Using Waste Heat

[Dockhead]

Originally Posted by tom1263

I saw such a system from "webasto" on the "Boot" at Düsseldorf, i mean it's a normal warm water heating system for bigger boats. The advatage of a system with calorifiers is, you storing heating energy, whether you need, or not.

Yes, I get that. Very elegant.

I don't think my calorifier is big enough to store enough to make a big difference, however. The original one was 50 liters -- so with a 50 degree rise of temperature it's storing about 10.5 megajoules of heat or a little more than 3 kW/hours. So 20 minutes or so of my Espar's maximum output. Bleh.

[goboatingnow]

Can't see it being anyway cost effective. I'd just run the eberspacher. Those things benefit by being run often.

Dave

[Dockhead]

Originally Posted by goboatingnow

Can't see it being anyway cost effective. I'd just run the eberspacher. Those things benefit by being run often.

Dave

Or use the immersion heater when I'm running the genset anyway.

That was my conclusion the last time I analyzed this question. Still, all that wasted heat down the drain bothers me -- so I'm having another go and the analysis.

[deckofficer]

On topic for "Using waste heat". Used to produce all our potable water from bringing sea water to a boil using the heat from the engines. Only trick was a reinforced chamber that could withstand being pulled to a vacuum so that water would boil at 180F.

[Dockhead]

Originally Posted by deckofficer

On topic for "Using waste heat". Used to produce all our potable water from bringing sea water to a boil using the heat from the engines. Only trick was a reinforced chamber that could withstand being pulled to a vacuum so that water would boil at 180F.

I presume this on a large commercial vessel, and not on your yacht

[deckofficer]

Originally Posted by Dockhead

I presume this on a large commercial vessel, and not on your yacht

Yes, but I don't know why it couldn't be scaled down. Maybe the vacuum pump would take as much electrical energy as a small RO watermaker.

[Stu Jackson]

Here's an example of extending the engine hw loop to the hot water heater.

Cabin Heater - C34

If you do this, you save engine waste heat. Dave's probably right about use it or lose it on the diesel heater.

[Jd1]

Originally Posted by Dockhead

Very cool -- that's one of the approaches I had in mind, but had never heard of anyone actually doing it.

I'm about half way there already since my existing Espar system does run fan coils as well as domestic hot water. I will probably be changing out the fan coils this winter, with something with thermostatic controls and quieter fans.

So does the coolant circulate through the Espar furnace without resistance, when the Espar is turned off? Or do you have to bypass it?

Do you have an additional circulating pump in the system, or do you use the standard Espar one?

Do you have a diagram of your system?

Thanks and cheers. I see you sail in a similar climate to mine.

I actually can't take credit for the setup. The boat came that way.
The coolant does circulate through the Espar (as far as I know) and as far as I know only the standard Espar circulator is used.
If you already have the Espar and all related plumbing, you are way more than half there - you only need to add the engine and/or generator heat exchangers into the return loop from the heating coils to the Espar. You will also need a seperate means of switching between the Espar heat or the engine/generator heat. That is as simple as a switch (or in my case a relay) that turns on the circulation pump when you want to recover engine/generator heat.
It should be a very easy upgrade.

[s/v Jedi]

The systems that I have seen are different than these diagrams. They are based on a single long loop, with just a by-pass valve for use during hot weather:

Start with the hydronic heater and it's circulation pump. This is the core of the system and designs show a loop all through the boat that have radiators and even forced air heaters. This all stays as it is, but just insert extra items in this loop, all in series:

- the coil in the water heater (calorifier for Brits I think)
- a heat exchanger for the engine
- a heat exchanger for the genset

So, the coolant circuit of the engine has an extra heat exchanger added. The other side of this heat exchanger is included in the big loop. Same for genset. I have seen die-hard installations that include an extra electric pump on the engine side of the heat exchanger. When you switch that on while another heat source is active, you warm up the engine for cold start.

The by-pass is simply a 3-way valve in the loop just before it enters the salon, followed by a pipe to a T at the location where the loop returns from the salon. This excludes all the space heaters from the loop.

[Jd1]

Originally Posted by s/v Jedi

The systems that I have seen are different than these diagrams. They are based on a single long loop, with just a by-pass valve for use during hot weather:

Start with the hydronic heater and it's circulation pump. This is the core of the system and designs show a loop all through the boat that have radiators and even forced air heaters. This all stays as it is, but just insert extra items in this loop, all in series:

- the coil in the water heater (calorifier for Brits I think)
- a heat exchanger for the engine
- a heat exchanger for the genset

So, the coolant circuit of the engine has an extra heat exchanger added. The other side of this heat exchanger is included in the big loop. Same for genset. I have seen die-hard installations that include an extra electric pump on the engine side of the heat exchanger. When you switch that on while another heat source is active, you warm up the engine for cold start.

The by-pass is simply a 3-way valve in the loop just before it enters the salon, followed by a pipe to a T at the location where the loop returns from the salon. This excludes all the space heaters from the loop.

Exactly! All the other stuff gets waaayyy too complex. The estimate of $3000 is also way out of line. Given the current setup, I expect that both engine and generator heat can be recovered for between $500 and $1000. Half that if you only choose one or the other.
To recap - engine coolant runs through a heat exchanger and back to the engine. Generator is exactly the same. your current diesel water heater loop gets cut and the secondaries of the two extra heat exchangers get inserted in series. A switch is installed to activate a circulation pump when the diesel heater is not on. There is the possibility that the existing circulation pump doesn't have enough oomph to push the hot water through all the heat exchangers, all the hot water space heaters and the diesel furnace. In that case you just upsize or add a second circulation pump in the loop.

[ssanzone]

i was JUST thinking that putting in a Y in my exhaust and looping PEX thru my bilge and mounted flush to the sole would give me the same heated floors that i have in my house.

is there any reason i cant user conventional baseboard forced hot water radiators on the boat? it is all the same principle... assuming i avoid actual freezing temps (the north east) i could very easily have a cozy main cabin by taking advantage of the settee and quarter berths...

what am i missing?

is it just the power to keep it all hot / moving?

-steve

[tom1263]

Originally Posted by ssanzone

is there any reason i cant user conventional baseboard forced hot water radiators on the boat? it is all the same principle...

No it's works fine, if you have a hot water circulation system. Here are some pics from an installation with an Car heater in a motorboat. You can also use an underfloor heating system...

[Captain Bill]

I did this with my boat. I got tired of freezing my butt off while I was heating the ocean. I have a bit of an advantage in that I have a catamaran on which only one engine was set up to heat water. I simply tapped the coolant loop on the other engine. I happened to get one of these on sale Heater Craft - Marine Heater Grill Face Unit Only Black, I needed a couple of fitting, some heater hose and a couple of valves. I put the valves near the engine so I could cut the system off if I got a leak somewhere. The only issue is the centrifical fan draws a lot of amps and is not exactly quiet. I have seen similar units with muffin fans and they were very quiet. Sailorchic has a point about the pump. My exchanger is located about 12 feet from the engine and 3 feet above it, which according to the instruction requires a boost pump. At idle the pump cannot circulate water through the system, but at 1200 RPM it starts to put out and is really cranking at 1800 rpm. The amps don't matter too much as I only use it when the engine is running. but if you rig it to run off of your water heater you may want to consider the muffin fan based units. Also if your heat exchanger is above the engine you will need to add a valve at the highest poing to bleed air and fill the system. You may also want to shut the valves before opening the pressure cap on the cooling system, though I have not found that to be a problem as air pressure easily supports a 3 foot high column of coolant. If the valve at the top happened to be leaking it would of course be a different story.

[Dennis.G]

Originally Posted by Jd1

...The estimate of $3000 is also way out of line. Given the current setup, I expect that both engine and generator heat can be recovered for between $500 and $1000. Half that if you only choose one or the other....

I think your cost estimates are low. A good quality SS shell and tube heat exchanger is going to be about $500 each by itself. Adding fittings, valves, brackets, hoses, valves and what not I think that the $3,000 figure might be on high end but not out of line.

Remember we are talking about a sailboat. How much waste heat is really available when it can be used? If this was a motor boat that was always running either main engines or generator it would be one thing, but I think any payback analysis on this installed in a sailboat would show this is not really worth the investment. Take a look at engine and generator run hours per year, figure what portion of those hours take place when heating is desired and figure on from there.

[Sea Frog]

Originally Posted by Dockhead

That's my Variant 3!!! Using the domestic hot water supply as a heat reservoir and exchange medium! So it's not just a crazy idea!.

If I am not mistaken, this is exactly a way Mar-IX suggests using it's Clima A/C systems. There was a diagram on their site. They have Espar hydronic built into A/C unit, by the way.