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

[Chotu]

Originally Posted by El Pinguino

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.

Yes. Definitely proximity of exhaust. That’s what I meant talking to Boatpoker about CO risk being higher in the case of heating outside air.

I think every install you can do pulling outside air has a risk at a dock, but does not at anchor or on a mooring.

I would characterize yours as outside air. That’s where it comes from. It’s not the preheated cabin air. It sounds like it’s coming from a locker. Ultimately that comes from outside.

[Chotu]

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

And that is why your heater and my old wood stoves used to be so great. They are constantly pulling in huge amounts of air. All of the air that’s roaring up the chimney is being pulled in from the gaps and cracks. That keeps things nice and dry all winter.

These heaters, however, recirculate the interior air by design. They do not have make up air. But I can choose to install it in such a way that it is 100% make up air being used to heat the cabin.

In this configuration, the cabin is pressurized by the fan blowing the air across the heater. Then, the resulting high pressure inside the cabin leaks out the cracks and gaps.

And to add a little something extra, I have noticed I have some problems in this boat.

If I keep it completely closed up in very hot weather without air conditioning on, there is some kind of chemical odor and it’s very troubling. I think it has to do with some of the construction items stored inside. Tubes of caulking, paint. I think I have to put them outside if I am closing up completely. The way I deal with it now is I just have lots and lots of ventilation going all the time. This is a factor.

I recently changed the location of all of the caulking to the explosives box out on the deck. And things are a lot better. But there is still some smell. I think it’s the paint.

[Jim Cate]

These heaters, however, recirculate the interior air by design. They do not have make up air.

If this was really true the Oxygen content would soon be used up and the combustion would stop. There must be some source of new air!

Jim

[Chotu]

Originally Posted by Jim Cate

If this was really true the Oxygen content would soon be used up and the combustion would stop. There must be some source of new air!

Jim

You aren’t understanding how the heaters we are talking about work.

Here is a diagram for you.

The main point is it’s a sealed combustion unit. Uses no inside air for combustion.

However, you can choose to draw outdoor air to heat or indoor air to heat/recirculate. This air you are heating goes in the left side of the unit in the diagram where it says “cold air inlet”

[El Pinguino]

Originally Posted by Chotu

....
I would characterize yours as outside air. That’s where it comes from. It’s not the preheated cabin air. It sounds like it’s coming from a locker. Ultimately that comes from outside.

Yes its in a cockpit locker - a very big standing headroom cockpit locker hence 'garden shed'.
When as is normal the watertight lid is closed the air comes from within the boat, essentially from the bilge , via assorted lowdown bulkhead penetrations for wiring, pipework etc.
The air gets into the bilge via the dorades, ports in the heads which are invariably cracked open, and through the hatch surrounds.
Some of the air is recycled into the cabin through the heater , some is vented to the outside via the exhaust. So more fresh air is coming into the boat than is being recycled through the heater. The difference being the exhaust 'air'.

Not sure where I am going with this, as the actress once said to the bishop 'its complicated'.

[Chotu]

El Pinguino: that’s actually a really nice installation. Dry bilges, lots of fresh air, very flexible

[El Pinguino]

Originally Posted by Chotu

El Pinguino: that’s actually a really nice installation. Dry bilges, lots of fresh air, very flexible

Lets pretend .

My Espaker draws in 1 cu metre of air from the cabin via the bilge per whatever. Half of that is heated and returned to the cabin, the other half is exhaust.
So every whatever there is half a cubic metre deficit in the cabin.
That half cubic metre must come from the outside.

If you compare the size of the cold air inlet and the combustion air inlet in the pic posted above I think the reality may be 90% cold air - 10% combustion air - that 10% has to come into the interior of the boat from outside.

Also - that inlet is big - maybe 3" diam - that is going to be a bb hole cut into the side of your cockpit just waiting for the chance to suck in some wet be it ocean or just ordinary rain.

The only pic I have ever seen showing a hose on the inlet is in this article https://www.yachtingmonthly.com/gear...our-boat-79192 but no clue as to where it is mounted on the hull or in the cockpit.

[Chotu]

Originally Posted by El Pinguino

Lets pretend .

My Espaker draws in 1 cu metre of air from the cabin via the bilge per whatever. Half of that is heated and returned to the cabin, the other half is exhaust.
So every whatever there is half a cubic metre deficit in the cabin.
That half cubic metre must come from the outside.

If you compare the size of the cold air inlet and the combustion air inlet in the pic posted above I think the reality may be 90% cold air - 10% combustion air - that 10% has to come into the interior of the boat from outside.

Also - that inlet is big - maybe 3" diam - that is going to be a bb hole cut into the side of your cockpit just waiting for the chance to suck in some wet be it ocean or just ordinary rain.

The only pic I have ever seen showing a hose on the inlet is in this article https://www.yachtingmonthly.com/gear...our-boat-79192 but no clue as to where it is mounted on the hull or in the cockpit.

Wow, that link.., I followed and read it in addition to looking at the pic. Any old moron can pretend to be an expert apparently. That’s what’s no good about the internet. The guy in that link makes 2 mistakes on his install yet pretends to be an expert.

But I did see the pic on the page with the cold air supply duct.

But yes. I understand your install. It’s very nice because of exactly what you’re saying. It is pulling all that air through the bilges. As I said before: That’s good ventilation for dry bilges, lots of fresh air and very flexible because you can open the “garden shed” to change air sources.

I don’t have a cockpit, so no worries about water in it.

What I do have is watertight bulkheads. 2 of them forward in each hull and 1 of them aft in each hull, that I’m not willing to compromise for any reason.

None of that matters for my simple question here really though.

My question is:

Are you recirculating indoor air or using outdoor air to heat your boat? That’s it. Checking what people are doing. You’re using indoor air with the option for outdoor air. Plus you are drawing combustion air from indoor air which is not how these were designed to be installed, but works perfectly fine until the fan breaks. There is a slight potential for exhaust gasses to back up into the cabin in that case. As you said “it’s complicated.” Your install is unique.

- they were designed to be installed on the floor of a vehicle so the bottom combustion tubes go through the floor and protrude outside

[Chotu]

Poll so far:

1 person using outdoor air.

4 people using recirculated indoor air.

[GordMay]

According to Eberspächer:
“... The air heater units can be operated using recirculated or fresh air.
We recommend the fresh-air operation in particular.
Heating air is drawn in directly from outside or can be pulled in indirectly from ventilated cavities (e.g. forward locker ). Pulling the air in this way keeps the air in the cabin constantly renewed and dehumidified...
... The combustion air and the heater air must be drawn in from outside
at a point you are absolutely sure is free from any possible gasoline fumes and exhaust...
... [In] Sweden: the combustion air must be pulled in from outside the boat...”
➥ https://www.butlertechnik.com/downlo...ion_Advice.pdf

[Chotu]

Originally Posted by GordMay

According to Eberspächer:
“... The air heater units can be operated using recirculated or fresh air.
We recommend the fresh-air operation in particular.
Heating air is drawn in directly from outside or can be pulled in indirectly from ventilated cavities (e.g. forward locker ). Pulling the air in this way keeps the air in the cabin constantly renewed and dehumidified...
... The combustion air and the heater air must be drawn in from outside
at a point you are absolutely sure is free from any possible gasoline fumes and exhaust...
... [In] Sweden: the combustion air must be pulled in from outside the boat...”
➥ https://www.butlertechnik.com/downlo...ion_Advice.pdf

Thanks, Gord.

You can see why it’s such a tough decision.

Most people are recirculating the air they are heating. Yet, fresh is recommended in the resources you just posted.

Personally, I’m leaning toward fresh, but I’m still pretty concerned about the efficiency of that setup. It’s quite a jump from outdoor, winter air to comfortable indoor temperatures.

[Matt Johnson]

We pulled fresh air from the cockpit coaming storage area. It acted as a dorade vent, protecting the intake from the water intrusion. It worked well and we had zero issues with efficiency - it typically ran at its lowest setting for days and days.

[rslifkin]

Originally Posted by Chotu

Thanks, Gord.

You can see why it’s such a tough decision.

Most people are recirculating the air they are heating. Yet, fresh is recommended in the resources you just posted.

Personally, I’m leaning toward fresh, but I’m still pretty concerned about the efficiency of that setup. It’s quite a jump from outdoor, winter air to comfortable indoor temperatures.

Put a tee into the intake line for the heater and a pair of damper valves. Then run one duct outside, one inside. Use the valves to adjust the mix of inside vs outside air until you're happy (or based on how much humidity you're seeing inside).

[Chotu]

Originally Posted by Matt Johnson

We pulled fresh air from the cockpit coaming storage area. It acted as a dorade vent, protecting the intake from the water intrusion. It worked well and we had zero issues with efficiency - it typically ran at its lowest setting for days and days.

Thank you! A good first hand report!

[Chotu]

Originally Posted by rslifkin

Put a tee into the intake line for the heater and a pair of damper valves. Then run one duct outside, one inside. Use the valves to adjust the mix of inside vs outside air until you're happy (or based on how much humidity you're seeing inside).

I was definitely thinking of doing this. It might be really nice like an older car where you could blend it.

Keep it closed up when you arrive at a nearly frozen boat to heat it up quickly, start opening it up and giving it some more outside air once things warm up.

And if you are feeling particularly cheap you can recycle the indoor air lol or if you are feeling like the heating bill is not an issue you can draw a nice fresh air wide-open.

If I do end up having to choose, I’m definitely leaning toward outdoor air. I like really good air quality for all my issues and it helps a lot to have fresh air all the time.