Venting

[Marks71]

Can anyone weigh in on the proper venting procedures when operating furnace and gas cooktop?

Specifically, i'm wondering whether and when it is advisable to draw through fresh air (e.g. open back window a little and run the vent fan) when operating either or both furnace and gas cooktop.

[Al and Missy]

Here's my opinion.

The furnace is designed to keep combustion products out of the interior. With a well maintained furnace and a functioning carbon monoxide detector there is little need to vent for that reason. The cooktop isn't used for long enough periods and should not create a significant risk either.

That said, there are reasons to vent. Use the range hood vent to carry cooking odors and moisture out of the trailer. And some venting is good in cold weather to minimize condensation of water vapor given off by the occupants.

Al

[nrgtrakr]

The furnace draws its combustion air from the outside and blows the exhaust out as well. Look outside of your rig near the heater for two small holes each about 2" in diameter. Turn the heat on and feel what happens.
The stove, range, burner top, just like a gas version in your home uses the same air you breathe to burn and dump the byproduct of combustion into. Range hood will help the exhaust gas leave. A window or vent cracked open even better.

[Len n Jeanne]

If we don't run the exhaust fan over the stove while cooking, our smoke detector goes off. The fan is noisy and uses up battery power, but it keeps the air at an acceptable level.

A good reason to leave a window or vent open a peep when running the furnace is to cut down on interior condensation.

[Protagonist]

Originally Posted by Marks71

Can anyone weigh in on the proper venting procedures when operating furnace and gas cooktop?

Specifically, i'm wondering whether and when it is advisable to draw through fresh air (e.g. open back window a little and run the vent fan) when operating either or both furnace and gas cooktop.

Since you're in an Interstate, here's what I do in my Interstate…

Cooktop - I open the tip-out window behind the stove, and turn on the MaxxFan overhead, to provide ventilation. The open glass cover of the stove in front of the tip-out window provides a windbreak and prevents a draft directly on the burners that might blow them out. This window selection also helps draw cooking odors out of the van through the MaxxFan since Interstates don't have a range hood to do it for us.

Furnace - Venting is recommended, and since I hate an icy cold draft on me while I'm sleeping, I open the passenger-side front window just a crack to provide ventilation. That's the window farthest from my bed, and farthest from the furnace exhaust as well, so there's less chance of the CO-laden exhaust blowing in. I added WeatherTech vent visors to the driver's and passenger's windows so that I could leave the window cracked open without letting rain in. Between the window cracked open and the wet bath's exhaust vent that I leave running all the time for odor control, there's an air inlet (window) and an air outlet (vent) to provide air exchange while the furnace is running.

[UKDUDE]

The OP has an Interstate so there's no range hood. It's recommended to open the overhead Maxxfan when using the gas burners since the products of burning propane will tend to rise towards the ceiling. If steam is produced, open the small window vent behind the stove and run the Maxxfan motor.
As mentioned, the furnace needs no ventilation, but to avoid interior stuffiness, open a vent just a little; if it's very cold use the vent farthest from the bed.
If running the generator, never open any vents or window on the driver's side since the generator exhaust is on that side.


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[InterBlog]

Our older T1N Interstate is smaller in terms of interior cubic feet, and if I don't turn on the Fantastic while I'm cooking, I quickly come to hate my situation. For me it's not a question of whether it's safe - it's more about comfort. The products of gas combustion and cooking odors will overwhelm the interior unless removed.

Running the toaster triggers the smoke alarm every time unless I crack open the sliding door, even if no toast gets burned.

While running the furnace, I have the flap windows cracked open, because I tend to have the flap windows cracked open 100% of the time. I want to hear what's going on outside regardless of the weather.

[Protagonist]

Originally Posted by InterBlog

Our older T1N Interstate is smaller in terms of interior cubic feet, and if I don't turn on the Fantastic while I'm cooking, I quickly come to hate my situation.

Really it's not. The non-EXT 3500 Interstates have the same interior volume as the T1Ns. The body is pretty much the same except for the rear wheelwells. Only the EXT models have extra volume, and that's only an increase of about 40 cubic feet.

But the interior arrangement of space is different in a T1N-based Interstate, so interior air circulation might be different.

[InterBlog]

Originally Posted by Protagonist

Really it's not. The non-EXT 3500 Interstates have the same interior volume as the T1Ns. The body is pretty much the same except for the rear wheelwells. Only the EXT models have extra volume, and that's only an increase of about 40 cubic feet.

But the interior arrangement of space is different in a T1N-based Interstate, so interior air circulation might be different.

I haven't looked it up yet, but the NCV3s seem to be taller inside (and they are without question larger at the sliding door). This is a Really Big Deal to my husband, who is 7 inches taller than I am. He notices the headroom improvement because he's constantly bashing his head in the T1N and he feels more comfortable when we preview the new models. I had assumed that this is associated with larger net volume inside, even in non-EXTs. I had also assumed that the larger volume is the reason why the overhead cabinets are vastly more spacious in the NCV3 Interstates. I should check the actual numbers because "larger volume" is a line of reasoning that my husband has used in arguing for a vehicular succession plan, that we plan to get a newer Interstate X years down the line, one that better fits his body instead of just mine.

[Protagonist]

Originally Posted by InterBlog

I haven't looked it up yet, but the NCV3s seem to be taller inside (and they are without question larger at the sliding door). This is a Really Big Deal to my husband, who is 7 inches taller than I am.

I had also assumed that the larger volume is the reason why the overhead cabinets are vastly more spacious in the NCV3 Interstates. I should check the actual numbers because "larger volume" is a line of reasoning that my husband has used in arguing for a vehicular succession plan, that we plan to get a newer Interstate X years down the line, one that better fits his body instead of just mine.

The differences in volume are minor, and mostly the result of different interior trim. For example the difference in overhead locker volume is due to a different method of blocking out the cable run behind the lockers, so less space is wasted. But if you look at the Sprinter vans before Airstream conversion, the T1N and NCV3 non-EXT are almost identical in interior volume.

The sliding door is definitely different, though, both wider and taller on the NCV3. Which is one reason the awning is mounted on the roof and not high on the side of the van.

[Marks71]

Everyone's replies have been helpful, but I have several follow up questions;

* "tip out window behind stove" ? I am pretty sure I don't have one in my 2015 interstate. So if I open a window while cooking, it's drawing from the rear. in chilly weather, this chills the inside of the van.
* I understand and like the functionality of running the fan with an open or cracked window. Draws air into and then through the vehicle. I have a harder time conceptualizing what happens if I run the fan without venting thru another window, or even venting through a window without the fan? what conditions lead to fresh air coming into, vs. stale air leaving the van? Let me give several examples that bother me

1) the poster who said the furnace uses outside air to combust, and then vents it back out. Ok, that's helpful. What if I open a window a crack, or the roof vent without running the fan ? Does that create reverse pressure and interfere with the furnace exhaust?

2) same question about the burners. So if the burner uses inside air and then releases its byproduct (what IS the byproduct anyway ? ) ...if I single vent with no fan, what is the air flow? If I double vent, with or without fan, I guess I'm creating a flow through the vehicle which will bring in fresh and release stale air right?

LOL I"m probably making this way too complicated. these questions have arisen with us waking up to very cool mornings in the high 30's, and wanting to run furnace a bit while cooking ... that I became insecure in knowing what combination of venting and exhaust fans to use while cooking and heating were going on.

Thanks again for the helpful comments

Mark

[Protagonist]

Originally Posted by Marks71

* "tip out window behind stove" ? I am pretty sure I don't have one in my 2015 interstate. So if I open a window while cooking, it's drawing from the rear. in chilly weather, this chills the inside of the van.

This comes as a huge surprise to me. I have yet to see an Interstate that did not have small vent windows below the large fixed windows on each side, operated by turning a knob to open or close them, and designed so they can safely be left open in the rain— as long as the van is parked. Unless you have a Grand Tour with the galley on the passenger side— there are no tip-out windows where the sliding door could hit them. I forgot about that until just now.

* I understand and like the functionality of running the fan with an open or cracked window. Draws air into and then through the vehicle. I have a harder time conceptualizing what happens if I run the fan without venting thru another window, or even venting through a window without the fan?

Air will not enter and leave through the same opening. If you operate the fan with no open window to let in air, all the fan will do is stir the air like a ceiling fan, so it's not much better than running the fan with the vent closed. If you want air exchange, you need to have at least one window open along with the vent fan, preferably with at least the same number of square inches of opening as your fan has.

the poster who said the furnace uses outside air to combust, and then vents it back out. Ok, that's helpful. What if I open a window a crack, or the roof vent without running the fan ? Does that create reverse pressure and interfere with the furnace exhaust?

No effect. The furnace inlet and outlet are next to each other on the driver's side of the van below the windows, and nothing you do to the van's inside air will affect furnace combustion in any way.

same question about the burners. So if the burner uses inside air and then releases its byproduct (what IS the byproduct anyway ? )

The byproducts of burning propane are water vapor, carbon dioxide, and a very small amount of carbon monoxide. One reason to vent while cooking is that burning propane uses up oxygen, and combined with the carbon dioxide produced, that can hurt you. And the more the oxygen in the van is depleted, the more carbon monoxide is produced instead of carbon dioxide. Mind you, you'd have to be cooking for a long time in an enclosed space for that to happen, but I for one do not want to be the crash test dummy that determines how long is too long. So I vent when using the stove.

...if I single vent with no fan, what is the air flow? If I double vent, with or without fan, I guess I'm creating a flow through the vehicle which will bring in fresh and release stale air right?

No real air exchange with only one window or vent open. Inside and outside pressures will equalize, but that's it. Minimal air exchange with two windows or vents open but with no exhaust fan running. There simply isn't enough pressure differential over that short a distance to create air exchange inside, unless there's a strong breeze blowing directly into one window. The fan creates a pressure differential that draws fresh air an open window in to replace what it blows out a vent, basically making its own breeze. The farther apart the window and vent fan are from each other, the more inside air gets exchanged with fresh outside air— fewer dead zones with no circulation.[/QUOTE]I'm probably making this way too complicated.[/QUOTE]De nada. I am a retired engineer. I was my job to develop complex solutions to simple problems. Or was that the other way around…?

[nrgtrakr]

In reply ...
1) The furnace doesn't care what you do - venting or not venting. Again the entire combustion process is isolated from your living space - combustion intake air comes from the outside and the carbon monoxide is vented back outside.
2) Cooking is different. The combustion air comes from the same air you are breathing and the result of burning propane (which includes carbon monoxide) is released into the interior of the RV for you to breathe.
Opening only one window or vent will not get much result as there is very little flow.
An example of why venting while cooking is a good idea. A few years ago I was the maintenance guy for a personal retreat center that had very nice new cabins about 300 sq ft. One winter a group came and wanted the ovens working so they could make their morning tea. The pilot lights set off the CO detectors. So the range top pilot was turned off and only the oven pilot was on - with a digital CO sniffer it took less than 5 minutes to be too high. We bought them hot plates to use and after they left the gas ovens were replaced with electric.

[73shark]

As another data point, my 2011 Interstate (2010 chassis) does not have the tip out vents behind the galley.

[InterBlog]

On a related note, here is a venting mistake that I made only once:

Flush the commode with the wet bath door shut and the bath fan running. The Interstate is so tight that the bath fan will draw air directly from the black tank via its vent, rather than through the bath door seam. Very, very undesirable result. Kitchen venting questions kinda pale in comparison.

[73shark]

Not a problem on the new ones since the movable wall is open at the bottom. This allows the exhaust fan to draw air from the main compartment.

[Marks71]

Thanks everyone. All very helpful, as usual.

[MILATV]

My 2014 doesn't have tip-out behind stove either (only in far back L/R + Sliding Door).

I open the curb side front door window a 1/2 inch or so and run fan while cooking (so I don't pull cold air over the bed - wife doesn't enjoy that much).

Just have to watch your windows and external exhaust if setting still and running vehicle or generator. I don't open Curb side if engine running, don't open driver side if generator running.