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Old 13-11-2010, 14:07   #1
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Compressor Cuts Out: Differential Pressure Too High

Hi people,

In May I bought a new Waeco Coldmachine with a VD16 evaporator. It has been running ok for a few months and now I moved it to a better location where I can put in 8 inches of foam. Didn't disconnect the two parts cause that would mean losing the R134a. I just moved as a whole. I've been very careful, I had to bend the copper somewhat but there certainly is no damage here.

Installed it. Started it for a test run and it started up ok but shut off after a few minutes. I connected the diagnostic LED between + and "D". This led flashes 3 times and that means (translated from German)
"Rotor stuck or the differential pressure in the cooling system is too high >5 bar".

Anybody who can shine some light on this?
Any use in putting a pressure gauge on the low pressure connection?
What should it say? What should it say after a few minutes running?
What do I do when it is too high/too low?

I appreciate your time.
Len.
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Old 13-11-2010, 14:24   #2
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not the best refer guy. Does it run so you hear compressor and then it cuts out? nothing happens and the circuit is in trouble? quick guess but answering the prior will help. You have a loose electrical conection. The fan fuse or comp fuse is not seated. The fan has gone out completly. Replace fan with pump issues if it is water cooled. I thought there were different codes for high pressure and comp failure. check that you are reading these right.
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Old 13-11-2010, 14:40   #3
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Quote:
not the best refer guy.
What makes you say that?

Quote:
Does it run so you hear compressor and then it cuts out? nothing happens and the circuit is in trouble?
First question: correct.
Second question: it's not that nothing happens. When I restart, the compressor runs (and makes familiar noises) but after 10 seconds it shuts off and the LED starts flashing 3 times.

Quote:
quick guess but answering the prior will help. You have a loose electrical conection. The fan fuse or comp fuse is not seated. The fan has gone out completly.
None of the above applies. This appl is brand new. All connections are clean and fit snug and firm in their "seats".

Quote:
Replace fan with pump issues if it is water cooled.
It is air cooled.

Quote:
I thought there were different codes for high pressure and comp failure. check that you are reading these right.
There are five codes and this is code 3, like I wrote in my OP.
I am reading these right. It's quite easy to see that the LED flashes 3 times.

Thanks anyway.
Len.
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Old 13-11-2010, 15:23   #4
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May be you kinked bent a line -that would cause high pressure.
condenser fan is not coming on or there is not enough room to draw air in. air is hot from a source like the engine. You moved some parts where are they moved too. Almost sound like the unit in the fridge cant or isnt dissipating the cold so freon is slugging. Yes put the gauge on the test port. This will tell you if its high pressure or low pressure. Soon a real refer guy will chime in I just babble along as I have one that once gave me a fit and hold a lowly certificate that lets me play with these things
3 blinks Compressor start-up fault Reduce load on cooling system:
Ensure good ventilation around the
cooling unit
Store pre-cooled goods
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Old 13-11-2010, 17:06   #5
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If you have a decent voltmeter, check right at the power connections of the unit.
Make sure your battery voltage doesn't drop too much.
Insufficient voltage would cause what you're describing as the unit builds up pressure after a few seconds.
After running for a bit, the temp and pressure drops.
Thus, the maximum current draw from the batteries (and the voltage drop) is within 30 seconds or so of startup.

We went through the same scenario last summer after reworking and recharging our refrigeration system.
It ran better with a little more R134 than originally, but if the batteries were down a little, it would stall.
I fixed the problem by installing a #6 feed wire to the main panel.
The boat came with a #10 feed wire to run the whole boat !
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Old 14-11-2010, 07:32   #6
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Quote:
Originally Posted by senormechanico View Post
If you have a decent voltmeter, check right at the power connections of the unit.
Make sure your battery voltage doesn't drop too much.
Insufficient voltage would cause what you're describing as the unit builds up pressure after a few seconds.
After running for a bit, the temp and pressure drops.
Thus, the maximum current draw from the batteries (and the voltage drop) is within 30 seconds or so of startup.

We went through the same scenario last summer after reworking and recharging our refrigeration system.
It ran better with a little more R134 than originally, but if the batteries were down a little, it would stall.
I fixed the problem by installing a #6 feed wire to the main panel.
The boat came with a #10 feed wire to run the whole boat !
Thanks, what you write sure is informative.
Unfortunately, I already put in 6mm2 wires, the voltage is 12,7 not running and only drops to 12,5 when starting. I will measure for the full 20 seconds but I do not suspect the voltage.
The LED flashes three times. If it would flash once, then it would mean voltage is/was too low.
Putting everything together, I think there is a little too much refrigerant in the system. I could release a bit but I need some advice here.

Thanks for your time. BTW, how did you establish that putting in a bit more R134a made the system perform better?

Len.
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Old 14-11-2010, 07:46   #7
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Mine is in my engine room. Not ideal. In the summer when temps were upper 90's and we ran the engine it would fault on high pressure. First time as I had little option I spurted a 1 second relief of freon. That worked but it was not as effecient when the air was 70 outside. Didn't get as cold. Now I am installing a supply air duct to bring in cooler not engine room temperature air. It might help if you described how and where you moved things. If you are not pushing good temerature air across the coil and the compressor you will get high pressure. The freon is starting to boil. If you can cool it better the pressure will drop.
Ohh earlier I said not the best refer tech not commenting on your status just a disclaimer that I am not the best but have played with a similar unit and found some solutions.
Hope that helps

I do recall that I had a loose connection and instead of the unit showing low voltage it tripped the high pressure. Or I confused the codes that was a few years ago worth checking
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Old 14-11-2010, 11:31   #8
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Originally Posted by svpresent View Post
Thanks for your time. BTW, how did you establish that putting in a bit more R134a made the system perform better?

Len.
It was a loooooonnngg process during a month's vacation.
My psychiatrist says I shouldn't talk about it. (sarcasm)

We thought we still had a slow leak after a repair had been performed by a refrigeration guy. He was experienced with commercial units, but grossly overcharged our system. At least he didn't overcharge me!

We had to bleed the unit down from 40psi on the low pressure side to about 24 with a cold box while keeping track of start, stop times and average current draw. It's surprising how much a little pressure difference can make.

It took DAYS but we finally found the point where it used the least amp hours while ALSO being colder than originally. The reason we finally found the insufficient panel source wiring was the stall condition first thing in the morning. That's when the batteries would be at their lowest point before the solar took off.

Originally before the problem cropped up, we had 25 degrees in the freezer, the unit drew about 5 amps on startup, went to 6 after a few seconds then dropped to around 4.
After the repair, and our "research" with a can of R134, we had 15 degrees in the freezer, but a max current draw after startup of almost 9 amps, but FEWER amp hours overall because the run time was so much less !

After replacing the #10 with #6, and upgrading the main buss bar in the pane, VOILA !! It runs great. That result made all the hours of searching for the perfect "nut" worth it.

Steve
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Old 14-11-2010, 16:45   #9
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My 2 cents.
To much refrigerant would frost the suction line right to the compressor ie larger of the 2 pipes. The system being only moved this frost would take may be 1 to 2 hours to appear if over charged.
A fully charged system will have frost just appear before the isolation valve of the compressor (when system has reach operating temperature.
The cause to me would be a blockage ( bent pipe) Check that the service valves are open)(or more likely a control fault in the danfoss compressor control.
Take care if fitting guages as these systems are charged to the gram and any loss when the system is up and running will cause a loss in proformance.
Check your pipe work, is your discharge pipe hot after the system runs ie (the compressor is running ?), when moving the system did the compressor get tilted alot this could allow liquid to cause the compressor to lock up (warm compessor with a hair drier may help.
It may come down to putting your hand in your wallet.
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