Anonymous wrote:

The Poor Man's Webasto

Len,
Here is a cheap way of circulating heated air...

Arne

I like it. I would also note that the "Taylor paraffin heater" pulls cold air (and CO2) from the cabin floor and exhausts it thus pulling warmer air from higher up towards the floor. Good job.

Anonymous wrote:

Len wrote:

[..] (dedicated air intake for heaters is dangerous in my opinion) [...]

Will you please explain why you think this is dangerous? I expected that an external air intake for the combustion chamber would be a good idea -- for preventing cold drafts.

All flues eventually gets holes in them. With outside air going into the burn chamber direct you are now pumping exhaust into your cabin (which being sealed will be at a lower air pressure than the flue gas). Contrary to popular belief... the cold drafts are actually a plus for someone who wants to stay healthy. The minimum required fresh air in a new house is one exchange per hour (one exchange means all the air in the living space is replaced in the hour). Note the word minimum, that is the amount that keeps biulding code people from getting sued. Of note, those who use rats for testing have found they need to replace the air the rats use with a 8 full air exchanges per hour to keep them healthy enough to test on. So I expect that 1 air exchange per hour is not keeping people healthy but it does keep them from dying. In a new "energy efficient" house, they use a heat exchanger that warms the incoming air from the exhaust air to help get around this. I suppose this is possible on a boat too but getting air movement that made sure all the air in the boat actually moves rather than just replacing a small local bit a air over and over would require ducting and fans etc. Is it really worth the space and time? The small space of the boat cabin is always collecting smelly as well as odorless but poisonous gases. Breathing even produces poisonous gas but so does cooking and the head. A working heater flue system is like a free exhaust fan. If you don't use it, you then need to provide your own "draft" for ventilation.

Staying warm at the expense of ones health does not seem reasonable but being able to advertise a higher percent heat kept in the living space does sell that living space and system even when after bought the windows must be left open to keep from getting head aches.

As a side note, all those steel box wood heaters that boast efficiency like 85% (note that legally 100% is 85% to allow the flue gas to be hot enough to "pull" so 85% is 85% of 85% or 72%) are tested in a sealed room and conditions that are not livable. That is the room they are tested in will reach very high temperatures. After the heater is installed in a house it will be used to keep people comfortable and when used that way will be about 10% efficient.

Getting heat is not the whole thing, but having a healthy space is also a concern. This is why heating the body by radiation and direct contact (hot coffee or tea) is better than heating the air which has to be exchanged anyway.

Sorry for such a wordy post...

Anonymous wrote:

Anonymous wrote:

I meant a stove dedicated for heating. However, I have seen postings here showing a makeshift heater with a flue, occupying one of the two burners of a cooking stove. I fear that at least half of its energy escapes up that flue.

If only half of it's energy escapes up the flue it would be a wonderful efficient heater. Most small heaters are not that good. (most large open fire heaters are not that good - masonry heaters aside)

My needs are modest. I only make day-sails, these days, and then choose the fine days. During winter I often visit the boat and then light a little gas heater, which makes use of all the heat, and quickly brings up the temperature.  However, without a flue, this has no de-humidifying effect.

quite the opposite in fact. Burning anything (like breathing) produces water (and CO2 of course).

So a flue even with all it's losses, is still a plus, it acts as a forced vent removing unwanted moisture and poisonous gases. There must be a place for new air to enter of course and I would suggest not having the air inlet too close to the heater (dedicated air intake for heaters is dangerous in my opinion) so it can remove bad air from as much of the living space as possible. Warming of the body from a heater on a boat is best by radiation rather than warming the air.

Any fancy ways of recovering heat before it exits, takes a lot of space and is not worth while. Make the heater small, run it hot and don't worry about loosing heat up the flue.

Years ago I bought an 80% efficient furnace for my home...... It used a plastic pipe exhaust, and an aneroid sensor to turn the gas on once it sensed that the exhaust fan was functioning.   I was disgusted with the flue temp, which was around 150F, and seemed like a lot of wasted energy.  As a result I took an aluminum car radiatior, and installed it after the primary heat exchanger, in a way that the fan drew the air through it also, but I angled it in such a way that the condensed water could drain out, and I attached a drain line to it.   The result was that the temp at the stack now runs about 10 deg above room temperature.   I'd call that very efficient..... and used it for over 20 years in that configuration.   It's amazing how much water condenses out.

     I prefer unvented catalytic heaters, and have switched over to them, as humidity is something I need in this climate in winter.   100% efficient, they wouldn't of course work on a boat.

                                                            H.W.

Here's a picture of Bill Churchouse's stove on Belgean, a Westerly Nomad (22') and Jester Challenge boat.  If he can do it, perhaps so can I.

Looks interesting, any more info?

The Poor Man's Webasto

Len,
Here is a cheap way of circulating heated air...

Arne