Hot air or Hot water heating

[LittleShip]

I have the Thermotop heater on board Little Ship, It has one towel rail in the heads and one radiator fitted in the V berth. The main cabin has a Matrix which works very well. I also have the ability to have Heating, hot water or both by just turning a knob.

Personally I think that it's the owners preference but I wanted to be able to get hot water when at anchor and as my engine doesn't provide hot water (again my choice) I needed to go with a wet system.

If I was installing again it would still be a wet system for me.

Tom

 

[David2452]

It really is a shame the Dual Top RV unit has not been developed for marine use, or indeed for non dealer fit even on RVs, it could prove ideal in the right circumstances.

 

[John100156]

Don't get me wrong guys, I really like both air and water systems. As long as the system is well designed and properly installed that's fine and it should work very well. Sad fact is there are a hell of a lot of heating systems, on boats and commercially, that are not!

We are all seeking I hope to put forward the various benefits and drawbacks for both air and water systems, so that the OP can make an informed choice.

Even experienced designers can get things wrong. At the end of the day us engineers can tell the end-users until we are blue in the face, that their systems are working perfectly - look the temp is within half of a degree, but if the end-user doesn't like it, we have failed, despite all the science!

I am sure (hope) the OP has benefited from this discussion and the arguements we have all taken the time to table.

 

[David2452]

Exactly right John, in the end its all about managing customer expectations, but when it comes to HVAC the expectation that most needs management among small boat owners is cost expectation.

 

[[2574]]

I have both air and water systems on board a 12m yacht. I wanted a water heater for hot water without the need for running the engine. So I fitted an Eberspacher D5W which runs the calorifier and 6kw of fan matrices. We tend to use this in the morning to heat water for showers and also warm the boat through. We then switch to the D3LC air heater for the evening session as we don't need hot water. So I would say its impossible to say that one is better than the other as they have different purposes and they both excel in their intended purpose.

 

[John100156]

Totally agree with that.

We are starting to see some high velocity duct systems entering the commercial market, that is, very small ducts/pipes conveying much hotter air that is mixed at point of delivery with room air.

All the normal considerations, fan power, insulation, attenuation, mixing but I also wonder if a system designed such as this might also work on small boats.

I suppose in essence it already does with the Eber, which on my last boat I thought worked very well, albeit not perfect, it was acceptable and I must say very reliable..... Oh well, horses for courses and all that....

 

[Scarboroughsloop]

Is it possible to get the heating and water system to work independently of each other? I'm looking at the Thermotop but it would be a pain to have to heat the radiators in the summer just for the sake of some hot water.

 

[Playtime]

Is it possible to get the heating and water system to work independently of each other? I'm looking at the Thermotop but it would be a pain to have to heat the radiators in the summer just for the sake of some hot water.

In theory yes.

You can design the system so that the radiators/matrix heaters can be isolated from the calorifier by a couple of quarter turn valves.

This might not be the most cost effective routing for the pipes, of course.

 

[LittleShip]

Is it possible to get the heating and water system to work independently of each other? I'm looking at the Thermotop but it would be a pain to have to heat the radiators in the summer just for the sake of some hot water.

Post 21.... I also have the ability to have Heating, hot water or both by just turning a knob.

You no read grasshopper

This is the valve I have

and this is where you can hopefully get one.
http://www.ebay.co.uk/itm/REGA-MANUAL-DIVERTER-VALVE-22MM-3-WAY-VALVE-/251169707232

Tom

 

[David2452]

Is it possible to get the heating and water system to work independently of each other? I'm looking at the Thermotop but it would be a pain to have to heat the radiators in the summer just for the sake of some hot water.

Yes, the simplest way and the way most narrowboat live aboards do is just turn the rads off at the valve (not the balance lockshield one that you have used to balance the system) but leave the heads towel rail open and only run the heater at full bore and long enough to heat the calorifier there is no need or really any benefit from doing anything else. If you are looking at Thermotops then calculate if the TTE at 4kw may be better suited to your loading than the 5kw TTC.

 

[Talbot]

I have a hot water system (Milkuni) - much easier to retro-fit as the pipes are smaller and easier to lag so that te heat goes where you want it rather than being wasted in places you dont want to heat.

It also provides lots of nice hot water for the calorifier without haveing to use the 240v

A lovely warm boat witjout quite the same noise level as an air system (and I have fitted one of those in a previious boat).

 

[owen-cox]

All great in theory, but you've missed the point. A hot water system uses more power than a hot air system. As an example, an Eberspacher D4 air heater uses 40W. The equivalent Eberspacher Hydronic 4 water heater uses 48W, plus the power needed by the matrix fans.

The power is only that much when the glow plug is on in the first few minutes after the heater is hot it drops considerably. Most matrix fans only have biscuit fans that are so small as to be almost negligible and the fan that is in the air units is swapped for the water circulation pump which is a very small centrifugal pump probably 10w max but it wont be using 100% of 10w unless there is a lot of resistance in the circulation circuit. net difference would be very small. You also could heat your engine circuit and calorifier so probably saves a ton in engine wear on start up and electricity to heat water when in a marina.

 

[prv]

You also could heat your engine circuit and calorifier so probably saves a ton in engine wear on start up and electricity to heat water when in a marina.

Should definitely have a connection to the calorifier (though whether it works out cheaper than marina power depends how they charge for it) but I've seen an article advising against routinely pumping hot water through a stopped engine:

We would recommend removing your Ardic heater from the engine circuit totally. If the heater is switched on and the engine is not started then not only is the engine acting as a big heat sink (approx 3kW) but if the engine heats up and cools without running, condensation builds up within the engine, if the engine is not run for some time the oil can run away from the top end causing excess wear when the engine is eventually re started.

The other issues are opening your engines cooling circuit to the entire heating circuit adds many more leak possibilities, removing too much heat from an engine will cause it to run inefficiently, if the water returning from the heating system is too cool it can create excess cylinder bore wear and deformation on the first cylinder.

Generally the engine header tank is also lower than the highest component in the heating system leaving half the system full of air and running inefficiently also making it very awkward to bleed and keep bled.

No personal experience as I've never had a heater of either type before

Pete

 

[LittleShip]

the simplest way and the way most narrowboat live aboards do is just turn the rads off at the valve but leave the heads towel rail open and only run the heater at full bore and long enough to heat the calorifier there is no need or really any benefit from doing anything else. If you are looking at Thermotops then calculate if the TTE at 4kw may be better suited to your loading than the 5kw TTC.

Your suggesting turning off all the radiators (1-2-3-4etc) rather than fitting one valve that will do all of them at once............ The valve I posted will allow you to set the system up with more or less heat to the rads or cylinder depending on what you need.

I do agree with fitting the 4Kw heater to keep the loading up.

Tom

 

[David2452]

Your suggesting turning off all the radiators (1-2-3-4etc) rather than fitting one valve that will do all of them at once............ The valve I posted will allow you to set the system up with more or less heat to the rads or cylinder depending on what you need.

I do agree with fitting the 4Kw heater to keep the loading up.

Tom

If fitting from scratch then yes, incorporate a valve for the calorifier and heads towel ral, but I thought this was PBO, surely nobody here would spend money on a valve they can do without?

 

[pvb]

The power is only that much when the glow plug is on in the first few minutes after the heater is hot it drops considerably.

Not true, the figures I quoted are the normal running power consumption. They take much more current when the glow plug is on.

 

[machone]

Looking for radiators/heat exchangers for my water system I'd really like trench heaters for under the floor (http://www.jaga.co.uk/products/trench/micro-canal/). What sort of output/heat exchange do I need for a thermo top C? What does a normal small radiator put out?

Thanks

 

[Talbot]

Looking for radiators/heat exchangers for my water system I'd really like trench heaters for under the floor (http://www.jaga.co.uk/products/trench/micro-canal/). What sort of output/heat exchange do I need for a thermo top C? What does a normal small radiator put out?

Thanks

I have Heater Matrix Kalori with twin speed fans as the primary heater matrixes running from a Mikuni MX60 water heater. This also heats the water in my calorifier (instead of a take off from the engine)

 

[David2452]

Check the pipe bore first, anything under 12mm could cause issues, the TTC is rated at 5.2kw so look for a total loading of around 7kw quoted, this is because the quoted numbers are not acheavable with a diesel boiler as fitted to vehicles and boats, (larger PJs aside) they run at a lower temperature and flow rate to that used in determining radiator KW so can be misleading.