Diesel exhaust smell with Webasto heater

[silvercreek]

I have a Webasto Air Top EVO 55 (link) and I noticed that every time I turn it on, right after it fires up there is a fairly strong diesel exhaust smell that momentarily comes through all the vents. It quickly dissipates and only reappears when the unit eventually restarts a new heating cycle. I have checked the installation and don't find any obvious exhaust leaks or similar infiltration sources.

Is this normal/expected?

The air intake is in the same locker that the unit itself is in, though the exhaust is plumbed to the exterior and appears to be air tight. It happens in all wind conditions and has been this way for months.

[Sam Woodbridge]

Originally Posted by silvercreek

I have a Webasto Air Top EVO 55 (link) and I noticed that every time I turn it on, right after it fires up there is a fairly strong diesel exhaust smell that momentarily comes through all the vents. It quickly dissipates and only reappears when the unit eventually restarts a new heating cycle. I have checked the installation and don't find any obvious exhaust leaks or similar infiltration sources.

Is this normal/expected?

The air intake is in the same locker that the unit itself is in, though the exhaust is plumbed to the exterior and appears to be air tight. It happens in all wind conditions and has been this way for months.

Hello Silvercreek, I’ve had a few beers (everything is a good idea after that) so take my advice with a bit of salt.

I have the same heater and setup. It sounds like to me. The wind is blowing that first initial exhaust which can be very strong and raw into your air inlet. But if your sure that’s not the case. I would wonder for a trouble shooting code on your display. Maybe your igniter is getting weak, but I’m grasping at straws with that comment.

I’ll stay in tune with the thread as it might happen to me.

Sam

[silvercreek]

Thanks Sam. No, I don't think the exhaust is being blown into the intake port, but I wonder if internally inside the Webasto unit, there could be some blowback? Do you notice that on your unit?

[BillKny]

Inside the unit there should be absolutely NO connection between exhaust and cabin air. That would be very bad. I would think this is obvious...

If it was my boat, I wouldn't use it until I had this figured out. A steady diet of diesel exhaust is NOT a good plan. If the unit burns fairly cleanly once it warms up, you might not smell it, but it is still very, very bad for you.

[silvercreek]

It would have to be a defect of some sort, certainly not by design.

I have a smoke pencil I can use to check for any latent exhaust leaks, however I would need to disable the cabin blower fan during this test as currently it creates too much wind movement to tell. I'll add this to the list of projects...

[Sam Woodbridge]

Originally Posted by silvercreek

Thanks Sam. No, I don't think the exhaust is being blown into the intake port, but I wonder if internally inside the Webasto unit, there could be some blowback? Do you notice that on your unit?

Hmm SilverCreek, no blow back or smell with my unit. Someone did chime in though, but I’m hoping for more replies on your issue. From last night to today. I still wonder if your igniter is getting weak at getting the fuel to burn on its initial first start. But I don’t know.

Sam

[goboatingnow]

Originally Posted by Sam Woodbridge

Hello Silvercreek, I’ve had a few beers (everything is a good idea after that) so take my advice with a bit of salt.

I have the same heater and setup. It sounds like to me. The wind is blowing that first initial exhaust which can be very strong and raw into your air inlet. But if your sure that’s not the case. I would wonder for a trouble shooting code on your display. Maybe your igniter is getting weak, but I’m grasping at straws with that comment.

I’ll stay in tune with the thread as it might happen to me.

Sam

I’ve had a few of these over the years , in my experience startup diesel is very pungent and I’ve noticed a small smell on startup. Never gave it much thought.

[silvercreek]

Checking in a year later here. Think I figured it out.

On initial startup I traced the diesel smell to the combustion air intake inlet. Yes — some diesel smell (a lot, in fact) comes out of there before the blower fan turns on and gets the combustion process fully kicked off. In my current configuration (stock from the manufacturer) the combustion air is drawn from the same lazarette where the cabin air intake is drawn from. I am going to plumb the combustion air to come from a cockpit through-hull and see if that fixes it, which I’m almost certain it will.

I also noticed the Webasto tech manual specifically warns not to draw combustion air from occupied areas, and this is probably why.

Hope this helps someone.

[goboatingnow]

Originally Posted by silvercreek

Checking in a year later here. Think I figured it out.

On initial startup I traced the diesel smell to the combustion air intake inlet. Yes — some diesel smell (a lot, in fact) comes out of there before the blower fan turns on and gets the combustion process fully kicked off. In my current configuration (stock from the manufacturer) the combustion air is drawn from the same lazarette where the cabin air intake is drawn from. I am going to plumb the combustion air to come from a cockpit through-hull and see if that fixes it, which I’m almost certain it will.

I also noticed the Webasto tech manual specifically warns not to draw combustion air from occupied areas, and this is probably why.

Hope this helps someone.

I have always drawn heating air from inside and combustion air from outside.

The main reason you can get smells is poor ignition and the surrounding intake grabs a small piece of the smoke. Not dangerous but a little off putting , very obvious in still autumn mornings.

Misfiring can generate lots of unburnt exhaust smoke , especially repeated failed starts.

In my experience run these units hard and often

[Baby tug]

I’ve had many of these heaters to resolve your problem try a separate tank with kerosene , they like to burn kerosene much better anyways especially in very cold environments , diesel gets pretty thick the units carbon up quite quickly sometimes smoke a lot during start up , I quite often will disassemble them and clean the carbon out of the combustion chambers, I know kerosene is inconvenient and much more expensive but your heater will love you for it

[Rumrace]

02 sensor in every boat. Should be in codes.

[ItDepends]

Originally Posted by Rumrace

02 sensor in every boat. Should be in codes.

Oxygen sensors? Seriously? I am glad you are not in charge!

Do you have them in YOUR boats? Of COURSE carbon monoxide sensors in every boat--in every cabin, for that matter.

But can you point to a single case where anyone died from lack of OXYGEN in a boat? While it is theoretically possible with a flame burning without dedicated external combustion air, but it is also EXTREMELY unlikely. I have never heard of it happening...

Of all the safety equipment to add to a boat, this one is way, WAY, WAY down the list...

[boatpoker]

Originally Posted by silvercreek

The air intake is in the same locker that the unit itself is in, though the exhaust is plumbed to the exterior and appears to be air tight. It happens in all wind conditions and has been this way for months.

This is is wrong. ABYC A-7 says ...

"Room Sealed Combustion System - a combustion system in which incoming air, the combustion chamber, and the outgoing products of combustion are sealed from the boat interior."

in simple terms intake air must be drawn from the exterior.

[goboatingnow]

Originally Posted by boatpoker

This is is wrong. ABYC A-7 says ...



"Room Sealed Combustion System - a combustion system in which incoming air, the combustion chamber, and the outgoing products of combustion are sealed from the boat interior."



in simple terms intake air must be drawn from the exterior.

Only combustion products the air being heated in a planar heater does not form part of the combustion process. Hence it can of course be drawn in from inside and commonly is.

When smells enter the cabin it’s typically because smelly partly combusted exhaust enters the boat via a number of means.

[boatpoker]

Originally Posted by goboatingnow

Only combustion products the air being heated in a planar heater does not form part of the combustion process. Hence it can of course be drawn in from inside and commonly is.

I don't understand that sentence as I believe there can be no combustion without air. Please consider re-writing.

But ... the OP has a Webasto not a Planar.

From the Planar Manual -

"3.2 Installation of the air intake pipe.
The air for combustion must not be taken from
the interior, living space, engine or luggage
compartment of the vehicle or vessel. Air should be
taken from well-ventilated areas or from outside of the
vehicle or vessel."