Hydronic heating. cabin/water

[transmitterdan]

Running radiators in series is not as bad as it sounds. But it depends on the length of the runs. Paralleling long runs makes for a lot of hose, water and weight.
Yes, you will need a header tank for expansion.
Our system uses a fixed resistor and form C switch for high/low speed operation of the radiator fan. This is not terribly inefficient and super reliable. I would not recommend rheostat or PWM controllers (too complex).
Note that if radiators are plumbed in series then lower fan speed on the first radiator will allow more heat to make it to the second radiator. So setting low fan speed right is important for equalizing the heat output.
Have an experienced person look over your design. It is easy to screw up the water paths. Also, don’t forget about air bleed devices at the right spots.
I would not run the hydronic heater through the calorifier. Things will get complicated with engine water mixed with hydronic heat system. You may end up overheating engine. There are dual loop calorifiers but they are rare.

[bcboomer]

The heat exchangers like these:https://www.amazon.com/Duda-Energy-H...4938594&sr=8-6
are cheap and effective.
We find it nice to have hot water available after a day on the water and, in the shoulder seasons, it's nice to have a warm cabin without having to burn more fuel. We're in an area that generally requires some motoring. YMMV.

[richwest3]

I second the notion: I wouldn't put the calorifier in the hydronic loop. Instead, we used a simple little heat exchanger for our hot water system. The unit we used was this: Webasto motor home plate heat exchanger with mixing valve 4111209A. We have hot water about three minutes after turning on the heater.

There's more on our installation here: https://twoatsea.com/i-took-a-shower/

[GILow]

Originally Posted by bcboomer

The heat exchangers like these:https://www.amazon.com/Duda-Energy-H...4938594&sr=8-6
are cheap and effective.
We find it nice to have hot water available after a day on the water and, in the shoulder seasons, it's nice to have a warm cabin without having to burn more fuel. We're in an area that generally requires some motoring. YMMV.

As John noted, the problem with those heat exchangers is you need the furnace running for them to work.

If you build this system the way John designed it the furnace does not need to be running to have a shower or do the dishes.

I’ve been running John’s design for a few months now and it really is brilliant.

[GILow]

Originally Posted by richwest3

I second the notion: I wouldn't put the calorifier in the hydronic loop. Instead, we used a simple little heat exchanger for our hot water system. The unit we used was this: Webasto motor home plate heat exchanger with mixing valve 4111209A. We have hot water about three minutes after turning on the heater.

There's more on our installation here: https://twoatsea.com/i-took-a-shower/

John’s design gives you hot water on demand. No delay.

[Dogscout]

Okay; I will plumb in parallel and just looked up PWM motor controls and yep that look simple.

I already have the calorifier so I wanted to use that instead of a plate heat exchanger to heat the water. I was thinking that leaving the engine connected to the calorifier would capture that waste heat so I could still use that for hot water when I did not need the webasto to heat the house. And connecting the webasto to the calorifier so on cold days hanging at anchor I would not need to run the engine to get hot water. I wish the calorifier had two loops to add heat.

So for now I will just plumb the webasto for heating the house and perhaps add a plate heat exchanger at a later date. That way the whole thing stays separate from the engine.

[GILow]

Originally Posted by Dogscout

Okay; I will plumb in parallel and just looked up PWM motor controls and yep that look simple.

I already have the calorifier so I wanted to use that instead of a plate heat exchanger to heat the water. I was thinking that leaving the engine connected to the calorifier would capture that waste heat so I could still use that for hot water when I did not need the webasto to heat the house. And connecting the webasto to the calorifier so on cold days hanging at anchor I would not need to run the engine to get hot water. I wish the calorifier had two loops to add heat.

So for now I will just plumb the webasto for heating the house and perhaps add a plate heat exchanger at a later date. That way the whole thing stays separate from the engine.

How similar is your system to John’s design documented at the start of the thread?

[Dockhead]

Originally Posted by Dogscout

Okay; I will plumb in parallel and just looked up PWM motor controls and yep that look simple.

I already have the calorifier so I wanted to use that instead of a plate heat exchanger to heat the water. I was thinking that leaving the engine connected to the calorifier would capture that waste heat so I could still use that for hot water when I did not need the webasto to heat the house. And connecting the webasto to the calorifier so on cold days hanging at anchor I would not need to run the engine to get hot water. I wish the calorifier had two loops to add heat.

So for now I will just plumb the webasto for heating the house and perhaps add a plate heat exchanger at a later date. That way the whole thing stays separate from the engine.

We have separate loops for hydronic circuit and engine circuit in our calorifier, and that is the way it is normally done over here.



If you already have the calorifier and it has only one loop, and you don't want to change it (they have somewhat limited life, so if it is old, I would consider changing it), then you could put in a heat exchanger to transfer engine heat to the hydronic loop.


I would not want to be without having the engine as a source of heating the calorifier myself. It is really nice to reach an anchorage or harbor after a long cold sail with a tank full of hot water, without having to fire up the furnace ahead of time.

[GILow]

John’s design did not use a calorifier for the holding tank. Not sure if Dogscout is thinking of recreating John’s design or the more traditional design.

But, point taken about the engine heat being a nice bonus on arrival.

Personally, I never motor, and the buffer tank holds heat for over 24 hours, so the engine heating ability is totally academic to me. And it’s a matter of remembering to flip a switch for the Webasto to start heating the buffer tank in a few minutes, so if it has somehow become cold, there’s not much to do to warm it.

[Dogscout]

So my thoughts do follow the design noted in the quote below except I have the existing calorifier instead of the buffer tank which actually sounds to be about the same thing. I can keep my calorifier on the engine loop or put it on the cabin heat loop. With all the discussion about having enough mass in the system, I considered putting the calorifier on the cabin heat loop.

Conversely I can leave the calorifier on the engine loop and use a plate heat exchanger on the cabin heat circuit to have an additional hot water source. I would like to keep from having valve things on and off all the time.

Question; Is a header tank or pressure tank needed in the cabin heat system?


[QUOTE=ColdEH;1871604]

The coolant plumbing goes as follows , out of the heater , to a air markup unit which has a large fan over a large heater core and has three air outlets in it , then to the forward cabin were there is a small heater core and fan , then to mid ships port side were there is another heater core and fan , then back to the ten gallon air/buffer/water heater , then back into the webasto . Lots of mass in the system . No short cycling, no carbon build up.

I always have the coolant doing the whole system ,no valves , I just control the fans on the heaters. They are on another thermostat, so if I choose to heat the cabin I just turn the fans on and when the coolant in the system hits a certain temperature they turn on the fans , I get hot water for free because it always travels thru the buffer tank.

[QUOTE]

[GILow]

I suspect your system is quite different to John’s unless you built it yourself. John’s design works in reverse to any commercial system I have seen.

But anyway, I think an expansion tank will be wise. Mine uses about 250 ml of expansion between hot and cold states.

To be clear though, my system is NOT pressurised. There should be no need for pressurising, at the temperatures involved. Why add the risk?

[mikedefieslife]

I use a Webasto ThermoTop C.

When it's not out of service it works well to heat my small boat. Two household sized single radiators and a towel heater in the bathroom/head. At less than 6kw I would say it is a little underpowered for extreme temperatures, but works well in UK/Spanish/Greek winters.

Since the raw water cooled engine cannot heat water, this unit also feeds into the heat exchanger of my calorifier. 60-80c water when needed. Not bad. I have an aftermarket ECU on mine. It seems to produce more heat, but also use more energy.

Problems I've had so far, are the gauze in the combustion chamber burning. Only £4 to replace but a bit of time and effort. Worn glow plug £80 to replace. Water damaged original ECU.

These units are expensive brand new, but can easily be bought on ebay for under £300 (almost new) to less than £100 for grubby one pulled from a car. In a bigger Cat, in lieu of anything better, I'd probably run two.

[Fendell]

Originally Posted by DavefromNZ

I have the Eberspacher 5Kw diesel heater (almost the same as the Webasto). I added a 75ltr dual coil calorifier (hot water tank) so I have heating from the engine, electric and from the Eberspacher.

The attachment shows the flow layout from the Eberspacher through the brazed plate heat exchanger (attachment), through the calorifier and on to the fan heaters in the cabin.

From cold I will have nearly continuous hot water in about 15 mins. The water flow rate is up to 9 ltrs/min. Worse case and high usage I get just warm water. Cabin heaters work very well.

Must fit a tempering valve and VERY important to have an expansion tank. I think mine is 8 ltrs.

Hi Dave, Just going back through your system design (thanks a heap for doing up a drawing by the way, makes stepping it out easy!) got a few questions, first is what size is/was the electrical element, and does it have enough balls to heat the hydronic/air heaters loop just on Electric power?

Also do you think if you used another heat exchange with the engine heat, and tapped in series between the Espar and the existing H.EX in your drawing it would heat the air heaters enough?

[DavefromNZ]

Hi Fendell,

Most elements are say 1KW. My Dual Coil Calorifier had the option and so I went with the 3KW. This element is just to heat the hot water clarifier and so there is no way of using it in the Eberspacher coolant loop.

I would expect that the engine coolant heat would be as high as the Eberspacher and so maybe you could plumb it in. But that would mean running your engine to heat the coolant circuit just to heat the cabins which is a terrible waste. Just run the genset and plug in an electric fan heater would be more efficient.

Cheers
Dave

[Fendell]

Originally Posted by DavefromNZ

Hi Fendell,

Most elements are say 1KW. My Dual Coil Calorifier had the option and so I went with the 3KW. This element is just to heat the hot water clarifier and so there is no way of using it in the Eberspacher coolant loop.

I would expect that the engine coolant heat would be as high as the Eberspacher and so maybe you could plumb it in. But that would mean running your engine to heat the coolant circuit just to heat the cabins which is a terrible waste. Just run the genset and plug in an electric fan heater would be more efficient.

Cheers
Dave

Thanks for the reply. with a 3Kw element heating the water in the calorifier, and with more heat exchanger in the calorifier do you think you would get enough heat transfer from the hot water to air handler loop?

The end game is to generate enough heat for all the consumers in the system from 3 different sources, Engine (while motoring), Electric (while plugged in) and Ebers (while on the pick).

Disclaimer: Im still a few years away from ownership, so this is all hypothetical but with a ship engineering background this system interests me so appreciate you taking the time discussing.