Do you run house AC while on the road

Some of these rigs have big inverters, battery banks and solar... does anyone try to use an inverter to power the AC - and pull power from an alternator? And solar?

I guess anything is possible, but practical? Each AC would be 1500 watts - 15 amps running. That doesn’t seem like a big load to add to an alternator.

I’m not worried about fuel use, just hrs of generator use.

Yes we run the generator so the passengers can see television and the a/c’s are running.

For Memorial Day weekend I traveled from north Florida to central Florida and back during the heat of the day, 90 plus. Just me and the wife, we only used dash air and were quite comfortable sitting up front. It got warm in the back but we never felt it up front. If had passengers the roof a/c's would have been on

If we are driving while it’s hot we get up and go really early. Even running the roof air doesn’t get forward enough to help the driver much. We also put a large fan in the hallway blowing forward to help the AC get forward

As most of have said, do what makes you feel comfortable. I like to exercise the generator and running the A/Cs (or heat strips) while on the road works perfectly for that purpose.

One other thing about running the generator is that our refrigerator stays powered the entire time we're travelling. We replaced our Electric/Propane model with a conventional refer a couple years back when the system started leaking. What I SAVED with that swap will pay me to run the generator on the road for decades!!!! :) Plus, with the generator running, every outlet in the coach has 120VAC power so the kids can plug their computers/games/whatever where ever they please.

Again, it's all about comfort & convenience. We're on vacation. When I put $125 (or more, now!) worth of gas filling the RV tank, I have never thought "Gee...if I only didn't run the generator, I'd be saving $5." LOL

Enjoy the ride & be safe!

~Rick

INSULATION, INSULATION, INSULATION.

Place your hand on the outside of a quality range when it temperature is 400-500 F...

Place your hand on the outside of a quality freezer when its temperature is zero.

Pay up front for insulation or pay later in fuel cost.

way2roll wrote:

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.

The genset is actually not more efficient at producing power if you have to run the main engine anyway, at least not in the vast majority of cases. The main engine almost certainly has a better specific fuel consumption than the generator's engine (especially if the generator is an air-cooled unit). It might be true that running the generator is more fuel efficient in producing electricity than idling the main engine solely for that purpose, but if so that's primarily because the main engine has a lot more moving parts and thus requires more fuel to idle (and producing only a few horsepower for a generator is effectively idling for it). It definitely is often true that idling the main engine for a long period of time is undesirable for various other reasons.

An Onan QG3000 has a brake specific fuel consumption of somewhere in the vicinity of 0.9 lb/(hp*hr), based on its published specifications, which is twice (or more) that of modern automotive powerplants. To put it another way, the engine in my motorhome's generator is half as efficient at turning gasoline into usable mechanical energy as a modern car or truck engine.

Of course, when talking specifically about air conditioning, one has to also compare the efficiency of the engine driven AC compressor vs. the electrically-driven one in a roof air conditioner, the efficiency of the electrical generator and motor (for the roof air), any energy loss in the belt and clutch for an engine-driven unit, and many other such factors. And indeed, when driving down the road, in either case the fuel used for air conditioning is very much dwarfed by that used for simply moving an RV along the highway.

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.

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.

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.