Do you run house AC while on the road

JaxDad wrote:

way2roll wrote:

JaxDad wrote:

dougrainer wrote:

JaxDad wrote:
I guess neither of my motorhomes listened to the experts, both can stay more than cool enough with just the dash A/C.

Mind you, I do understand their limitations and help them a little. Don’t try to block of the cab, that makes it worse, open the rearmost roof vent.

The weak part of dash A/C is not the cooling capacity, a Ford dash unit has more than double the cooling capacity of a rooftop unit, it’s the fan, it’s horrendously undersized.

By opening the rearmost roof vent you create a vacuum at the back of the coach which pulls the cold air to the rear for you.

If your statement about Ford is true, then why does Ford and Chevy option a REAR AC cooling system and control on Suburbans and Expeditions family SUV/Truck?????? I don't listen to experts, I AM one. I base my comments on 42 years as both a RV service Tech and USING both Class A and C's in 90 plus Texas heat for those 42 years. Doug

Because, as I said, the fan is the weak link, it's not a difficult concept to grasp. In order to get cool air to the back they put in a second unit so you don't have to freeze in the front to be comfy in the back.

Frankly I'm kind of surprised an expert wouldn't realize that Suburbans, Ecursions and other units with rear A/C DON'T have TWIN A/C compressors.

Why? Because the single one will provide far more cooling than required.

I DOo listen to experts, they know what they're talking about.

Doesn't the dash AC compressor put drag on the engine thus decreasing MPG? I would think adding a second compressor would rob a good bit of power. The genset is far more efficient at producing power. I am not sure I believe the dash AC is more powerful but even if it were it's far less efficient at cooling a large space compared to the rooftop air.

I think you’re holding that stick by the wrong there friend. An engine driven A/C compressor cycles on & off as needed so it’s only a load (decreasing MPG as you put it) when it’s actually working, the genset to run the rooftop runs continuously. BTW, studies have proven that the engine-driven A/C compressor is such a tiny load in the overal scheme of things that driving with the /C off and the windows open will actually burn more fuel than using the A/C. Again, that is mostly because A/C is an intermittent load, open windows are a constant load.

I also think you misread my post, I said there is NO second compressor running, not unless you have the rooftop running that is.

The RPM's on the gen set likewise only run high when under load as the AC cycles on and off. The studies about windows open are based on the physics of open window creating drag compared to the dash AC. Closed windows and no AC gets better mileage than with the AC- ergo, AC impacts MPG. It's not comparing the dash AC to the rooftop AC. You won't convince me that the dash AC is more efficient at cooling the coach than even one rooftop AC and likewise trying to say the MPG impact of the generator running over the dash AC is probably not even measurable. So, genset and rooftop air = a cooler coach and likely the same MPG loss as the dash air alone. At the end of the day, I wouldn't care anyway. I never measured MPG when we had our MH and don't measure it now towing a FW. Always chose the roof air over dash AC and everyone in the coach was happier about it. To each his own.

Back to the OP, do what makes you comfortable, the impact to MPG is negligible when comparing the 2. On a hot day, I doubt the dash air keeps you cool, especially anywhere other than sitting in close proximity to it. 30 feet away, it won't.