Author Topic: Correct High/ low pressures for a bd 35/50. No frost on evaperator!  (Read 15306 times)

Richard

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #15 on: July 11, 2012, 02:09:19 pm »
You should have unloaded the refrigerant flow circuit by replacing it with a unrestricted line between high pressure service port and suction port. By turning unit on compressor's output flow would be unrestricted allowing compressor to run drawing around 3 amps.  What happened as I understand it is Troubleshooting LED started to flash 3 times every four seconds, Correct. This means there are three possible causes:
1. There is flow blockage between compressor and high service port. I remember this condition occurred on four other systems when someone had soldered line into compressor outlet blocking high pressure outlet.
2. Three LED flashes normally result from high amperage too much refrigerant and not normally caused by a module failure but module can not be totally ruled out. I would try another module.
3. Locked compressor armature common on other electric compressors but not so on Danfoss BD 12 volt units is the last cause of  an overload LED signal I believe.

Before I replaced a compressor I would first unsolder high pressure line from compressor and turn system power on. If passage into compressor is open (no Solder Blockage and compressor runs  line between compressor and high service port is blocked. If compressor still does not run and LED still flashes then replace complete system. Replacing just compressor is too expensive in most cases.

heron

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #16 on: July 11, 2012, 08:49:34 pm »
The system did run and produced frost after I refilled the system with 80 grams of refridgerant. So it seems that a blockage from soldering would always be present and not change many years after installation. Is that correct?

Is there any way to isolate the power for the compressor from the module and check the compressor or module?

Rparts has compressors for $300 and a whole new system for $1000. Is your last comment about compressors being too expensive meaning that you end up replacing everything anyways because the whole system is contaminated?

Richard

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #17 on: July 12, 2012, 10:41:40 am »
You are correct blockages in those areas only occur after soldering. Any blockage after condensing unit will not trigger troubleshooting LED if system has correct charge.

The only check of compressor is to check resistance between its electrical pins and from each pin to ground. I can test module on a my test stand you must pay return shipping.

Hear are my reasons for not replacing compressor:
•   New compressor cost $300
•   If module was weakened or failed by overloads caused by bad compressor add another $300
•   Chances are whoever you purchase compressor or module from will not warrantee them.
•   Labor costs if you can not do the work yourself
•   Risks involved in replacing compressor, Original life expectancy of evaporator is around 12 years, contaminating system during compressor replacement, and additional expenses to re-commission system to an expectable standard. 



heron

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #18 on: July 13, 2012, 11:04:39 am »
Richard you have been very helpful and informative throughout this exploration of my refrigeration system thank you very much. I will take the system apart and see if I find any thing. Also, your 12v book arrived the other day and what I have read so far (two kids under 3 doesn't leave much time for reading) has been easy to read and understand the information.

heron

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #19 on: July 13, 2012, 09:24:21 pm »
One more question for you Richard. I can get a new A/B compressor and module. Should I replace the evaporator and lines as well or can I leave the old parts. Does leaving the old evaporator risk contaminating the new compressor?
« Last Edit: July 14, 2012, 10:54:46 am by heron »

heron

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #20 on: July 13, 2012, 11:17:48 pm »
In thinking about it more I realize that you have to replace both the condenser and evaporator at the same time because they are both precharged at the factory. This enables the quick connect application. 

Richard

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Re: Correct High/ low pressures for a bd 35/50. No frost on evaperator!
« Reply #21 on: July 15, 2012, 06:34:20 pm »
I do not think you have proven compressor is bad but if you want to replace it by all means replace complete system.

It seems to me you are confusing air conditioning pressures with refrigeration pressure and yes you now probably have air contaminating refrigerant high pressures.

On these small systems efficient refrigeration low pressure with 134a refrigerant is 5 to 10 psi.  If your evaporator is small then 6 to 8 psi suction pressure is in the ball park. Suction pressure above 15 is air conditioning pressures.