Adding heating to boat

[colinroybarrett]

The boat is very well insulated, except for the window frames and glass (single glazed and alloy frames, no thermal break). Also the heater draws fresh air from the upper helm position, i.e. always from outside air.

Agreed, leaving a window or three open helps a good deal, but we still find considerable condensation on windows and frames.

We would appreciate any advice?

 

[Anonymous]

The eberspachers and webastos have a heat exchanger so the air outlet does not contain any combustion products or added water. Air from the cabin or a mix of cabin and outside air is passed over the heat exchanger, where it is heated. Since the temperature rises the relative humidity falls, so air that enters the heater at, say, 80% RH comes out at a higher temperature at, say, 50% RH. There is exactly the same moisture content per Kg of air, of course, but the air is 'drier' as the RH is lower. Have I helped or muddied the water? It's difficult to reply to technical queries when you don't know how technical the other person is /forums/images/graemlins/smile.gif

 

[savageseadog]

It might help if the inlet aitr for the heater (not the combustion air) was drawn from outside the boat or from a locker that lets air in from outside. Otherwise as another reply says the air and moisture pulled into the heater equals the air and moisture put out. The penalty is of course is that in cold weather you are expending energy in warming cold air so it won't get as warm. In my view moisture is as great if not a greater enemy than cold so get fresh air into the boat. Another approach would be to simultaneously dehumidify.

 

[colinroybarrett]

Lemain, thanks for this. I am pretty conversant with the Eberspächer, having had to perform major surgery twice on the unit.

I think our problem is that the unit is simply too large for the space it has to heat, it reaches the set cabin temperature very quickly, drops down to the ‘holding mode’ but then cabin temperatures continue to rise until the unit closes down completely on overtemp (cabin). As far as I can tell, there is nothing technically wrong with the unit; this is as it is intended to perform given the conditions.

Once the unit closes down, the cabin temperature drops; drawing in cold external, humid air overnight and the heater often re-starts early the following morning. It is only on very cold nights that the heater will stay on all night (and condensation is then much less). We do have a large expanse of glazing in our main saloon, which does not help the situation.

Thanks to all for the advice, we will just have to experiment some more this coming winter!

 

[charles_reed]

It's a pain.

Cutting all those holes for the air-vents is difficult.

Whilst the hot air heaters are quite useful for drying out a boat, they use power and diesel - if you intend to cruise and winter in marinas then a electric fan-heater is both more effective and infinitely lower in capital cost.

If you do intend to anchor all the time think about an all-fuel stove, easier to fit, far more cheery and burns driftwood.

If you do want to go with central heating go the whole hog and get the Eberspacher hot water system - it provides hot water, uses rather less diesel and infinitely less power and is far, far easier to fit.