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Old 21-02-2018, 22:34   #16
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Re: Adding engine heating to diesel heater

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Originally Posted by osprey877 View Post
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?
I have DD 671 mains.They have a bypass circuit so the engine never starves for water if the thermostats are closed. The hot coolant leaves just before the thermostat and returns just in front of the circulation pump. See pics. Not my engine. Rubber hose under water tank passes to the other side thru lifting eye. On the other side it returns in front of the circulation pump where coolant comes from the exchanger. The valves are: one opens the boiler supply, one opens the boiler return, and a third shuts off the bypass between the two other valves. Hot coolant goes to the supply and the returns to in front of the engine coolant pump. With only the engine running, the engine coolant pump provides circulation forcing the hot coolant into the top of the boiler and drawing back coolant from the normal boiler return. The flow is from the top down. When there is a heat call the boilers circulation pump comes on, automatic valves open and the flow changes from bottom to top. Engine coolant in the supply line goes to the heater (mixing with boiler water) and returns via the return line to either the boiler or engine.
The boiler shares the coolant with the engine. There is no coil for heat transfer. There is a coil in the boiler that heats the hot water tank if the boiler is hot.
If you really want a diagram, give me a couple days and I'll make one. I switching computers and don't have a lot of stuff handy.
I have valves because if there was a leak somewhere I can stop coolant loss. I have both mains plumbed into the boiler but only have one providing heat at a time. I have a walk in engine room so operating valves are no big deal. All my plumbing runs in the bilges so it's not easy to see or photograph.
A small engine may not warm up in a timely way with a heating circuit always open.
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Old 22-02-2018, 10:01   #17
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Re: Adding engine heating to diesel heater

OK, thanks. That makes sense. Can you give me some more detail what the connection with diverter looks like? Is it a Tee or a Y connection? Is the hose to the heat exchanger same diameter as the engine cooling hose? What does the diverter look like??
Thanks
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Old 22-02-2018, 10:13   #18
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Re: Adding engine heating to diesel heater

If all else fails, read the documentation.
My Lugger had a small heat exchanger, I plumbed the domestic hot water through this heat exchanger. The heat from the engine accepted the water flow from bottom of the HW heater, heated it and put it back into the tank. REALLY surprised the guest just how hot that water got. With the engine running, you have a constant supply of HW, no waiting. The HW heaters will shut off automatically with the tank water reaches a specified temp.
I do recommend isolation valves on the engine.
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Old 22-02-2018, 10:49   #19
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Re: Adding engine heating to diesel heater

Here's the factory diagram for the W46

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Do you have an engine manual? If so there should be something similar showing. If not you need to get on as there are lots of idiosyncrasies in marine
conversions.
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Old 14-11-2018, 12:36   #20
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Heat exchanger sizing for Espar M12/Perkins 4.236 ?

Bula from Fiji,


We are sitting in the heat doing the final planning for Phase II of our hydronic heater install in preparation for heading up to Japan and Alaska and then living aboard in Victoria, BC for a few years with our family of five on our 47' monohull.



I already installed a Espar M12 -II (max 41,000 BTU/Hr or 12 kW) with fan units in the aft cabin (10,250 BTU/Hr) and saloon (10,250 BTU/Hr) plus heating the hot water tank (or calorifier). This was Phase I and was tested in the NZ autumn (not quite Alaska or a Canadian winter but there was at least frost on the deck in the mornings).


Phase II is adding a heat exchanger to utilise the waste heat from the engine and to add a fan unit (9400 BTU/Hr) to the children's cabin up in the bow.



My question is about sizing the heat exchanger: how big of a heat exchanger can one use before adversely impacting the engine ? We have a Perkins 4.236 84HP that previously used 1/2" hose to heat up the hot water tank. The hot water tank is quite a distance from the engine so I am looking to find a place closer to the engine for the new heat exchanger so that should reduce the drag on the coolant pump. However, the two heat exchangers I am looking at online are 30,000 BTU/Hr or 40,000 BTU/Hr. Will that be too much drag on the coolant pump or take too much heat from the engine ?


So much good information on Cruisers Forum and I have taken some notes from the the posts on heaters but I did not see anything specially on sizing the heat exchanger.


Much thanks as always,


Max
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Old 14-11-2018, 13:26   #21
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Re: Adding engine heating to diesel heater

When I added my hydronic heating (ITR) I removed the engine coolant loop. It is just a complication of a critical system, the engine, in my opinon. If I want hotwater I run the heater.
So far the only leaks in my engine cooling circuit I've had were in the hot water tank loop, before I removed that for circuit. In a power boat where you regularly run the engine all day it makes sense.
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Old 14-11-2018, 13:50   #22
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Re: Adding engine heating to diesel heater

Thanks for the feedback Paul. Always a balance of risks and rewards isn't it. That was one of the reasons we did not install a heat exchanger in Phase I but we have found we were annoyed that we did not get "free" hot water when we ran the engine in and out of atolls or if we needed to do a long motor. As our solar will not be as much good in Alaska we will likely need to run the engine everyday on passage for battery charging so we would like to get the heating and hot water that would go with that. At least it will be a simpler and shorter install from when our engine was connected directly to the hot water heater.


Are you still in Bellingham ? We started our cruise nearby in Anacortes six years ago.
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Old 14-11-2018, 13:58   #23
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Re: Adding engine heating to diesel heater

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Thanks for the feedback Paul. Always a balance of risks and rewards isn't it. That was one of the reasons we did not install a heat exchanger in Phase I but we have found we were annoyed that we did not get "free" hot water when we ran the engine in and out of atolls or if we needed to do a long motor. As our solar will not be as much good in Alaska we will likely need to run the engine everyday on passage for battery charging so we would like to get the heating and hot water that would go with that. At least it will be a simpler and shorter install from when our engine was connected directly to the hot water heater.


Are you still in Bellingham ? We started our cruise nearby in Anacortes six years ago.
My setup is a little different as it is ITR. We get hot water on demand within a few minutes, so firing up the heater is not an issue. In the summer time we have a summer loop valve for the heater coolant. It then only routes through the hot water heater, not the cabin radiators.

Just left Bellingham a few days ago by plane. Getting ready to relaunch today in Australia.
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Old 14-11-2018, 14:10   #24
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Re: Adding engine heating to diesel heater

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As our solar will not be as much good in Alaska we will likely need to run the engine everyday on passage for battery charging so we would like to get the heating and hot water that would go with that. At least it will be a simpler and shorter install from when our engine was connected directly to the hot water heater.
I do not know about your ER but mine gets very hot/warm. If I get cold, I guess I could run the engine with the floor access open. Or wait until I shut down the engine and then open the floor access to release the heat into the saloon.

I remember that tiny heat exchanger on my Lugger..... It really would heat the hot water HOT HOT NOT.
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Old 14-11-2018, 14:20   #25
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Re: Adding engine heating to diesel heater

Why can't you just add a heater element, like an auto/truck ! You can get them online with fans ! My hot water for showers etc. comes fro our hot water heater ! 110/motor ! When we run the motor we have hot water, and heat for the cabin if we want! Simple system!
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Old 14-11-2018, 14:29   #26
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Re: Adding engine heating to diesel heater

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I do not know about your ER but mine gets very hot/warm. If I get cold, I guess I could run the engine with the floor access open. Or wait until I shut down the engine and then open the floor access to release the heat into the saloon.

I remember that tiny heat exchanger on my Lugger..... It really would heat the hot water HOT HOT NOT.

Yes, our engine compartment gets pretty warm and as it is in the saloon it does heat the saloon but it does not heat the other parts of the boat nor heat the water.
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Old 14-11-2018, 14:52   #27
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Re: Adding engine heating to diesel heater

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Why can't you just add a heater element, like an auto/truck ! You can get them online with fans ! My hot water for showers etc. comes fro our hot water heater ! 110/motor ! When we run the motor we have hot water, and heat for the cabin if we want! Simple system!

Yes, as above always trade offs between simplicity and complexity. In this case we have chosen to go the more complex route already with a hydronic system, backed up with a Webasto air heater, as this is our family home we live and travel on full time.


The question is not whether we should do it or not, a valid question for sure, but rather what size of heat exchanger we can add to utilise some of the waste heat from the engine to put into the already installed hydronic heating system.
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Old 14-11-2018, 14:53   #28
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Re: Adding engine heating to diesel heater

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Yes, our engine compartment gets pretty warm and as it is in the saloon it does heat the saloon but it does not heat the other parts of the boat nor heat the water.
Not knowing the layout of your boat, perhaps a bit of duct work and a 12vt fan can redistribute as you wish?

Hmmm, what is the make and model of your engine and have you read the docs to see if there is a small heat exchanger you can tie into the hot water heater?
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Old 14-11-2018, 15:02   #29
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Re: Adding engine heating to diesel heater

Understandably, in south Florida we do not hanker too much for a strong heating system. SMILE
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Old 14-11-2018, 15:12   #30
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Re: Adding engine heating to diesel heater

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Not knowing the layout of your boat, perhaps a bit of duct work and a 12vt fan can redistribute as you wish?

Hmmm, what is the make and model of your engine and have you read the docs to see if there is a small heat exchanger you can tie into the hot water heater?

Yes that is of course possible but that is not what I am trying to do as I already have a back up Webasto air system. As per my first post, we already have a hydronic system installed and I am looking to add a heat exchanger to use some of the waste heat from the engine.


The original question on adding to my existing hydronic system: My question is about sizing the heat exchanger: how big of a heat exchanger can one use before adversely impacting the engine ? We have a Perkins 4.236 84HP that previously used 1/2" hose to heat up the hot water tank. The hot water tank is quite a distance from the engine so I am looking to find a place closer to the engine for the new heat exchanger so that should reduce the drag on the coolant pump. However, the two heat exchangers I am looking at online are 30,000 BTU/Hr or 40,000 BTU/Hr. Will that be too much drag on the coolant pump or take too much heat from the engine ?
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