View Full Version : Mysterious burnout
09-16-2006, 11:00 AM
I have a Mammoth 100% outside air watercooled fresh air heat pump that is 2 years old. It serves a Carecenter facility for the elderly. Got a call Sunday eve that both elevators in facility were down. Found Ground fault circuit breaker had tripped knocking out panel that serves elevators and outside air unit. Both compressors in unit had burned out, blew a hole thru "pecker head" electrical connections at compressors. Big puddle of oil under compressors, obviously both refrigeration circuits out of gas. Also knocked out Metasys controller, but blower fan still works. Warranty no longer applies, only one year. manufacturers warranty on compressors only one year. Did not pickup 5 year optional warranty. Company that installed (THERMA) sending there "TOP NOTCH" Tech next week to determine cause. Anybody have any Ideas which may have caused problem??? Also burned off one load side wire off of contactor for compressor circuit #2 which is the one that kicks in on rise in heat load. Checked all electrical connections in MSB Panel and sub panel all very secure, no burning of insulation. No other electrical problems in buiding.
09-16-2006, 11:39 AM
Are they making their own condensor coils again? You can always recognize them them, looks like someone made them in their backyard and it was the first time they had a torch in their hand. They leak, are full of flux and torch residue. I've seen sight glasses go to a very dark green an hour after start-up. Also check to see if they are piped backwards. Leaving coolant should be on the hot gas side of the water coil, entering coolant, on the liqiud side of the coil in cooling cycle. Makes a big difference on head pressure. Does this unit have the dual water reg valves? A lot of techs think you set them up with the valve you aren't adjusting blanked off. You have to adjust one reg. valve first then the other with all valves open, then repeat till the system is balanced on heating and cooling pressures, or you'll slug the comprssor.
09-17-2006, 12:32 AM
It's possible you could have had a very high SPIKE in power, Did the buildings Generator come on and have a phase reversle? Do you have a phase-voltage monitor on the system? If not, you should install one. Thay cost a lot less then (2) Compressors.
09-17-2006, 11:42 AM
At what point in the system would I Install a Phase/Voltage Monitor? And how are they sized? Any particular brand?
09-17-2006, 01:02 PM
I'm on to a hunch...
If a compressor shorts to ground, there is more carbon to clean up.
If it shorts line to line, there is less.
Any input on this?
09-17-2006, 03:54 PM
any chance the building was hit by lightening?
sounds like it,
09-18-2006, 08:16 PM
If you are in the SF Bay Area and need a 2nd opinion please contact me.
09-19-2006, 06:08 AM
Here's instructions for a real spiffy one.
Voltage range has to be in the right range.
Current is measured with either current transformers or passes of each of the current carrying wires through the device.
If you get a unit that just looks at voltage only then it will generally protect against phase reversal, phase loss, phase unbalanance and generally will delay start-up.
Ones that measure V and I offer better motor protection.
09-20-2006, 12:17 PM
Anytime I've seen the terminals blown off a compressor its been an acid burn-out, not something that happened in an instant. I noticed its a 100% outside air unit, is there anything to lock out the compressors in real low or real high ambient? Was the unit shipped cut frame, or did the installing contractor cut it in two to install? Then didn't properly secure, evacuate, and recharge the unit? Are the two compressors tandem or on two separate circuits? You really should have an air handler ahead of the refrigerant coil that will exhaust the inside air, filter intake air, with a wheel type heat exchanger, to save you some energy, and precondition the air before it hits the refrigeration coil.
09-20-2006, 08:16 PM
Read what KEEPITSIMPLESTUPID wrote, He has right, The TECH. Knows what he's talking about.
09-20-2006, 08:33 PM
For what it is worth I have seen lots of phase/voltage protectors installed after failures, not becuase there was an electrical problem but because they didnt know how to find the root cause of what caused the failure in the 1st place.
Not bashing phase protectors, just do your homework in the field and in most cases you will find out why the failure occured.
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