Active or inert boat heater.?

[noelex]

Prefer my Refleks, of course Used to stay lit constantly for days on end living onboard up in the freezing UK

I also love our Reflex heater. Very simple, quiet, nothing to go wrong or service.

There are specific installation requirements, so it can be difficult to retrofit on many boats, but if it is a possibility this is an excellent choice.

This photo was taken during construction:

 

[PetiteFleur]

If you go for a cheapy Chinese heater, don't forget that you'll pay roughly 1½ to twice the purchase price for all the additional marine fittings, ducting, copper fuel pipe, cable upgrade etc you will need. The hose clips supplied are rubbish for instance. My cheapy works well.

 

[black mercury]

Don't forget about Wallas. I have a 1.8 kw Wallas which i use as a night heater. Sits under the cockpit table with ducts going to the cabins. Uses less electric and fuel than the Eber, great heater but they are expensive. I use the old Eber when its really cold during the day. The point I would like to make is if you have a blown air heater, go the extra expense to insulate the ducting. I did both the Eber and the Wallas and the difference is huge.

 

[BabaYaga]

Now, we humans give off water vapour so if your heater recirculates the air in the cabin that vapour stays inside such as in a Taylors. If you have an Eberspacher that draws the air to be heater from the outside which in turn pushes some of the heated air that contains your vapour, you will get "even dryer" heat.

www.solocoastalsailing.co.uk

Thanks for the explanation. I read this as the Eber and similar blown air heaters take from the outside not only the combustion air but also the air to be heated and distributed around the boat interior. Correct? That would produce a drier climate perhaps, compared to the more moist, interior air being heated by a Refleks or solid fuel stove.
But some posters to this thread seem to make a point of the opposite being true?

 

[prv]

I read this as the Eber and similar blown air heaters take from the outside not only the combustion air but also the air to be heated and distributed around the boat interior. Correct?

Certainly they take it from outside the accommodation; I’m not sure how often it comes from directly outside. The intake port on mine isn’t ducted anywhere, so it will be drawing air from the cockpit locker it’s mounted in. Ultimately that might be coming in through the vent in the coaming locker above, but perhaps also around some of the pipes passing into the engine bay, or even through small gaps in and around the bulkhead to the heads compartment.

Pete

 

[jiris]

It depends on the installation. You can do it either way. Inlet for heated air from the inside is certainly more common and especially on a boat it can prevent a lot of problems. The outside inlet is used mostly in cases when the heater is also being used for cooling.
As for the combustion air - Ebers were always using the outside air as they were extremely sensitive to pressure difference between exhaust and suction port. Often there was a need to place both the port close together because just the pressure difference caused by airflow around the hull or car body could stop the heater from operating properly. In my experience the Chink heaters are not bothered by this and both of my heaters are happily sucking the combustion air from the inside now. Again, on a boat it simplifies the installation and prevent some ugly problems.
I would say the difference could be traced to a finely tuned combustion of the Ebers and I am sure if we properly analyse the heating, we would find the combustion of Ebers more efficient and precise. Not sure how big the difference is and if it makes a noticeable difference on the fuel consumption.

 

[Plum]

Thanks for the explanation. I read this as the Eber and similar blown air heaters take from the outside not only the combustion air but also the air to be heated and distributed around the boat interior. Correct? That would produce a drier climate perhaps, compared to the more moist, interior air being heated by a Refleks or solid fuel stove.
But some posters to this thread seem to make a point of the opposite being true?

If your Eber type takes it's heating air from the outside then you will have a dryer environment. In my experience that is the better option and certainly better with more people on board. I have both an Eber and a Taylors (drip feed diesel type). They are both good but the choice is more dependant on space, noise and energy consumption.

Www.solocoastalsailing.co.uk

 

[jiris]

If your Eber type takes it's heating air from the outside then you will have a dryer environment. In my experience that is the better option and certainly better with more people on board. I have both an Eber and a Taylors. They are both good but the choice is more dependant on space, noise and energy consumption.

Www.solocoastalsailing.co.uk

Something what shouldn't be overlooked making the choice: taking the heating air from the outside means higher fuel and energy consumption. Especially in a cold environment the difference can be enormous.

 

[lw395]

Something what shouldn't be overlooked making the choice: taking the heating air from the outside means higher fuel and energy consumption. Especially in a cold environment the difference can be enormous.

It's not beyond the wit of man to have a fresh air/recirculate control as cars do.
Personally I favour a 'wet' type eber which heatd water as well as heating the cabin via matrices.
Some extraction of stale air might be a good idea if you want to be economical at high latitudes.

 

[Lucy52]

Sorry to be thick but if the air outside is saturated, as in raining for example, then surely the air drawn in will contain moisture which will be heated and then distributed around the boat. No?

Or, any moisture in the air outside will of necessity be drawn into the boat. Tell me otherwise. Oh yes, it will then condense on colder surfaces?

 

[geem]

Sorry to be thick but if the air outside is saturated, as in raining for example, then surely the air drawn in will contain moisture which will be heated and then distributed around the boat. No?

Or, any moisture in the air outside will of necessity be drawn into the boat. Tell me otherwise. Oh yes, it will then condense on colder surfaces?

Thats not how it works. If you draw air in from outside at 0degC that is 100% saturated, then heat it to 20degC it will have a relative humidity of 26%. A good humidity level for comfort it 40-60% so the outside are you drew in to the boat is now at 26% and can therefore absorb moisture from the boat. They air is very dry. If you recirculate air that is at 70-80% RH it will not have the ability to absorb moisture from within the boat so you will get a higher RH in the boat and condensation on cool surfaces. If you heater is powerful enough to heat outside air up to say 35-50 degC then then that is the way to go. A nice warm and dry boat. It also means you can close all the hatches as you wont need any additional ventilation. Recirculate the air and you will need to crack a hatch for ventilation

 

[Lucy52]

Thank you, that is very helpful. I can't quite get my head around the idea that when drawing air into the boat from outside I can close all the hatches. The internal pressure would tend to restrict new air coming in so that I would have to allow some air to exhaust from the cabin. I believe heating engineers allow for so many air changes per hour, or you might end up rather drowsy or with a SAWB.

A solid fuel or oil burner stove will of itself produce a dry heat but will recirculate the moisture in the cabin the effective humidity dependant on the air temperature achieved. It will necessarily exhaust some air up the chimney and will in turn need to have some fixed ventilation for combustion.

The blown air heater is not much different, whether drawing air from the outside or recirculating cabin air, again the humidity will be dependent on the air temperature achieved. If drawing the combustion air from inside you would still need some form of cabin ventilation.

The choice of which is best seems to be about what it is practical to install, the convenience and utility for you, and an element of personal preference and the cost. What is preferred may be different for the same person in differing circumstances.

 

[geem]

Thank you, that is very helpful. I can't quite get my head around the idea that when drawing air into the boat from outside I can close all the hatches. The internal pressure would tend to restrict new air coming in so that I would have to allow some air to exhaust from the cabin. I believe heating engineers allow for so many air changes per hour, or you might end up rather drowsy or with a SAWB.

A solid fuel or oil burner stove will of itself produce a dry heat but will recirculate the moisture in the cabin the effective humidity dependant on the air temperature achieved. It will necessarily exhaust some air up the chimney and will in turn need to have some fixed ventilation for combustion.

The blown air heater is not much different, whether drawing air from the outside or recirculating cabin air, again the humidity will be dependent on the air temperature achieved. If drawing the combustion air from inside you would still need some form of cabin ventilation.

The choice of which is best seems to be about what it is practical to install, the convenience and utility for you, and an element of personal preference and the cost. What is preferred may be different for the same person in differing circumstances.

There is normally plenty of gaps around the main hatch for makeup air on a forced air heating system but if you need extra air you could crack a hatch a little. The drip feed heaters tend to need more ventilation as its passive heating. We used to point the dorade over the heads in to the wind and this gave lots of ventilation. It would be possible to have a dorade with a supply pipe to the bottom of a drip feed heater to feed it fresh air without drafts or a cold spot in the boat but it might take some engineering.

 

[Kelpie]

Don't the Dickenson or Sigmar heaters offer a balanced flue option?

 

[ffiill]

Active-needs a power supply-webasto, Chinese etc hot air heaters.
Inert-Refleks, Tay lors, etc
Active Chinese a little over £100 whereas it will cost you £500 upwards for an inert heater.
Which do you prefer?

Just reviving this thread
Diesel blown air great but what about the electrics.
Designed to heat a cab in the winter how to they respond to long periods of use before motors wear out.
Pricing per kW at £100 per unit compares favourably to domestic 20 kW burners.

Whilst refleks et al look good the £1000 ish price tag is silly.
Boat specific solid fuel again is overpriced compared to domestic stoves