JaxDad wrote:
ArchHoagland wrote:
Always close the roof vents and windows when you are running the air conditioning whether it be parked or moving down the highway.
The air conditioners bring their air in from the interior of the coach. If you leave the vents open then you are drawing in hot air.
Actually that's wrong.
Unless the dash a/c is set to 'max' or 'recirculate' the system cools outside air and vents stale air. All vehicles operate this way.
As for cooling efficiency, if you leave the rearmost roof vent open (hot air rises) and set the dash a/c to highest fan and set to blow down the back the hotest air will be drawn out the roof and the cooled air will be drawn towards the back to cool the rest of the coach.
I've been doing this for years and have proven how well it works to many non-believers over the years.
On a typical dash unit the blower fan is the weak part and it usually can't keep up with the cooling capacity of the rest of the system. This method dramatically increases air flow and really helps.
Maybe in Toronto you can use the Dash AC to cool a 30 foot plus Motorhome. BUT IT WILL NOT in the rest of the world. The Dash AC on "Normal" brings in hot outside air and then attempts to cool it. BEST case on this mode is 56 to 60 degree output air AT THE VENT closest to the Evaporator. We are talking 90 degree ambient outside heat. Now, if you put it on MAX(recirc) that will recycle the Inside air at the DASH area only and will put out 5 to 10 degrees colder air. But to think by opening a rear roof vent that will allow the RV DASH AC to PULL 60 degree area rearward and COOL the rest of the RV, well, you are mistaken big time. Besides that would actually pull needed cold air from the Dash seat area. The Dash AC systems in Motorhomes are designed to do one thing. COOL the front Cockpit only. RV roof AC units are sealed systems for the inside of the RV. They have no way to draw in outside air. The recirculate the inside air only. Motorhomes have a natural vacumm in transit. They will suck in hot air even with all doors and windows/roof vents closed. This is more of a problem due to Slide rooms and how many slide rooms you have. Now, I have 38 years as a RV technician and still working at it. I have worked on ALL brands and types of RV motorhomes(under $750k) for almost 40 years, the Dash AC and the Roof and basement systems. YOU CANNOT COOL A LARGE MOTORHOME WITH THE DASH AC SYSTEM. PERIOD. Regardless of any thing you try to do. Doug
