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Old 19-02-2018, 17:29   #1
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Adding engine heating to diesel heater

I currently have a hydonic diesel heater that uses either shore power or a diesel burner. It provides both domestic hot water and cabin heat by means of small radiators and fans. I would like to add the option of using the engine heating so that when I run the engine I also heat my domestic hot water. From what I have been able to glean from the internet, the best way of doing this is to plumb in a separate heat exchanger into the cold water supply to the water tank (this is the way a Hurricaine Combi unit is plumbed into the engine coolant system, according to their online installation manual. It says don't mix the engine coolant with the hydronic heating coolant). Assuming this is correct, I have a few questions:
1. Is the new heat exchanger plumbed in series, or in parallel with the existing engine coolant loop?
2. If in series, do I need to worry about the ability of my engine water pump to handle the extra load?
3. So long as I keep the new plumbing below the level of the engine expansion tank, do I not need to worry about air locks in the system?
4. How do I get the water in the hot water tank to cycle through the heat exchanger in order to heat up the tank? Or do I put it on the hot side of the tank and just have "instant hot water" as opposed to a tankful of hot water?

Thanks for the help.
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Old 20-02-2018, 01:10   #2
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Re: Adding engine heating to diesel heater

I have an 83' boat. Hot water boiler in the engine room with supply and return lines running parallel to the center line to the bow and stern. I have 5 zones. I don't use a heat exchanger between the engines and the boiler. They share the same coolant. When a main is running, I can open a set of valves and the engine coolant is diverted thru the boiler. The boiler runs at about 15psi as do the engines and I have no issues. My engine water pump only moves water to the boiler and back. The boiler circulation pump takes care of the heat zones.
I also have a pellet and wood stoves, both with added water coils that, with valves, connect to the boiler. They both have a circulation pump. So in the winter with my pellet stove going, the boilers oil burner never lights. And cruising in cold weather, the engines do the heating.
A side benefit, if the boiler is hot before starting the mains, I can circulate hot water thru them for faster starts.
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Old 20-02-2018, 11:40   #3
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Re: Adding engine heating to diesel heater

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I have an 83' boat. Hot water boiler in the engine room with supply and return lines running parallel to the center line to the bow and stern. I have 5 zones. I don't use a heat exchanger between the engines and the boiler. They share the same coolant. When a main is running, I can open a set of valves and the engine coolant is diverted thru the boiler. The boiler runs at about 15psi as do the engines and I have no issues. My engine water pump only moves water to the boiler and back. The boiler circulation pump takes care of the heat zones.
I also have a pellet and wood stoves, both with added water coils that, with valves, connect to the boiler. They both have a circulation pump. So in the winter with my pellet stove going, the boilers oil burner never lights. And cruising in cold weather, the engines do the heating.
A side benefit, if the boiler is hot before starting the mains, I can circulate hot water thru them for faster starts.
How is the line to the boiler plumbed into the engines cooling loop? Does the loop to the boiler take off and return to the engine just before the engine thermostat? Is there some reason why you have incorporated valves into the system that allow you to bypass the boiler? I ask because I don't think I have the room to add the valves without major replumbing. A single continuous loop would work better for me, unless there is some reason not to do this?
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Old 20-02-2018, 11:47   #4
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Re: Adding engine heating to diesel heater

Also, I assume your boiler must have a heat exchanger coil inside it that your engine coolant is using to heat the water in the boiler?
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Old 21-02-2018, 08:24   #5
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Re: Adding engine heating to diesel heater

> I don't use a heat exchanger between the engines and the boiler. They share the same coolant.
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Old 21-02-2018, 10:55   #6
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Re: Adding engine heating to diesel heater

Doesn't your engine have a pair of connections for a heating loop?
If not, I'd want to make it parallel. Don't know what heater you have but my Espar is designed to heat the engine coolant, so no need for a separate loop, BUT you're putting your engine at risk of overheating from any leak in your domestic heating system.
When I installed my system I was advised by the forum to use a heat exchanger, so I did. One less thing to worry about.
A plate exchanger is cheap on ebay.
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Old 21-02-2018, 11:20   #7
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Re: Adding engine heating to diesel heater

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Doesn't your engine have a pair of connections for a heating loop?
If not, I'd want to make it parallel. Don't know what heater you have but my Espar is designed to heat the engine coolant, so no need for a separate loop, BUT you're putting your engine at risk of overheating from any leak in your domestic heating system.
When I installed my system I was advised by the forum to use a heat exchanger, so I did. One less thing to worry about.
A plate exchanger is cheap on ebay.
My engine doesnít have connections for a heating loop, but I can add them without too much trouble. What I donít understand is how do you get the domestic hot water to flow through the plate heat exchanger to pick up the engine heat? Do you have to Remember to run your boiler pump to circulate the water, or is it somehow automatic??
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Old 21-02-2018, 12:09   #8
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Re: Adding engine heating to diesel heater

I have to run the pump. If you're clever, and the space is available, you might be able to get it to siphon, but that's way above my pay scale.
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Old 21-02-2018, 12:12   #9
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Re: Adding engine heating to diesel heater

Here is what ITR recommends. Figure 1.2. They recommend that you do not combine the heating and the engine coolant but use a heat exchanger between the two.
http://itrheat.com//wp-content/uploa...v-Feb-2011.pdf
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Old 21-02-2018, 14:05   #10
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Re: Adding engine heating to diesel heater

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Here is what ITR recommends. Figure 1.2. They recommend that you do not combine the heating and the engine coolant but use a heat exchanger between the two.
http://itrheat.com//wp-content/uploa...v-Feb-2011.pdf
Thanks. The other thing Iím still not clear on is the connection to engine cooling system. Can I just add the new heat exchanger in series so that the coolant always goes through it, or should I put valves on it so I only reroute the coolant through the heat exchanger when I need it? Anybody know how the heater loop is plumbed on a yammer?? Parrellel or series? Always on or separate valves??
Thanks
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Old 21-02-2018, 15:45   #11
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Re: Adding engine heating to diesel heater

I would definitely install valves on both hoses to the heat exchanger and connect those hoses close to the engine. You will need a small circulation pump to circulate the engine coolant through the heat exchanger. If you leave the valves open when the engine is running you should be able to add heat to the system from the engine.

I saw a much more detailed diagram than the one I linked to but I don't remember where. It might have been on one of the other heater manufacturer web sites.
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Old 21-02-2018, 19:37   #12
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Re: Adding engine heating to diesel heater

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I would definitely install valves on both hoses to the heat exchanger and connect those hoses close to the engine. You will need a small circulation pump to circulate the engine coolant through the heat exchanger. If you leave the valves open when the engine is running you should be able to add heat to the system from the engine.

I saw a much more detailed diagram than the one I linked to but I don't remember where. It might have been on one of the other heater manufacturer web sites.
I can see I will need a circulation pump to move the domestic water through the heat exchanger but why isnít the engine pump sufficient to move the engine coolant through the heat exchanger and back to the engine??
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Old 21-02-2018, 20:47   #13
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Re: Adding engine heating to diesel heater

What Yanmar do you have? What heater are you using?

Whatever engine you have but there must be lots of people using it with heating loops for their hot water tanks. This is the same thing.
At any rate you want to branch off some water close to where it leaves the engine and put it back in closer to the heat exchanger. No additional pump required.
Then you just need to activate the heat circulation pump. You might want to talk to the heater manufacturer to see if activating the pump might affect the ECU.
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Old 21-02-2018, 22:13   #14
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Re: Adding engine heating to diesel heater

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What Yanmar do you have? What heater are you using?

Whatever engine you have but there must be lots of people using it with heating loops for their hot water tanks. This is the same thing.
At any rate you want to branch off some water close to where it leaves the engine and put it back in closer to the heat exchanger. No additional pump required.
Then you just need to activate the heat circulation pump. You might want to talk to the heater manufacturer to see if activating the pump might affect the ECU.
Sorry but I canít follow your reply:
Same thing as what???
What does the ďbranch offĒ look like? A tee connection with a separate shutoff valve, or just an elbow routing the coolant to the heater and then back to the engine??
What is ECU??
Btw, the engine is a marinised VW. The heater is a hurricane.
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Old 21-02-2018, 23:34   #15
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Re: Adding engine heating to diesel heater

Your heating loop to and from the heat exchanger has the same function as a heating loop to supply hot coolant mix to the typically installed hot water heater.
My Westerbeke W-46 has a short length of tubing in hot coolant line with 2 pipe barbs for the heater loop. There is a diverter to encourage the coolant to flow out the 1st tube and back in the 2nd. No valves. If the boat doesn't use this type of heat then there is a U shaped hose to replace it. I don't know what your engine has.
I thought you asked about Yanmar but, if your VW engine is the Pathfinder version, there were a number of boats built with it. Maybe you can find someone on CF who has one with a hot water loop. If it's in a Freeport they have a very active user group.
As far as the heating side of your system is concerned, Hurricane is a high end product and they can probably give you any info you need.
The ECU is the "electronic control unit" that runs heaters like Espar and others. The ECU may become confused if it sees the pump running without the furnace blower running - don't know - but when they see something they don't understand they set a fault code and shut down.
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