A/C Maintenance

[mmdesmith]

Was going to do some maintenance on the Mermaid 16,500 BTU A/C unit in my 361 this weekend:
1) it says to add 5 to 10 drops of SAE non-detergent oil to the electric motor - it was not obvious where to add the oil as it had stated. I was looking for a small nipple of some kind - any suggestions?
2) went to remove/clean the air intake filter and didn't find one. I could run my fingers along the evaporator coils and could feel dust/etc. Did the best I could with a diluted solution of bleach/water and a toothbrush to clean the coils (very hard to reach). I noticed velcro down the sides of the evaporator - to hold a filter in place maybe? Also found a piece of foam like material that was about the size of the evaporator folded on the floor next to the unit - could that be the filter? It was old and literally fell apart in my hand as I picked it up.
3) Saw the thread about the condensate – I believe mine drains into the section before the bilge and collects there. Note sure if I want to add the pump or just clean with a sponge regularly.
4) Any other suggestions on maintenance? It’s getting hot here in Texas and I set the thermostat at 85 to 88 so the unit runs quite a bit. If I don’t, the boat easily gets to over 100 degrees and cannot cool down to 78 to 80 without pipes freezing. I had to have the unit serviced last summer because it stopped cooling.

 

[TAK]

Looks like you found the remains of the filter. You should be able to find something better through a dealer or your local marine store. I have a Beneteau 381 with two Cruisair units. Mine has a slot in front of the evaporator coils that holds a woven plastic mesh filter. I also have a coarse wire mesh filter that fits inside the intake grid. Seems to keep most of the crud off the coils.
My forward AC unit also dumps the condensation drain into the section forward of the center section with the bilge pump. This winter I contemplated the Mermaid Condensator but elected to extend the front condensation drain line by slightly enlarging the drain hole between the bilge sections since the condensation never seemed to make through. My rear AC unit is way back behind the aft cabin bulkhead. I was able to snake an extended drain line from that unit, running it forward, under the fuel tank, alongside the engine and come out in the bilge sump. That one also seems to be all downhill (barely) as well. Seems to be working but have not had any really hot weather yet with extended AC use at the dock. I'll follow up if any issues develop.

 

[Gunni]

I have good luck with a 12"x12" paper furnace filter. Wedge it in place. Easily changed. Aluminum (condenser fins) doesn't like bleach. Try a shot of disinfectant (Lysol) spray. If it is excessively filthy pull it for a vacuum cleaning.

There is a typically a small hole on top of the electric fan motor at 12 o'clock. Drop the oil in there.

Make sure that your water pump has good flow and your intake strainer is clean. If your refrigerant charge is correct then the freezing could be relative to blocked airflow across the coils.

How old is the unit? The manufacturers have a no-fix mentality on AC. I've seen 5 year old units go into the dumpster. It is ridiculous.

 

[mmdesmith]

I have good luck with a 12"x12" paper furnace filter. Wedge it in place. Easily changed. Aluminum (condenser fins) doesn't like bleach. Try a shot of disinfectant (Lysol) spray. If it is excessively filthy pull it for a vacuum cleaning.

There is a typically a small hole on top of the electric fan motor at 12 o'clock. Drop the oil in there.

Make sure that your water pump has good flow and your intake strainer is clean. If your refrigerant charge is correct then the freezing could be relative to blocked airflow across the coils.

How old is the unit? The manufacturers have a no-fix mentality on AC. I've seen 5 year old units go into the dumpster. It is ridiculous.

- Will give the paper filter a try if I don't find something that fits the velcro
- Used a few drops of bleach to 12oz of water so hopefully I didn't do any damage to the fins - may need to pull and clean with the vacuum as you suggested - is it difficult to remove the unit? I hope only a few screws and the main duct - looks like there is enough room on the electrical and hoses to go on top of the seat.
- Will look again for the oil hole
- I check the water supply and strainer each trip to the boat as it is right by the bilge. I learned - maybe the hard way - to check the flow each time I return to the slip. I have found that 75% of the time I need to re-prime/get the air out of the supply line for a good stream. That could have caused the problems last year.
- I believe the unit is original to the boat - 2002 - I have had her for 18 months now.

Thanks for the feedback/advice!

 

[Gunni]

The lack of water flow will trigger a refrigerant pressure fault and auto shutoff of some units. As you know, the pump is not self priming and ABYC specifications detail the component layout and elevations. A marine HVAC mechanic should know them. Consider back-flushing the water lines to clear out sediment, algae and other flow restrictors.

 

[TAK]

Regarding your previous comment: "I have found that 75% of the time I need to re-prime/get the air out of the supply line for a good stream."

Someone posted a comment last year that worked for me. Try closing the water intake supply line before you go sailing. That seems to reduce the need to re-prime supply line.

 

[Mike B]

If you've cleaned the filter and need to reprime just crack open the bleed valve until you get good water flow out the attached tube. You'll also hear the pump change tone once you have good water flow.

 

[joncro55]

When you say a "coarse" wire mesh, that is pretty broad. Any idea of the exact mesh count? Something like a 100 x 100 or a 20 x 20 mesh? Coarse is only in the eye of the beholder. Some basic measurement principles found here:
http://www.bwire.com/

Anyways, read the sounds of the pump. Like a motor or anything else, when it is running correctly, there is a certain hummm that you can hear and you know that it is running better than it had been previously.

 

[TAK]

Question: When you say a "coarse" wire mesh, that is pretty broad. Any idea of the exact mesh count? Something like a 100 x 100 or a 20 x 20 mesh? Coarse is only in the eye of the beholder.

Answer: The pre-filter is coarse like the wire mesh on a range exhaust hood or a Jenn air downdraft filter. My installation has this pre filter inside of the air intake grid about 1 inch in front of the fine plastic filter in front of the coils. I have a yellow lab that inhabits the boat on weekends and after two seasons of periodic cleaning, the filters seem to trap 99.9% of debris. I vacuum the coils but there does not appear to be any noticeable amount that gets through.

I found the link below for the Cruisaire (dometic) website. These look the filters that are selling may be better that what I a currently using.

http://www.dometic.com/14f96ac6-819f-467f-aa9f-ef24bd6df5e5.fodoc