Air Conditioning for the TomCat

M

Mike...

New member
Hello everyone.

I have read through many, many posts regarding this subject, but I still don't see what I am looking for. Hopefully someone here can help.

I want to install air conditioning in the TomCat, but I don't prefer the portable or window unit solution. I also don't prefer swamp coolers, ice coolers, or anything that requires drilling holes through the hull.

My first preference would be a split unit, were I would mount the coils outside under the raw water washdown connector.

My second choice, would be roof mounted like Dr. Bob's, but I prefer to not lose the roof space. And the thought of cutting a big hole in the roof freaks me out. :shock:

If possible, I would like a DC/AC unit that can also run on shore power, when it's available.

But before we get into options, here is my first question. All the posts I read implied that a generator is necessary for Air Conditioning. Are there not units will run off the current generated from the Honda outboards?

I have two Honda 150s, but I am a little embarrassed to say that I don't know how many amps each puts out. I guess I should have tracked that little bit of info down before I started typing. :)

Anyway, any suggestions?

All help and heckling appreciated :)
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mike
 
When you are under way with the outboards running, you won't need the A/C. We just got back from a 700 mile round trip down the ICW from Galveston to Port Isabel in the Texas summer, and the Tomcat running at 30 MPH generates more than enough breeze :?

You will need A/C at anchor. Even if the Hondas put out enough amps (I have no idea if they do), are you planning to idle your motors all night long?
 
Alok":2jl6wbjb said:
When you are under way with the outboards running, you won't need the A/C. We just got back from a 700 mile round trip down the ICW from Galveston to Port Isabel in the Texas summer, and the Tomcat running at 30 MPH generates more than enough breeze :?

You will need A/C at anchor. Do you plan to idle your motors all night long?
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Yeah I hear ya, but we not are always going to be running at 30mph. :)

So to be clear, I am only looking for an A/C solution while under way or tied up in the slip. For now, running the A/C while anchoring is not a requirement.

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mike
 
Agree with Alok (almost all of the time anyway)--with widows open, even in 110 on Lake Powell, or 95 in S. Florida--you don't need AC. We cruised the tropics for years in our sailboats, with no AC--just a good breeze thru the boat, even at night. No breeze a problem.

With the Roof Air, you can use the Honda EU2000i, Cutting that hole does not weaken the boat--especially if you do it the way I did (putting a glass flange on the top, and woodend frame under the AC unit. If you just bolt the AC to the top, there is substantial risk that it will change the contour of the top.

Loss of top space is not a problem--if necessary you could put a rack over. But we have put the inflatable over the aC (not when running).

The Roof top--will run when the boat is on a trailer (tom cat camping)--or aground, or on a lift. It gets away from mud, sea weed, critters etc. I have owned several boats with built in AC--and it can be a pain with the sea water pumps etc.

It makes no sense to separt the coils and the compressor--you can use direct sea water cooled cooled, like keel cooler--but not practical in the C Dory.

You might be marginal with the Hondas with 35 amps output per engine. The Suzuki's are 45 amps. BUT this is hard on the alternators. You will need somewhere near 80 to 90 amps from a good inverter. At that pace your house batteries will not last long. Golf carts are OK--I used them with an inboard and 5,000 BTU super effecient (Mermaid)--and could get about 5 hours out of 6 Golf carts (420 lbs weight).

Some of the C Dory boats have used standard marine AC units, but they take up at least one cabinet-sometimes two.

I also used a 15,000 BTU roof air on the enclosed Flying Bridge of a 42 foot trawler we owned at one time. But there we had about 40,000 BTU of AC below decks and a 9 KW genset.

Look at my photos of how to install.
 
wannaboat-

I've looked at all these AC alternatives and solutions over the many years on this and other sites and Bob's RV style Polar Cub AC installation is the Blue Ribbon Winner, hands, down!

You'll need a generator if you ever decide to run at anchor or underway, but for plug and play at the dock you'll be all set with a minimum investment with an RV style unit.

The thought of cutting a hole that big in your roof is indeed a bit scary to many, but beats the heck out of all the other installations in the overall analysis.

Read about it and give yourself some time to get comfortable with it.

Good Luck!

Joe. :teeth :thup
 
Hi Dr. Bob!
thataway":2lzrq2x8 said:
with widows open, even in 110 on Lake Powell, or 95 in S. Florida--you don't need AC.
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Yeah - but for those lazy trips up one of our many rivers, I can tell you from experience that it is just too damn hot. Yes, I know that TomCat is inefficient when not up on plane. :)

thataway":2lzrq2x8 said:
You might be marginal with the Hondas with 35 amps output per engine. ... BUT this is hard on the alternators.
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Wow, really? What's the starting and running current on these things?

thataway":2lzrq2x8 said:
You will need somewhere near 80 to 90 amps from a good inverter.
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If I can find a AC/DC unit, I don't think it will need to run on an inverter, correct?

I don't plan to run it off the batteries any great length of time, but you are right, it is an issue to be addressed, even for short-term use.

thataway":2lzrq2x8 said:
Look at my photos of how to install.
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I have, and I just don't know that I have the nerve enough to tackle it!
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mike
 
Sea Wolf":5h33rr2z said:
I've looked at all these AC alternatives and solutions over the many years on this and other sites and Bob's RV style Polar Cub AC installation is the Blue Ribbon Winner, hands, down!
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Yes, that looks great! But i am confused about something.

Do these RV or marine air conditioners all run on 120V? Do they not make them to run on 12V DC?
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mike
 
Would someone please explain what "Compressor Locked Rotor Amps" means?

If that is start-up current, well then wow!
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mike
 
Our TomCat has an 8000btu roof top RV air conditioner. Recently when cruising in southwest Florida with daytime temperatures around 90F, this unit barely held the interior to 78F in direct sunlight. We closed the curtains to help with the temp.At night, after sundown with the temp in the 80s, the interior temp dropped to 72F except for the berth. The circulation forward next to the lockers is poor and the temp there was about the same as the exterior. Our Honda 2000 powers the air conditioner OK.

When underway under these same summertime conditions, we are comfortable with the middle hatch just cracked and the side windows open. We cruise with the rear door closed. When at idle for those pesky manatee zones, we open the center hatch and find the boat comfortable. We could run the air conditioner while cruising with the Honda, but do not find it necessary.

We have had marine air conditioners for more than 20 years. It is nice to get away from the problems and high maintenance of those units. I can replace the roof top for less than a service call on one of my marine units.
 
Yes, the forward berth gets no air flow even when the cabin is frosty. We use a small table fan placed on the floor of the cabin about a foot in front of the forward berth to blow cold air into the berth area. Works great.

BTW, we only use A/C at anchor or in the marina. We place a $100 window A/C in the front hatch and employ life jackets to make a seal around the unit. In June in Texas, the night cabin temperature rapidly goes down to 72 degrees or lower. When not in use, the A/C is stored in a plastic box in the cockpit.

Not the most elegant solution, but it is inexpensive and works for us. Takes less than five minutes to set up and even less to take down. Once summer is over, the A/C goes off the boat so we are not carrying the weight around.

We have a 2 KW Honda generator. It runs the A/C and the fan, charges the batteries, and has plenty of juice left over.
 
Notwithstanding the differences between AC and DC currents, the 12 volt DC unit is going to use 10 times the amperage that a 120 volt AC unit would to do the same work, since volts x amps = Watts= power = work done over a time period.

Stated otherwise, it simply takes ten times the amperage to do the same work with a 12 volt circuit that it takes to do with a 120 volt one, since the (electromotive) force of the 12 volts is one-tenth that of the 120 volt one.

There are very few DC air conditioners made because the amperage demands are so huge.

Yes, the compressor locked up rotor amps is indeed the surge current needed by the electric motor at start up with a AC unit with the compressor locked up on the compression stroke.

Joe. :teeth :thup
 
Well I have been searching and reading for a few hours now, and I have caught up with the rest of you on this.

Joe, you are correct, a DC air conditioner is not practical.

And an AC air conditioner will take a big inverter, that will be a heavy load on the batteries, which was Dr. Bob's point. So an AC air conditioner with a generator is the way to go.

See? I do catch up eventually. :)

Joe, the Polar Cub looks interesting. However, Tom's comment makes me think that I might be better off with the 9203 or 9204 Polar Mach (13.5kBTU/12.7A and 15KBTU/14.8A respectively).

For those of you who have mounted roof air conditioners, is there any interference problems with the radome? Obviously, I'd need to make sure the radome is elevated above air conditioner, but by how much?

I do have a height-on-trailer issues to deal with here.
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mike
 
Mike-

Bob can tell you much more about the capacities of these units in relation to the Tomcat.

The Polar Cub is a smaller unit (9200 btu's) probably more suitable for a CD-22 or maybe a CD-25 depending on the climate and intended use.

As I remember, Bob was using about an 11-12K btu unit in his Tomcat. (But my memory may not be what it used to be, at least I don't think so, but I'm not sure, because I can't remember what I used to remember.) :disgust

Yes, you do catch up/on quickly!:lol:

Joe. :teeth :thup
 
We put the CARRIER LOW PROFILE - 13.5K btu roof top unit on our CD25 and I'm very happy with it. It has heat as well which can take the chill off when it's cool. Although not in the heat of summer yet we've had a few upper 80's and high humidity days and this unit kept the cabin very nice.
 
SouthLake":3w4cwfgq said:
We put the CARRIER LOW PROFILE - 13.5K btu roof top unit on our CD25 and I'm very happy with it.
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That's also an interesting unit. It's only 7.5 inches high.

Carrier makes it tough to find any info on it. It took a while, but I eventually found the specs.
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mike
 
That is a very nice looking R/V unit. Much less obtrusive than the bigger usual style ones.

IMG_2063.jpg
 
Yes, PPL are good folks; I have dealt with them on some difficult to find RV parts and they are first rate.

The 13,500 or 15,000 BTU units will require two Honda EU 2000i generators, or a EU 3000 (which I don't see as really practical because of its weight).

78 degrees is about what you will expect. We leave the AC unit running night and day when the boat is on the lift during the summer--and the mid 70's to mid 80's is what we find--but it will be over 100 under the camper back! We often put the bubble wrap foil in the windows, and it will bring the temp down considerably more. The AC unit also dehumidifies the air, so it seems cooler. I have used "shade cloth" on the sides of the boat, or even taken canvas awnings out to keep the direct sunlight out. I see the AC in the C Dory series as for eveings when you want to keep the bugs out, and sleeping--sometimes just cool the boat down, and get to sleep. That is what we did with the inverter operated unit we had--when the voltage got to a certain level, it shut down--and that was somewhere about 2 AM--we were well asleep--and if we heeded to open up hatches and turn on fans, that worked well.

Yes, we have 4 fans in our Tom Cat--two by the windshield--and 2 in the bunk, plus a "Vantastic " fan. With that you can circulate air all around the forward cabin--and it is fine. You have to remember that there are some trade offs in the C Dory--it is not boat with unlimited resources.

We do fine with the slow speeds--the Caracal 18 cat which is our "Bay boat" often runs at 5 knots--and we have enough breeze to be comfortable.

In the C Dory 25 in Petaluma a couple of years ago, we were very comfortable with the 5,000 BTU window air (also see my photos)--. The outside temp was somewhere over 100 and we had the inside temp down to the mid 70's--which is pleasant. If you come from the PNW--you don't do well in the heat, until you acclimate. We had spent a couple of years in the tropics--and were ready for the long johns when we got to Acapulco and it was down to 72 degrees at night on one trip back up the coast....So it is all relitative!

Generally start up amperage is 1.8 x running amperage. We use the Kill a watt meter to measure our 110 volt power draws. If you have a water cooled air conditioner, you need to add one amp for the raw water pump. , so if the AC unit uses 6.5 amps, with the water pump it will be 7.5 amps, and start up would be close to 13.5 amps. Locked rotor is max draw with the compressor locked due to a hyraulic lock up.

Another option might be to go with the Mermaid 5200 BTU unit--which is made to run with a 1000 watt inverter--and just air condition the bunk area--or perhaps put a curtain to exclude the aft part of the cabin--head and hanging locker--with bubble foil in the windows.

Another factor is to insullate the hull and deck. Using the back packing pads is the best and most effective way. That gets rid of a lot of the hull heat.

There is a true "DC Marine air"--and that is the "DC Breeze" by Glacier Bay--it also uses about 48 amps. http://www.dcbreeze.com/ So about the same as the roof air unit you found. This may be slightly be more effecient than the inverter/RV unit.

If you do the numbers--the cabin of the C Dory needs somewhere about 8800 BTU (windows, not well insullated), and then add in aonther 3200 BTU for an insullated forward cabin (bunk area)--and this comes out near to 12,000 BTU miminum in the heat of the day. Some folks have gotten a 12,000 BTU unit to run on a Honda EU 2000. This requires some "easy start capaciters on the start up.

You take what relief you can get--and make do with it!
 
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