Which refrigerant??

My rear 16,000 btu Cruisair unit has begun to freeze up after several hours of running. It appears to be a slow leak. I believe it is original to the boat, 1983, and I read somewhere that pre 1995 used R12 refrigerant. Very rare (read expensive). Does anyone know if this is true?

R-12 IS almost impossible to find, probably illegal to install.

Beware , some of the R-12 "replacement" is simply propane and butane (which IS more efficient than the R-12) but could be a problem with out a bilge sniffer.

In the future I'm guessing ammonia will be the refrigerant of choice , 50c a pound and no BS "ozone" problems.

Best its even 20% better as a refrigerant than any Freon .

Energy will cost dearly as the billions in the 3rd world play catch up, so a 20% break in operating costs will be hard to pass up.

There should be a metal tag on the unit which has model and serial number and type of refrigerant used.

Some R12 units can be converted but a unit from 1983 might be better replaced with new.

IMHO* JohnP

R134 is a drop in replacement. Just google "r12 replacement" and you'll get all kinds of hits.

Turns out it's R22. Thanks Steve at marine-ac !

When replacing the refrigerant, flush the system first and check the TXV or orifice tube for debris and replace as necessary. Vacuum down all the way too so as to make sure you got all the moisture out of it.*

Anthonyd wrote:


When replacing the refrigerant, flush the system first and check the TXV or orifice tube for debris and replace as necessary. Vacuum down all the way too so as to make sure you got all the moisture out of it.*

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Thanks!

Uhm, a question -- what do you mean by "freeze up" and why do you think there's a refrigerant leak?* I assume you mean ice on the evaporator coils, no?*

Chris Foster wrote:


Uhm, a question -- what do you mean by "freeze up" and why do you think there's a refrigerant leak?* I assume you mean ice on the evaporator coils, no?*

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Yes, the evaporator coils. A couple of weeks ago while moving the boat to Biloxi this happened. It's a split system, the coil is in a locker in the saloon. It takes a mirror to see/ replace the filter. I discovered it was very dirty. I replaced it and thawed the unit by running just the blower. That night it "froze up" again. Last weekend I went to the boat prepared to charge the system if needed. After running it two nights and watching the temperature differential (15 degrees plus) I have decided that she was not low on freon, but I think that when I "thawed" the unit the previous weekend it had not completely thawed- thus it froze up again.

I don't know exactly how this unit works, but frequently the expansion valve is thermostatically controlled to keep the coils above freezing.* They often have a little temperature sensor that mounts on or in the coil - if that comes loose or breaks, the coils run too cold.*

Some have a temperature adjustment that may need to be tweaked.

*

Chris Foster wrote:


I don't know exactly how this unit works, but frequently the expansion valve is thermostatically controlled to keep the coils above freezing.* They often have a little temperature sensor that mounts on or in the coil - if that comes loose or breaks, the coils run too cold.*

Some have a temperature adjustment that may need to be tweaked.

*

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Good point. I have that sensor with capillary tubing in front of the coil, and the filter fits between it and the coil. Maybe with the dirty filter I was getting a bogas reading on the sensor?

It really needs to be touching the fins so that it gets the temperature of the coil, not of the air.* Sometimes it's wedged between two fins or there's some sort of metal clamp.* Perhaps it came out either through age & vibration or when the filter was cleaned?

Chris,
You know- The capillary tube bulb is NOT fastened to the coils. In fact, I cut the fiberglass filter to size and then slip the filter between the bulb and the fins. I definitely need to correct this.

That would surely explain the problem you're having.* The coils are supposed to be in the high 30's so that they don't freeze, but the capilary being in the warm intake air would run it as cold as it can get.

A TX valve uses the temperature bulb to regulate the suction behind the valve.

In refrigeration suction is the measure , of temperature the unit will operate at.

Chris Foster wrote:


That would surely explain the problem you're having.* The coils are supposed to be in the high 30's so that they don't freeze, but the capilary being in the warm intake air would run it as cold as it can get.

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That's true. I am working with a knowledgable buddy also and have found the my supply grills are not large enough (square inches) for the CFM's coming out of the air handler. He is designing a new plenum and we will add an additional vent and this should help also.

Forkliftt wrote:Chris Foster wrote:
*

That would surely explain the problem you're having.* The coils are supposed to be in the high 30's so that they don't freeze, but the capilary being in the warm intake air would run it as cold as it can get.

Click to expand...

*

That's true. I am working with a knowledgable buddy also and have found the my supply grills are not large enough (square inches) for the CFM's coming out of the air handler. He is designing a new plenum and we will add an additional vent and this should help also.

*This is more likely your problem...Lack of air flow as your buddy says...

The sensor bulb you are reffering to is for your manual t-stat, and should Not touch the fins or coil if you want to maintain cabin temp...It should be in the return air path so as to get a constant sample of cabin air temp with the fan running.

Most All Marine A/C built till 2011 with R-22 refrigerant use a Capiliary Tube metering devise...Not TXV...However...Dometic's new "Emerald" series split systems with R-410a use TXV valves (2) at both the condensing unit & the air handler...

Self Contained units still use Cap tube...Even with the 410a

A trick: To de-ice that coil quickly...Switch the unit to the heat mode....That is if the T-stat will allow it...If it's too warm in the cabin it may not...

Also: If you hear the compressor run & the reversing valve switch but get no heat...You are most likely low on refrigerant...When slightly low the system may cool but won't heat.

Steve~

Got it. Don't touch the coils! I'm working on more air flow. Thanks!