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Old 08-05-2018, 03:18   #1
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Need help with a water based diesel heating system

I'm looking to do a heating system in a new boat that i'm building. But i lack experience in water based heating systems, so i hope to get some help and advise with my project.

The boat is a 35ft center cockpit, located in the Baltic and i want it to be comfortable to sail all year. This meaning both a warm cabin and hot water.

I have been looking at different types of systems, but due to lack of space. I think that a water heated - diesel heating system from Webastro would be a good fit. Properly the Thermo Pro 90 with stepless output, ranging from 1,8 KW to 7,6 KW.

What i would like to do:
  • Heat the main cabin and sleeping cabins
  • Have hot water
  • Preheat the engine?? (I would like some advise on this, the engine is a volvo MD11C with 0 hours and fresh water cooling). Is it worth it?
  • Use the engine heat for the system when it is running.
  • Having the hot water boiler to be able to use electrics when on shore power.

The reason why i would like a water based system, is mainly due to having hot water and that water pipes to radiators will not take up a lot of space in the cabinets - compared to hot air ducts.

First off - What do u think? Is this a good solution?

2nd - I'm having problems grasping the schematics of the systems and what components to use. I can't find a similar system layout - But it must have been done. Is there someone with schematics for a system like this - or can give me a point in the right direction.

Any advise would be helpful.


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Old 14-08-2018, 01:13   #2
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Re: Need help with a water based diesel heating system

You are heading in the right direction with a multi purpose system. Great because you now have only one system to do many tasks. Not so great is you have only one system. When it goes down, and it will, you have many things that do not function.

The first question I would want an answer to, about any hydronic equipment. "Where is the nearest support"? It's been over a decade since my liveaboard days ended. I live in SE Alaska and for 8 years I lived on my 42' Uniflite Sportfisher. It was a constant challenge of keeping the boat warm and dry. Which had the added benefit of keeping me warm and dry.

Being a boat rat in a town with the largest municipal harbor system on the west coast of N. America was as good for me as the warm and dry boat. Year round the harbor is busy. It gave me access to a huge base of knowledge. The downside is that knowledge is provided by people in Alaska. The information is provided along with opinions. As we all know opinions are like (anatomical orifice), everyone has one and none are pretty.

People come to Alaska because they are slightly out of step with the world they came from. Get a bunch of folks together who had trouble with the right and left concept in the real world. Ask for an opinion or just wait you'll get it anyway. Well, not only right and left are off the table but up and down took off with them.

So it can make a person nervous when there is a consensus. That being; keep it simple.

Simple doesn't mean bricks on your deck with a burn pot on it. It means: Do you know the system inside and out. Can you keep a supply of consumables and repair parts on hand. Do you have the skills to make the repairs. What is your contingency plan if your system is redlined for two weeks. These were all considerations that the professional, private and recreational operators have to live with here. I don't know much about the area you are going to but I wouldn't be surprised if you have similar challenges to face.

It is true I live on an island in SE Alaska. The only way to get here is by air or water. But it is not the bush. We have regular jet service with at least two scheduled flights in and two out 7/365. During the summer it grows to six flights. And it is still almost impossible to get orders in quickly. Paying for overnight will definitely get your order here in three, at the most, four days.

I do not know the current views or ratings for Webasto or Espar systems. A decade or so ago the operators who had them, forced air or hydronic, liked them. When they worked. A consensus at the time was to keep yearly budget of $500 - $700 for the heaters. It was said they were like like clockwork. Needing a new control board or rebuild when you needed heat the most. And like clockwork the service centers were back logged two weeks or the service centers repair parts were on back order.

This forum is international. If I were you I would put a shout out to the folks in the regional forum for the area you are heading to. Find out what they use and recommend. You might be in the bricks and burn pot market after all!

Since you posted here you know you have a powerful source of knowledge at your fingertips. It is actually why I am on the Cruisers forum and found your post. I am looking for information on part sources for my International Thermal Research Hurricane hydronic system. I have only owned this current incarnation of the Pirate's Son since the Spring off 2017. This is the first opportunity I have had to dig into the Hurricane.

There is surprisingly little documentation available on the technical details of the system. Going online there are many forums dedicated to the ITR hydronic system. Some really great information on maintenance and repair. That is if you own the RV version of the system. If you do, and as many of these RV owners do. You just stop by their American headquarters in Vancouver Washington. They come right out to the parking lot and take a look at what is ailing your motorhome.

The Hurricane and its successor models have a great reputation and their systems will do what you are looking for. I know I'll find that gold mine of information somewhere. When I do find it I have hopes that I'll get the answers I want. Such as; I don't have to wait three weeks for the manufacturers $300 diesel fuel pump. The $50 one at the local auto parts store will work, with some modifications, of course.

What skipper worth his salt can't make it work! Good luck.

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Old 14-08-2018, 17:03   #3
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Re: Need help with a water based diesel heating system

Anyone know of gasoline or propane burning hydronic systems?

I guess all the generic bits are the same, just swap out the burner.
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Old 20-08-2018, 12:58   #4
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Re: Need help with a water based diesel heating system

Take a look at the Sure Marine services website. They have Webasto heaters and quite a lot of installation info.

Sure Marine Service, Inc. | HEAT

Here is an example of some of the docs that may be useful:
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Old 20-08-2018, 13:09   #5
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Re: Need help with a water based diesel heating system

If space is an issue, take a look at the ITR Hurricane Zephyr. It does not require a hot water tank, as it provides hot water on demand. Mine fit in the space I was using for the prior hot water tank.
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Old 23-08-2018, 19:08   #6
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Re: Need help with a water based diesel heating system

+ for the Hurricane, mine is 4 zone and demand hot water........toasty warm when it snows
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Old 23-08-2018, 20:20   #7
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Re: Need help with a water based diesel heating system

I have a boat with a walk in engineroom and other room for options others may not have. And I've lived on the water many years, mostly in cold climates. I like having options in heating. Except for a couple sailboats or speed boats, I've always preferred a big boat for many reasons. Insulation in a cold climate makes a huge difference in cost and comfort.
I have a hydronic system with a diesel fired boiler and insulated main line plumbing the length of the boat. Each zone has one or more forced air heaters controlled by a thermostat. When a zone calls for heat, the main circulation pump starts and valves open for that zone. When the forced air heater is up to 90F, the fan starts. The main line is divided by valves so only the needed lines are circulating water. If the boiler temp falls below 130F, the oil burner starts. But I have other, cheaper heat sources that can maintain the boiler temp. I have a wood stove with a water coil, circulation pump, and valves that heats the system if fired. I also have a pellet stove that has a coil, pump and valves and is my primary heat source.
Then I have manual valves that tie the system into my main engines. If the boiler is hot and the engines cold, I can preheat. Or when running, one main will maintain the boiler heat. I have several electric heaters I run if a generator is running, but on shore power cost about the same as $3-4 diesel. By far pellets are the cheapest heat. Wood is cheap only if I cut, split, and haul, but difficult to store a reasonable supply. $4/gallon diesel is the most expensive. At $2 still more expensive than pellets. By using some of the cabins, I can store a winters supply of pellets. At the most a months supply of wood. I have a large diesel galley stove that has a coil and pump for heating the hot water tank. The hot water has a supply and return so I can circulate and don't have to dump a gallon of water to get heat at a shower.
I can heat a 83' boat for about $150/month in 35 weather or $300 in 0 with pellets.
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Old 24-08-2018, 05:19   #8
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Re: Need help with a water based diesel heating system

Webasto make both gasoline and diesel versions and in 12v or 24v. One thing to keep in mind is that these units were originally intended for intermittent use in vehicles and when pushed hard for space heating 24/7/xxx they require more frequent parts replacement. I have a 12v gasoline unit in my VW camper. It is intended to warm the engine first, then will turn on the front defroster fan and start pumping hot water through the coils. It's not intended to warm the camper, and drawing about 3amps it would kill the battery quickly anyhow.

The complexity of plumbing one heater for washing water, engine heat, interior heat will be significant and all your eggs are in one basket if the heater fails. When designing your system I'd include one direct air heater unit to provide fast warmup of interior space with a minimal installation. Look for a Thermo-Top or similar unit. If you want cheap air-handlers to take water heat to air then look for rear under seat heaters from VW T3 ('83-91) They are compact boxes with 3 speed 12v fans and control valve.

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diesel, heating, water

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