Small thread, big poll: outside air or inside air for your diesel heater?

[Chotu]

I have been talking to a lot of people about diesel heaters.

A larger number of them than expected take outdoor air and heat it, then blow it inside.

Benefits would include a very dry and fresh cabin.

Negatives would include poor fuel efficiency.

How do you have yours set up?

[JPA Cate]

Downsides are our Dickinson look-alike is very old fashioned, and until Ambler told us how to absolutely prevent a downdraft blowing out the burner, we had one fireball below, very short lasting, but very scary to watch, and two snuffing out minus the fireball. Are we satisfied with it? I think Jim may find it a good compromise (better, certainly, than no heater at all), but for years we've carried an inexpensive electric fan/heater for marina use; and I bet our friends, mentioned below, would say the whole deal is inadequate. I would say it is marginally adequate.

We have some friends with a Webasto, forced air to saloon and bunk area and it warmed their boat MUCH faster than ours, which took hours. Theirs, usually inside a half hour, according to the lady.

If you're going to go where it is really cold, I think some kind of forced air heating to where you'll need it most would be the best deal. It will be $$$!!!, but then, you'll be more comfortable, quicker.

I don't know about recycling the insider air, I'd be concerned about oxygen depletion if you really seal up the boat; however, if there is always a dorade open for fresh air to the interior, then recirculating, that should be okay.

Ann

[rslifkin]

Same logic as with air conditioning. Recirculate the inside air for better efficiency. If you want, you can run an outside air duct to the return and add a damper so you can optionally draw a mix. Otherwise you can open a window for fresh air.

All of the HVAC on my boat recirculates and it's never been an issue. It's not a perfectly airtight boat though. Humidity has never been an issue unless it's very humid outside.

[El Pinguino]

My eberspacher draws air from inside the 'garden shed' - within which live assorted other items , calorifier, Fridge compressor, etc - so is really neither one nor the other.

Cold fresh air finds its way into the 'garden shed' by ways mysterious.

Warm air in the cabin isn't recycled as it tends to escape through the hatch and dorades.

[Chotu]

I wasn’t really trying to make a big thread since I have a huge one going for rigging lol

I have a pair of 8kw diesel heaters (like webasto/espar).

I’m trying to determine if I should use outside air or recirculated indoor air to feed them.

A whole lot of people are using outdoor air, but I’m somewhat concerned about the efficiency doing that.

Air conditioning (other than cars which are grossly over air conditioned), is all recirculated air which makes sense since you are dehumidifying and all that.

With heating, you are not dehumidifying. You are only raising the temperature of your potentially wet, steamy pasta cooking type air. So, it’s quite a different situation compared to air conditioning. The only way to keep humidity down is to draw outside air, which my old wood stoves on previous boats did very nicely. They used to pull outside air in through gaps and cracks to replace all the air roaring up the chimney.

I was thinking I could always just open some windows to get drier air. But so many people drawing from outside have me thinking differently.

[rslifkin]

You're not in a tiny cabin where humidity will be a big issue. So I'd think of it like heating a house where you want to go for efficiency.

[boatpoker]

CO poisoning is cumulative. It takes up to 2 weeks for CO to clear from the blood.

Diesel does produce less CO than gas but what happens to the amount of CO in your blood if you run a diesel heater recirculating air for a week ?

[rslifkin]

Originally Posted by boatpoker

CO poisoning is cumulative. It takes up to 2 weeks for CO to clear from the blood.

Diesel does produce less CO than gas but what happens to the amount of CO in your blood if you run a diesel heater recirculating air for a week ?

Nothing unless the exhaust is leaking. That gets vented outside either way.

[Chotu]

Originally Posted by boatpoker

CO poisoning is cumulative. It takes up to 2 weeks for CO to clear from the blood.

Diesel does produce less CO than gas but what happens to the amount of CO in your blood if you run a diesel heater recirculating air for a week ?

Wow. A rare swing and a miss. I’ve actually never seen you miss one before so it’s kind of a something. It’s an event. Lol

You aren’t understanding how these heaters work.

CO exposure is more likely drawing outdoor air in than recirculating.

Poll results are showing indoor air recirculation in the lead currently.

[boatpoker]

Originally Posted by rslifkin

Nothing unless the exhaust is leaking. That gets vented outside either way.

So no possibility of a leak between the output of the furnace and the end of the exhaust hose ?

[boatpoker]

Originally Posted by Chotu

Wow. A rare swing and a miss. I’ve actually never seen you miss one before so it’s kind of a something. It’s an event. Lol

You aren’t understanding how these heaters work.

CO exposure is more likely drawing outdoor air in than recirculating.

Poll results are showing indoor air recirculation in the lead currently.

No swing at all, just a question. Here's another one ...
How does fresh air being drawn in produce CO ?

[El Pinguino]

Originally Posted by Chotu

...

Poll results are showing indoor air recirculation in the lead currently.

I don't think 3 votes total is a good indicator and as I said mine is sort of 50/50 - outdoor air drawn from the inside.


If drawing directly from outside lots of consideration would need to be given to proximity of exhaust and also risk of getting bits of ocean in the intake.

[Jim Cate]

Heaters that draw air from the cabin (like ours) are not recirculating the air. Air enters the burner, is involved with combustion and exits, along with the combustion products, up the stack. There is, thus, a need for makeup air to replace that exhausted... and that comes, via vents, dorades and just plain leaks, from the outside of the vessel.

The exhaust has a strong odor and if even a small amount was to get back into the cabin your nose isn't a bad warning system, but a smoke/CO alarm is rather better if you are worried about this issue. Still, getting the exhaust isolated from the various entry points for makeup air is part of a good installation and should be carefully considered.

Jim

[El Pinguino]

Originally Posted by Jim Cate

Heaters that draw air from the cabin (like ours) are not recirculating the air. Air enters the burner, is involved with combustion and exits, along with the combustion products, up the stack. There is, thus, a need for makeup air to replace that exhausted... and that comes, via vents, dorades and just plain leaks, from the outside of the vessel.

The exhaust has a strong odor and if even a small amount was to get back into the cabin your nose isn't a bad warning system, but a smoke/CO alarm is rather better if you are worried about this issue. Still, getting the exhaust isolated from the various entry points for makeup air is part of a good installation and should be carefully considered.

Jim

Hola Jim, this is what Chotu is installing

'I have a pair of 8kw diesel heaters (like webasto/espar). '

[Chotu]

Originally Posted by boatpoker

No swing at all, just a question. Here's another one ...
How does fresh air being drawn in produce CO ?

Ok. Ok. I thought you had a leading question going on there.

So, there is absolutely no CO involved in running these heaters recirculating interior air. Not unless the solid aluminum housing is broken.

Fresh air being drawn in has the potential of drawing exhaust in when the wind changes from odd directions at a dock so you could pull in combustion byproducts.

Recirculating interior air has no chance of this.