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Old 16-01-2015, 11:24   #16
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Re: Eberspacher D2 heaters..

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Originally Posted by jtsailjt View Post
I'm currently installing a Webasto heater and in the directions it recommends getting the combustion air from outside the boat and I don't understand why. It's not like any boat is so tightly sealed that plenty of air can't be sucked in to replace air that is used for combustion and this would tend to increase the portion of fresh air on the boat while the heater is running. Does anyone have any insight on why it's recommended to get combustion air from outside?
AFAIK they all do this. Think of it this way; it's a cold night and you go to bed with the heater on... and everything shut up as tight as possible to keep the boat warm. ....during the night it burns up all the oxy in the cabin.
Propane stoves do too, but you only cook for a limited time.
You are right that many boats have air coming in, but how much is enough?
These heaters are often installed in enclosed spaces too.. under a V berth or quarter berth etc...
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Old 16-01-2015, 13:43   #17
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Re: Eberspacher D2 heaters..

Also think what happens if the fan for the cobustion chamber fails. I _should_ shut down but what happens if not...
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Old 16-01-2015, 18:02   #18
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Re: Eberspacher D2 heaters..

Quote:
Originally Posted by Cheechako View Post
AFAIK they all do this. Think of it this way; it's a cold night and you go to bed with the heater on... and everything shut up as tight as possible to keep the boat warm. ....during the night it burns up all the oxy in the cabin.
Propane stoves do too, but you only cook for a limited time.
You are right that many boats have air coming in, but how much is enough?
These heaters are often installed in enclosed spaces too.. under a V berth or quarter berth etc...
I can understand and agree that you don't want it to be starved for air by getting the combustion air from a small, enclosed space. But it seems to me that it would be impossible for all the oxy in the cabin to get burned because that would create a vacuum in the whole cabin and there's no sailboat built THAT tight! Assuming your theory that it's possible for all the air in a tightly closed boat to have all the oxygen burned up by one of these heaters, what would take the place of the oxygen and where does it come from? It just doesn't make sense to me.

Propane stoves are a different story because the combustion gasses remain in the cabin so the combination of decreasing amounts of oxygen as it gets burned by the stove, and increasing amounts of CO2 can quickly do you in. But that's not the case with a heater that vigorously pumps the combustion gasses overboard, removing the CO2, which creates a vacuum that causes fresh air to be sucked into the boat.

My home heating system (in Maine so it runs a LOT lately) is based on a very much larger version of a diesel boat heater and the air used for combustion is ambient air from inside my house, as is the air used for combustion in my pellet stove, and yet neither ever seems to run out of air or oxygen. Why are boat heaters different? If there is an adequate supply of ambient air to supply the combustion in the engine and genset, why is there not enough air to also supply the relatively small amount of air required for combustion for the heater?

I would definitely plan to have a CO2 detector mounted in the cabin nearest my diesel heater.
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Old 16-01-2015, 18:10   #19
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Re: Eberspacher D2 heaters..

A house is way bigger with way more leakage. However maybe it will work.

Just give it a try and report back. Or maybe tell a close friend to report back, because you and your loved ones may be gone. Sounds like an application for the Darwin award
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Old 16-01-2015, 18:45   #20
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Re: Eberspacher D2 heaters..

My home heater is gas and it has a separate flue to draw fresh from the outside for combustion. But that's different than the air drawn from inside for air flow thru the system. But the reality is the furnace makers like espar are going to always take the safe route in instructions due to liability...
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Old 16-01-2015, 19:00   #21
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Re: Eberspacher D2 heaters..

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Originally Posted by Lancerbye View Post
"... a double-walled angled through hull exhaust .
Please ignore totally silly comment:
There is something precious about this statement. Weren't we all just going to go sailing? How did all this slide in? "... a double-walled angled through hull exhaust..." and the Queen of May, if you please? Why not?
Really. Must find those on every chandlers shelf.
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Old 16-01-2015, 21:16   #22
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Re: Eberspacher D2 heaters..

Quote:
Originally Posted by jtsailjt View Post
I'm currently installing a Webasto heater and in the directions it recommends getting the combustion air from outside the boat and I don't understand why. It's not like any boat is so tightly sealed that plenty of air can't be sucked in to replace air that is used for combustion and this would tend to increase the portion of fresh air on the boat while the heater is running. Does anyone have any insight on why it's recommended to get combustion air from outside?
I'm thinking along the same lines.
Using cabin air for combustion will increase the air drawn in through my dorades and help dry out the cabin.
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Old 17-01-2015, 01:40   #23
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Re: Eberspacher D2 heaters..

I would just let the unit draw and heat fresh air instead of havig the air circulate. This will expell out far more humid air without any risk. The heat loss is neglectible, air itself doesn't hold much energy ( except for the evaporated water, but this you want to get rid of anyway).

Using your breathing air for combustion may work but bears a risk. The combustion has a much higher CO tolerance than a human.
Again, why take your chances for almost no benefit???
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Old 17-01-2015, 06:23   #24
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Re: Eberspacher D2 heaters..

I doubt this combustion air that some are so worried about is much volume. I've run the engine with the hatch boards closed up, no one passed out and died etc.
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Old 17-01-2015, 06:55   #25
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pirate Re: Eberspacher D2 heaters..

The Gas worries me far less than the elec/diesel Eber... as a former gas fitter fitting a secure system does not concern me overmuch.. however with the Eber I will have doubled the source of possible problems.. think I'll follow the Cozy Cabin route.. or a solid fuel bulkhead fitted unit..
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Old 17-01-2015, 10:08   #26
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Re: Eberspacher D2 heaters..

Quote:
Originally Posted by td0tz View Post
Please ignore totally silly comment:
There is something precious about this statement. Weren't we all just going to go sailing? How did all this slide in? "... a double-walled angled through hull exhaust..." and the Queen of May, if you please? Why not?
Really. Must find those on every chandlers shelf.
I'm not even sure what this post means... but double wall pipes are common, some for insulative properties and also some that draw fresh air in and exhaust by a pipe within a pipe...
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Old 17-01-2015, 10:09   #27
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Re: Eberspacher D2 heaters..

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Originally Posted by rabbi View Post
I would just let the unit draw and heat fresh air instead of havig the air circulate. This will expell out far more humid air without any risk. The heat loss is neglectible, air itself doesn't hold much energy ( except for the evaporated water, but this you want to get rid of anyway).

Using your breathing air for combustion may work but bears a risk. The combustion has a much higher CO tolerance than a human.
Again, why take your chances for almost no benefit???
Not sure what you mean in your first sentence, or second sentence either? We are talking about combustion air, not the air that circulates. I agree that to dry the boat out it's important to draw that air from outside the boat and plan to do that in my own installation. The reason it helps dry out the boat is that it is drawing in and pressurizing fresh, cooler (which holds less moisture) air and distributing it throughout the boats interior, which forces some warmer, moister to be expelled through dorades or small openings around the companionway or other openings in the deck. Drawing the combustion air from inside the boat will require that even more fresh, cooler, dryer, air be drawn into the boat, thus drying it even more, not less.

You've compared doing this to an application for a Darwin award and talk about additional risk but you don't explain what causes this risk or how the CO2 could be drawn back in through the combustion air intake. Since the circulating air drawn from outside will attempt to slightly positively pressurize the inside of the boat, and this will displace air currently inside the boat through any available opening, including into the combustion air intake, what could cause the CO2 to backup into the cabin and cause a problem? My own feeling is that the warning is there for the reason Cheekako mentioned, liability, but I'm interested in learning what circumstances could possibly cause any additional risk with the combustion air drawn from inside the boat and the circulation air drawn from outside the boat. So far, I haven't been able to learn that.
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Old 17-01-2015, 12:25   #28
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Re: Eberspacher D2 heaters..

As I understand them, these heaters are designed to burn outside air and expel the waste gases outside. The heated air is cabin air via a heat exchanger. No outside air is drawn in so there is no improvement in moisture.
If you use cabin air for combustion outside air will be drawn into the cabin to replace it. When that cooler air is warmed, it will have a lower relative humidity and make the cabin drier.
I guess the other issue is the noise from the intake. It would be difficult to get a comparable sound level with a cabin intake.
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Old 17-01-2015, 13:14   #29
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Re: Eberspacher D2 heaters..

There are two options in installing a D2. 1. Is to have the heated air drawn from the outside ( outside fitting to be separated by a long distance from the exhaust fitting). 2. Install the heating air intake inside a good distance away from the heated air outlets. ( this provides good circulation of air) The combustion air is a totally different thing. This is supplied via a 24mm hose which should be drawn from outside or in my case a vented engine room which sealed from the living space. The exhaust is a 24mm at the heater increased to a 30mm via an elbow with a condensation drain to a double-walled angled through-hull fitting. To prevent sooting up of the combustion chamber(most common problem) is to run kerosene through it for an hour once a month, if it is being used full time.
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Old 17-01-2015, 13:56   #30
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Re: Eberspacher D2 heaters..

Hundreds avid hundreds of eberspacher draw air from the accommodation , the most common install in Europe is to draw air from the locker it's installed. In. All mine use internal air. This is completely supported by eberspacher

The point is there is no connection between combustion air and heating air.

PS boatman that gas heater must be room sealed , ie room air can not mix with combustion air. Otherwise its illegal on Europe. I don't think anyone makes a direct gas heating stove that is legal for installation . In Europe l

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