AC issue on 2019 C40

[Swish]

We are new to this so here we go... New to us this spring C40. Everything surveyed fine and worked flawlessly during the couple of weeks were able to enjoy the boat when first purchased. Now we can't seem to get things to cool down below 78 degrees. The boat was maintained during our absence (8 weeks or so) including system flushes (Barnacle Buster)
Recent history, we had the boat out of the water for a couple of weeks for bottom paint and other repairs. Had HPF message in master shortly after splash down. Tech found what must have been a very clogged line (1 of 3). The other two seemed to be at full stream. After two unsuccessful Barnacle Buster flushes, an acid flush opened up #3 so all three units were flowing enough to consistently provide 78 at night and 80 degrees-ish during the day (Sarasota area day time temps 90ish).

Within a week the master unit outflow stream looked to be about half of what appeared to be full streams out of the other two. However, it kept up with the temps as stated with no HPF. Asking around I'm consistently hearing "something isn't right, you should be able to get much lower room temps even in FL. I leave the units running 100% of the time and by generator when cruising or on anchor. I was told that is necessary in FL due to the growth issues.

Today same tech says he thinks I need to replace the AC water pump as the current one seems to be not pushing enough water through the system. He supported this with stating the unit felt very hot to the touch and the impeller looked very warn. I'm a rookie but this seems plausible, yet odd that only one of the streams is showing weakness. He thought barnacles or some other debris may have made its way into the pump to cause problems. Wouldn't a weak pump essentially provide weak flow relatively equally? His response was the extra distance the water had to travel up and back to the master made it more susceptible to low flow issues. My BS meter kicked in on that one. Hope I’m wrong.

We already have some real money in the previous “fix” earlier this month and hope to get it right once and for all. Your input is greatly appreciated.

System description:
"High Velocity" System
single 8,000 BTU unit
two 9,000 BTU units
Current pump capacity is “985 GPH at 3 ft Head”

Questions for Carver-ists:
Is 78 degrees all we should expect in this heat?
Is it really necessary to run the AC 100% of time to prevent growth from getting started? Seems silly to be running the gen when cruising and we’re up top.
Is more GPH the really the answer?
Knowing more is not necessarily better, how much addition GPH do I consider upping the game if a replacement is in order?
fyi - the "fix" earlier this month included the flushes and replacement of the strainer.

[Midnightsun]

There is no fancy plumbing in these boats to equalize flow between units so yes the farthest unit will naturally get less water output which is also the case in my boat. That being the case, I have no issues keeping the cabin cool. You should easily be able to drop the temps into the lower seventies with cabin doors closed and plugged into shore power.

Have you looked at the units after they have been running for some time? Maybe frosting up due to a blocked or kinked air handling duct? Are intakes blocked or are the water intake filters partially plugged up?

Looking at a C40 there does seem to be a lot of windows which do not help in keeping things cool. Also I am surprised by the 9,000 btu units you listed. In comparison I have a 16, 11 and 9. Does sound a little undersized for Florida summers but not that it will not get the temps down below 78.

Never heard of running the AC 100% of the time to prevent clogging. There are several boats out there equipped with AC and no generator, how would they handle the AC issue when away from shore power if they need to run all the time. I am not in salt so maybe I missed something but after all these years on various forums I would have heard something about salt/AC issues.

Welcome to the forum by the way.

[Swish]

Thanks for your response. Actually one 8000 BTU unit and two 9000 BTU units. No visible frosting after use that I've seen. Water intake filter is clear. The previous owner kept it in a covered slip so perhaps the break from the sun masked an issue a bit for him. We are in full sun.

[Viper]

Welcome aboard.

Source of the post .....tech says ....the unit felt very hot to the touch and the impeller looked very warn.....He thought barnacles or some other debris may have made its way into the pump to cause problems.....

Some pumps get hotter than others, it would help to know which pump you have. Is it air cooled/all black with cooling slots in the motor and a white pump face, or is it a water cooled unit with a red cube and white pump face? If it's a black pump with vents, is the motor's housing rusty?

I'm curious what the tech considers "worn." These impellers aren't tight against the pump housing to begin with, there is quite a gap. If he's looking for a tight fit, he's barking up the wrong tree. This is why they can run, the down side to this design is that it's not self priming. If the impeller is indeed in bad shape, then why not just replace the impeller instead of the entire pump?

Source of the post.....He thought barnacles or some other debris may have made its way into the pump to cause problems.....

Wouldn't he have made a positive determination about that when he had it apart to inspect and render his opinion about the condition of the impeller? Or is it a water cooled unit and he's talking about growth in the pump's cooling passages? If that's the case, that would affect cooling but not discharge volume.

I sure hope other possibilities have been checked out before condemning the pump, like how about ensuring the pump is getting proper voltage, maybe there's a voltage drop due to a poor/corroded connection at the control board. That would definitely affect the pump's output and is an easy check.

I think if salt water applications required running the units 24/7/365 in warm climes, most people would be having problems as most don't run them like that. It's also not recommended running them when you're not on board for safety reasons, but that's another thread.

There's several possibilities here but based on your comments, I don't know if they're taking the right approach. Having said that, I'm sure we don't have all the facts yet but so far I'd say more diagnosis is in order before you start throwing parts at it. If they feel they've done their due diligence then fine, replace the pump, but if the problem persists, the new pump is on them.

[Tireless]

Is it possible there is a couple of things going on here. I recently had a water flow issue through my water pump that cause the error to appear. I checked the impeller and it was fine. I checked the strainer and it was clear as well. As it turned out it was a clump of weeds that I had stuck to the pick up on the bott on of the hull. I shut the A/C off so the pump would not draw water. I started the boat and put it in reverse tied to the slip to push water past the pick up and push the weeds away. This was the fix for that and it has been fine since.

As far as your not being able to get the temps lower in the boat than 78F, this is an issue for sure. Should get lower in the boat than that.

I ran into this issue with my boat a couple of years ago. I discovered that there was an air flow issue that if left alone would freeze up the unit. It would run, but not cool the air down to the desired temps. I immediately checked the thin air filters on each units coils and found they were plugged with dust and carpet fibre. I washed the filters with a hose and let the unit thaw out. If the unit is frozen, you can thaw it quicker by putting a fan over it. Once thawed out and the filters were dry, re-install them and turn on the A/C. This fixed the issue and now I monitor monthly for dust.

Air flow is a major issue with all A/C units and cause this issue for sure. This is also in addition to other issues but this is a quick and easy check.

Greg

[km1125]

Source of the post....If the unit is frozen, you can thaw it quicker by putting a fan over it. ....

If it's a unit that features reverse-cycle heat, then just turning on to heat mode for a short bit should unfreeze it as well.

[Swish]

The pump is a Dometic, black encasement with plastic impeller. Pump capacity is “985 GPH at 3 ft Head”

System description:
"High Velocity" System
single 8,000 BTU unit plus
two 9,000 BTU units

[lakeerierocks]

When we went down to see our 2019 c37, both air conditioners were not working that well. Luckily the owner paid to replace both units. I thought it was from over use down in Florida but our guy who put in the new ones said they were not used and everything got clogged up. Hope you got this fixed. Ours will get our boat down in the 60's - which is great at night. The AC unit under V berth was an easy switch out by the way. It was the one by our helm that was a bear to replace due to access.