Question for Air Cond. techs

[formula31]

I am installing an old ac unit in my boat. Its a split system and I want to air pressure check the evaporator before I finish the lines and have it charged. What pressure should I use?

[mcollinstn]

R12 auto systems see as much as 250 psi on the condensing side. The evap rarely runs over 40 when in operation, but will see around 70 when the compressor is off and the system has equalized out.

Marine systems are designed for a "reverse cycle" option, which means that the pressures reverse in Heat mode. I'd expect an R22 marine system (or a 134a one) to see 160 regularly on both sides (if reverse cycle).

[LapseofReason]

your going to want to put a vacuum on it and suck it down to get all the moister out and most vacuums will have a Gage so you can see if it is air tight. If it's a R12 system change it over to R134 now it's a hell of a lot cheaper. If you use air psi to test the system you are just pumping more moister in and you want to get it all out. Make sure you check to see if it need's oil to so you can put it in when you charge it up.

[formula31]

Thanks, this is a reverse cycle r22 system so ill check it at 160. My buddy has the vacuum pump and guages and will help me charge it when Im ready. I wanted to check the evaporator now since it will be buried very soon.

[Waterfoul]

Like I told you the other night Tom (when I was stoned on pain killers), you put A/C in your boat and you will SUCK!!!! LOL!!

Just jealouse.

[hp500efi]

Lapse is right, you want to pull the system into a vacuum NOT pressurize it. Pulling it into a vacuum not only tells you if it is sealed but also removes all the moisture from the system. Let the system sit for a while in a vacuum, verify it is not leaking then charge it while the gauges are still on. You will end up with a moisture free, leak proof system.

[Sonic30ss]

Use dry nitrogen to pressurize system. I've seen new installs hold a vacuum, and as soon as pressure was added leak!. If your buddy has guages and a pump he'll probably have a nitrogen cyl. too.

[Tinkerer]

I agree with SONIC. USE NITROGEN and pressure test it to 100 psi and soap solution the joints for leaks.

[formula31]

The evaporator has been open to air for months if not years. I dont see where some clean, dry air is gonna make things any worse than they are already. Nitrogen will set me back another week or more and the system wont be pulled down and charged until june or july. I have half the boat interior torn apart for the installation and it needs to be put back together soon. The compressor and condensor are hiding in the engine compartment.

[Tinkerer]

The nitrogen will help with the drying process. Also replace the freon filter drier. It will be a bulge in the liquid line going from the condenser to the evaporator. It may be inside the condenser assembly. If it has one it MUST be replaced.