Problem with Grunert Passagemaker AC450 Refrigerator

[BugOutBoat]

Hello All,

Hope someone has experienced this problem and may have some helpful debug guidance.

Problem Description:
When I turn on my refrigerator AC breaker on my A-bus power panel the sea water pump does not turn on, my generator voltage drops to about 30 AC Volts. The breaker on the power panel then may trip, may not. Some times the system will come up, other times the compressor will barely operate, the sea water pump doesn't turn on, I get high current demands and the breaker trips.

Debugging done so far:

Assumption: sense the pump sometimes will turn on and the refrigerator will run without issues due to intermittent problem, I'm assuming the pump and the compressor unit are good.

1. Pulled the Grunert electrical box cover off and checked the run capacitor with a multi meter. The capacitor charged from 0 ohms to infinite ohms indicating it is a good capacitor. AMRad P/N 33291 15 uF 370VAC 50-60Hz Motor Run capacitor
2. Checked the Motor Start capacitor BMI 092A270B330DE8X 270-324 uF 330VAC. The DE8X capacitor has a resistor tie between the pin connections thus should increase the RC time constant for a tuned charge time. I don' know if it should be long or short. The multi-meter check showed that the capacitor charged by very slowly. It was in the low ohms for several seconds. This to me suggests possibly the capacitor may be bad. I could never get it to go to infinity (fully charged).
3. When I measure the start capacitor in-circuit I measure 0 ohms across the leads. I don't have a schematic of the Start Relay so I don't know if the start capacitor is normally made when de-energized.

Any Idea's are welcome.

 

[BugOutBoat]

So I've started looking into the starter relay. It was very hard to find the manufacturer and I'm still not sure I can get the correct part. The Start relay numbers on the part are 74-502414 1. When I chased it down on the web I came up with Tecumseh Product P82965 Potential Relay W-RRMB Mara industrial ID: 102647-114846. Tecumseh sells different compressor and AC units. They do sell K kits but the part number didn't come up.

 

[BugOutBoat]

So I've started looking into the starter relay. It was very hard to find the manufacturer and I'm still not sure I can get the correct part. The Start relay numbers on the part are 74-502414 1. When I chased it down on the web I came up with Tecumseh Product P82965 Potential Relay W-RRMB Mara industrial ID: 102647-114846. Tecumseh sells different compressor and AC units. They do sell K kits but the part number didn't come up.

There is a good post on how to test the Start Relay: Its at: https://www.achrnews.com/articles/90387-troubleshooting-the-potential-starting-relay going through it now to verify my start relay didn't take out my start capacitor.

 

[BugOutBoat]

There is a good post on how to test the Start Relay: Its at: https://www.achrnews.com/articles/90387-troubleshooting-the-potential-starting-relay going through it now to verify my start relay didn't take out my start capacitor.

1. From the article I'll need to measure across pins 1 and 2 with an ohm meter. The contact between pins 1 and 2 should be normally closed so in the de-energized condition with leads removed it should read 0 ohms.
2. Between pins 2 and 5 sits the relay coil. The article suggests that the coil is a high resistance form a few 100 ohms to 1000 ohms. It should not read infinite. If it's infinite then the coil is bad and the relay should be replaced. If its 0 ohms it's shorted and the relay should be replaced.

 

[BugOutBoat]

I measured my Pins 1 and 2 and they read 0 ohms as suggested in the article. I then measured pins 2 and 5 and could see the coil charge and give a resistance of 1.2 K ohms, not a short nor an open. Assuming the start relay is good.

 

[BugOutBoat]

The only abnormal measurements were with the start capacitor. It did not charge.

So this is what I believe is happening:

"The start capacitor gives the start winding circuit more capacitance and gives the current a leading effect (phase shift) on the voltage. The more the current leads the voltage wave, the more phase shift there will be, and the motor will have more starting power or torque. Without the start capacitor, the motor will usually lock its rotor and draw locked rotor amps (LRA). This will cause the motor’s overload to open and the motor will short-cycle on the overload. This short-cycling is detrimental to motor windings, starting relays, and capacitors because of its overheating effect." (Reference: Tomczyk, "Troubleshooting the Potential Starting Relay," the News, November 3, 2002, para: 2, URL: https://www.achrnews.com/articles/90387-troubleshooting-the-potential-starting-relay)


Once I can obtain a replacement BMI Motor Start Capacitor PN: 092A270B330DE8X - replace it and verify it's fixed I'll post the root cause and replacement procedure.

WARNING: When working with power supplies and capacitors it's extremely important to use a shorting probe to discharge all capacitors before attempting to conduct any maintenance. Failure to do so can result in electrical shock as capacitors and the resistive characteristics of the circuit they are installed in could cause capacitors to store electrical energy for extended periods of time can could discharge resulting in electrical shock if not properly discharged before handling. If you are not familiar with how to properly discharge a capacitor please hire a trained electronics technician or electrician to replace the parts.

 

[BugOutBoat]

Note: From the BMI website the 092A refers to EIA reference 2 standard which I believe is supposed to have a failure mode of open circuit. In my case I don't think this is happening, I think it's actually shorted.

 

[Dave Webb]

Note: From the BMI website the 092A refers to EIA reference 2 standard which I believe is supposed to have a failure mode of open circuit. In my case I don't think this is happening, I think it's actually shorted.

Bug
Have the same unit on my boat ( so far no problems)
Sounds like a motor failure ( compressor) or low voltage start
Keep us posted
Dave

 

[Dave Webb]

Bug
Have the same unit on my boat ( so far no problems)
Sounds like a motor failure ( compressor) or low voltage start
Keep us posted
Dave

looking at the wiring drawing now and will think about it

 

[BugOutBoat]

Ya Dave it’s a tough problem. It could still be the stator winding in the sea water pump. This issue actually fried my AC transfer relay board in my Magnasine inverter. We are without power on our A bus in winter due to the failure in the frigerator. My magnasine inverter costs more than the refrigerator. Grunert obviously does not apply Failure Mode Effects Analysis in their engineering practices or the frigerator would not nock out vessel power. A refrigerator nocking out vessel power is a serious safety issue.

 

[BugOutBoat]

The company BMI does not list my part number in their motor start capacitor data sheet so I wrote them to find out if they still manufacture the cap. Won’t know until tomorrow.

 

[BugOutBoat]

The electric panel I have is Grunert 256-000122.

 

[BugOutBoat]

 

[BugOutBoat]

The top relay is the motor run capacitor and the lower one is the motor start.

 

[BugOutBoat]

 

[BugOutBoat]

The start relay is in the upper right in the pic above. If you zoom in you can see the part number.

 

[BugOutBoat]

The start capacitor I could not get any suppliers that had or could get the part. I contacted the good folks at BMI the gent Paul Shockley helped me out and is sending me one strait from the factory at cost plus shipping. They were a great help and my wife and I are very greatful to the wonderful folks of BMI!!!

 

[BugOutBoat]

I’ve gone ahead and hunted down the start relay. Mine is a GE Tecumseh relay 3ARR3B3TP4. The part has the following numbers on it. 74-502414 1

 

[BugOutBoat]

Parts will arrive Friday.

 

[BugOutBoat]

Parts came in on schedule. I replace the Motor Start Capacitor from BMI and the Start Relay. Refrigerator is operating and functioning perfectly. No overshoot current. Inspecting the old capacitor there was a mild trace of electrolytic leakage on the inside edge of the top of the capacitor that was not visible while it was installed.

The indications for the problem is your refrigerator Circuit breaker will likely trip, the sea water pump and compressor may both not operate or operate poorly and you will have high current readings on the A-Bus amperage meter. The sea water pump and the compressor are both fed by the Motor Start Capacitor through the Start Relay. If the two pumps are not operating correctly its very likely your Motor Start Capacitor or the Start relay.

If you have any questions on this repair please feel free to contact me.

Take care,

BOB -- Bug Out Boat