Replacement AC - Project Options??

[PNM]

My 1979 Ocean 40+2 Trawler had two Cruisair 16K BTU ACs. One is a split system with 2 evaporators: one in each of the fore and aft cabins. The second is split system with one evaporator in the salon - over the refrigerator, near the aft companionway. Both condensers are in the engine compartment.

I replaced the fore and aft cabin AC condenser a few years ago with an Ocean Breeze condenser that works great.

Now, I want to replace the salon ac with a stand-alone 16K BTU Dometic (?) AC installed under the settee in the salon. The warm air return will work great, by installing the input vent in the "side" of the settee near the middle of the salon.

Reasons for going to stand alone unit: old evaporator, old copper freon tubing, R-22 (407C??) gas, cost, etc. Dumb???

I am trying to find a way to run a 6" insulated flexible AC cold air duct (about 8" OD) to the current location of the evaporator above the refrigerator, about 25'.

Mabe I am working too hard???

"I think" I should try to put the cold outlet high, since the room temp air return is near the floor, to get better circulation. "I think" putting the cold outlet where the evaporator is now, would be optimal.

Alas, I cannot find a way to get the 6" (8" with insulation) flexible duct to the area above the refrigerator without running the duct through the floor under the settee, then across the top of the engine compartment. Would this be an acceptable approach? Or, do you have a better idea?

The easiest installation is to just output the cold air in a 90 degree different direction from the other side of the settee - pointing vent louvers "up" to improve circulation high in the salon.

Does the cold air duct need to be insulated if it is running through the bottom-back of the salon galley cabinets?

The 6" flexible duct cross section is about 28 sq in. I can run 2 rectangular "un-insulated" pvc ducts through the galley cabinets, but they will only have a 25 sq in cross section. Will that be a big problem for the compressor?

I could build-in a plywood enclosed pathway in the back-bottom of the galley cabinets, but the only insulation would be the plywood. Is this approach acceptable?

Ugh! I obviously need a lot of help

Your experience and expertise is appreciated.

 

[O C Diver]

Don't over think this. For the saloon, the best thing you can do is to have the supply and return ducts as short as possible ( my supply is less than 2' and no return duct). If you point the supply so that it sweeps across the ceiling, it does a much better job of mixing the air up in the room. Keeping the supply duct short means more CFM to mix the air up in the room.

Ted

 

[mvweebles]

I can't really picture what your challenge is, but here's a couple pics of how I ran my ductwork.

Compressor is beneath the settee. I built a rigid duct that protrudes into the stateroom a bit. I used a piece of square 5" PVC used for vinyl fencing and put 3/4" rigid insulation panels around the outside, the wrapped in mahogany to match interior. Also allowed me to put a vent in thr dashboard to defog windshield.

Only downside is it's a bit noisy. Longer duct run would be better.

BTW - in my opinion, ducting must be insulated or condensation will invisibly destroy your paneling from inside out.

Peter

 

[PNM]

Thanks for your suggestions.

 

[Turtle Blues]

New SC units are about the same footprint as old style evaporators. Is it not possible to install the whole unit at the evaporator location? Usually means a step up in the cooling water pump and some new hose but trades off freeing up some floor space removing the condensor.
I want to echo Ted's note about moving the air off the ceiling and Peter's duct idea to use rectangular PVC is great for square spaces. Yes, insulation tightly adhered is very important.
In tight spaces we often pull the insulation off of round flex duct and pull it over the blue flexible bilge exhaust duct knowing it will get pressed out of shape, it is a lot sturdier.
In any installation make sure the return air is at least equal to the size of the coil face or connector collar if the unit has that fitting. Less static resistance on the intake gives greater cooling efficiency.

 

[RRPrather]

You will also have to run the supply and return sea water lines. The copper refrigerant lines are ok to re use and I would just replace the condensing unit and air handler.

 

[Turtle Blues]

The current technology, size and cost of 16k self contained units has rendered single split systems virtually obsolete. Yes you need to pipe cooling water to it but thats a lot simpler for most people than charging a system.