Heating With Waste Heat

[Kenomac]

Do you have a diesel heat system comparable to a Webasto forced hot air unit? If not, it's the answer to your problem. Uses very little diesel and heats the entire cabin in a few minutes. We don't even use our heat pump/ac unit any longer.

I don't understand why your engine doesn't heat your hot water tank. We always have loads of hot water for hours after we anchor for showers, dishes etc., then the generator will heat an additional 14 gallons in just 30 minutes while we cook dinner and charge the batteries. I assume your set up is similar? Most of the time here in Sardegna, we sail everywhere and rarely use the engine. Still, our generator is able to provide ample hot water after even 30 minutes of run time.

Ken

[Terra Nova]

Don't compromise your engine and generator by combining their cooling systems.

[sailorchic34]

Dockhead has a hydronic diesel boiler with hot water piping serving three fan coils. A bit different then forced air heaters, which are also good systems.

Depending on where his water heater is and what height it is above the engine. it might be air bound. Which just requires that air be removed from the top of the system. Basic hydronics 101.

[sailorchic34]

Originally Posted by Terra Nova

Don't compromise your engine and generator by combining their cooling systems.

Agree that you do not want to combine two engine cooling systems together, without a means to decouple the water pumps and water circuits. We're also talking smaller piping such as going to a water heater/ calorifier.

I'm an engineer, I actually know how to do this safely.

[Jd1]

For what it's worth, here is my setup (very much like Sailorchic describes)
engine coolant loop goes through a liquid to liquid heat exchanger driven via the coolant pump on the engine. Diesel hydronic heat loop goes through the same heat exchanger driven by the hydronic circulation pump (at the end of it's loop just before the diesel boiler).
In operation, if the engine runs I have heat in the heat exchanger. If I want that heat in the boat or in the hot water storage tank, I just turn on the hydronic circulation pump. If the engine is not running and I want heat, I turn on the diesel boiler which automatically turns on the hydronic circulator. The domestic hot water tank only has a single heat exchanger built in so in order to have hot water from either the engine or the diesel heater, there is a tap off the hydronic loop for hot water to flow through the tank heat exchanger and heat the domestic hot water.
Since you already have the hydronic heat, all you need is the heat exchanger and a bit of re-plumbing.
The one thing I wish was different in my system is that I would rather have a second heat exchanger in the hot water tank so I don't have to run the circulator pump when the engine is running. It is a minor issue.
When it's cold, and the diesel boiler is on, the engine heats up much quicker.
In my case the hydronic circulator is turned on automatically with the ignition key (but that can be over-riden) or by the diesel boiler starting up.
I would avoid combining the coolants of the different heat sources (personal preference).

[sailorchic34]

I've had a yet another wild thought. Since the OP's calorifier already has two loops, one for the hydronic side and one for the engine side, Guess what. That my friends is a heat exchanger. If you add a switch to run the pump without turning on the boiler, your now taking heat out of the calorifier for the heating loop, while the engine provides heat to the calorifier. All for the price of some wire and a dpst switch.

The only issue with this is it's probably only 3KW ish of heat due to the relatively small size of the heat exchanger tubes in the calorifier. Depending on system arrangement the might not have ideal flow capacity, but it would give you usable heat from the engine for very little cost.

If you wanted to use all the heat from say the generator then you would need a heat exchanger. As the main engine KW rating probably far exceeds the heating requirements, using the calorifier as a heat exchanger would probably work pretty well. I expect the generator will be much closer to the heating KW size, though it too may be larger.

OK, I just thought of one tiny issue with my original thought of combining all three systems, while it would work, the down side is a single leak in any part of the system would take down all three systems. Which in my book is a BIG no no. Sigh.

The part above of using the OP's calorifier as a hydronic heat exchanger would work pretty well. You could also change out the engine lines and connect the generator to the calorifier as that might be running more at anchor. Though a separate heat exchanger sized for 10KW would give you more heating capacity. Though try the calorifier trick as it might be enough heat for your boat

[Jd1]

Originally Posted by sailorchic34

Though try the calorifier trick as it might be enough heat for your boat

While I am not an engineer, I will venture out and say "I would be VERY surprised if that would work satisfactorily". As far as I know, the loops that are normally in the domestic hot water tank have limited flow through them and then there is the issue of having to heat up the hot water tank first (completely because the loops are on the bottom/cold end of the tank) before you have any transference to the second loop. Because you are not going from one medium through a single wall to the second medium, a lot of efficiency is lost. I would be surprised if the heat exchanger loops in the domestic hot water heater are longer than a couple of loops of plain soft copper pipe with not an awful lot of surface area.
I suspect that the little heat you might extract will dissipate in the lines and leave nothing for the actual water to air heat exchangers in the cabin.
As mentioned above, this is only a guess though. Might be worth trying out just for the heck of it!

[sy_gilana]

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[sailorchic34]

Originally Posted by Jd1

While I am not an engineer, I will venture out and say "I would be VERY surprised if that would work satisfactorily". As far as I know, the loops that are normally in the domestic hot water tank have limited flow through them and then there is the issue of having to heat up the hot water tank first (completely because the loops are on the bottom/cold end of the tank) before you have any transference to the second loop

While your are correct where it comes to american water heaters, that the hot water loops are dinky, many british calorifiers (same thing different name though low pressure rating by US standards) have a pretty impressive coil design. But it's only 1/2" /13mm. So that limits flow rate a bit. But allowing for a 20 degree delta T would get you to about 2-2.5kW ish. which might be enough for space heating.

[TeddyDiver]

As a former plummer speaking...
You having now three separate sources, Eber, the main engine and the genny. All of them having their own circulation pump and two of them having their own cooling loop.
The issue you having now (no circulation) is due a couple of reasons. The resistance of the hydronics is too much compared to cooling loop to have proper circulation, hence the air lock issue. Automatic air valves do not work in non pressurized systems. The same will be true for the gennie too if installed as the main engine is installed now.
I see two possible solutions. First one, more simple one, has all three sources sharing the same hydronics loop. The issue in this solution is the pressure which has to be at least head +0.5bar to work properly. Each inlet should be with a backpressure valve. Every higher place in the plumming needs automatic air bleeder. The need of a separate circulation pump is a complicated question. Depends so much about the pipe and hose diameters, lengths and curves, as well as the other installed items items. If the loop is truelly short, piping the same diameter as the cooling circuit it should work well without. Only one of the heat sources should be running at any time.
The second possibility has a heat exchanger in every heat source which cannot be pressurized. A separate circulation pump is mandatory.
BR Teddy

[Arthur Garfield]

Thought provoking utilizations of waste heat/kw usage.
One suggestion for eliminating heat loss due to piping/hosing throws-PEX hose.


All the Best

[Lepke]

It's probably better for your generator to have a load bigger than just a charging circuit. Generator engines that run for long periods on light loads seem to glaze the cylinders. Then you do rings and sleeves.
I live on a powerboat with two mains and two generators that also came with a hydronic baseboard system. One issue I had with the heating system is that for the baseboards to heat in cold weather, I had to run at near steam temperatures. I burned 5-6 gallon of diesel a day. Also, the piping ran thru the bilges (this is a wood boat) and were not insulated. Depending on the area heated, I lost about 30° (F) getting to the baseboards and some more heat going back. I pulled the baseboards, went to marine (similar to car) heaters, insulated the piping and saved about 1/2 the heating cost. I also installed valves on the mains to divert cooling water to the boiler. Much like sailorchic34's diagram. The main fresh water pump moves the water. If you don't like turning valves you can get electric valves. When running I heat with waste engine heat. Later I put in a pellet stove, built a coil and use it to heat the boiler when anchored or docked. I burn $5-8 a day in pellets in really cold weather - below 20°F. Way cheaper than oil.

[Dockhead]

Originally Posted by sailorchic34

While your are correct where it comes to american water heaters, that the hot water loops are dinky, many british calorifiers (same thing different name though low pressure rating by US standards) have a pretty impressive coil design. But it's only 1/2" /13mm. So that limits flow rate a bit. But allowing for a 20 degree delta T would get you to about 2-2.5kW ish. which might be enough for space heating.

I thought of this -- using the calorifier as a heat exchanger. I effectively have this already -- if I can get my engine loop working. Coolant returned from the calorifier is effectively preheated, reducing the load on the Eberspacher.

But I think after all this good advice I've decided to get the heat into the main hydronic system.

[Dockhead]

Originally Posted by Lepke

It's probably better for your generator to have a load bigger than just a charging circuit. Generator engines that run for long periods on light loads seem to glaze the cylinders. Then you do rings and sleeves.
I live on a powerboat with two mains and two generators that also came with a hydronic baseboard system. One issue I had with the heating system is that for the baseboards to heat in cold weather, I had to run at near steam temperatures. I burned 5-6 gallon of diesel a day. Also, the piping ran thru the bilges (this is a wood boat) and were not insulated. Depending on the area heated, I lost about 30° (F) getting to the baseboards and some more heat going back. I pulled the baseboards, went to marine (similar to car) heaters, insulated the piping and saved about 1/2 the heating cost. I also installed valves on the mains to divert cooling water to the boiler. Much like sailorchic34's diagram. The main fresh water pump moves the water. If you don't like turning valves you can get electric valves. When running I heat with waste engine heat. Later I put in a pellet stove, built a coil and use it to heat the boiler when anchored or docked. I burn $5-8 a day in pellets in really cold weather - below 20°F. Way cheaper than oil.

Yes -- I try to avoid running the genset for long periods without a load of at least 25% of its 6.5kW capacity, so 1.5kW or so. Anyway below 25%, fuel consumption doesn't fall, so the power is free anyway if you're using less than 25%. I have electrical resistance heaters and an electric immersion heater to create a load for the genset if needed. But my usual tactic, and I think most cruisers do this, is to run the genset when I have other things to do with the power like running the washer or dryer, cooking, etc.

As to the rest -- my problems with the general design of my heating system are less severe than yours, as my boat was built in 2001 and the installation is modern. The plastic pipes are special heating pipes, and they are well-insulated with foam, and I have less of a heating load altogether because my boat's hull is balsa cored and so warm and condensation-free in cold weather. The problems I have with my heating installation are two:

1. Very ineffective, noisy fan coils.
2. Primitive controls for the fan coils which does not switch the fans off when heat is not needed. In fact, I'm not sure that any thermostatic control at all is being provided.

I have a good heating guy on the Isle of Wight I'm going to consult about these problems.

I wish I had some passive radiators, but there really isn't anywhere to put them.

[Dockhead]

Originally Posted by sailorchic34

Dockhead has a hydronic diesel boiler with hot water piping serving three fan coils. A bit different then forced air heaters, which are also good systems.

Depending on where his water heater is and what height it is above the engine. it might be air bound. Which just requires that air be removed from the top of the system. Basic hydronics 101.

The calorifier is at the same level, or slightly below, the level of the engine. I guess the more important fact is that the connections to the calorifier are slightly lower than the connections to the engine.

I have assumed that the circulation is being blocked by air, since the hoses are run up over the fuel tank, which creates a high spot in the hoses higher than either engine or calorifier. I am guessing I need some way to get the air out at that point. I tried to solve the problem by disconnecting the hoses,holding the ends higher than that high spot, pouring in fresh coolant through a funnel, then quickly putting the hoses back on, and this worked one season. But this season it didn't work -- I guess I wasn't getting enough of the air out.

I am think that a simple manual bleed valve would be enough. I don't want anything which could fail open, because this is part of the main engine's fresh water cooling circuit, and a leak could disable the main engine. I wouldn't mind manually bleeding this thing from time to time.