Air Conditioner question

[docsouce]

When the Coleman Mach A/C in my class C is running in the cool high/low position does it pull outside air into the coach, or does it circulate the air. Also when in the fan position does it pull in outside Air? I'm asking because we are going to riding and camping in the 4 corners area and there could be smoke from the forest fires north of there. My owners manual wasn't much help. It's a Coleman Mach 3 #48253c966.

[wa8yxm]

dougrainer wrote:
ALL RV ROOF MOUNT AC UNITS RECIRC THE AIR. THERE HAS NEVER BEEN A RV AC UNIT THAT PULLS IN OUTSIDE AIR AND NEVER WAS AN OPTION TO DO THAT. Of course, I have only worked on RV AC's for 39 years. Doug

I have seen them. but it may have been more than 39 years ago. Let .. No.. I've seen them since then but the A/C's were already years old when I saw 'em. As i said. they don't make 'em that way any more. any more is... Well Sometime last century... The ones I've seen (and this applies to Window A/Cs for houses as well) date back to the 80's at least for home units. likely before that for RV's.

WHY did they stop making them that way? Efficiency THere was a mandate, came out in the 70's as i recall to make things use less energy. and they use less energy if they just recirculate. no exhaust or intake.

[docsouce]

I know this is way off topic, butttt, 1968 Yamaha DT-1 enduro...It was my second motorcycle, I was 16..I was working in my Dads machine shop for $2.25 per hour. (Pretty good at the time for a kid). Paid $750 for the bike. My Dad cosigned a $250 loan from the dealer. Ran the wheels off that bike in the woods and on the road.
Again sorry for the off topic/forum comment but I just couldn't resist. Thanks Chum Lee for bringing that great memory back..

[dougrainer]

j-d wrote:
Doc, Your conclusions are correct. Some room A/C window units have a little passage that can be opened to bring in some outside air. We had an old Coleman Mach RV A/C that I thought had something like that, but it's been a long time so don't hold me to it. Our newer Mach does NOT.

BTW, that diagram is what you need to understand to periodically clean your Roof A/C. It's pictured without the plastic shroud. The angled shrouding over the Blue Part (evaporator) has to come off in order to clean the blue coil, and the drain pan and drain outlets directly under the blue coil. The red coil (condenser) may trap a few leaves but that's usually it. Notice, the air blows through from the front side of that coil.

What the OLD Colemans had was a lever on the inside shroud that caused a damper door inside the metal plenum to open and close to direct more air out the REAR than the FRONT. But not to allow outside air IN. The only units I saw with the Delta's were the original Winne Elandan and Itasca Windcruiser from the mid 80's. Doug

[Chum_lee]

drsteve wrote:

Chum lee wrote:


If you still think an RV is air tight, drive one into a lake and see how long it floats!

Yeah, I've seen those. Now the question is, "For how long?" (floating) Do they give a Nobel Prize for RV design? Renamed "The Murphy Prize" after Murphy's Law. While it's an interesting design idea, it reminds me of Yamaha's first version of a motorcycle called an "Enduro." It was a dirt bike that was also street legal. If you were a serious rider, it did neither very well. I suspect the same is true for the above pictured . . . . . . . well, what would you call that thing anyway?

Chum lee

[drsteve]

Chum lee wrote:


If you still think an RV is air tight, drive one into a lake and see how long it floats!

[Chum_lee]

In order to create air flow, the rooftop AC unit(s) must create pressure/vacuum. We could argue about that all day but lets not. No RV is air tight. There will always be air leaks of some type through vents in the roof/floor/slides, plumbing vents, the range hood vent, bath vents, dash AC vents (chassis AC), stateroom vents, partially open windows, etc. The vents WOULD NOT WORK if the RV was air tight. They would stall out. Think about it. Just the fact that moving air flows past an exterior vent will create some small pressure differential that will exchange air from inside to outside. It the leakage of air through these vents (leaks) that provides fresh air inside the RV.

If you still think an RV is air tight, drive one into a lake and see how long it floats!

To my knowledge, an RV rooftop AC unit differs from residential/commercial/industrial AC in that the latter is REQUIRED by the Uniform Mechanical Code to provide a certain % of fresh air to the recirc air. (usually 25% or less) Not so in vehicles. In vehicles is usually an option when/if provided.

Chum lee

[smthbros]

Chris Bryant wrote:
There was a Coleman Delta T model that had an exhaust option, but I've only seen one, a long time ago.
Fwiw, I drew that diagram 17 years ago 😉

Thanks for all the knowledge you have brought to the forum.

[j-d]

dougrainer wrote:

Chris Bryant wrote:
There was a Coleman Delta T model that had an exhaust option, but I've only seen one, a long time ago.
Fwiw, I drew that diagram 17 years ago 😉

The Coleman Delta models were over 30 years ago and were quickly dropped from their line up. Doug

Chris, wish that diagram was easier to find, that and the "Tune up your rooftop A/C" post.

Doug, the Coleman A/C I mentioned, was built around 1983. It's easily possible that what I found under the interior shroud, wasn't an outside air control. Maybe a way to re-direct discharge air to/from the front and rear outlet vents. It wasn't a ducted system. Whatever I found, I either disabled it or set it the way I needed it, recirculate inside air only, allow discharge from all its vents, and left it that way.

[dougrainer]

Chris Bryant wrote:
There was a Coleman Delta T model that had an exhaust option, but I've only seen one, a long time ago.
Fwiw, I drew that diagram 17 years ago 😉

The Coleman Delta models were over 30 years ago and were quickly dropped from their line up. Doug

[MrWizard]

when I run fan only
I usually have the windows open
Stirring up the air inside with windows open helps draw a little fresh air in

[Chris_Bryant]

There was a Coleman Delta T model that had an exhaust option, but I've only seen one, a long time ago.
Fwiw, I drew that diagram 17 years ago 😉

[dougrainer]

ALL RV ROOF MOUNT AC UNITS RECIRC THE AIR. THERE HAS NEVER BEEN A RV AC UNIT THAT PULLS IN OUTSIDE AIR AND NEVER WAS AN OPTION TO DO THAT. Of course, I have only worked on RV AC's for 39 years. Doug

[wa8yxm]

If everything is properly installed on most all modern RV air conditioners (That model is included) outside air stays outside and inside air stays inside (Recirculated)

Some older (last century) models you had the option to select either intake or exhaust or both but most any newer ones do not have that option. Outside stays out and inside in, You want fresh air use roof vent or window.

[wolfe10]

donn0128 wrote:
Actually RV air conditioners, at least all I have seen bring in air from outside suck it across the coils and dump cold air inside.

Let's clarify.

Air from the INTERIOR goes through the EVAPORATOR and back to the INTERIOR (no outside air).

As with 100% of A/C's, the CONDENSER takes outside air and returns it (warmer, no doubt) to the OUTSIDE.