Eberspacher intake venting?

[Yacht Yogi]

I have an Eberspacher mounted in a large cockpit locker and I think it might be lacking sufficient ventilation to run properly. What do you think?

The locker fills half of the rear of the hull, aft of the heads compartment and is bounded by the engine enclosure and the side wall of the aft cabin. It has a large hatch, easily big enough to climb into but not especially closely sealed when closed. The Eber sits on a shelf in the top, aft corner. The exhaust goes out through the transom, the heating air is drawn through a duct from the aft cabin and the hot air goes along another duct out though the heads compartment wall. The combustion air intake is drawn straight from the locker enclosure through the little stub intake pipe sticking out the bottom of the Eber itself.

The heater starts well enough but when running will begin to make blue smoke and become intermittent after 5 or 10 minutes. Sometimes it will shut itself down. Last weekend while doing some boatwork I ran the heater to check it. With the locker open it started and ran fine but after a while it began raining so I shut the locker lid. After a few minutes it started making smoke and running intermittently. So I opened the hatch and looked in to see what was going on. The locker was a bit "fumey" but no smoke in there, it might have been steam from stuff drying out. After a couple of minutes the Eber began running properly again.

That's odd, I thought. So I did an experiment by closing the locker, waiting for the smoke and intermittent thing to start and then opening the locker to see if it went back to running properly. This cycle repeated consistently for a few times until I got fed up with being rained on and turned it off.

I think there is a ventilation problem and the heater is being starved of air. I am thinking of cutting a hole in the boat and adding a dedicated vent to feed fresh air to the heater.

Before I cut a hole in the boat, does anybody agree that I am on the right track? Has anyone else had a similar problem? Am I deluding myself and there is some other common cause of this kind of behaviour? Where is the best place for a vent hole and should I connect a duct to the heater intake pipe or continue to let it draw air from the locker space with just some better ventilation?

All advice welcome.

Cheers

 

[David2452]

If it is in a compartment that is unable to draw outside air for combustion then it needs venting, they need quite a few CFM of air per hour, how long have you had the boat and is this recent? I think you have answered your own question with the result of leaving the lockwer open, perhaps do it for a bit longer when it is not raining to confirm.

 

[skyflyer]

We have a Mikuni, but same principle; the exhaust hose is corrugated stainless steel and attached to the exhaust pipe spigot using - essentially - a jubilee clip. I discovered that this was not quite gas-tight and small amounts of exhaust fumes were leaking past it and - when the locker lid was closed - being drawn into the fresh air intake and thus delivered into the cabin.

With the lid open the problem went away. We resealed the exhaust pipe and its now okay although we still get a hot plastic smell as the hot air is ducted through pvc corrugated tubing rather than the usual cardboard/foil combination!

Anyway - worth checking maybe?

 

[rob2]

Even if there is another underlying problem it will do no harm to give the heater a good combustion air supply. Either a hose and skin fitting (with gooseneck arrangement) to a suitable place where no-one will sit and block it or a considerably larger vent into the locker side.

Rob.

P.S. You'll really appreciate it when we have this chilling winter rain!

 

[VicMallows]

The combustion air intake is drawn straight from the locker enclosure through the little stub intake pipe sticking out the bottom of the Eber itself.

I can't see that it is directly relevant to your problem, but generally there should be a hose on the combustion air intake approximately equal in length to the exhaust (so the suck/blow resistance to the fan is equalised).

 

[westhinder]

We had a similar problem with a Mikuni installed in a big cockpit locker. After a few minutes the cabin began to fill with exhaust fumes. When i opened the lid of the cockpit locker, the problem did not manifest itself. I have not got round to fitting a vent to the locker, so we make do by setting the locker lid ajar whenever we run the heater.
Any ideas as to what size vent would be needed?

 

[single]

A tiny vent would do.As rule if thumb you need 12" square vent for every 1000 cubic metres per hour fan.

 

[lynall]

Mines in the engine bay and the intake is approx 6 feet long and comes up out the back of the rear seating area, works well but to bloody noisy!



Lynall

 

[john_morris_uk]

Mines in the engine bay and the intake is approx 6 feet long and comes up out the back of the rear seating area, works well but too bloody noisy!

Lynall

Do you mean the exhaust noise is too loud? Why not fit a silencer to the exhaust? I am assuming you don't mean that the air being ducted into the boat is noisy as the fan blowing the air in is virtually silent.

 

[David2452]

Do you mean the exhaust noise is too loud? Why not fit a silencer to the exhaust? I am assuming you don't mean that the air being ducted into the boat is noisy as the fan blowing the air in is virtually silent.

Actually the combustion air intake is one of the nosiest parts of these type of heater its quite small and has to pass a lot of air. If you have just the stub then very noisy indeed, a hose makes it a bit quiter and a hose with an air intake silencer makes it quiter still, Webo have just introduced a new silencer that knocks another 3db off the old silencer level. A similar problem exists with the recirculated air intake when ducted, it's not the fan noise per se but the vortex around the intake, if you take the air cleaner off your engine intake you get just the same.

 

[vyv_cox]

The locker fills half of the rear of the hull, aft of the heads compartment and is bounded by the engine enclosure and the side wall of the aft cabin. It has a large hatch, easily big enough to climb into but not especially closely sealed when closed. The Eber sits on a shelf in the top, aft corner. The exhaust goes out through the transom, the heating air is drawn through a duct from the aft cabin and the hot air goes along another duct out though the heads compartment wall. The combustion air intake is drawn straight from the locker enclosure through the little stub intake pipe sticking out the bottom of the Eber itself.

My installation is identical. It has never given a problem in around 12 - 13 years. The only air into the aft locker comes through a slot beneath one edge of the locker lid, probably about 12 x 1 inch.

 

[lw395]

I can't see that it is directly relevant to your problem, but generally there should be a hose on the combustion air intake approximately equal in length to the exhaust (so the suck/blow resistance to the fan is equalised).

Doesn't that make the resistance to air flow twice what it needs to be?
What does it achieve?

 

[Sandyman]

''The locker was a bit "fumey" but no smoke in there, it might have been steam from stuff drying out.''

That's your problem. Open locker steam ventilates Spacher runs fine.

It is often hard to get a seal on the exhaust pipe connection to the spacher with just a jubilee clip, so what I do is put a blob of Fire Cement on the exhaust outlet first.

 

[john_morris_uk]

Actually the combustion air intake is one of the nosiest parts of these type of heater its quite small and has to pass a lot of air. If you have just the stub then very noisy indeed, a hose makes it a bit quiter and a hose with an air intake silencer makes it quiter still, Webo have just introduced a new silencer that knocks another 3db off the old silencer level. A similar problem exists with the recirculated air intake when ducted, it's not the fan noise per se but the vortex around the intake, if you take the air cleaner off your engine intake you get just the same.

Our Eber is in a cockpit locker and the only sound inside the boat is the very subdued click of the fuel pump and a very faint air rush from the heated air coming out of the various outlets.

If you open the hatch and listen carefuly you can hear the exhaust.

 

[lynall]

Do you mean the exhaust noise is too loud? Why not fit a silencer to the exhaust? I am assuming you don't mean that the air being ducted into the boat is noisy as the fan blowing the air in is virtually silent.

No the exhaust is almost silent it already has a silencer fitted, its the rush of air into the intake trunking.
I will try and video it so you can see how noisy it is.


Lynall

 

[Chris_Robb]

It is essential that ventilation air is drawn from a separate air source to the compartment where the heater is mounted.

The official fitting instruction I saw recently say that if you have a small exhaust leak in the same compartment from where you draw your fresh air, you will end up poisoning the occupants with CARBON MONOXIDE.

I have never yet seen one fitted correctly! My own (professionally fitted) has not been installed properly, and I need to vent the installation with a pipe to another compartment.

This type of sloppy installation is an accident waiting to happen.

 

[Hoolie]

It is essential that ventilation air is drawn from a separate air source to the compartment where the heater is mounted.

The official fitting instruction I saw recently say that if you have a small exhaust leak in the same compartment from where you draw your fresh air, you will end up poisoning the occupants with CARBON MONOXIDE.

I have never yet seen one fitted correctly! My own (professionally fitted) has not been installed properly, and I need to vent the installation with a pipe to another compartment.

This type of sloppy installation is an accident waiting to happen.

+1 It must be very common But with interlinked cockpit lockers it's difficult to rectify.

Even though we have a CO detector in the living space we shouldn't rely on it though.

 

[lw395]

From my experience, provided the exhaust is properly sealed and not facing into a strong wind, you don't tend to get measurable CO or noticeable odours coming out of the combustion air intake.
You might have the odd issue if moored stern into a strong wind I suppose?

I used high temperature RTV instant gasket to seal the exhaust.

 

[Chris_Robb]

From my experience, provided the exhaust is properly sealed and not facing into a strong wind, you don't tend to get measurable CO or noticeable odours coming out of the combustion air intake.
You might have the odd issue if moored stern into a strong wind I suppose?

I used high temperature RTV instant gasket to seal the exhaust.

It is nothing to do with exhaust gases once they have gone over the side - though there was a tragedy a couple of years back. Its to do with a leak internally within the boat of exhaust gases, which get sucked into the hot air ventilation, and thus spread through the boat.

Relying on a perfect joint - which might get bumped in the locker is just not good enough.

 

[lw395]

It is nothing to do with exhaust gases once they have gone over the side - though there was a tragedy a couple of years back. Its to do with a leak internally within the boat of exhaust gases, which get sucked into the hot air ventilation, and thus spread through the boat.

Relying on a perfect joint - which might get bumped in the locker is just not good enough.

In your opinion it's 'just not good enough', but it seems to be standard practice on boat installations. There are many thousands of boats with heaters installed in this way.
The exhaust joints are safety-critical, but that's equally true of the exhaust of your diesel engine, not to mention the gas system.
Perhaps it is significant that the heater is removing a fair quantity of air from its surroundings and pumping it out of the boat via the exhaust? Hence there is a net flow of clean air into the boat via the cabin vents.
Compare with the gas cooker which just exhausts into the cabin space.