Dash air vs generator

[racechaser]

I'm sure this has been beat to death but, is it more efficient to run the dash air or to run the generator and one roof air.This is on a gas Ford v-10 and a 7000w Onan. Thanks for any input.

[xctraveler]

And some of us may keep track of expenses for reasons other than budget. I know I have a lot of expense data that I look at from time to time out of curiosity. No way I need to change my behavior as a result of having the data. If I do plan a long trip I like to know I can position the cash to cover it in advance so when the bills come in they get paid without my having to do anything further.

Also when someone asks about expenses I can report what my expenses have been based on my own experience not a SWAG. Just one person's rationale for seeming to be OCD about expenditures.

To get back on topic, I run what I need to be comfortable and to keep DW comfortable (even more important).

[Effy]

Mile High wrote:

Effy wrote:

Mile High wrote:

Effy wrote:

SoCalDesertRider wrote:
The most economical way, is to run only one engine, not two.

Not necessarily true. While the engine does a good job of producing power to move the vehicle, it's not so good with the added load of driving the dash AC compressor. Thus why it's been argued that MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach. The generator is more efficient at producing the electrical power. So, in this case 2 engines being used at greater efficiency is better than one at a lesser efficiency.

1.2 gallons an hour for the generator isn't paltry. At 60 mph that brings fuel consumption down to 7.2 from 8.3. I don't think that AC compressor would impact mileage on my diesel anywhere close to that.

The efficiency difference is in how many btu's the dash air can push vs the full 40,000 btu's the generator can push through 3 ACs for that 1 mpg. When its hot and the passengers are miserable, none of the math matters.

What I said was" MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach"
Quite possibly with your set up, yes I would agree. Dash AC probably does tax that V10 that is already stretched to its limit, and that 15,000 btuh AC on a 4,000 Microlite gen probably doesn't use much, but still the spec says .5 half load an .7 full load.

Your rig is quite different than mine.

so my comment was relative of the fuel usage of cooling the entire coach as opposed to the mileage suffering via dash air alone.

And yes to me the .5 MPG - my gen usage is nowhere near 1.2 - I doubt anyone else's is either - is paltry. Again, speak for what you know, not what you guess I have - (I'm strictly going off the specs) All things considered when a rolling apartment gets 9mpg - who cares if it becomes 7 or 8? Heck a good headwind or hills will do that for you.

It's all a moot point for me as I don't measure MPG. I didn't buy my MH to monitor how much fuel I am using. I knew it used a lot before I bought it so 6.6 or 10, I don't really care. And so many factors affect MPG that it's such a moving target that gen usage becomes the least of my worries. I bought my MH to travel in comfort. I bought the unit I did so my budget wouldn't force me to watch mpg. It's smiles to the gallon for me.Are you implying that all of us that drive rigs bigger than yours are budget challenged?

Just some points in red above. I would argue that your theory would not apply to all configurations.

Agreed.

And no I don't think everyone is budget challenged. If anything I am, I wish I had a DP and could forget mpg at the same time. But some folks behave as if they are budget challenged in a MH with Curtains and all sorts of creative things to keep from using the gen

[Mile_High]

duplicate

[Mile_High]

Effy wrote:

Mile High wrote:

Effy wrote:

SoCalDesertRider wrote:
The most economical way, is to run only one engine, not two.

Not necessarily true. While the engine does a good job of producing power to move the vehicle, it's not so good with the added load of driving the dash AC compressor. Thus why it's been argued that MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach. The generator is more efficient at producing the electrical power. So, in this case 2 engines being used at greater efficiency is better than one at a lesser efficiency.

1.2 gallons an hour for the generator isn't paltry. At 60 mph that brings fuel consumption down to 7.2 from 8.3. I don't think that AC compressor would impact mileage on my diesel anywhere close to that.

The efficiency difference is in how many btu's the dash air can push vs the full 40,000 btu's the generator can push through 3 ACs for that 1 mpg. When its hot and the passengers are miserable, none of the math matters.

What I said was" MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach"
Quite possibly with your set up, yes I would agree. Dash AC probably does tax that V10 that is already stretched to its limit, and that 15,000 btuh AC on a 4,000 Microlite gen probably doesn't use much, but still the spec says .5 half load an .7 full load.

Your rig is quite different than mine.

so my comment was relative of the fuel usage of cooling the entire coach as opposed to the mileage suffering via dash air alone.

And yes to me the .5 MPG - my gen usage is nowhere near 1.2 - I doubt anyone else's is either - is paltry. Again, speak for what you know, not what you guess I have - (I'm strictly going off the specs) All things considered when a rolling apartment gets 9mpg - who cares if it becomes 7 or 8? Heck a good headwind or hills will do that for you.

It's all a moot point for me as I don't measure MPG. I didn't buy my MH to monitor how much fuel I am using. I knew it used a lot before I bought it so 6.6 or 10, I don't really care. And so many factors affect MPG that it's such a moving target that gen usage becomes the least of my worries. I bought my MH to travel in comfort. I bought the unit I did so my budget wouldn't force me to watch mpg. It's smiles to the gallon for me.Are you implying that all of us that drive rigs bigger than yours are budget challenged?

Just some points in red above. I would argue that your theory would not apply to all configurations.

[Effy]

Mile High wrote:

Effy wrote:

SoCalDesertRider wrote:
The most economical way, is to run only one engine, not two.

Not necessarily true. While the engine does a good job of producing power to move the vehicle, it's not so good with the added load of driving the dash AC compressor. Thus why it's been argued that MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach. The generator is more efficient at producing the electrical power. So, in this case 2 engines being used at greater efficiency is better than one at a lesser efficiency.

1.2 gallons an hour for the generator isn't paltry. At 60 mph that brings fuel consumption down to 7.2 from 8.3. I don't think that AC compressor would impact mileage on my diesel anywhere close to that.

The efficiency difference is in how many btu's the dash air can push vs the full 40,000 btu's the generator can push through 3 ACs for that 1 mpg. When its hot and the passengers are miserable, none of the math matters.

What I said was" MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach"

so my comment was relative of the fuel usage of cooling the entire coach as opposed to the mileage suffering via dash air alone.

And yes to me the .5 MPG - my gen usage is nowhere near 1.2 - I doubt anyone else's is either - is paltry. All things considered when a rolling apartment gets 9mpg - who cares if it becomes 7 or 8? Heck a good headwind or hills will do that for you.

It's all a moot point for me as I don't measure MPG. I didn't buy my MH to monitor how much fuel I am using. I knew it used a lot before I bought it so 6.6 or 10, I don't really care. And so many factors affect MPG that it's such a moving target that gen usage becomes the least of my worries. I bought my MH to travel in comfort. I bought the unit I did so my budget wouldn't force me to watch mpg. It's smiles to the gallon for me.

[J-Rooster]

I run the genset w/ air on when it gets up over 95* when, I'm on the road driving.

[Mile_High]

Effy wrote:

SoCalDesertRider wrote:
The most economical way, is to run only one engine, not two.

Not necessarily true. While the engine does a good job of producing power to move the vehicle, it's not so good with the added load of driving the dash AC compressor. Thus why it's been argued that MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach. The generator is more efficient at producing the electrical power. So, in this case 2 engines being used at greater efficiency is better than one at a lesser efficiency.

1.2 gallons an hour for the generator isn't paltry. At 60 mph that brings fuel consumption down to 7.2 from 8.3. I don't think that AC compressor would impact mileage on my diesel anywhere close to that.

The efficiency difference is in how many btu's the dash air can push vs the full 40,000 btu's the generator can push through 3 ACs for that 1 mpg. When its hot and the passengers are miserable, none of the math matters.

[Effy]

SoCalDesertRider wrote:
The most economical way, is to run only one engine, not two.

Not necessarily true. While the engine does a good job of producing power to move the vehicle, it's not so good with the added load of driving the dash AC compressor. Thus why it's been argued that MPG suffers greater when using the engine to drive the dash AC to cool a portion of the coach rather than the paltry amount of fuel the gen requires to run the electric to power the ducted air and cool the entire coach. The generator is more efficient at producing the electrical power. So, in this case 2 engines being used at greater efficiency is better than one at a lesser efficiency.

[Strabo]

Hey travel in comfort, use the Genny and AC,s. Works great!!!

Tip....When your ready to shut down the Genny, allow it to run a few minutes to cool it down without a full load in hot weather.

[Goldencrazy]

If you just cool cab area the rest of the coach is quite warm when arriving at destination. I like it comfortable upon arrival hence run what is necessary to accomplish that.

[SoCalDesertRid1]

The most economical way, is to run only one engine, not two. So that means, dash air is most economical. Summertime, it will feel much better with both A/C's running, and it doesn't really matter the cost, cause after all, these big vehicles only get 10mpg anyways!

[xctraveler]

For the sake of the environment I would love to burn less fuel. Given that argument I should travel in a Prius not a DP. My generator burns 1/2 gal per hour under moderate load and 1 gph under full load. If we are driving for 4 hours a day (not unusual for us) and running one roof AC on the gen I will burn through 2 gal of diesel for the privilege of keeping the house cool for when we stop. Worth it to me!
Run the dash air too as the panorama windshield functions as a greenhouse.

[fivejackie]

Leaving Julian, CA going to our home in Lake Elsinore, CA. the temp was 100 degrees plus. The dash A/C was unable to keep up so we got the generator going and turned on the coach A/C. Its so nice to travel in comfort.

[jplante4]

Whether your ScangaugeD sees the fuel usage on the genny or not depends on where fuel flow is measured. If it's where it leaves the tank, then yes. If it's measured at the input to the lift pump, no.

My gen runs on propane and the dash air doesn't do a great job of cooling the pup if he's on the couch. So far I haven't needed to run the house A/C, but it's there.

In the last such discussion, I think I saw a number of 0.5 MPG to run the generator.