New A/C time - recommendations?

Its time to replace our aft A/C and originally I was going to go with a Flagship Marine unit because they don't have reverse cycles to worry about. However, they are a unit at a premium price.

Realistically we may only live on board for a couple more years and then we'll probably end up with a condo on the water. Because of this we are starting to look at A/C options. Something that may last a while, and is reliable, but isn't the Mercedes. We're looking more for a Toyota.

What are your recommendations?

Take a second look at Flagship. Heating element and no reverse cycle to mess up. Control components all cheap and replaceable. No expensive circuit board or proprietary thermostat. Use a house thermostat. There is another company with these attributes but I do not remember their name. Good Luck.

obthomas said:

There is another company with these attributes but I do not remember their name. Good Luck.

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Mermaid Mfg?

WHOA! I sent an email for a quote to Flagship Marine and Steve called me within the hour. He gave me a quote that's less than all the other comparable units. This makes me happy.

If you are serious about heating, take a serious look at the amps drawn by electric heating. Had one on a previous boat and replaced it with reverse cycle. Have one on our current boat and with the heat running can't run much of anything else, especially the hot water heater.

BobH said:

If you are serious about heating, take a serious look at the amps drawn by electric heating. Had one on a previous boat and replaced it with reverse cycle. Have one on our current boat and with the heat running can't run much of anything else, especially the hot water heater.

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We've used heat exactly twice this year so far, so it's not like its a major issue in our region.

BobH said:

If you are serious about heating, take a serious look at the amps drawn by electric heating. Had one on a previous boat and replaced it with reverse cycle. Have one on our current boat and with the heat running can't run much of anything else, especially the hot water heater.

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My electric heat uses every so little more amps than the reverse cycle.

My 16500 BTU Flagship unit is about 15 amps including pump in AC and about 19 amps in heat

My 12000 BTU Flagship unit is about 12 amps including pump in AC and about 16 amps in heat.

None of the heat involves starting a compressor. I have never blown a circuit.

We've lived aboard in Kemah area and used heat quite a bit. Have run the heat earlier this year. I think the small extra cost for reverse cycle is well worth it. My two cents.

I have put Mermaid A/Cs in 4 boats and had good success and support.

I think my AC guy was against those but I can't remember why. Or I may be misremembering. If you are not doing your own work, I recommend Brent Williams at Upper Coast Marine. Best AC guy on the lake and usually very reasonable on his labor rates.

obthomas said:

My electric heat uses every so little more amps than the reverse cycle.

My 16500 BTU Flagship unit is about 15 amps including pump in AC and about 19 amps in heat

My 12000 BTU Flagship unit is about 12 amps including pump in AC and about 16 amps in heat.

None of the heat involves starting a compressor. I have never blown a circuit.

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Electric heat produces less heat for that power draw, however.

A 1500 watt space heater draws 12.5 amps at 120 volts and puts out 1500 watts / 5118 btu/hr. On the other hand, my largest A/C unit is rated for 16k BTU in heating or cooling mode. It draws 13.6 amps / 1630 watts in heat mode. But for that power draw, it's putting out 4690 watts / 16,000 btu/hr of heat.

Basically, moving heat from one place to another (heat pump) is significantly more efficient than just converting electricity into heat.

"Basically, moving heat from one place to another (heat pump) is significantly more efficient than just converting electricity into heat."


True,,, BUT the water or air has to be above about 40F or the unit will simply make ice and shut down.


The 40 year more modern mini splits have a system that solves this hassle so a COP if 2.5 or 3 is possible , reverse cycle heat at -10F easy as pie. No thru hulls either.

Why not try a mini split unit, pretty cheap easy to install, and one less hole in the boat to worry about. No pump to go bad, no hair-strainer to clean. Amazon has them pretty cheap.
dang, just realized FF already made suggestion, just edited

BobH said:

We've lived aboard in Kemah area and used heat quite a bit. Have run the heat earlier this year. I think the small extra cost for reverse cycle is well worth it. My two cents.

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Here's a thought. Most boat, be they 30amp or 50amp, have 2 legs. They put the reverse cycle on one leg and the house on the other leg. Given a choice, I would recommend 2 50amp legs. (2 30amp.... will support 2 reverse cycle AC/heat.) The other 50amp leg will handle the house easily even with an electric stove and oven but, nothing else.
If you have enough batteries and a strong inverter, you are home free.
Then other options, larger alternator on the main engine, a 12kw generator, tack on 2 or more solar panels.... but, this a subject covered in other blogs.

We, as live aboards, were lucky this year wintering in the water just south of Annapolis, MD. The coldest water temp we experienced, as measured by a transducer, was 38 degrees. At that temp we were still getting heat good enough, more than good enough, to keep our boat warm (72 degrees). We have three reverse cycle units. We used only two of them. The main cabin unit needed to be recharged.

I have no way of knowing how much lower of a temp at which good heat would have been produced nor do I know how accurate the transducer is. Perhaps the water temp was 40 degrees but the fact is even if 40 degrees was the actual temp the heat being produced was remarkably warm. One unit produced heat that was 30 degrees in excess of ambient temp, the other 20 degrees. At 45 degrees water temp we were getting 40 and 30 degrees over ambient temp. Our electric bills for January and February were $350, combined. Overnight temps were as low as 20 degrees. We did not heat the boat during sleep time. Foam mattress, down comforter, and flannel pajamas kept us warm and toasty. We turned the heat on around 6am, brewed some coffee, and the cabin became comfortable in an hour or so.

FF said:

"Basically, moving heat from one place to another (heat pump) is significantly more efficient than just converting electricity into heat."


True,,, BUT the water or air has to be above about 40F or the unit will simply make ice and shut down.


The 40 year more modern mini splits have a system that solves this hassle so a COP if 2.5 or 3 is possible , reverse cycle heat at -10F easy as pie. No thru hulls either.

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Our boat (50 amp service) is a little easier to manage loads. We have three reverse cycle units. The pump and one unit is on one leg, the remaining two units on the other leg. We have a 12kw generator which supplies 50 amps to each leg. We also have a 7.7kw generator we use when demands are lighter. The boat came to us equipped so.

OldDan1943 said:

Here's a thought. Most boat, be they 30amp or 50amp, have 2 legs. They put the reverse cycle on one leg and the house on the other leg. Given a choice, I would recommend 2 50amp legs. (2 30amp.... will support 2 reverse cycle AC/heat.) The other 50amp leg will handle the house easily even with an electric stove and oven but, nothing else.
If you have enough batteries and a strong inverter, you are home free.
Then other options, larger alternator on the main engine, a 12kw generator, tack on 2 or more solar panels.... but, this a subject covered in other blogs.

Click to expand...