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Old 09-01-2004, 12:29   #1
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Space Heating from Engine Coolant

My catamaran has two Yanmar 2GM20s, with freshwater cooling via a heat exchanger. The primary cooling loop of the port engine is used to heat domestic water in a Isotherm hot water heater.

I would like to purchase a space heater to run off the starboard primary cooling loop. Any experience with these? Any favoured manufacturers? Any pitfalls?

Sure would make a difference in the Gulf of Maine and the Bay of Fundy.
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Old 09-01-2004, 14:36   #2
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Hydronic Heating

You've got a great idea (heat recovery & re-utilization); but I don't think it's practical - the required Radiators would be huge.
Assuming a Delta T of 25 dgrees C, and little insulation; I'd assume a heat loss of something on the order of 35,000 BTU/Hr - which would require about 41 Feet of Tripple-Tube Baseboard Radior (also assuming 190 degree water @ 1 GPM flow).
It's kind of complex, but I could show the calculations if anyone's really interested.
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Old 14-01-2004, 05:19   #3
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Gord:

I'm confused. I just stepped out of my small car and it is -28C with a windchill taking it to -42C. My little engine heated up the inside of the car reasonably well. As I understand it, all there is to the heater is a radiator taking a loop of the coolant and using a 12v fan to blow hot air into the car. Considering that the port Yanmar in my boat gives me an inexhaustible supply of hot water when it is running, why can't I expect some reasonable heat output from the starboard Yanmar?

Why are there a number of industries selling these little space heaters for boats?
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Old 14-01-2004, 05:53   #4
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Hydronic Heat Transfer

I wasn't commenting on the amount of heat available from the engine. My comments were directed to radiant distribution, or utilization of that heat.
Once you capture the heat from the engine, you've got to distribute it to the space. Herin lies the problem. You could use a Fan-Forced heater, which would be much smaller than the Convection Radiator I described.

Also remember that your car's cabin might be about 130 Cubic Feet in volume, where as your boat might be 2000 Cubic Feet (for example) - the car represents <7% the volume (to be heated) of the boat.

Please direct me to a specific product (to which you refer below), and I'll try to comment, further.

I knew I was opening up a can of worms, and I don't really have time to write a complete tutorial on heat transfer.

Quote:
Sonosailor once whispered in the wind:
Gord:

I'm confused. I just stepped out of my small car and it is -28C with a windchill taking it to -42C. My little engine heated up the inside of the car reasonably well. As I understand it, all there is to the heater is a radiator taking a loop of the coolant and using a 12v fan to blow hot air into the car. Considering that the port Yanmar in my boat gives me an inexhaustible supply of hot water when it is running, why can't I expect some reasonable heat output from the starboard Yanmar?

Why are there a number of industries selling these little space heaters for boats?
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Old 14-01-2004, 10:20   #5
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No worms, Gord, please. I can see the problem with convection systems (and I apologize for not being specific), and I also acknowledge the problem with volume. Both issues are quite real with a catamaran. Fountaine Pajot boast an insulated ceiling, but I doubt they had the Bay of Fundy in mind. I want your input, and am thankful for whatever you provide.

As I search again for sources of this type of equipment, I find I may have to apologize again. I keep finding the same manufacturer, but at different locations rather than other manufacturers. HeaterCraft's product appears to me to simply connect to your engine and your battery.

http://www.heatercraft.com/

also at

http://www.mmwatersports.com/Boat_parts.htm

Better layout of info at:

http://www.go2marine.com/frameset.js...Page&id=74566F

The same manufacturer has peppered Ebay with their gear:

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2454003868

And, WestMarine also sells them.

I should change the question to why is there only one manufacturer? It may very well be for the reasons you have provided.

Maybe I should stick to heating up the cast iron pan on the propane stove. Trouble is, I have to fight the urge to sit on it when I come in from watch.
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Old 14-01-2004, 13:51   #6
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Heaters

Sonosailor,
Have you considered propane heaters? They're fairly efficent, heat quickly, do not smoke and apparently you already have propane.
Here in the Pac. N.W. (Cold and wet) one heats the inside of our 40'er fairly quick. With a multihull you could put in a couple smaller ones and isolate compartments if not using other spaces.
And they work even when the motor's not running.

Just a thought!
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Old 15-01-2004, 02:15   #7
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Acu-Heat Forced Air

I am embarrassed that forced air heat distribution didn’t occur to me.

The Heatercraft ‘Acu-Heat’ Liquid-Air Heat Exchanger looks OK as to heat recovery.
The smallest #1H unit claims to capture 22520 BTU/h from 3gpm of 170 degree engine water.
Δt (Heat Rise) = (BTU/h / gpm) / 500 = (22520 /3) / 500 = 15 Degrees Rise
Supply Air @ 55 degrees + 15 Degree rise = 70 degree Output.

However, they also seem to be trying to push 230 cfm of air through a 3" diameter round duct. This would require about 6100 fpm of air velocity. We usually design for less than 1000 fpm, which keeps us under 20-30dB of noise.
If doable, this would be one very noisy system!

Also note that Volvo-Penta offers a similar “QL” line of cabin heaters.
See: www.great-water.com and locate the “QL Cabin Air Heaters”.

Neither website offers the kind of information I would require to grant approval to an equipment “shop drawing” (commercial projects) - and something’s bothering me about the numbers (above). I’m going to run this by an HVAC Engineer (I don’t do HVAC design, just project coordination), and will report back.

Stand by for further comment, next week.

As suggested, "Southbound" utilized a Force 10 Propane heater. It was OK, for a small boat (C&C29).

Regards, and sorry for the inconclusive opinion
Gord
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Old 20-01-2004, 08:54   #8
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Delmarrey:

Can you recommend a propane heater that I should look at? Would these be with or without chimneys?
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Old 20-01-2004, 13:13   #9
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There are only two manufactures of propane heaters that I know of, Dickinson and Force 10.
I have the Dickinson 12000, It does the job for this climate. I chose this one because it fit right onto a plain bulkhead on the centerline of the boat. When there's a frost it'll heat the boat up in 15 minutes and then I turn it down. These also have a 12V fan to force heat to curculate. But if your at the dock or motoring, no problem. At sea, I just shut down the fan.

Any time you have a burning fuel you will need an exhaust pipe. My exhaust is between the shrouds and mast but forward about 16" and it doesn't smoke like diesel or solid fuel so no mess on the deck or sails.

Dickinson makes a smaller one, a 9000. And Force 10 makes a 6000 and a larger one as well.
As far as recommending one, there is not too many choices so whatever fits in would be my choice. Some models have oxygen sensors too. I believe that Dickinson makes radiators for hotwater heating but I would think it would take one so big that it wouldn't fit any where. You would have to have several placed through out the spaces and all the hoses to run. Plus fans to get any efficiency.

As cold as it got this year (in the NE) you must have gone to extreams to keep from freezing up.
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Old 18-09-2004, 08:04   #10
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heating

Take a look at these:

http://www.defender.com/cgi-bin/Web_...=yes&store=yes
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Old 18-09-2004, 10:57   #11
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On my cat I have a diesel fired hot air system that is more than capable of keeping the boat warm (4Kw) I exhaust the combustion air between the hulls and thus lose a lot of the noise from both myself, and adjacent boats. The noisiest item is the combustion air intake, but that has been sited to minimise the problem, thus I have a system that not only warms the boat very efficiently, but also is not intrusive. Its main drawback is the amount of electricity to run it if not in dock, but I have a 170 watt solar panel which manages nicely!
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Old 18-09-2004, 22:06   #12
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I have an Epsar diesel forced air heater that will boil you out in zero Degree (F) conditions. we have 5, 3" ducts throughout the boat. The diesel exhaust is at the stern. It's very quiet from the outside. On the inside it is quiet as well, except in one aft berth. It is mounted in the engine compartment on the other side of the wall from the berth and it makes a bit of noise when the thermostat turns it on and it lights off. It seems to only sip fuel. I wouldn't go any other way than diesel myself. With the dangers of propane I like to minimize it's use on the boat, and I want to be able to valve it off when I am sleeping, or away from the boat for any period of time.

http://www.espar.com

What I need now is a low power diesel AC unit for here in Florida...

Woody
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Old 19-09-2004, 03:46   #13
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Woody, I think your system is the same as mine (eberspacher = espar) I also have 5 outlets, but 2 of mine are 2 1/2" (cabins).

I have been considering for some time whether I could fit a car's air con system in series with the inlet tube for the eberspacher so that you could suck the cold air through using the fan only setting on the eberspacher. I would need to cool the air-con with a keel-cooled danfoss compressor. I have established that the gases used in the systems are compatible, but am having trouble getting info from the car manufacturer about cooling capacity, and without that it is impossible to size the danfoss. expect that the system will probably need in the region of 10-12 amps to run, so more solar panels are required!

If I ever discover whether it is possible, I will post some more data.

BTW, have you ever sailed the non-elite version of the snowgoose, and do you think that the extra accomodation is worth the reduction in sailing performance?
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Old 19-09-2004, 08:04   #14
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Yes, eberspacher = espar. Mine burns about .05 gal/hour on low.

I think you will find the compressor requirements for the AC unit are much more than the danfoss compressor can handle. Most small boat AC units draw about 10-15 amps at 110V here in the states. Thats at least 1110 watts which translates to 92 amps at 12V or half that at 24V. Start up currents are about twice that. Thats just not practical. Some folks use a generator to power AC units when on the hook.

Auto compressors run off the engine. Often when they engage there is a noticable load on the engine. 1110 watts is 1.5 hp.

The danfoss compressor will not make a dent in the temperature. They have to work hard to cool a small refer, let alone a whole boat.
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Old 19-09-2004, 12:32   #15
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What you are saying is that I will need to get a bigger boat in order to carry enough solar panels

Oh well, back to the drawing board.
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