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Old 08-07-2018, 03:28   #1
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Fridge unit electrical problems.

Voltage supply issues are the primary reason why a 12/ 24 VDC compressor may fail to operate.

It really is simple, there are two voltage issues, both quite separate from each other and each with vastly different consequenses.

Firstly, poor or erratic power supply. (Power including all from the battery through to the module terminals.)
All of these 12 / 24 VDC compressors employ a Motor Driver Module. DC power enters the MDM where it is inverted into an alternating 3 phase current to power the compressor motor. TheMDM has several ‘Fail-safe ‘ facilities to protect against under / over voltage, excess current draw, over heating etc.
If the voltage to the MDM falls away due to a faulty connection, wiring or battery etc, then the fail-safe may prevent the MDM from starting and running the compressor.

Remedy: It is simple to check your power supply with a common multimeter. Simply put your meter onto DC volts then hold probes onto the positive and negative terminals at the MDM (See sketch). Monitor the voltage both BEFORE start up, while attempting a start and if it runs, keep monitoring. If the voltage ‘dies away’ then work backwards checking all connectors, devices and wiring. Finally do the same test at the battery during a start attempt.

Secondly, ‘High Voltage Spikes’ (Low voltage spikes don’t exist!)
These high voltage spikes can originate from many external sources, usually extremely high voltage yet with little current. These spikes can travel along any wiring circuit and can damage electronic devices like the fridge Motor Driver Module as their high voltage arcs across insulation barriers specially on printed circuit boards etc. causing damage Trying to identify or eliminate these rapid spikes is futile. Best to accept that they can occur and protect against them, besides protection is simple and low cost albeit never providing 100% protection.

Remedy: A simple Transient voltage clamp, AKA ‘Zorp’ or omni-directional DC voltage spike arrestor connected to the compressors DC input terminals (+ & -) is best. (As indicated in in the sketch below in yellow on the Motor Driver.) This will also protect other electronic devices connected to the same DC power supply. These things cost less than $2 and should be on all fridge / electronic equipment but unfortunately they are not, so best to add one asap and that issue is resolved!

I hope this helps to prevent unnecessary fridge issues. ...

Click on sketch to expand.


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Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 08-07-2018, 06:33   #2
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Re: Fridge unit electrical problems.

Link to one of theses Zorp high voltage clamps? Maybe an Amazon link?
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Old 08-07-2018, 07:28   #3
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Re: Fridge unit electrical problems.

Electrical isses are so common I have a YouTube Video walking through the basic troubleshooting process. The basic troubleshooting steps are good for almost all brands and refrigeration systems and this video has saved me hundreds of hours on the telephone over the years.


https://youtu.be/r9FoE1uHzy8
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Old 08-07-2018, 08:12   #4
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Re: Fridge unit electrical problems.

Quote:
Originally Posted by SV THIRD DAY View Post
Electrical isses are so common I have a YouTube Video walking through the basic troubleshooting process. The basic troubleshooting steps are good for almost all brands and refrigeration systems and this video has saved me hundreds of hours on the telephone over the years.


https://youtu.be/r9FoE1uHzy8
Watch Rich's video link completely to the end paying attention to the #1 reason for 12 volt compressor failure to run. This is the correct way to locate trouble not relying on a volt meter reading that can can cause you to purchase a new refrigeration unit.

This is step number 5 from myNon Destructive Danfoss BD trouble shooting chart:
5. Run correct size and correct polarity jumper wires direct from a fully charged battery in order to bypass all boat’s wiring. Volt meter readings are of no value when looking for voltage spikes. Compressor still does not run electronic module needs to be removed and tested on another unit. If there are no other units available to test your module on I will test all 12 volt Danfoss control modules free, you pay only shipping.
Forty out of 100 modules I test are good indicating boat's wiring is the real problem.
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Old 08-07-2018, 13:44   #5
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Re: Fridge unit electrical problems.

Not sure if right thread, but I have a cold plate refrigerator system in my 1981 Grand banks. All is working well temp wise, but the water pump">raw water pump is running all the time and no longer cycling when fridge and freezer reach correct temperatures. It just keeps right on pumping. Anything obvious to look for?
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Old 08-07-2018, 13:47   #6
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Re: Fridge unit electrical problems.

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Originally Posted by kelbylinn View Post
Not sure if right thread, but I have a cold plate refrigerator system in my 1981 Grand banks. All is working well temp wise, but the raw water pump is running all the time and no longer cycling when fridge and freezer reach correct temperatures. It just keeps right on pumping. Anything obvious to look for?
The Raw water pump on a water cooled system should cycle on/off with the compressor, usually through a relay.
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Old 08-07-2018, 14:58   #7
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Re: Fridge unit electrical problems.

Rich, do you believe as Pete states "Low voltage spikes don't exist" that causes so many of the Danfoss compressor failure to start up and run problems?
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Old 08-07-2018, 17:16   #8
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Re: Fridge unit electrical problems.

[QUOTE=Richard Kollmann;2669008]Watch Rich's video link completely to the end paying attention to the #1 reason for 12 volt compressor failure to run. This is the correct way to locate trouble not relying on a volt meter reading that can can cause you to purchase a new refrigeration unit.

Totally disagree. In my opinion your highlighted comment is absolute nonsense and malicious, and seeing as your comment disputes my test method presented, perhaps you could explain how "a volt meter reading that can cause you to purchase a new refrigeration unit?

And for a clearer picture, view this video... http://www.ozefridge.com.au/?page_id=3017

Cheers OzePete
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Old 08-07-2018, 17:41   #9
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Re: Fridge unit electrical problems.

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Originally Posted by Richard Kollmann View Post
Rich, do you believe as Pete states "Low voltage spikes don't exist" that causes so many of the Danfoss compressor failure to start up and run problems?
Richard, Firstly Rich from CoolBlue and myself are long-term hands on practical refrigeration people and don't appreciate your attempt to cause conflict, specially when what you quoted is totally incorrect.

Please read what I posted again, it has no similarity to what you are quoting.

Now for your information relative voltage spikes means a spike or rise in voltage. These are often hundreds if not thousands of volts but of negligible current. They usually are of extremely short duration (like milliseconds!)
They can originate from a solenoid being de-powered (Like starter motor or winch solenoid) but can come from anywhere that is why I say forget trying the eradicate them just protect against them with a transient voltage clamp.

BTW Low voltage transients can occur but they are NOT spikes and extremely rare, extremely unlikely to be a problem and the origins of these are not to be found on-board.

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Old 08-07-2018, 18:13   #10
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Re: Fridge unit electrical problems.

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Originally Posted by a64pilot View Post
Link to one of theses Zorp high voltage clamps? Maybe an Amazon link?
Hi Pilot,
This is the Transient Voltage Clamp we have fitted to our systems for many years.
I don't understand why all manufacturers don't fit them standard, but after reading some strange comments regarding spikes, it maybe because they don't understand what these high voltage spikes are or appreciate the harm they can cause...

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Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 08-07-2018, 18:39   #11
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Re: Fridge unit electrical problems.

OK, on the aircraft we manufactured, we put a diode across all the solenoids to block the possible voltage spike when the field collapsed in the solenoid. We were blocking the source, not the victim though. Some solenoids we used were quite large, many times an anchor solenoid. For instance it took 1000 amps at 28V to start a Honeywell turbine.
You can buy solenoids that are protected, one of the things I did was to ensure we did.
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Old 08-07-2018, 18:50   #12
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Re: Fridge unit electrical problems.

Pete, Low voltage spikes do to dirty boat electrical wiring cause technicians in many cases to recommend replacing a compressor or complete system. It is wrong for you to suggest using a voltmeter to eliminate possibility of low voltage spike as a cause of compressor start problem.

As far as high voltage spikes Rich is also correct, if Danfoss compressor installation follows Danfoss wiring directions the battery acts as a giant capacitor that absorbs high voltage spikes returning from most on board equipment except a run away alternator. A properly wired wire system can absorb high voltage spikes from electric windless relays and electric engine driven clutches without added another gadget to confuse troubleshooting techs.
Most of the manufacturers of mobile refrigeration for boats like Technautics and others design to keep their unit simple reliable and repairable.
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Old 08-07-2018, 22:19   #13
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Re: Fridge unit electrical problems.

Quote:
Originally Posted by Richard Kollmann View Post
Pete, Low voltage spikes due to dirty boat electrical wiring cause technicians in many cases to recommend replacing a compressor or complete system. What you describe is NOT a low voltage spike! There is no such thing! It is the failure of current to reach the MDM at the required voltage due to a bad connection, bad wiring or a faulty battery. EXACTLY the situation that using a multi-meter as I described will detect. It is wrong for you to suggest using a voltmeter to eliminate possibility of low voltage spike as a cause of compressor start problem. Totally disagree, please look at this video again and tell us why it doesn't clearly indicating how simple it is to read start up supply voltage!
Check this Richard: Video tests and Data record. | Ozefridge

As far as high voltage spikes Rich is also correct, if Danfoss compressor installation follows Danfoss wiring directions the battery acts as a giant capacitor that absorbs high voltage spikes returning from most on board equipment except a run away alternator. A properly wired wire system can absorb high voltage spikes from electric windless relays and electric engine driven clutches without added another gadget to confuse troubleshooting techs. Correct the battery can absorb many high voltage spikes but NOT all so why risk it?
Most of the manufacturers of mobile refrigeration for boats like Technautics and others design to keep their unit simple reliable and repairable. So do we at Ozefridge, that is why we consider our clients and fit transient voltage clamps to all systems.
Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 09-07-2018, 00:14   #14
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Re: Fridge unit electrical problems.

Sorry Pete but again you are dead wrong about how to isolate a very short microsecond duration low voltage spike using a volt meter. I believe helping boaters to repair their units with common sense procedures that are guaranteed to work is best. As you know we have had these debates before when helping boaters located where qualified technical help was not available. I also use the boat wiring bypass method to locate three phase pulse overload variation on Danfoss variable speed compressors. Again I leave it up to the people I help and those who read these threads as to who is offering the best help in problem solving.
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Old 09-07-2018, 02:00   #15
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Re: Fridge unit electrical problems.

Quote:
Originally Posted by Richard Kollmann View Post
Sorry Pete but again you are dead wrong about how to isolate a very short microsecond duration low voltage spike using a volt meter. I believe helping boaters to repair their units with common sense procedures that are guaranteed to work is best. As you know we have had these debates before when helping boaters located where qualified technical help was not available. And as you know from before it was agreed that if anyone wants to contradict technical substance then the objector was to provide evidence and links to support their case, not just waffle on with bad advice.. I also use the boat wiring bypass method to locate three phase pulse overload variation on Danfoss variable speed compressors. Again I leave it up to the people I help and those who read these threads as to who is offering the best help in problem solving. What a great idea, and to help let me post a link here:

Ozefridge | 12 Volt Refrigeration Systems
BTW I will have my staff produce some more videos to support our simple test... with a MULTI-METER


Video tests and Data record. | Ozefridge
Cheers OzePete
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