharge pressure in several places in the piping...the discharge pressure is a good reading....but you do have a good point...I have seen this problem before but more like a pitot tube...
we checked some more last night and are wondering if the CPR valve may not be working properly...a simple regulator but perhaps it is stuck.. will check some more thanks
Regular Guest
the more we look at it it appears the CPR valve is the problem see this link
http://www.real-world-refrigeration....-valves-3.html
will let everyone know if this is the problme..thanks
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