Diesel Heater Air Intake Pipe

[afblangley]

I am installing a diesel heater in my van. I understand the need to run the exhaust pipe outside the vehicle, but I don’t understand why it is beneficial to have the air intake pipe run outside. Why not allow it to draw from the air inside the van? I see the advantages (less of a heating load, one less hole to drill out) but its not typically installed that way, so what are the disadvantages that I don't see?

 

[kklowell]

The disadvantage that I can think of without really knowing a thing about these is that it will use oxygen from your living area.

 

[BelgianPup]

^^^
That's the reason. Cold outside? Windows tightly closed?

Also, having the intake pipe inside, some kind of clutter can accidentally block the intake.

 

[hugemoth]

My guess is that having the intake inside creates a low pressure in the enclosed space so air has to be sucked in through whatever openings exist. If the exhaust is close to one of those openings it will be sucked into your van.

 

[eDJ_]

I've thought about this for when I put one in my rig. I'm considering a split intake system where a small tube from the inside joins the main intake from the outside. It would just bleed a little outside air into the interior to keep a good supply of oxygen. The opening the air would be drawn into the interior from would be as far from the heater exhaust as possible.

 

[jasper]

Cold air is denser and provides for leaner combustion. One of the major complaints of diesel heaters is running rich and sooting, especially at higher altitudes. I replaced the 22ml pump with a 16ml on my 2kw after sooting up, for a leaner mixture, and it has run for five years now without problems.

Sadly, I almost wish my van was airtight enough to restrict combustion intake flow.

 

[frodo2222]

well all those are good points the main issue is that if you have a hiccup with the diesel and it stops working correctly and a backfires all the exhaust fumes can go through it into the living area that's why you want the intake and it exhaust outside so that happens they exit outside if you put the intake on the inside it could happen and kill you

 

[eDJ_]

Interesting point of caution there. A one way valve installed on the small interior intake tube may be worth considering so a backfire would be diverted thru the outdoor intake so exhaust wouldn't enter the interior.. In the past a member (Sternwake) spoke of creating a vent in the back door of his rig behind the license plate as a fresh air intake. I remember him using small computer fans like for a computer CPU and powered thru a timer that cycled the fan(s) on and off several times thru the night and providing oxygen/fresh air. (thus it would eliminate the diesel heater issue)

 

[hugemoth]

I'm pretty sure a diesel heater can't backfire.

 

[AmargosaWayne]

Searching with "can a diesel heater backfire?"

Produces results only for backfiring in diesel engines.

 

[JP-SLC]

My understanding is you have two very isolated systems/circuits. One uses fuel, air, and a little electricity (glowplug) to heat the inside chamber producing a "toxic" gas byproduct (CO) that must be exhausted outside. The other circuit passes fresh/cool air over the heatsink fins of the chamber resulting in fresh/warm air being pushed out ot the "clean" output.

I think the most important point of keeping the intake for the "clean" and the "toxic" circuits separate/isolated is if there are ever failures in flow (e.g. a blocked or kinked exhaust, or other malfunction) that it is less likely to result in toxins being pumped out or leaking out of the intake end and into your living quarters. I have a limited understanding of these systems and have only been using them for a few years now, but this is what I have gathered.

I once thought of experimenting with improving efficiency by twisting the intake and exhaust tubes together, effectively transfering heat from the exhaust tube to the intake tube to pre-heat the intake air. It could be improved by also covering the twisted pair of tubes with a suitable insulating covering. The intake tube would then be extended and located away from the exhaust to prevent it from drawing in exhaust

I never got around to experimenting with this idea because these diesel heaters are so effective, I don't think the effort would really pay off. My heater is so effective at lowest settings that it feels like it's overkill. Mine is one of the pricier Planar-brand heaters, but from what I hear the Chinese ones are just about as effective and a much better value.

My 2cents

P.S. if my Planar ever dies, I won't be forking out another $800 for a new Planar, Webasto, etc. I'll instead be buying two cheap ones for ~$300, keeping one for parts if ever needed.

 

[maki2]

Start adding a lot of twist and curves and you will impede the air flow. Effiency of intake and exhaust airflow is far more critical than a minor amount of heat gain. You do not want to make your equipment have to work harder.

 

[user 19146]

my understanding of a diesel heater is they have 2 intakes and 2 exhausts. both separate sides. the intake and exhaust for the burn chamber must be outside the vehicle. and the intake and exhaust for the heating side is inside the vehicle, the intake moves inside air over a heat sink (heated by the burn chamber) causing the air to heat up, its then exhausted to inside the vehicle to heat the inside. like a wood stove would move air around a stove to heat air in an air duct. so after a short time its using the preheated air inside the vehicle. note: no fresh air is used or added in a diesel heaters standard install.

 

[Sasnak]

Cold air is denser and provides for leaner combustion. One of the major complaints of diesel heaters is running rich and sooting, especially at higher altitudes. I replaced the 22ml pump with a 16ml on my 2kw after sooting up, for a leaner mixture, and it has run for five years now without problems.

Sadly, I almost wish my van was airtight enough to restrict combustion intake flow.

I’m at 9000’ right now and I was happy with how my diesel heater was running. Now you got me worried that I should be expecting sooting problems if I keep running it.

 

[RV411]

I have a Shuttle Bus with a Diesel Heater. I elected to have my intake kept inside. My heater is installed just inside the rear door, and exhausts on the opposite side of the Vehicles exhaust system. The air intake has been nestled between the unit and the rear wall.
I've experienced no problems this winter; also I have a pretty "open" No-Build plan.

 

[PlethoraOfGuns]

Follow manufacturers specs. You're trying to heat the inside space. Sucking your warm interior air out into your heater seems like a waste. It's diesel, it wants cold air to the intake to run efficiently.

 

[JP-SLC]

Start adding a lot of twist and curves and you will impede the air flow. Effiency of intake and exhaust airflow is far more critical than a minor amount of heat gain. You do not want to make your equipment have to work harder.

I think you're picturing somethning different than i was. I'm talking about a gradual twist. Plus we are not dealing with high velocities/volumes here and as long as the inner diameter is maintained and bends are gradual, any change to flow is negligible.

 

[JP-SLC]

I have a Shuttle Bus with a Diesel Heater. I elected to have my intake kept inside. My heater is installed just inside the rear door, and exhausts on the opposite side of the Vehicles exhaust system. The air intake has been nestled between the unit and the rear wall.
I've experienced no problems this winter; also I have a pretty "open" No-Build plan.

As long as I had a monoxide detector, I think I'd be comfortable with this approach.

 

[maki2]

Shuttle buses are not even close to being airtight. You should have plenty enough fresh air for the heater without an outside air intake.

I do not have a Chinese diesel brand of heater but the USA distributor of my diesel heater knew I would be just fine without an outside fresh air intake. Quite true as my entry door is not even close to being an airlock worthy door. At 50 years old that door has enough of a warp in it that plenty of fresh air comes in along part of the edges and also where there sliding window in the door is. My sliding windows on the sides are also not airtight. Sometimes drafts are an advantage rather than just an annoyance, this is one of those cases. Being a very small trailer I have plenty enough heat from my diesel heater that the drafts are inconsequential in terms of heat loss.

 

[hugemoth]

Another minor disadvantage to having the combustion air intake inside is noise. It is a bit noisier than having it outside.