Cabin heat from engine

[a64pilot]

I don't know Stu,
I think it can work, if for example boat is in a slip with shorepower, it starts out already heated. It is a Rube Golberg idea and overly complicated, but if properly managed it would work.
Reminds me of the Space pen story, untrue of course, but story goes on about how NASA spent bunches of money developing a pen that would work in zero gravity, ended up with an accumulator pressurized with nitrogen gas, so that the gas pressure kept ink at the ball, like gravity normally does.
Russians just used pencils

[Stu Jackson]

Originally Posted by a64pilot

I don't know Stu,
I think it can work, if for example boat is in a slip with shorepower, it starts out already heated. It is a Rube Golberg idea and overly complicated, but if properly managed it would work.
Reminds me of the Space pen story, untrue of course, but story goes on about how NASA spent bunches of money developing a pen that would work in zero gravity, ended up with an accumulator pressurized with nitrogen gas, so that the gas pressure kept ink at the ball, like gravity normally does.
Russians just used pencils

Yeah, a64, except he said he wants to use it at anchor.

...but if properly managed it would work.

Yeah, but so many folks still can't figure out how to wire and use a 1-2-B switch. All he has to do is to forget ONCE and his engine is toast.

And the heat transfer simply doesn't work.

Before he retired, my buddy Dave sailed with me every single Friday for over five years. One day our only ball point pen died (before I had backups for backups). He just calmly handed me a pencil!

[Pizzazz]

Originally Posted by Stu Jackson

Adding that additional hot water will take over four hours to heat from your engine. Why? 'Cuz it takes almost a half an hour to heat six gallons when your engine is at cruising speed (this is empirical from 18 years of experience). Do the math. 6=1/2 hour. 46/6=7.666 half hours.

What's your entire engine worth to you?

Stu,

Thank you for the feedback, it is much appreciated coming from a professional. Just to clarify, I am proposing to bypass the heat exchanger in order to speed up the heating process. Once the large tank is heated the raw water will be allowed back into the exchanger via a valve or thermostat. Conceptually, I see no difference if you have small fresh water loop with a raw water heat exchanger vs. a large fresh water loop with a raw water heat exchanger that kicks in half an hour (or as long as it takes) later.

I believe your concern is that doing so may result in the engine running warmer than usual. This is a valid point but it can easily be verified by checking the temperature sensor of the engine. Need to think about it and definitely test it to see how much faster the 6 gallon will heat. I agree that the project is not worth it if the engine rapidly overheats.

I am coming from the other side... the engine has low hours and barely gets used. I might as well find some uses for carrying so much weight in my boat. But now, I definitely do not want to replace the engine before I replace the boat .

[a64pilot]

See, I would not bypass the raw water from the heat exchanger, reason is the thermostat should prevent the majority of coolant from flowing through the heat exchanger now, so bypassing would gain little, yet bring in a possible problem of overheating, though I think it unlikely you would overheat enough to cause damage, and you should have an over temp alarm anyway, but don't bypass it, that is the purpose of the thermostat.

Now while I have not verified it, I believe the hot water heater circuit is like the heater on an automobile, that is there is full flow even with thermostat closed, in fact I believe the hot water heater circuit is just the heater circuit for an automobile.

Downside is I believe that your engine will take a long time to warm up, which won't kill it, but isn't the best thing for an engine, ideally you want on to come up to operating temp quickly

[Stu Jackson]

Originally Posted by Pizzazz

Stu,

1. Thank you for the feedback, it is much appreciated coming from a professional. Just to clarify, I am proposing to bypass the heat exchanger in order to speed up the heating process. Once the large tank is heated the raw water will be allowed back into the exchanger via a valve or thermostat. Conceptually, I see no difference if you have small fresh water loop with a raw water heat exchanger vs. a large fresh water loop with a raw water heat exchanger that kicks in half an hour (or as long as it takes) later.

2. I believe your concern is that doing so may result in the engine running warmer than usual. This is a valid point but it can easily be verified by checking the temperature sensor of the engine. Need to think about it and definitely test it to see how much faster the 6 gallon will heat. I agree that the project is not worth it if the engine rapidly overheats.

3. I am coming from the other side... the engine has low hours and barely gets used. I might as well find some uses for carrying so much weight in my boat. But now, I definitely do not want to replace the engine before I replace the boat .

1. You're welcome. Thermostats fail. Forgetting to operate the valve cooks your engine. What's not to like in those scenarios? With a fresh water cooled engine and water lift muffler, the water from the engine goes to the HX and then to the nipple where it mixes with the exhaust gases and cools them before entering the muffler. If you interrupt this flow of the water to mix with the exhaust gases before the muffler, how does the muffler work without melting?

2. Yup, you REALLY need to think about it. Reducing the time to get the engine up to operating temperature should not be a goal. The engine will do just fine getting warm all by itself under cruising speed load. There is a tad of misunderstanding in a64's post about having hot water in the heater, to reduce engine warmup time, 'cuz the heater uses "excess" heat in parallel with the engine freshwater coolant and the amount of time "saved" is actually minuscule compared to the heat being exhausted through the muffler/HX system. I could disconnect my domestic water heating loop and the engine wouldn't heat up much slower than if it was there.

3. This idea is completely counter intuitive to your OP where you want to heat the water. The LESS time the engine runs, the less time you will have for thermal conductivity to heat MORE water. It doesn't make any sense. How would you heat your new 46 gallon tank if you don't run your engine? You have a newer little used engine. You might want to re-prioritize your thought process, and make the longevity of your engine your highest priority.

Let's try another tack: If this was such a good idea, don't you think more people or builders would be doing it? They don't, for the reasons I've explained.

Carrying so much weight in your boat is called an engine, it is used for propulsion. A byproduct of engine operation is heat. That heat is used, in PARALLEL with the engine cooling system, to heat modest amounts of hot water for domestic water uses. It is NOT done instead of cooling the engine. Cooling the engine, whenever it is operating, is the primary function of the engine's cooling system. It should remain so.

Look, I live in California, too. I have been sailing here on and around SF Bay for 35 years. I use a trawler lamp and a catalytic heater. It works for me. I close the head, aft cabin and V berth doors and remain toasty even as cold as the high 40s outside at night. If I wanted more heat, I'd use the stove/oven or buy a diesel heater. I had a friend who sailed his Catalina 34 from Vancouver, BC to Mexico. Here's what he had to say about heating his boat:

- diesel heater - never would have believed how cold it is. You expect it offshore in Washington and Oregon, but California has been very cold.

And he came from where it is REALLY cold, compared to here. His diesel heater was already in his boat, 'cuz you'd have to be crazy or otherwise not use your boat often in the PNW without a diesel heater. I wouldn't buy a boat up there that didn't have one. It's not like some Floridian came to visit me with his blood thinned out by too much wine! These were hardy folks who came from Vancouver and had sailed their boat for years up there, into Desolation Sound and the Broughtons. He didn't need his heater in Mexico, but used it even in San Diego. June Gloom can be pretty cold even as far south as San Diego.

Your concept has little validity, it is fraught with potentially huge problems, makes little sense in the real world of boating and doesn't work in heating engineering terms.

Have you read the link I provided?

Get your kids some long johns and wool sweaters. And heat your boat with proven systems instead of something that could cost you your engine.

[Pizzazz]

Very good comments so far. The key issue here is that marine diesels, when under a light load, run colder than optimal. My revised approach is to insert a diverting valve themostat ($60 online, separate from the main engine thermostat) that will cut raw water cooling until the fresh water coolant and related hot water (all 46 gallons of it) reach a decent temperature. This allows more efficient water heating at idle speeds and it may even be good for the engine as it will operate at more optimal temperatures in idle speed. I do not see the problem that Stu is so worried about. I agree that a thermostat is better than a valve that you can forget and ruin the engine this way.

By the way, I just checked and my Raritan heater on the Yanmar 2GMF engine is connected in series, not in parallel. This means that the coolant exits the engine, goes through the heater and then goes back into the heat exchanger. All I am doing is making the water heater 7x bigger.

Regarding comments on the complexity of the system, once we get the concept clear, all there it is to it is a water tank, two hoses, a check valve and a thermostat. To me this is less complicated than installing a separate heater with a through deck exhaust. Plus, it is dual use since you get 40 gallons of additional fresh water capacity. When racing you can always empty the tank (as I do with my holding tank).

[waterman46]

I see a lot of comments about engine temperature. My experience with a bit larger engine (Perkins 4-154) is the gauge goes to normal operating temperature by the time I motor out of the harbor and have the sails up as fast as I can (maybe 20 minutes, just guessing). My point is, don't mess with the cooling system of your engine, as mentioned it's too expensive but moreover you will gain no advantage other than maybe 10 minutes faster warmup time.
So you can leave the engine cooling system intact, but there are two big problems with the OP's plan: one, it will take one heck of a long time under power to raise a cold 40 gallons to the final temperature and two, the normal engine water temperature will not be high enough to create an efficient heat transfer system to the cabin air. You'll have a fan blowing air over a radiator of some kind but the air coming out will only be a few degrees above ambient.

[bcboomer]

Stu Jackson +1

You say you don't use your engine much so this will result in your engine running cold for most or all of the time. A sure recipe for a prematurely worn out engine. I know first hand that running a diesel below its designed temperature for most of its hours will result in a worn valve train as well as seized oil control rings. (40 years in the diesel service field) You'll be lucky to get 1000 hours out of it.

Not to mention 400 lbs of water and tank and plumbing plus lost storage etc. etc.

Find a better way!

[tankersteve]

Zeehag mentioned it, but oil lamps provide a very pretty glow and a surprising amount of warmth in a smaller enclosed space. I also own a 31 footer, and an oil lamp seems about perfect for cooler evenings.

Tankersteve

[Stu Jackson]

Originally Posted by Pizzazz

Very good comments so far. The key issue here is that marine diesels, when under a light load, run colder than optimal. My revised approach is to insert a diverting valve themostat ($60 online, separate from the main engine thermostat) that will cut raw water cooling until the fresh water coolant and related hot water (all 46 gallons of it) reach a decent temperature. This allows more efficient water heating at idle speeds and it may even be good for the engine as it will operate at more optimal temperatures in idle speed. I do not see the problem that Stu is so worried about. I agree that a thermostat is better than a valve that you can forget and ruin the engine this way.

By the way, I just checked and my Raritan heater on the Yanmar 2GMF engine is connected in series, not in parallel. This means that the coolant exits the engine, goes through the heater and then goes back into the heat exchanger. All I am doing is making the water heater 7x bigger.

Regarding comments on the complexity of the system, once we get the concept clear, all there it is to it is a water tank, two hoses, a check valve and a thermostat. To me this is less complicated than installing a separate heater with a through deck exhaust. Plus, it is dual use since you get 40 gallons of additional fresh water capacity. When racing you can always empty the tank (as I do with my holding tank).

OOOPS, you're right, I should have said series. My Bad. But that even makes my case stronger. You are planning to interrupt a series system. That's like the old Christmas tree lights, right? One bulb goes out and the whole string STOPS WORKING.

The reason I made that mistake is that I was thinking that the byproduct of the engine heat is used in parallel to heat the water in a series arrangement. Sorry about my fingers and my brain getting whacked out by this whacky idea.

You haven't addressed the muffler issue. No cooling water, it melts the muffler. You seem to be missing the concept of how the exhaust gases get cooled.

I do not see the problem that Stu is so worried about.

Because you don't want to.

I tried.

[Cheechako]

I think you will find a fan/radiator will deplete the stored heat very fast. It gets cold on a boat at maybe 3am and later. You will have nothing left at that point.
Btw, I had a little powerboat with a V8 engine. It had a fan/radiator small heater in the cabin like a car heater. With the fan on low that little radiator would cool the engine cooling system so low within 10 minutes that it was blowing cool air!
If you want to be toasty and dry get a small diesel Webasto forced air heater. it can be as simple as just installed on a bulkhead if you want.
The other thing is boats deplete heat fast. The fiberglass just pulls it out. And of course all the heat rises quickly to the ceiling. Your feet can be cold and your ears hot when sitting at the table. A small boat with a 1000 watt electric heater on will be cold in the middle of the night.

[a64pilot]

Stu,
Way I read it, is he wants to bypass the heat exchanger, but still dump raw water into the exhaust, but I don't think he needs to as there is very little coolant flowing through the heat exchanger until the thermostat opens up.

I can assure you , my engine comes up to temp faster if the heater loop runs through an already hot 12 gl water heater as opposed to heating 12 gls of water and warm the engine both

[Stu Jackson]

Could be, but he hasn't said that clearly for me to understand. If true, then he is still putting his engine at great risk.

Could also be you;re right about that, too, but I say it's still comparatively small, doesn't hurt anything either, 'cuz you haven't messed with the system, right?

[Pizzazz]

I understand the "don't mess with something you do not understand comments" but I really think the situation here is different. Let me repeat the setup in a final attempt to convince myself that this may work.

The fresh water system circles the water through the engine, the heat exchanger and the water heater, all in series. There is a thermostat that stays closed initially (meaning only the water in the engine block circulates). The Yanmar manual says that it takes about a minute! for the engine to reach minimum operating temperature, then it opens up allowing the fresh water loop. I am not touching this system. All I am doing is expanding the water heater capacity from 6 gallons to 46 gallons via an additional tank. It may or may not be enough to provide enough heat but my calculations show that 46 gallons of water at 140F cooling down to a target temperature of 70F is equivalent to 27,000 BTUs. This just math. The water tank will be in the cabin, so the heat will stay there and I may accelerate the release with a radiator, fan, whatever.

The second piece of the project that Stu is trying to kill attempts to deal with the problem that when the engine is running at idle or low load, it just stays too cool to efficiently transfer heat to the larger tank. By the way, I just did a test, run the engine at idle for 20 minutes and it warmed up the 6 gal too hot to touch. So it may be more efficient that I think. Anyways, in order to increase the engine temperature at idle, I am proposing to install a diverting thermostat in the raw water circuit that bypasses the heat exchanger. This will allow the engine to reach higher temperatures faster, which is both good for the engine and for my application to heat water faster.

Where is the problem? The thermostat in the raw water loop will revert to normal operation once a certain temperature is reached (need to find the right temperature, I guess equivalent to medium load working temperature).

May be I am daft today but I am beginning to look at this as an improvement to the engine cooling system rather then an issue.

[wrwakefield]

Pizzazz,

What you are proposing sounds overly complicated for your stated needs and cruising climate. I have had very elaborate hydronic heating systems on past vessels and they work great, but are overkill for your stated needs in my experience...

I do understand you are trying to capture waste heat from the engine, but...

I know you mentioned you ruled out diesel [but it was unclear why...?] so have you considered one of the small bulkhead mounted propane powered heaters? [e.g., Dickinson Newport propane model.] Very safe with dual flue pulling outside combustion air, and instant on, and soot free...

I have used them with great success on past vessels about your size even in Alaska... I suspect they will cost you about the same cash outlay, but save you much more time in installation and maintenance.

As ZeeHag mentioned, we also did well using an Aladdin oil lamp for light and cabin heat when the delta T was benign. [i.e., not that cold outside...] Aladdin lamps have a mantle above the wick, so they look like a pressurized lantern, but without the pressure. More efficient than wick only kerosene lamps...

However given the price of a new Aladdin lamp, I might be persuaded to double that and get the Dickinson propane heater...

Best wishes suiting your needs.

Cheers!

Bill