Cab Air con

Not being very technical in these matters, can anybody tell me what produces the air con that gives a nice chill on a hot day in the cab. (Obviously don't tell me to press the switch cos I ain't a total numpty!).

Also is it the case that the mpg is reduced when air con is switched on and if so is it, say, 5mpg that I lose or more/less. Or do i get it for free?

Many thanks!

pablo wrote:Also is it the case that the mpg is reduced when air con is switched on and if so is it, say, 5mpg that I lose or more/less.

There is no simple figure on how much it reduces your MPG - that depends on how hard the aircon has to work, which depends on how big a difference you want in temperature between outside and inside, and on how well the inside is insulated from the outside, among other things (for example some types of system are more efficient than others).

However, from what I've read, you would expect the system to be working very hard indeed for it to drop your average fuel consumption by 5MPG...

pablo wrote:..........

Also is it the case that the mpg is reduced when air con is switched on and if so is it, say, 5mpg that I lose or more/less. Or do i get it for free?

...........

Hi there,

I don't know by how much air-con reduces the mpg on a vehicle ....  

.... but I do know that it was enough to stop me buying and using a vehicle fitted with air-con when I lived in the Middle East!!  

We have a simple rule when travelling in warm or hot climates which is "Try not to drive south between 10am and 3pm." ....  

.... which is why in summer you will see hundreds of motorists having siestas on the French peagé service areas between these times. 

Hope this helps. 

Best regards,

On a hot, sticky day a 5 % reduction in MPG when running your air con can be offset by the drag that you would get if you kept your windows wide open to cool the van by alternative methods.

The difference the air con makes to you in increasing your ability to function and react in traffic is well worth the very slight extra cost.

Q

Never mind the indicators, never mind the mirrors all vehicles should have aircon and heated seats by law...

Have no idea the cost of aircon but I bet by shedding a little of the weight we all carry around and making sure the tyres are inflated properly the extra would be negated anyway!

Hi there,

I lived and worked in the Middle East and India for many years without air-con in my car OR (with the exception of the bedroom) my house.

I worked outside most of the time where air-conditioning just wasn't an option and unlike many of my fellow workers I was able to enjoy the country in which I lived and worked.

Many of my fellow workers (especially hose who were office based) went from an air-conditioned house to an air-conditioned car to an air-conditioned office to an air-conditioned car to an air-conditioned shop to an air-conditioned car and back to their air-conditioned home.

These people did nothing but moan about how hot it was and missed most of the reality of the places where we lived.

It was always "too hot" to go for a walk, "too hot" to go to the bazaar and for some of them even "too hot" to go to the swimming pool.

Needless to say, when we had one of the many power failures, the people who relied on air-conditioning suffered badly and just couldn't function at all.

On the Shedgum Gas Plant in Saudi Arabis there was no air-conditioning on the squash courts; so we waited until the temperature fell to thirty degrees before we started playing.  

Best regards,

Only when I lived in Singapore did we have air con at night and then only because of very high humidity. I have spent much of my working life in southern and Eastern Africa and then did not have, or need, air con.

Dry heat is not a problem and most people can function well if they dress sensibly and don't race about or stand in the sun. What really saps the will to live and restricts clear thinking and functioning is high humidity. Unfortunately many of the high summer days we have, both in UK and Europe, are humid. Air con when driving helps the driver function safely and comfortably. Physiologically high humidity is of more danger to the human body than high temperatures alone.

Q

I never understand why people with air con in cars don't use it. For the tiny amount of extra fuel it uses, its well worth it. We have 2 cars and our van, all have air con ( or climate control its now called) and it is switched on all the time, even in winter. Obviously, when its cold, the heater is on too.
The air con keeps the humidity down and makes the car more comfortable to be in, whether heated or cooled. I used to have a Mercedes car, the aircon was on by default, you had to physically turn it off. I never did.
I have never seen a reduction of 5mpg, more like 1mpg or less.

Hi there,

A few links that explain the costs of vehicle air-conditioning.

This one states ....



http://www.streetdirectory.com/travel_guide/55765/mileage_and_fuel/does_running_your_cars_air_conditioner_really_affect_gas_mileage.html

Then explains that due to more fuel efficient engines air conditioning doesn't cost as much.

It also goes on to point out that at low speeds the reduced "drag" factor of opening the windows means that running the air conditioner is more expensive.  Oh, dear!  It's when sat in traffic that most people switch on their air conditioner isn't it? 

Here's a good one for air conditioning costs once you buy one ....

http://www.andys-kars.co.uk/what-we-offer/air-conditioning-servicing/

Pennies?  I don;t think so!!

Here's the brochure for Webasto air conditioning units for small commercial vehicles.  The smallest they make cools at 3.5kw which consumes 68 Amps at 24 volts (= 1.632kw)

Compare this to the Ford Transit Mk5 Duetto which has a power output (depending on engine) of 63kw, 74kw or 85kw.

So, the smallest air conditioning unit in the Webasto range will consume from 2.6% to 1.9% of the available power being put out by the engine.

This can be directly translated into fuel consumption.  The air conditioning unit will, depending on engine size, use up to 2.6% of the fuel being used.

Not only will this decrease the mpg it will also decrease the amount of available power that can be used to power the vehicle.

Finally, when considering the costs of air conditioning take a look at this site ....

http://www.whatcar.com/car-news/run-air-conditioning-once-week/1195476

Personally, we get so little heat in the UK I am loath to spend money to get rid of it when it arrives!   

Hope this helps. 

Best regards,


References

https://en.wikipedia.org/wiki/Ford_Transit

http://www.webasto.com/fileadmin/webasto_files/documents/international/hd/brochure/light-duty-brochure.pdf


PS

Please note that, for example, the Webasto "Portofino" produces 4.0kw of "cooling" and 5.0kw of "heating" for the same electrical power consumption.

This is due to the enthalpy/entropy of the refrigerant when it is compressed as a gas under adiabatic conditions and then cooled to a liquid.

It is one of the very few situations where you can get a "free lunch"; unfortunately, it doesn't apply to cooling, just heating.  

We average around 28mpg in our van and have the A/C on all the time. In March, I reset the trip computer and average fuel consumption settings and drove to central Brittany, just under 400 miles with the a/c off and the heater on. Average fuel consumption showed as 28.2mpg
Pulling almost 4 tons around all day, the extra load put on the engine by using the a/c apparently makes very little difference.
Reducing top speed and accelerating slower, anticipating traffic conditions and generally driving smoother makes far more difference in consumption.
On the way back from Brittany, it was warmer, we had the a/c on all the time ( as normal) but I reduced my cruising speed from 65 to around 62 ( 100kph displayed on the sat nav)) and we averaged 31 mpg. 
I almost saved enough money on the trip back for that free lunch.....

Hi there,

I agree entirely that a greater saving will be had by driving a vehicle at more economical speeds and by treating the accelerator and brake with suspicion than will ever be made by not using the air conditioning unit .... 

.... but that wasn't the question asked by the original Post.    

We average just over 30mpg with "Petal"; a 1998 Duetto with 103,000 miles on the clock and no air conditioner.  

Best regards,

There can be very few cars and vans these days that are produced without air conditioning, as ajrm says if you are that worried about the little extra cost just drive a little more intelligently.

Perhaps I should be turning the aircon off on my wife's BMW Z4 when the top is down though - we don't normally!

Anyway tonight I am going to sleep on the floor beside the bed and save money on washing the sheets....yeah

The answer to the OP is that really the difference is not that much and could easily be negated but in most peoples opinion the difference in comfort is vast.

Just out of interest Dutto what sort of 'cruising' speed do you drive at to get that return? Genuinely interested.

Kind regards

groundhog wrote:Just out of interest Dutto what sort of 'cruising' speed do you drive at to get that return? Genuinely interested.

Kind regards

Hi there,

As a general rule, I only "speed up" on single-lane roadworks with 50mph speed-limits so that I don't hold up any workers .... 

.... otherwise I try and maintain a steady 46mph which is bang in the centre of the green band on the tachometer.  

For about 50% of the time I am towing a trailer.  I am limited to 50mph (60mph on motorways) and even towing the trailer (with a quad onboard) the mpg very seldom drops below the 28mpg mark on long runs.

Needless to say, racing starts, death-defying braking and heavy cornering are not part of the menu; which is probably another reason why I am also at the 42,000 mile mark on the set of Continental Vanco 2 tyres that we fitted four years ago!
(They are borderline so I am expecting an "advisory" on this week's MoT!) 

Hope this helps. 

Best regards,

I have not really noticed any reduction in fuel economy using aircon and I think as arjm said effects of aircon Vs the weight and brick like aerodynamics of the MH is almost irrelevant. I don't keep the temp very low though, just enough to make the heat a little more pleasurable.
Yes I too have worked in the Sudan, Yemen, Pakistan etc but that discomfort (or as Dutto said enjoyment) is now in the past. Enjoy aircon and the benefits it brings 

Thanks Dutto, there is a genuine reason for asking.

I too have worked in about every corner of the World, anyone that has done that will know the difference between humidity is what makes aircon even more necessary!

I would never buy a vehicle without it even in Europe.

We use our motorhome for pleasure. Even though I do work out the fuel consumption on our trips, the actual amount of fuel we use is not an issue to us. We use the air-con most of the time! Our van has a 3ltr diesel which is a superb engine in a small van, I like using the performance! When we go on some trips, we tow a bike trailer, we still get approx. 28mpg which I think is good for this van.