Heaters - Air or Water??

stefan_r

stefan_r

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Southampton & Greece (Chios)
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Interested in getting heating on board and was about to go for an Eberspacher air unit (and all the cutting of big holes) when a local bloke suggested going for the Eberspacher Hydroponic range which use hot water circulated around and then blown using a fan.

I have a calorifier so don't need hot water but the idea of running 22mm pipes around the boat is a lot more appealing than cutting 100mm holes in every bulkhead on a 46 footer!!!!

--Has anyone used this system for heating?
--Is it noisy running the fans at night (is it effective without the fans running???)?
--What efficiency issues are there?
--Any other thoughts??

Cheers
Stefan

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Go for water...

...I suggest!
At least if you intend to use the boat when its really cold. If you only need the system for the occasional cold evening, or for drying up the interior on a rainy day a sytem heating the air might be a better choice, despite the large holes to be cut.

The pros for a water heating systems are:
Smaller holes to cut through bulkheads etc.
Hoses can be led under bunks etc. making them nice and dry.
Heat more evenly distributed.
With an heat exchanger the engine can be used as heat source when motoring.
A mains heater can be plugged into the system.
A heat exchanger for heating tap water can be used.
Quiter. (Exept when using fan-aided radiators)
In most cases less current drain.

Cons are:
Takes longer time to heat up.
Airlocks can be hard to avoid, troublesome bleeding.
More expensive.

I live in Stockholm and use to sail as long the ice situation allows.
I have a 9 kW Webasto heater running on diesel with the addition of a heat exhanger plumbed into the engine and a 2 kW AC heater in my Moody 42.
I have a mix of 3 fan assisted radiators and 15 passive radiators. The former are used only when arriving to a cold boat or when sailing with main hatch open. There is about 60 metres of hose in the system and I have added an additional pump to ensure good circulation.
I also have a 80 litre holding tank in the system. This ensures that when the boat has warmed up and the thermostat switches the heater off, the hot water will continue to circulate and giving away its residual heat for a long time before the heater goes on again.
Normally the fans are off and then the system is really quiet, with the heater under the cockpit.
I been living on board when temperature has been below -20 and having +20 under deck.


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Hi,

I have the blown air Eberspacher (3 outlets) which I think is pretty good and certainly warms up the cabin nicely. The drawback is that it does make some noise during the warm up stage but once warm is quite quiet (it regulates itself so once started it doesn't keep cycling on and off). The only drawback I can see is that you do need to cut some rather large holes in the bulkheads for the ducting.

Advantages are, no chance of water leaks, no chance of water freezing, no corrosion to worry about, each duct output is easily controlled (uses much the same fitting as a car), very fast warm up. The current drain isn't too bad, I would have thought less than the water pump and blown radiators on a water system. There is no maintenance to do on the system.

Currently our system recycles the air in the cabin and heats it. I think it would be good to have the option of bringing in fresh air from outside to dry out the boat if is is particulary damp. Should be quite a simple mod to do. A useful feature on our boat is that one outlet is in the wet hanger in the heads compartement. As the heads are vented, the moisture is not retained.

Good luck with your choice, it certainly nice in cold weather.

Poggy

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have just fitted an eberspacher to a beneteau 351, only one outlet to the saloon, had to drill three bulkheads 60mm holes. the corrugated pipe thru the aft port cabin warms that lovely and there is enough heat from the saloon to heat the forward and aft stbd cabin. only prob with the water heating is that you will draw 2amps for the diesel heater continuous plus some for the fans on the heater matrixes. webasto do a heater matrix for about a £100 which you can plumb into the engine cooling system or piggy back onto the calorifier
stu

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Re: Go for water...

I have had both fitted on different boats my current boat has Eberspacher Hydronic 5Kw with 3 outlets fitted. I personally would never go back to the air system. Hydronic is easy to install (2 weekends) very quiet in operation and each outlet is themostaticaly controlled so no hot or cold spots, with the added advantage that if at anchor you do not have to run the engine for hot water.
It might be more expensive but you get what you pay for.

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Amount of radiators

These radiators are rather long and narrow, a type usually seen in coaches. I have 3 short ones in the forecastle, one long in the second sleeping cabin, 3 in the owners cabin, one in each of the two toilets and 7 in the deck saloon. Actually this ends up in 16, not 15!
By keeping the radiators rather short and instead spread them out evenly instead of having fewer bigger ones, the result is much more evenly ditributed heat, which also keeps the condensation under better control. The biggest sources of condensation are the large windows in the deck saloon, these should really have been double-glassed. A project for the future!

I agree, if the heater mostly will be used during chilly summer evenings and for drying the interior in a rainy day the air heater probably will be a simpler system.

We usually sail as long there is no ice, which in Stockholm normally happens between March and January.
We also use to also live on board for a weekend now and then during January - March when our boat is stuck in the ice, with temperatures staying well below 0, often down to -20.
This puts a different demand on the heating system!


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