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Old 05-05-2017, 16:36   #1
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3 flashes on Danfoss control

We've been running a Danfoss BD50 for 5 years or so and it's worked well. Sometimes at startup we get three flashes from the LED but repeated tries (8 or 10, 10 seconds apart) have always "fixed" the problem. Alas, not this time. We removed some of the refrigerant in case it was overcharged. Still no joy. So we looked at voltage. About 12.8 V. But then when turned on the switch we were surprised to see no voltage drop, not even 0.01V on our digital multimeter. I infer the compressor is drawing no current at startup. So how can the controller be detecting an overload?

The one piece of this whole system that can be easily removed is the controller. Should we get it checked? If so, where?
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Old 05-05-2017, 17:06   #2
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Re: 3 flashes on Danfoss control

Three flashes means the compressor can't get started. My understanding is if you get the three flashes right away, you have a problem with the electronics and controller must be replaced. If it starts and chugs a while, could be thermostat or power interruption/connection. Fan and/or pump will continue to run with 3 flash fault, so make certain you aren't hearing that. Most of the time three flash is not the compressor. The controller is a easy change out and it's not a bad part to have a spare if it turns out to not be the problem. Remember a controller is cheaper than a service call. Good Luck.
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Old 07-05-2017, 12:17   #3
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Re: 3 flashes on Danfoss control

Quote:
Originally Posted by Akka View Post
We've been running a Danfoss BD50 for 5 years or so and it's worked well. Sometimes at startup we get three flashes from the LED but repeated tries (8 or 10, 10 seconds apart) have always "fixed" the problem. Alas, not this time. We removed some of the refrigerant in case it was overcharged. Still no joy. So we looked at voltage. About 12.8 V. But then when turned on the switch we were surprised to see no voltage drop, not even 0.01V on our digital multimeter. I infer the compressor is drawing no current at startup. So how can the controller be detecting an overload?

The one piece of this whole system that can be easily removed is the controller. Should we get it checked? If so, where?
Three LED code is an overload amperage signal if it is the first code displayed. If no one has tampered with refrigerant problem is not likely too much refrigerant. Because eventually the compressor after several tries will boot up OK it is also not likely a faulty module. A low or dirty current to these variable speed BD50 compressors in boat’s refrigerator wiring has been know to trigger 3, 4,and 5 LED codes.

When reporting refrigerator problems on BD compressor systems you can get more precise help if you identify the manufacture and model of the system. There are over 100 applications in use today for this type compressor. Troubleshooting the 3 LED code is not the same on each manufacturers system. On Adler Barbour units troubleshooting must include the electrical board, EZ Kold would include seawater in refrigerant, Water cooled and keel cooler units compressors oil contamination do to compressor heat, to name a few.

Suggestions

Follow up by describing your unit and its maintenance history.

Run correct size and correct polarity fused jumper wires direct from a fully charged battery to module in order to bypass all boat’s wiring. Volt meter readings are of no value, Compressor still does not run electronic module needs to be tested on another unit.
If your shipping address is in the US I will test at no charge your module on my Danfoss compressor refrigeration test stand. This test stand will run at max compressor load for a one hour. Because of the start up problem I will extend run overnight monitoring cycle times. I will then return your module to you insured Priority shipping and handling charge of $20.
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Old 17-05-2017, 16:39   #4
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Re: 3 flashes on Danfoss control

Richard, thank you for the good information, always. I went out and bought a new controller. I got the 3 flashes once, then the compressor started fine. So as you say, it probably wasn't the controller after all. Oh well, now we own a spare controller

The system is home built, using the holding plates and copper tubing from the original 1980s era A/C system. The BD50 compressor is wired directly to the house bank, with just a switch and a fuse in line. All connections look good.

In any case it's running again. But I'm a little concerned about the oil. We've had several leaks, replaced the dryer, etc. over time and I'm afraid I might have reduced the oil too much. I let a little gas escape from the high side and it didn't feel very oily. Can I add oil without draining and vacuuming the system? If not, how do I get oil into the system without risking some air gets in, too?
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Old 18-05-2017, 06:39   #5
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Re: 3 flashes on Danfoss control

If you built this system from an old AC system there is a good chance you have larger tubing and you could be getting oil collecting inside the low spots. These small compressors have very low refrigerant velocities and will have a hard time returning oil to the compressor in larger tubing . 1/4" is usually the best to use .

You can charge the oil with something like this ,
Set of 3 R-134a Refrigerant Ester 100 Oil Charge Auto Air Conditioner 3oz. #312

Regards John
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Old 17-09-2017, 22:00   #6
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Re: 3 flashes on Danfoss control

Quote:
Originally Posted by Richard Kollmann View Post
Three LED code is an overload amperage signal if it is the first code displayed. If no one has tampered with refrigerant problem is not likely too much refrigerant. Because eventually the compressor after several tries will boot up OK it is also not likely a faulty module. A low or dirty current to these variable speed BD50 compressors in boat’s refrigerator wiring has been know to trigger 3, 4,and 5 LED codes.

When reporting refrigerator problems on BD compressor systems you can get more precise help if you identify the manufacture and model of the system. There are over 100 applications in use today for this type compressor. Troubleshooting the 3 LED code is not the same on each manufacturers system. On Adler Barbour units troubleshooting must include the electrical board, EZ Kold would include seawater in refrigerant, Water cooled and keel cooler units compressors oil contamination do to compressor heat, to name a few.

Suggestions

Follow up by describing your unit and its maintenance history.

Run correct size and correct polarity fused jumper wires direct from a fully charged battery to module in order to bypass all boat’s wiring. Volt meter readings are of no value, Compressor still does not run electronic module needs to be tested on another unit.
If your shipping address is in the US I will test at no charge your module on my Danfoss compressor refrigeration test stand. This test stand will run at max compressor load for a one hour. Because of the start up problem I will extend run overnight monitoring cycle times. I will then return your module to you insured Priority shipping and handling charge of $20.
Richard,

I ran the jumper cables test you suggested, and still no go. The refrigerant has been messed with plenty -- I've had leaks, repaired them, evacuated the system and refilled it several times in the last 10 years or so since I built it. I think it still has a leak somewhere but we go a year or so without having to top up the system.

Two things bother me. The first is, how can too much refrigerant be the problem after the system has equalized completely? The documentation says the three flashes indicate too high a differential in pressure, but right now, the pressure differential is 0! The static pressure is about 35 psi, so there shouldn't be any condensed refrigerant in the system (ambient temperature is about 65°F).

I measured the amperage at startup, and it's less than 0.1A until the LED starts blinking and the fan comes on. Once the fan is on, there's about 0.5A, as you'd expect from that fan. If the compressor is somehow jammed, I'd expect infinite current at startup, rather than negligible current.

In any case, does your offer still stand, to test the controller? If so, how can I take you up on it? I don't think I have your address.

Cheers,

Rob
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Old 18-09-2017, 00:54   #7
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Re: 3 flashes on Danfoss control

Rob, remove the electronic unit completely from the compressor. Use a multi-meter to check the ohms between each two of the three terminals on the compressor. (Each terminal represents a leg of one of the three motor windings and any combination should read about 2.0 Ohms. If one pair indicates an open circuit then the compressor is shot. Possibly due to oil starvation caused by oversized evaporator tubing as John suggested.
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Old 18-09-2017, 09:40   #8
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Re: 3 flashes on Danfoss control

Danfoss’s new variable speed direct current BD compressor systems require a different trouble shooting program than other electrical compressors. The BD 35 and BD 50 compressors are designed to be controlled and monitored by voltage and amperage not refrigerant pressures. Low on refrigerant will not prevent this compressor from running but too much refrigerant will. Static pressure on a 70 degree F day of less than 45 psi will not cause an overload.
• If control module sees a high or low voltage spike lasting only a few milliseconds, many times too quick to see on a voltmeter compressor start up electrical pulses are terminated at module. LED trouble code one flash every 4 seconds.
• If an overload condition exists on start up high amperage at module will terminate start sequence. Air cooled Danfoss BD Compressor rarely fail although water cooled compressor with out supplemental cooling have experienced system failures. The Three LED code does not always identify a faulty compressor. The most likely overload signal on the BD35 and BD50 is weak or dirty refrigerator power wiring during compressor start up. The correct troubleshooting is to bypass all power and ground wiring from module to battery. A poor ground system may not trigger a trouble code but will alow compressor to run single phasing pulses to compressor rotor producing little or no cooling. Fan wires on Control module are limited to ½ amp amperage above this will cause control module to terminate electrical pluses to compressor.

Correct trouble shooting for standard configuration Danfoss BD compressors:
Disconnect non standard gadgets from control module including thermostat wires and place a jumper wire between terminals C and T. Compressor still does not run.

Disconnect Black fan wire from F- Terminal. Compressor still does not run.

Bypass Power and ground wires from Control module and connect direct to battery terminals. Still does not run.

You could try OzePete’s Pulse coil ohm test including no continuity from any post to case ground.

After following the above tests I would try another control module. Danfoss has worked through over 15 different control module designs and still have trouble with control modules standing up to a mobile marine environment.
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Old 18-09-2017, 19:34   #9
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Re: 3 flashes on Danfoss control

OK so maybe it's a good time to provide a 'KISS' list of things to check if your DC compressor will not run: (This is a check list we send to our Ozefridge customers and others if needed.)

First disconnect any high voltage supply.

1:Check DC voltage-in on the compressors electronic unit, both with compressor off AND when it runs or tries to run.
A: If the voltage is low, or if the voltage is OK but drops away more than say half a volt at start up attempt, then check the power supply, terminals, wiring and batteries. (An amp meter reading when attempting to start would be useful. If the amps go way above normal then the compressor may be mechanically stuck.). If the voltage is OK and there is little dip upon a start attempt then go to step 2.

2: Bridge the lowest and third lowest terminals and power up. (These terminals C & T on Secop, Danfoss and most other compressors, are the thermostat switch)
A: If the compressor starts and runs normally, leave the bridge in place and run manually until you can replace the thermostat. (YOU become the thermostat!) If still not running go to step 3.

3: Remove both fan wires from electronic unit and attempt a start.
A: If this allows the compressor to run, replace fan. Note.. fan should not exceed 6 watts. If still not running go to step 4.

4: Remove electronic unit from the compressor revealing three terminal pins on the compressor. Use a multi-meter to check resistance between each combination of two pins (of the three) and from these pins to the compressor case (Ground)
A: The resistances should be uniform at approx 2.0 Ohms for BD50, 2.3 Ohms for BD35. Others may have different Ohms readings but OK if they are all similar. If there is no reading or a much higher reading between the pins or if there is leakage to the ground then the compressor is dead. If the readings are OK the compressor is most likely OK so go to step 5.

5. Replace the electronic unit.

I hope this helps..
Cheers, Ozepete from Ozefridge.com.au
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Old Today, 08:22   #10
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Re: 3 flashes on Danfoss control

Pete, I receive three to five emails a week asking for help when a Dafoss BD compressor fails the start boot up sequence. What is the next step recommendation when you’re troubleshooting and module replacement does not solve the no start up problem? Do you Start over with recommend tests again, Add more oil, Dehydrate vacuum and add correct amount of Danfoss recommended refrigerant, Replace Evaporator flow expansion device, Replace compressor or replace complete system?
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Old Today, 15:31   #11
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Re: 3 flashes on Danfoss control

Good question Richard but if the system passes the first four steps I described then it is highly unlikely that the compressor is faulty. These suggested steps are in order of likelihood of identifying the fault.
As you know by far the most common cause of DC system failure to run is a faulty power supply, so step 1 will identify the cause in most cases . Past history helps greatly in system diagnosis but If a system that has been running ok for years then suddenly fails, these steps should isolate the fault. If the compressor is not mechanically stuck and therefore dead (as in step 1) and it has similar resistance between any pair of the compressor terminals and no continuity to ground (as in step 4) then it should run.
In the most unlikely event that having passed steps 1 to 4 and the electronic unit replacement does not solve the problem, I agree firstly double check steps 1 to 4, otherwise replace the entire system.
Your final question is similar to those we ( and most likely you too) receive from some so called refrigeration mechanics who simply should never be allowed to touch any equipment. The try this, woops that don't work so lets try this method is a sure sign of a mechanic with no analytical abilities. They make me shudder and worse still when a client is at an island in the mid Pacific and the local 'refrigeration guru' has to ask "what is a vacuum pump" OMG!

Cheers OzePete from ozefridge.com.au

BTW Richard, feel free to use/ forward the check list to your contacts if it will help, but please acknowledge as being from Ozefridge.. thanks
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