Upgrading Phoenix Cruiser 2551 A/C

Your 30A service will run a 15K just as well as a 13.5. The difference in power draw is roughly an amp.

You bought used, correct? Pull the 13.5 apart from the roof and clean it. Chris Bryant has an article HERE. It's incomplete, broken links to the pictures, but it tells you what to do.
I'll venture that your 13500 IS adequate for your size coach and will keep you cool if you keep it clean.
The intake filters too, of course. I salvaged a 20 year old Coleman Mach 13500 that I thought I was going to have to replace, following Chris' article.
While the shroud (the pretty finish one) is off, make sure that (if it's Coleman) that there's a foam baffle running vertically along both ends of the Condenser (rear Coil). If missing you can make them out of foam pipe insulation or a swim noodle. Again, this thanks to Chris Bryant.

Thanks j-d! Will check this out!

I saw an rv mechanic use a spray to clean it, I think it was this one by ZEP in the link.

Air Conditioner Coil Cleaner PROD.# 0202 BENEFITS : Designed to simplify the task of cleaning the exterior surfaces of coils on window and rooftop air conditioning units. Eliminates the need for buckets, sprayers, and water hoses. Reduces cooling expense by promoting efficient heat transfer on coils.



http://www.superkleendirect.com/cleaners/automotive-machinery/zep-foaming-coil-cleaner/

I just got through putting the cover back on. I should have seen this first. :-) I decided not to clean the coils but to blow them out with air as they don't look dirty. The rest of the compartment is filthy but the coils are pretty clean. Another reason I didn't use the cleaner I bought is there is no way I'm spraying water into that compartment. There isn't any way to prevent making a hell of a mess inside the rig. I'd have to remove the unit to clean it that way. If I'm going to do that I'd rather go ahead and do an upgrade. I think upgrade is going to happen anyway since the coils aren't dirty so pretty sure that's not the problem; this unit is just too small or old top keep up.

Another reason I want to upgrade is the current unit has no fan off function. If the A/C is on the fan is on; doesn't turn off after the compressor shuts off. Gets old having the fan blow all night long. My previous rig had a house type thermostat where the fan had a Auto/On function. Not sure why this much more expensive rig does not.

I'll keep y'all posted.

Thanks for all the input.