Hot Water Heating/Calorifier/Engine Options/ideas

[SHUG]

This may be suitable. Has anybody used one of these heat exchangers.
http://www.asap-supplies.com/brands/hotpot/hotpot-cabin-heater-722112

 

[rob2]

A twin coil calorifier is the answer to your prayers! One coil is used for the engine circuit and the other for the Diesel heater circuit, so no interaction except that they both heat the hot water, whilst the Eber could also run a few radiators or matrices as well. It doesn't make the two inputs directly interchangeable, although if you need heating whilst motoring, at least the calorifier won't be loading the circuit when you fire up the Eber and I doubt you'll really mind spending a little on heating the cabin. Alternatively, you have a tank of hot water already - so fill a HW bottle! Much underated.

Rob.

 

[jdc]

This may be suitable. Has anybody used one of these heat exchangers.
...

We have a heat exchanger in parallel with the calorifier, not the model in the ASAP catalogue but a Mikuni Silencio which is the same idea. We wouldn't be without it, but then we cruise the arctic about 1 year in 2, and cruise NW Scotland in between. It's certainly worth having as well as the Eberspantser/Webasto/Mikuni system: when motoring along gently - as is often required for extended periods in high latitudes - the core of warmth below is well worth having for free.

There was some question about it cooling the engine too much. Oh for some numeracy in this forum: an engine, the most efficient in the world, will run at about 40% efficiency (it's the second law you know, https://www.youtube.com/watch?v=VnbiVw_1FNs), ie about 1.5x as much goes into the cooling system as into the water. What drive is required at say 5kts? About 7kW for our 42'boat, so 7 x 1.5 = 10.5kW is available as heat. This is huge compared to the maximum output from a radiator. It won't over cool the engine even were the thermostat to be broken!

I'm not at all sure I'd try to combine the two systems however; I like the idea of two completely independent (apart from running out of diesel that is systems which gives some redundancy/fault tolerance.

 

[vyv_cox]

There was some question about it cooling the engine too much. Oh for some numeracy in this forum: an engine, the most efficient in the world, will run at about 40% efficiency (it's the second law you know, https://www.youtube.com/watch?v=VnbiVw_1FNs), ie about 1.5x as much goes into the cooling system as into the water. What drive is required at say 5kts? About 7kW for our 42'boat, so 7 x 1.5 = 10.5kW is available as heat. This is huge compared to the maximum output from a radiator. It won't over cool the engine even were the thermostat to be broken!

Very true, but it is well known that fitting a calorifier to a small single cylinder engine will result in a large increase in the time it takes to achieve its maximum coolant temperature from cold, and in some cases that temperature will be reduced permanently. Probably more true of raw water cooled engines than indirectly cooled ones, where the coolant temperature set by the thermostat is already somewhat low. Excessive bore wear may well result from low coolant temperature.

 

[NormanS]

I have a deck saloon, so if motoring, I can helm either from outside or inside. When motoring in cold condition, some heating within is very welcome. My engine is an VP MD22, which already gives some of its waste heat to a calorifier.

To get some heating from the engine, I merely got a heater matrix from a Transit van, from a scrappy for a tenner, and connected it to the supply to the calorifier. Some ducting and an in-line fan, gives me plenty of heat for the saloon. I have no way of measuring the heat output, but I would put it at no less than 3kw. Taking out this extra heat has had no measureable effect on the engine operating temperature.

There would, of course be nothing to stop me from using the Eberspacher, when underway, but I like the idea of using "free" heat which would otherwise go to waste. I am amazed that this is not standard practice on boats. When did you last have a car without a heater?

 

[mattnj]

Hi Again,

Thanks to all (especially Vyv for the eber plumbing options)
Having thought about it, I have bought a Webasto from a Rover 75 (£65) thanks to skipper_stu for the tip! and am going for the following plumbing, unfortunately the eber manual is geared towards pre-heating the engine which I don't think Im too interested in. The 45deg mixer valve is there there (a) as I have one kicking around (b) so the calorifier is prioritised, so nothing circulates round the heaters until the return from calorifier is > 45degC

I am going for 3 of these heaters:-

http://www.ebay.co.uk/itm/290970793472


Before I start plumbing it in, thought I would throw it to the wolves for any comments.....

Undecided on 16mm bore coolant hose, or 15mm or 22mm heating pipes for the pipe, any thoughts?

I may even try one of these inline too....so it runs of the 230v too:-

http://www.ebay.co.uk/itm/200976099197

View attachment 45649

 

[mattnj]

Ive just been reading my own post again....and thought.....is it actually a good idea to heat the engine? Its in the middle of the boat and a pretty decent size lump of a radiator!

Maybe I will re-jig so it heats the engine too.

 

[vyv_cox]

The output of those matrices is described as 4.25 kW, in which case three of them plus a calorifier plus heating the engine is going to tax the abilities of a Webasto heater's 4 or 5 kW quite considerably.

The trend in today's caravans is not to have any blown matrices. Instead they have finned tube radiators placed all over the living space. My son's van is like this and he speaks very highly of the rate at which the interior warms up.

 

[lw395]

I had a hydronic system on one boat.
I fitted valves to stop the engine heating the eber and v/v.
The biggest problem I had was effective matrices to get the heat from the water to the cabin air. I started with heater rom a Polo, but the fan from that drew 16A at full chat!
Computer fans struggle to push much air through the fine fins of a heater matrix. There were issues with expansion vessel capacity, and on cooling, air tended to enter via the wrong place, leading to coolant being pumped out. Sorted that in the end.
I found it was actually best to let the eber heat the engine, as otherwise it was prone to short cycling which they don’t like. The engine heat is like a storage heater, it goes into the air space of the boat slowly.
It is nice to be able to get hot water, but for air heating, unless you have space for ‘normal’ rads, the matrices and airflow need a lot of thought and can be costly. I think there is better stuff on the market now than 10 years ago? Still not easy to retrofit to many yachts perhaps?
Like many yacht systems, there aren’t right or wrong answers, you need to define exactly what you want from the system.
As an aside, I have a friend who takes Land Rovers to silly cold places, his has both air and water eberbastos fitted.

 

[lw395]

The output of those matrices is described as 4.25 kW, in which case three of them plus a calorifier plus heating the engine is going to tax the abilities of a Webasto heater's 4 or 5 kW quite considerably.

The trend in today's caravans is not to have any blown matrices. Instead they have finned tube radiators placed all over the living space. My son's van is like this and he speaks very highly of the rate at which the interior warms up.

4kw is a lot of air flow with a delta T of say 80 to 30degC.
The engine does not lose heat that quickly, it stores it and damps the system. It slows the warm up, for sure, depending on how the thermostat controls flow through the engine.
And if you have even a slight diesel or oil leak, it smells.

 

[pyrojames]

I had computer fan blown matrices in the boat when I first fitted my Webasto Thermo Top, 6 in total, which were fine when the Webasto was running, but the boat colled quickly when the Webasto turned off. The Webasto also didn't run at full output for long as the matrices wouldn't dump the heat in to the cabin fast enough. In the end I changed to domesetic rads. The Webasto now heats them up nicely over an hour, and then they stay warm enough for another hour or two. It cut down on running time and power consumption. You just need enough space for the rads..

 

[mattnj]

The output of those matrices is described as 4.25 kW, in which case three of them plus a calorifier plus heating the engine is going to tax the abilities of a Webasto heater's 4 or 5 kW quite considerably.

Could go for these at 1.7kw, I was assuming bigger is better (running slower with less temp drop)

http://www.ebay.co.uk/itm/271384723937

 

[vyv_cox]

I was assuming bigger is better (running slower with less temp drop)

There is certainly some logic in that approach. I went the opposite way, with one of these http://www.t7design.co.uk/index.php?main_page=product_info&products_id=189. I sent the first one back as its perfomance was so poor. The second one was no better. Very small heat exchanger with quite high airflow doesn't work. There is no way it was delivering 2 kW, less than a 1 kW electric fan heater was my estimate.

 

[mattnj]

All depends on the ambient temp and the water temp, at -10deg with boiling water it probably manages 2.2kw

i've ordered 2 of the 4.7kw ones, and will give it all a run up in the garage with the calorifier before I start installing it, I will report back.

 

[pvb]

All depends on the ambient temp and the water temp, at -10deg with boiling water it probably manages 2.2kw

i've ordered 2 of the 4.7kw ones, and will give it all a run up in the garage with the calorifier before I start installing it, I will report back.

What current do the 2 fan units need? Wouldn't a simple air heater be more efficient?

 

[mattnj]

What current do the 2 fan units need? Wouldn't a simple air heater be more efficient?

That doesnt give hot water....or free heating when engine is running.
Ive had air on the last 3 boats and not really used it...so trying a water system this time.

Will need more current....but im not too fussed about that.

Plus with a webasto from a rover 75 it should be much cheaper.

 

[Cloven]

Hi,

Is it possible/practical to have a hot water (eber hydronic) system connected inline with coolant system for hot water and heating for free (when engine is running) and on the eber hydronic when the engine is off?

Thanks

Exactly what my boat has. Dual coil calorifier, engine works through one, Eber Hydronic through the other plus also a 240v element for when on shore power. Eber has the option of just water heating, just cabin heating or both via a simple system of valves.

 

[David2452]

Except that wouldn't do what I asked for....which was run heating off the engine when that's running.



mmm, read that, no mention of integrating with engine cooling (other than a few words of not recommended) not to worry, I will keep searching.

Do not worry about integrating with the engine cooling system, that's what they are designed for but you need to arrange the system so that it does not circulate around the motor (except possibly for a reduced wear or easier cold start) The major drawback of integration is that the high concentration of antifreeze is less efficient at heating, we normally use 15 to 25% on heating systems.