Keeping cool

[Four_Winds_Guy]

How do other Class C owners stay cool in the hot summer months?

Do you drive with generator on and air conditioner running? Or do you use the engine air conditioning on the road with generator off, and open the vents to release hot air when you stop?

And does starting the A/C plugged in at a campsite with the roof vents open speed up the cooldown?

We're returning to RVing after 10 years and trying to re-learn all the tricks. Once we plug in at a campsite and turn on the A/C high, it takes a while to get cool, but if we forget to turn it down, we'll be popsicles in the morning.

[sprint99]

Ran the Genny and Roof AC for the majority of our journey to and from Wisconsin and Maine. Kept the wife and sister inlaw cool and happy as well as allowing use of their chargers for phones and tablets. Usually not to adverse of an affect on the mileage that it bothers us as we'll also run them when we have our dogs with us.

[Bordercollie]

I have read a number of interesting posts , on various forums and websites, on this subject. I intend to use my genset and roof AC more, with or without the dash AC, and with various settings of roof and dash AC/vent settings. I was merely interested in affects on mpg, out of curiosity. Increased usage of the genset and roof AC and dash AC is probably good for their seals, etc.

[pnichols]

JaxDad wrote:

AJR wrote:
I don’t know about all the above said. I do know in my two class Cs with only the engine AC working. The cab and the living space up to the kitchen area were cooled. Past that when I stopped I had to turn on the coach AC to get the bedroom cool also with the house AC. I do insulate the cab from the house when stopped.

When I had a class A I had to run the house AC on the road when driving into the sun. The chassis AC did not compare to the AC in a class C.

Just me experience with a gasser Class A.

Which is EXACTLY why I was trying to share some knowledge.

The Ford E-Series A/C is incredibly powerful, but it’s ability to blow air around is severely lacking. It has a puny little 12 volt fan that just isn’t up to the task of moving enough air to cool a M/H.

However, using the above-noted method of opening the rearmost roof vent allows the vacuum to overcome what the fan can’t, getting cool air to the back and draw out the hot air back there at the roof level.

Some people however prefer to argue instead of learn, nothing new there.

That method will of course work if the dash A/C is NOT SET to recirculate -> so that new air from the outside can come in from the front via the A/C fan and replace the air that the vacuum at the rear is removing through the rear vent.

As I mentioned earlier, this method constantly carries outside air - with all of it's dust content - throughout the coach interior.

[JaxDad]

AJR wrote:
I don’t know about all the above said. I do know in my two class Cs with only the engine AC working. The cab and the living space up to the kitchen area were cooled. Past that when I stopped I had to turn on the coach AC to get the bedroom cool also with the house AC. I do insulate the cab from the house when stopped.

When I had a class A I had to run the house AC on the road when driving into the sun. The chassis AC did not compare to the AC in a class C.

Just me experience with a gasser Class A.

Which is EXACTLY why I was trying to share some knowledge.

The Ford E-Series A/C is incredibly powerful, but it’s ability to blow air around is severely lacking. It has a puny little 12 volt fan that just isn’t up to the task of moving enough air to cool a M/H.

However, using the above-noted method of opening the rearmost roof vent allows the vacuum to overcome what the fan can’t, getting cool air to the back and draw out the hot air back there at the roof level.

Some people however prefer to argue instead of learn, nothing new there.

[Happytraveler]

We have friends from Arizona that sold their motorhome and bought a truck and trailer because when they were on the road the motorhome never got cool inside with the dash air on. We said why didn't you turn your generator and air conditioner on when you are traveling. . They said they didn't know you could do that, LOL.

[AJR]

I don’t know about all the above said. I do know in my two class Cs with only the engine AC working. The cab and the living space up to the kitchen area were cooled. Past that when I stopped I had to turn on the coach AC to get the bedroom cool also with the house AC. I do insulate the cab from the house when stopped.

When I had a class A I had to run the house AC on the road when driving into the sun. The chassis AC did not compare to the AC in a class C.

Just me experience with a gasser Class A.

[JaxDad]

Bordercollie wrote:
That's pretty amazing, the engine driven AC compressor doesn't diminish gas mileage. OK, that's good to know.

You were thinking the additional part-time (compressor cycles on & off) load of maybe 1.5 hp would have a significant effect on the fuel consumption of a 6.8 litre V10 that’s already pushing what is basically an 8’ x 8’ brick that weighs ~15k pounds at 60+ MPH?

[Bordercollie]

That's pretty amazing, the engine driven AC compressor doesn't diminish gas mileage. OK, that's good to know.

[JaxDad]

Bordercollie wrote:
I guess we have a choice to believe the conclusion of "somebody's" test a few years back vs some "expert's" silly statement about use of RV generator and roof AC. It would probably be difficult to get reliable results comparing gas mileage with generator running vs use of dash AC, but we could try it on long runs over relatively flat land.

The “somebody” was Consumer Reports and their mileage on the small car was identical to that of the EPA’s testing.

But if you need a more reliable test, Jamie & Adam did a Mythbusters episode on A/C and couldn’t measure the loss in fuel mileage running A/C or not with the windows closed. With the windows open yes, the parasitic loses are significant.

I know that several on units I’ve come across including my 2 m/h’s and several of the V10 fleet units we have the OBD data stream doesn’t show any difference in mileage with A/C on or off.

[Bordercollie]

I guess we have a choice to believe the conclusion of "somebody's" test a few years back vs some "expert's" silly statement about use of RV generator and roof AC. It would probably be difficult to get reliable results comparing gas mileage with generator running vs use of dash AC, but we could try it on long runs over relatively flat land.

[pnichols]

JaxDad wrote:

Bordercollie wrote:
"Dave", the generator expert at Smith Powerhouse, Inc, recommended using the RV generator and roof air conditioner while underway as the generator uses a lot less gasoline than the dash AC requires.

I'm not sure how much faith I'd put in an "expert" that makes such silly statements as that one.

A basic 4kw genny at idle uses 0.3 gallons per hour, 0.5 at half load.

I saw a test a few years back where they concluded thata V10 in a large vehicle would consume an extra 1% in fuel. That makes sense since they figure an econo-box will use an extra 3% with A/C on, smaller engine, proportionately larger load.

If an RV then gets (for easy math) 10 MPG, running the A/C compressor will decrease that to 9.9 MPG if said RV is going 60 MPH then it will use 6.06 gallons per hour instead of 6 gallons.

If somebody thinks 0.3 to 0.5 gallons is "a lot less" than 0.06 they're no "expert" in my books.

A politician maybe, but NOT an expert.

Well stated comments and analysis above!

Plus ... adding to your analysis and math ... in our case I pretty much trust that the Ford E450's air conditioning equipment powered by it's V10 computer controlled engine, when taken together as an air conditioning system, is probably "better and more modernly engineered" than our Onan generator and Coleman rooftop air conditioner. 😉

[JaxDad]

Bordercollie wrote:
"Dave", the generator expert at Smith Powerhouse, Inc, recommended using the RV generator and roof air conditioner while underway as the generator uses a lot less gasoline than the dash AC requires.

I'm not sure how much faith I'd put in an "expert" that makes such silly statements as that one.

A basic 4kw genny at idle uses 0.3 gallons per hour, 0.5 at half load.

I saw a test a few years back where they concluded thata V10 in a large vehicle would consume an extra 1% in fuel. That makes sense since they figure an econo-box will use an extra 3% with A/C on, smaller engine, proportionately larger load.

If an RV then gets (for easy math) 10 MPG, running the A/C compressor will decrease that to 9.9 MPG if said RV is going 60 MPH then it will use 6.06 gallons per hour instead of 6 gallons.

If somebody thinks 0.3 to 0.5 gallons is "a lot less" than 0.06 they're no "expert" in my books.

A politician maybe, but NOT an expert.

[Bordercollie]

"Dave", the generator expert at Smith Powerhouse, Inc, recommended using the RV generator and roof air conditioner while underway as the generator uses a lot less gasoline than the dash AC requires. I'm not sure that the comfort level in the cab will be as good as when using the dash AC. We'll try using one or the other or both. Best to travel in mornings and evenings when practical to be easiest on you and your rig. I worry about hot tires pounding on cupped concrete or superheated asphalt highways on hot days.

[Hank85713]

As to cooling when parked, I read someplace a recommendation to keep slides in initially when turning the ac on. Less area to cool down, thus will cool quicker (?). Havent really tried this but sounds reasonable.

Also camp world sells vent covers about same as MAxair but at lesser cost. Just have their logo on them.