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Old 08-02-2015, 17:39   #1
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Using Waste Heat

I've been thinking for some time about whether it makes sense to recapture some of the tons of waste heat dumped into the ocean by my two diesel engines. In a climate where we need heat practically year around.

My first thought was to get the heat into the central heating system, which is powered by an Eberspaecher (Espar) D10 hydronic furnace. The idea was to use heat exchangers to transfer heat from the fresh water circuits of the two engines into the main central heating circuit.

But I've thought and thought about that and have rejected it. I realized that there is no point in putting heat into the system just to temporarily unload the furnace. How much fuel will I save? And is it even good for the furnace, which apparently doesn't like running at idle (soots up)?

When I need continuous heat in the cabin, the furnace will run continuously -- that's all there is to it. It would be silly to shut down the furnace for a couple of hours a day just because I'm running the generator.

So my thinking now is that it would really be useful to get heat from the generator into the calorifier, for times when I'm not running the furnace continuously. And if I were to add a bus heater under the companionway steps, then this is a supplementary source of space heating which can be used when motoring, for example, or just to add more heat to what the central system can do. This might be really useful to take the chill off when it's not cold enough to be running the furnace all the time.

Another thing I would like to do is add a towel dryer in the aft heads. I've got a good place for it and it adjoins the engine room so will be easy to connect. We all know what a pain it is to dry towels in cold, wet weather, and how nice it is to have extra heat when you're bathing. But I don't think I could run the whole volume of coolant through it -- it would need some branch. I don't have any idea whether that will circulate naturally or not or how to engineer it.

What do y'all think? Waste of time and money? I could pay for a fair amount of fuel for the Eber for what this would cost. But it just seems so wrong to dump all that heat into the ocean, while at the very same time I'm burning fuel to make heat.
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Old 09-02-2015, 01:44   #2
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Re: Using Waste Heat

Ha, spent many hours motoring past burgs wondering the same thing. Ideally a heat storage system, for example using your engines waste heat to warm up your diesel tanks. Then over the next 24 hours the warm diesel tanks keep your cabin toastie and warm.

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Old 09-02-2015, 04:43   #3
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Re: Using Waste Heat

Two words: Bus Heater.

I don't know your setup, but with the mains running, wouldn't their jacket water be able to keep your hydronic system hot?

I do like the idea of some extra warmth in the head though. The towel warmer should do just fine on jacket water straight from the engine. I'm assuming those are typically plumbed directly into a hot water loop in a FHW home heating system.
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Old 10-02-2015, 06:41   #4
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Re: Using Waste Heat

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Originally Posted by Snowpetrel View Post
Ha, spent many hours motoring past burgs wondering the same thing. Ideally a heat storage system, for example using your engines waste heat to warm up your diesel tanks. Then over the next 24 hours the warm diesel tanks keep your cabin toastie and warm.

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Now THAT is a really good idea - fuel and or water tanks would work for me. Your thinking has not been wasted - thanks.


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Old 10-02-2015, 07:01   #5
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Re: Using Waste Heat

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Originally Posted by Dockhead View Post
But I don't think I could run the whole volume of coolant through it -- it would need some branch. I don't have any idea whether that will circulate naturally or not or how to engineer it.

What do y'all think? Waste of time and money? I could pay for a fair amount of fuel for the Eber for what this would cost. But it just seems so wrong to dump all that heat into the ocean, while at the very same time I'm burning fuel to make heat.
We plumbed in an inexpensive small radiator, maybe 1 ft**2 with a small 12 volt muffin fan on a switch behind it. To get the fan in the right place we branched in a loop putting two ball valves on the input side (one on each leg) so we could switch it out if need be, hot climates for example. We put a valve on the bottom branch of the new loop where it joins the return. The valves prevent the fluid in the higher new loop from spilling out of the engine radiator fluid overflow that is mounted somewhat lower when doing maintenance.

This is an old Lake Superior trick for getting some heat in the cabin. The system worked like a charm to drive off moisture and heat our Mason 44 whenever charging the batteries or running under power.

I suppose if you had a fluid-to-fluid heat exchanger you could heat up the fuel or water and then with a fluid to air exchanger you heat the cabin for as long as the fluid was warmer than the air. A lot of plumbing and pumps to get this working. But with the right setup, lots of water or lots of fuel, it may be worth it.
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Old 10-02-2015, 08:32   #6
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Re: Using Waste Heat

This is what I use.....

Heater Craft 11H Lavatory or Cuddy Cabin Boat Kit 1113-H-G - Boat-Heaters.com - Marine Heaters - Boat Heater Systems

Although heated water flows through it whenever the engine is running, it only produces heat when air from the fan blows through the heat exchanger.
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Old 10-02-2015, 08:38   #7
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Re: Using Waste Heat

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Originally Posted by David M View Post
There is no need to reinvent the wheel. This is what I use.....

Heater Craft 11H Lavatory or Cuddy Cabin Boat Kit 1113-H-G - Boat-Heaters.com - Marine Heaters - Boat Heater Systems

Although heated water flows through it whenever the engine is running, it only produces heat when air from the fan blows through the heat exchanger.
Yes, I found that aspect of it very clear. You will see that there is a "bus heater" in my diagram.

What concerned me more was the design of a branch to go into the heads. That was one problem.

The other question was whether anyone had an opinion about whether it is stupid to go to so much trouble with heat exchangers and all that.

I could put in a bus heater without any real trouble -- just splice it into the existing loop which takes the main engine's coolant through the calorifier. That would be cheap and easy and maybe that's Plan "B" in case the rest of it seems like too much trouble. That part of it, at least, seems totally clear -- when motoring or motor sailing in cold or cool weather, just put on the bus heater to keep heat pouring into the cabin. I can even imagine putting up the cockpit tent and leaving the washboards open so the (free) heat can waft up there as well.
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Old 10-02-2015, 08:45   #8
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Re: Using Waste Heat

Why not just remove one of the engine access panels when the heat is needed? We've done that... low tech, free, and it works great.
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Old 10-02-2015, 08:47   #9
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Re: Using Waste Heat

Hydronic Radiators, Towel Warmers, Wall Panel Home & Commercial Heating - Express Radiant Ltd. - Stelrad Canada
I know that Waterline Yachts uses something like the ladder towel warmer shown on the link home page and they circulate water from the hydronic heater through it. The ladder and the Str might be adaptable to your boat, either in the main line or heated from the engine/generator.
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Old 10-02-2015, 09:04   #10
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Re: Using Waste Heat

Quote:
Originally Posted by David M View Post
This is what I use.....

Heater Craft 11H Lavatory or Cuddy Cabin Boat Kit 1113-H-G - Boat-Heaters.com - Marine Heaters - Boat Heater Systems

Although heated water flows through it whenever the engine is running, it only produces heat when air from the fan blows through the heat exchanger.
This is also something I have periodically wanted to do. two things stop me each time:

1. The idea of running heater hose from the main engine out of the engine room.
2. Adding more points of failure to my main engine.
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Old 10-02-2015, 11:11   #11
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Re: Using Waste Heat

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This is also something I have periodically wanted to do. two things stop me each time:

1. The idea of running heater hose from the main engine out of the engine room.
2. Adding more points of failure to my main engine.
Pretty low risk if done properly all other risks considered. This assumes you are on the engine side of the heat exchanger and don't run sea water through your engine. Worst case is radiator fluid in the bilge.

Use hangers for routing the hose with smooth sufficient radius to prevent kinks. Folks have used these type of system for years.
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Old 10-02-2015, 11:29   #12
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Re: Using Waste Heat

Bus heater

Cabin Heater - C34

Yup, old Great Lakes idea.
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Old 11-02-2015, 12:23   #13
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Re: Using Waste Heat

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Why not just remove one of the engine access panels when the heat is needed? We've done that... low tech, free, and it works great.
That wouldn't work on my boat -- big blowers circulate a lot of air through the engine room, and there's no heat.
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Old 11-02-2015, 12:27   #14
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Re: Using Waste Heat

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Originally Posted by Stu Jackson View Post
Bus heater

Cabin Heater - C34

Yup, old Great Lakes idea.
Thanks -- that's a great link with a lot of useful ideas

I like the "t" connection and bleed line -- I'm going to copy that for my engine-calorifier loop if I don't do a more global reconfiguration of the system.
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Old 11-02-2015, 12:49   #15
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Re: Using Waste Heat

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Originally Posted by DeepFrz View Post
Hydronic Radiators, Towel Warmers, Wall Panel Home & Commercial Heating - Express Radiant Ltd. - Stelrad Canada
I know that Waterline Yachts uses something like the ladder towel warmer shown on the link home page and they circulate water from the hydronic heater through it. The ladder and the Str might be adaptable to your boat, either in the main line or heated from the engine/generator.
Just what I had in mind! Thanks.
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