Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rating: Thread Rating: 3 votes, 5.00 average. Display Modes
Old 19-12-2010, 20:04   #16
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
Question

Nice thread, timely too.

I have a pair of Frigoboat (Danfoss 35 F) air cooled evaporator plate systems on my boat. One of them is not working. Since they are installed next to each other I can (somewhat) easily exchange the controllers. Both systems have LED trouble lights on them. Neither is showing system errors. I have confirmed that the the controllers both work on the functioning side and both fail to make the non-functioning side work. I tested the controllers with both power supplies, thermostats, and fans so I am convinced that none of those are at fault on either system.

On start-up the faulty system draws an appropriate amount of amps, usually creates a small amount of frost just after the capillary but quickly drops down to a very low amp draw and there is little or no circulation of coolant after the initial pulse. The compressor is running and doing some work (barely above ambient temp) but the high pressure line is not warm to the touch and there is no sound of circulation in the evaporator plate. In the past both systems have had similar failures very intermittently and have been "cured" by fully defrosting the system and then restarting -- typically good for six moths to a year. I had the side that is currently working looked at by a tech a few years ago when it last failed and he was unable to find the fault with it (he did put a gauge set on it but otherwise didn't tamper with it). The other side is still factory sealed. I have assumed that the previous faults were caused by blockages /contamination/ice. Based on that history I suspect that there may be a more complete blockage now. But, perhaps the system has low coolant... Or maybe something else?

I do not have a gauge set. I have a bottle of R134a and an automotive A/C recharge kit with an entirely inappropriate low side gauge. The system does not have a sight glass and I'm resisting the temptation to do the obvious. Any thoughts on what the next step in testing should be?

Many thanks!

Tom
__________________

__________________
tsmwebb is offline   Reply With Quote
Old 20-12-2010, 14:23   #17
Marine Service Provider

Join Date: Aug 2004
Location: Ft. Lauderdale
Posts: 784
Tom, Here is a simple approach to understanding troubleshooting of a variable speed Danfoss BD 35 or BD50 compressor refrigeration system:
  • Compressor does not run and there are no troubleshooting LED warning flashes. This indicates there is no power to electrical control module or faulty thermostat wiring or thermostat is faulty.
  • Compressor runs but only a portion of evaporator has frost coverage and the frosted portion remains less than 80% of evaporatorís surface area while compressor runs, System is low on refrigerant.
  • Poor refrigeration unitís performance can be caused by poor condenser cooling, line from condenser should be only warm, say 110 degrees F.
  • If compressor runs and there is no cooling would indicate there is NO problem electrically and control module is good.
  • When refrigerant flow is blocked on this type system compressor will continue to run as if there is no refrigerant in system and amperage will be very low. There are two kinds of capillary tube blockage, ice formation and solid material blockage. Ice blockage is easy to determine by observing evaporator frost and listening to evaporator sounds. Gelled or solid material blockage is more difficult to confirm as it requires adding refrigerant to rule out low on refrigerant. Ice blockage will be a reoccurring condition melting and refreezing every few minutes. On a warm start up frost will form on evaporator until capillary tube reaches freezing temperatures and blocks refrigerant flow. In a few minutes ice will melt allowing refrigerant to again flow. This freezing and thawing of capillary tube will regulate evaporatorís temperature to just above the freezing point of water. By listening to refrigerant flow sound inside refrigerator and evaporatorís temperature of just above freezing will confirm that moisture is present in refrigerant.
If you confirm refrigerant is low you can add refrigerant by using a digital ammeter to determine approximate refrigerant charge by amperage. Always test system for leaks and repair them fist. On Frigoboat units if refrigerant is so low that no frost forms on evaporator then line connecter O rings need to be replaces and system needs to be dehydrated with a good vacuum pump for several hours. Even if your system had a sight-glass it could not be used on a capillary tube system to determine correct refrigerant charge.
__________________

__________________
Richard Kollmann is offline   Reply With Quote
Old 20-12-2010, 15:57   #18
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
Quote:
Originally Posted by Richard Kollmann View Post
  • When refrigerant flow is blocked on this type system compressor will continue to run as if there is no refrigerant in system and amperage will be very low. There are two kinds of capillary tube blockage, ice formation and solid material blockage. Ice blockage is easy to determine by observing evaporator frost and listening to evaporator sounds. Gelled or solid material blockage is more difficult to confirm as it requires adding refrigerant to rule out low on refrigerant. Ice blockage will be a reoccurring condition melting and refreezing every few minutes. On a warm start up frost will form on evaporator until capillary tube reaches freezing temperatures and blocks refrigerant flow. In a few minutes ice will melt allowing refrigerant to again flow. This freezing and thawing of capillary tube will regulate evaporatorís temperature to just above the freezing point of water. By listening to refrigerant flow sound inside refrigerator and evaporatorís temperature of just above freezing will confirm that moisture is present in refrigerant.
Richard,

Thank you very much. That is an extraordinarily good post.

These systems have a history of intermittent failure. The failure mode has always been that at some point the working system will stop drawing amps but run continuously. This happens after months of even years of cycling correctly. Once they are completely warm (box at ambient temp) they usually restart and then work again properly for months or years. Until they warm up cycling them causes a brief run with expected amps drawn and a bit of frost after the capillary followed by a drop in amps and continuous running without cooling. I have always assumed this was caused by some kind of blockage. I suppose bits of solder or rust etc might be getting to the capillary tube and only get passed when the tube is warm... Perhaps the filters are defective? They symptoms don't sound like ice given your description of the ice cycle. The mystery to me is that the systems work so well most of the time (except now that I haven't been able to get the usual restart)... Could the systems really work well most of the time and yet have low refrigerant?

I will try warming the capillary tubes a bit to see if that expands them and frees things up and will report back...

Thanks again,

Tom
__________________
tsmwebb is offline   Reply With Quote
Old 20-12-2010, 17:09   #19
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
Quote:
Originally Posted by Richard Kollmann View Post
Ice blockage will be a reoccurring condition melting and refreezing every few minutes. On a warm start up frost will form on evaporator until capillary tube reaches freezing temperatures and blocks refrigerant flow. In a few minutes ice will melt allowing refrigerant to again flow.
Okay, tested by adding heat to the capillary tube and did get a freeze thaw cycle. Then removed the heat source and if I wait long enough I get it without heat too... Given the history of the system I suspect there may be other contaminants in it but it now seems likely to me that there is moisture. So.... Is there a DIY kind of fix for this? I notice that amazon sells a guage kit and vacuum pump for about $150. I suppose one would also need something to filter the refrigerant and to hold it while the system was being vacuumed... I did call the only local tech I know of on the island and he is out of town so it would be nice if I could fix this myself... His suggestion was to add more coolant...

Many thanks again,

Tom
__________________
tsmwebb is offline   Reply With Quote
Old 21-12-2010, 07:50   #20
Marine Service Provider

Join Date: Aug 2004
Location: Ft. Lauderdale
Posts: 784
Tom, it sounds like moisture in system the question is how did it get there? It surely did not come from factory that way. If you have confirmed moisture is cause of intermittent operation then extensive dehydration is recommended. As a last check for moisture in refrigerant, bypass thermostat so compressor will run continuously for 24 hours. Moisture in refrigerant is confirmed if compressor runs for 24 hours and evaporator is cold with condensation but no frost.

There are reports of Frigoboat models with keel coolers having problems with solid material blocking cap tube inlets but not air cooled condensing unit models where filter/dryer is located between condenser and cap tube.

The only way I can theorize the condition you describe of system working well at times and failing to cool after a warm up period is location of moisture in refrigerant. When a system is warm moisture in liquid form can pass through expansion device cap tube and not restrict flow. A properly designed evaporator will accumulate oil carrying moisture near outlet end of evaporator. Suction line accumulators built into roll bond evaporators look like a series of circles in the embossed refrigerant tubing. If moisture freezes first in the accumulator area this ice will remain there as long a evaporator has frost on it. When evaporator warms up water is free to circulate around to the only major restriction the capillary tube where it will freeze if cold enough.

Because the BD35 compressor has ester oil that refuses to release moisture under normal vacuum, extensive dehydration is required. Complete system needs to be warmed to around 100 degrees F while being evacuated to below 300 microns for at least 4 hours.
__________________
Richard Kollmann is offline   Reply With Quote
Old 21-12-2010, 12:04   #21
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
Quote:
Originally Posted by Richard Kollmann View Post
Tom, it sounds like moisture in system the question is how did it get there? It surely did not come from factory that way. If you have confirmed moisture is cause of intermittent operation then extensive dehydration is recommended. As a last check for moisture in refrigerant, bypass thermostat so compressor will run continuously for 24 hours. Moisture in refrigerant is confirmed if compressor runs for 24 hours and evaporator is cold with condensation but no frost.
Thanks Richard. I don't have any good ideas on how the moisture got into BOTH systems while both were factory sealed. With no evidence whatsoever I kind of suspect the quick connect fittings since they are the only bits that are not factory soldered. Also, they provide a lot of extra O-rings with them which makes me wonder about their expectations... These systems have been running in the tropics for about ten years so they've had lots of exposure to moist air.

I will try the long run of the compressor.

Quote:
Because the BD35 compressor has ester oil that refuses to release moisture under normal vacuum, extensive dehydration is required. Complete system needs to be warmed to around 100 degrees F while being evacuated to below 300 microns for at least 4 hours.
You make that sound so easy ... But, I'm completely and utterly clueless. I presume I need a vacuum pump that can draw a good vaccuum for a long time and a set of connections. But how exactly does the vacuum get connected to the ports? What happens to the refrigerant? Do I need to replace the filter/dryer? etc...

Tom
__________________
tsmwebb is offline   Reply With Quote
Old 21-12-2010, 13:24   #22
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
FWIW, on the warm part of the cycle the plate is at just about at ambient temp ~75F and there is no frost. When there is frost it is only on the first few inches of the tubing after the cap. That area also warms to ambient on the warm cycle. There is little or no condensation on the plate and it doesn't seem to cool very significantly at any time.

The compressor is warm ~115F degrees according to my not very reliable non-contact thermo. The compressor next to it that is working correctly is showing ~130F.

Tom
__________________
tsmwebb is offline   Reply With Quote
Old 21-12-2010, 15:57   #23
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
Stop press:

I got frustrated and added a little bit of r134a... The system seems to be working now... The local tech suggested adding a very little bit of refrigerant by attaching a new can to the low side with the compressor off, opening it and letting the pressure equalize between the coolant can and the reefer... I was too cowardly to do that much and only opened the can for a few seconds... At the moment the system seems to be working like a charm... I will report back after it has run for a day or two or if it fails.

Thanks all. And, thank you very much, Richard!

Now I'm interested in suggestions for hunting down leaks (in this case I assume they are very slow ones given the years of service).

Tom
__________________
tsmwebb is offline   Reply With Quote
Old 26-12-2010, 12:06   #24
Registered User

Join Date: Apr 2007
Location: Hawaii
Boat: Atlantic 42 Catamaran
Posts: 293
It's still working so I guess that it was just low refrigerant. Thanks again for the help.

Tom.
__________________
tsmwebb is offline   Reply With Quote
Old 22-12-2015, 23:33   #25
Registered User

Join Date: Jun 2013
Location: Bellingham, WA
Boat: Bruce Roberts 44' Steel Mauritius
Posts: 578
Re: Danfoss Compressor 'Bumps' but then Doesn't Run

If you are near someone who does a lot of refrigeration work many times they will have a pile of old Danforth compressors lying around with controllers since they upgrade by installing pre-charged units and have no use for the old ones. I got a few controllers free that way.
__________________

__________________
Mithril Bham is offline   Reply With Quote
Reply

Tags
compressor

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Portable Fridge/ Freezer, Danfoss Compressor Boatguy30 Classifieds Archive 3 13-12-2010 18:31
Air Conditioner Makes Bumps on Deck ? Huh ? MikeZ Construction, Maintenance & Refit 9 09-06-2010 00:48
Wanted: Danfoss compressor controller sorino99 Classifieds Archive 4 27-10-2008 10:03
Danfoss bd 50 question George Elliott Plumbing Systems and Fixtures 4 11-09-2008 20:40
Danfoss BD35 Celestialsailor Plumbing Systems and Fixtures 2 24-11-2006 15:16



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 06:52.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.