... Brand new here; first question...
... I moved into a mobile home earlier this year that has a packaged AC system (Comfort-Aire PC30-1J) connected to it. It works, but it has a tendency for the evaporator to ice up. I'm getting ready to call in a professional to check out/service the unit, but I have some questions I'd like to bounce off the more knowledgeable folks here...
... First, I'm not a complete stranger to refrigeration/air conditioning systems (had training in that area while in the military), but I'm also not in the trade, either. I don't have the proper certifications for handling refrigerants, so I'll be leaving that to the people who do. This is an R-22-based unit (42 oz charge), and everything I've been reading suggests that a low charge is a likely cause of the evaporator freeze-up. (Also a clogged drier-strainer, I suppose; this unit has one right before the capillary tubes... there are six capillary tubes feeding the evaporator... I've found the manual to the unit that includes a wiring diagram and an exploded view, so I have an idea of what's what)... also, the suction line to the compressor gets a nice coating of ice on it...
... Anyway, anyone know what the operating pressures are supposed to be on this critter? (I do know how to use a manifold for checking pressures)
... And another question: Would it be worthwhile to retrofit something like this to run on a non-CFC refrigerant? R-22 is supposed to be going away next year, and any subsequent servicing of this unit with R-22 could get very expensive when the supply of refrigerant is limited to whatever can be reclaimed/recycled... I understand that a retrofit itself would involve a number of steps (remove the old refrigerant and oil, replace the oil with a different type (POE), which could require additional charging and purging to remove as much old oil as possible, then leak test and repair if necessary, replace drier-strainer, and finally recharge with suitable substitute refrigerant)... could be substantial initial cost there, too... also, what is the availability of substitute refrigerants and how expensive are they? (Especially R-427a, which is supposedly a very good sub for R-22 and even has a high tolerance for residual R-22 oil?)
... Also, this unit does not have a separate fan relay for operating the blower independently of the compressor. According to the diagrams, it doesn't look all that difficult to wire one in. Is there a specific type of relay that is recommended for this? (Looks like a simple SPST relay with a 24V coil and sufficient contact rating would work; would just be a matter of mounting it and wiring it in)
... a lot to ask for a first question, I suppose... :eek:

Anyway, anyone know what the operating pressures are supposed to be on this critter? (I do know how to use a manifold for checking pressures)

The operating pressures will change with the outside temperature,the inside temperature,the inside humidity etc. Use superheat or subcooling for setting the operating pressures only anything else is just a guess.

Would it be worthwhile to retrofit something like this to run on a non-CFC refrigerant?

No changing it would be impossible cost wise. R-22 will not be that expensive unless someone is ripping you off. There will be R-22 around for the next 25 years so do not worry about it. There are SUPPOSED to be drop in R-22 replacements BUT I have never seen one yet that had the same glide as the original R-22 so leave it alone or study this industry IE take many classes and find out for yourself.

Also, this unit does not have a separate fan relay for operating the blower independently of the compressor. According to the diagrams, it doesn't look all that difficult to wire one in. Is there a specific type of relay that is recommended for this? (Looks like a simple SPST relay with a 24V coil and sufficient contact rating would work; would just be a matter of mounting it and wiring it in)
...a lot to ask for a first question, I suppose

Why do you want a separate fan switch for a unit like that. They have so much leakage in the air ducts to start with. Now if you just want to blow some air around that can be done with a relay but you might have to add some low voltage wires to the outside unit since it is self contained. Look on the access door for a wiring diagram and see which are the power wires for the fan that blows indoors and go from there.

A few things to check for your problem.

If the air is cool outside your unit could be showing frost. Most normal A/C units do not like to operate when it is below 60-65 degrees. Some units will and some will not. Low ambiant kits are sometimes required for proper operation if the outside temps are to low.

Make sure the air filter for that unit is clean or replaced. A lack of air flow will freeze them up right now. Also make sure the damper is opened all the way on the return air if so equipped. If this is only a A/C package unit and the heat is taken care of by a different furnace there is usually a damper or block off plate for the A/C unit especially if it is piped into the regular duct system. This is done to prevent the cold air in the winter from getting into the mobile home.

Make sure your evaporator and condenser coils are clean. A dirty evap coil will also cause a freezing condition. There are other items but you have enough ammo for now. Happy hunting.