refrigeration - blocked capillary

[Foeboat]

Hi,

I have a Alder-Barbour cold machine that sprung a leak in the aluminum part of the evaporator tubing and, despite repeated attempts, was unable to aluminum braze the hole closed. New evaporators are expensive for what they are so, working in my garage, I am attempting a franken-repair. I took old small fridge with an evaporator and capillary tube set-up that looks very similar to the failed unit and removed the evaporator and connecting delivery and suction lines. I cut the suction and delivery lines in the copper section of the old fridge and managed to solder them to the long copper cold machine suction and delivery lines. Rest assured that I checked the label on the old fridge and the refrigerant is 134a not freon. Using a manifold, I filled the suction side with a small amount of 134a to a pressure of 10 psi or so. When the compressor is turned on, the suction side drops to -30 (units?), and the delivery side rises quickly to 60 psi. Nothing gets cold. When I turn the compressor off, the suction side remains under vacuum (at -30 whatever units) and the delivery side pressure slowly drops. I suspect that I screwed up the solder job on the delivery side. I made the joint in the larger diameter copper delivery pipe in the replacement evaporator just in front of a large copper bulb (drier I assume) that bridges the capillary tubing to the larger diameter tubing. I may have heated the bulb -- is this bad? Or I may have plugged the tube with soldier. by the way, I checked for leaks and there are none apparent using soap bubbles.

I'd appreciate any insight into the question of the symptoms -- does this sound like a blocked capillary tube?

Best,

David

[Typhoon]

Hey David. Even if you had not plugged the captube and you did a perfect solder job , the system would probably not have worked.

You probably would not have been able to achieve a pressure drop across the tube , they are specifically designed for the pumping volume of the compressor . Unless that fridge you took the captube from had a BD35/50 compressor in it .
If your condensing unit is in good shape I would consider getting the right plate and captube setup for it and maybe getting a tech come in with all the right tools to put it together for you . Remember if the system has been open to the air for any length of time you will have to dry it out with a long deep vacuum down to 500 microns applied . Make sure to replace the filter/drier, and have him install resealable couplers so you can take it apart and install the system back in your boat without loosing the charge. Not sure if this would be any cheaper then buying a new system.

Regards John,

[Kenomac]

Buy a new evaporator and be done with it.

[Foeboat]

Thanks for the comments. I truly appreciate your help and realize that there are challenges to this but .. common, (with respect) really? Unless I am totally off track, the capillary is just a metering device. If the tube length and ID are the same (which they look very close to being) then the pressure drop should be correct. If they weren't, the capillary tube gas conductance could be adjusted by changing the overall capillary length. The fridge volumes and temperature specifications are similar so how can the pump power be so very much different? Unless there is magic that I don't understand (there very well may be), the $500 + cost of a new evaporator is completely out of line with the cost of manufacturing these things (this can be seen from the cost of fridges (non-marine) with similar performance that use capillary metering. Charging the system with 134a is straightforward enough and i have a vacuum pump to suck the water vapor and air out of the system. As for going nuclear, (calling a refrigeration technician), that isn't in the budget.

My plan is to unsolder the joint in the delivery side and see if it really is blocked and if it is, try to cut out the blocked section. If all else fails, I'll buy a new evaporator (and curse the market forces that allow them to charge so much!)

Best,

David

[Typhoon]

Hey David , look up the numbers on the compressor on the fridge you took out the captube out of . You should be able to search it and find out what its BTU rating is.

I have an old evaporator plate here just kicking around with a captube on it , I will give it to you if you like . Its in good shape no leaks .

Let me go snap a picture of it and post it . Give me a moment.

[Typhoon]

Originally Posted by ColdEh Marine

Hey David , look up the numbers on the compressor on the fridge you took out the captube out of . You should be able to search it and find out what its BTU rating is.

I have an old evaporator plate here just kicking around with a captube on it , I will give it to you if you like . Its in good shape no leaks .

Let me go snap a picture of it and post it . Give me a moment.

Ok here are a few pics the plate is 10 by 20 inches if you straighten it out . the cap tube is intact . This plate came from a system based on a BD35 compressor .

Its yours if you want it no charge , just pay the shipping , Im in Toronto Canada .

[Foeboat]

Thanks Coldeh! I'll take it! I'll send you a PM.


The btu rating on the salvaged fridge evap plate is 191 btu/hr, 2 oz recharge 134a, minimum compressor capacity vacuum 18 in, minimum equalized pressure @70 and 90 F is 30 and 34 psig.


Thank you, thank you!


David

[Typhoon]

Originally Posted by Foeboat

Thanks Coldeh! I'll take it! I'll send you a PM.


The btu rating on the salvaged fridge evap plate is 191 btu/hr, 2 oz recharge 134a, minimum compressor capacity vacuum 18 in, minimum equalized pressure @70 and 90 F is 30 and 34 psig.


Thank you, thank you!


David

That really is a small compressor , you need to know at what evaporator temperature the BTU is rated .

Not to worry , I will send you this plate and you will be good to go.

Glad to help. I will check for your PM.

Regards John.

[Kenomac]

The hard work and persistence pays off.