Air Conditioning and inverters

[Jackal]

Planning to do another hot weather trip this summer, last year was Corsica. Was going to be Greece but will probably be Southern Italy instead.

 

Don't have any problems travelling or during the day but boy do those hot nights kick in.

 

Am seriously considering air-con despite having a preference for wild-camping.

 

The idea would be to whack it up just before sleeping to enable us to get to sleep but not to sleep with it on.

 

Read on here about people's use of inverters and second leisure batteries, so could anyone explain how this sort of set up would work?

 

Even 1 or 2 nights on hook-up with the ability to sleep well would be worth the outlay, in our humble opinions.

 

[olley]

Hi Jackal, as a general rule of thumb, for every 100watts at 230v the inverter will draw 10amps, I would think an AC would be around 1000watts so thats around 100amps, unless you have massive battery capacity, running an AC from your batteries only is not on.

 

You could run your engine on tick over so the alternator powers the AC or buy a portable genny.

 

Olley

[davenewellhome]

Waeco's 1500 Watt air con unit draws about 87 amps on 12 volts so gives a seriously BIG hit to a battery. The 12 volt systems generally work through an inverter and will all clobber a battery. Also bear in mind that the actual capacity of a battery will reduce drastically as the current requirement is increased. A single 85AH battery will in theory give 4.25 amps for 20 hours (most battery capacities are quoted on the 20 hour rate), 8.5 amps for probably 8 - 9 hours but 85 amps for less than ten minutes. your only chance of running an AC unit through an inverter without killing your batteries would be to have the engine running at a fast tickover (1500-2000rpm) and heavy duty split charge capable of carrying the full current requirement of the AC.

 

D.

[Jackal]

Thanks Olley and Dave.

 

As I thought, whilst wild-camping I'd have to run the engine to realistically cool the van down sufficiently.

 

Roughly how long would a suitable Air Con Unit take to cool a 7m coachbuilt? More than the 10 minutes you mention?

 

I wouldn't consider 10 minutes to be too excessive but double that every night would start to grate, I'm sure.

 

Would I be advised to get a second leisure battery and a split charger?

 

[davenewellhome]

"Roughly how long would a suitable Air Con Unit take to cool a 7m coachbuilt? More than the 10 minutes you mention?"

 

That depends on the ambient temperature at the time and how powerful your AC unit is. I'd say at a rough guess that a 1.5KW system would take 30 minutes to an hour to bring the temperature down from 30 to 20 degrees but that is purely a guess.

 

D.

[Guest JudgeMental]

 

I have a WAECO roof unit and in last 2 years summer use only felt the need to run at night on a few occasions as temperature in Italy at night was OK. but further south I would probably use at night more.

 

A 20 minute run would probably be enough to cool down a locked up van and (as long as well ventilated) possibly you could be asleep before it gets uncomfortable. But wild camping can you leave all your windows open? I'm not sure...depends on location I suppose *-)

 

we run it every day, as temp was 30-35 deg and it was a relief to get away from the heat sometimes.

 

mine is soft start and runs fine on a 6amp supply. it also runs on 12v when driving. for wild camping the only option is a generator. IMO preferably one with a gas conversion and if you have refillable bottles probably the most efficient way of doing it.....But probably cheaper to stay on a site.and use their supply :-D

[Jackal]

Thanks, Dave.

 

I know it was like asking "How long's a piece of string?".

 

I suppose if you were still driving to your destination and had 30 minutes or so to go and whacked it on for the final 30 minutes of the journey and another 10 to 15 whilst you were getting ready for bed...

 

What would a 1.5KW unit cost to be installed at yours, Dave?

 

[Brian Kirby]

Jackal - 2009-01-11 8:03 PM Thanks Olley and Dave.

As I thought, whilst wild-camping I'd have to run the engine to realistically cool the van down sufficiently.

Roughly how long would a suitable Air Con Unit take to cool a 7m coachbuilt? More than the 10 minutes you mention?

I wouldn't consider 10 minutes to be too excessive but double that every night would start to grate, I'm sure.

Would I be advised to get a second leisure battery and a split charger?

I think you may be missing something.  During the day the van, and its contents, will get hot.  After sunset, and into the night, the external heat will gradually subside, but the van structure and its fittings and contents will retain most of the heat they have gained during the day. 

Unassisted, this heat will only be lost through the (insulated) van roof and walls etc.  This is, inevitably, a slow process; its pace being depenent on the difference in temperature between inside and outside, which is seldom great, but generally increases toward dawn.

Enter one air con unit.  This will remove heat from the air inside the van.  However, all the contents of the van, which are much denser than air and so store much more heat, will take much longer to cool down.  Because they are trapped in the van, they can only lose their heat to the air inside the van.  Thus, although you will get an immediate "hit" from the air con, as soon as you switch it off, the temperature in the van will begin to rise again as the hot contents begin losing their heat, and in doing so re-heat the internal air.

To maintain comfort inside the van, it is necessary to keep it, and its contents, cool.  This implies running the air conditioning 24/7 or, alternatively, getting it going as soon as the sun sets and running it most of the night to prevent the heat building up again.

Last point, many people run air conditioning with windows, rooflights, or doors open.  This is madness, as in effect they are trying to air condition the whole region they are in.  All doors, windows, and rooflights must be closed for maximum benefit, and to economise on electricity consumption. 

You will need mains electricity to run air con, no amount of batteries, whether via inverters or not, will be sufficient to maintain comfort.  You may find sites charging extra for vans with air conditioning, simply because of the amount of electricity these units consume.

[Jackal]

Gas conversion???

 

Pardon my ignorance but does the air-con unit need gas, Judge?

 

We only found the nights to be a problem in Corsica, to be honest. The baby slept like a log and so did the old man. The Missus and I, just tossed and turned all night even with all the windows open and a large desk fan moving the hot air around.

 

What unit have you got, Judge?

 

[Jackal]

Thank you Brian.

 

I suppose what you are saying is that the one way of ensuring a cooler vehicle of a night is to cool it down during the day.

 

What I suppose I'm trying to avoid is that initial struggle to get to sleep because you cannot breathe.

 

Surely, if the van is cooled somewhat an air-con unit might buy you a window of opportunity, Brian?

 

[davenewellhome]

Jackal - 2009-01-11 9:45 PMThanks, Dave.

 

I know it was like asking "How long's a piece of string?".

 

I suppose if you were still driving to your destination and had 30 minutes or so to go and whacked it on for the final 30 minutes of the journey and another 10 to 15 whilst you were getting ready for bed...

 

What would a 1.5KW unit cost to be installed at yours, Dave?

Well I don't generally fit air con units, mainly because their 12volt power consumption will cause the vehicle's alternator to run at, or near, its maximum output. This will, in my humble opinion, lead to premature failure of the alternator and therefore I have resisted the urge to sell ac/dc air-con units. If however you really do want to go down this route I can work out a price for you but you'll have to phone me to sort it out as the most suitable unit for you will depend on the size of your 'van, how many people will be using it and the average ambient temperature and humidity. ;-) D.

[Jackal]

Dave,

 

I will bear in mind what you say about the alternator issue and give you a ring in the week. Thanks.

[PJay]

We have a WEACO unit like The Judge, Great to run when driving in heat, It has a remote control, so I can point at the unit to switch on/off while my other half is driving we usually cool the van down before going to sleep. to noisey to run all night, but does need hook up, to run it. The beauty of this unit is, it is also a heater, so extra heat in winter if needed, and seems to be quiker than the truama, usefull for a faster warm up.

[BGD]

Brians point about the heat retention of the vehicle itself (all fixtures and fittings, seats, plastics etc etc) is very well made.

 

Even if the volume of air within the MH is kept roughly constant (doors/windows closed), the AC unit does NOT just have to cool that air volume, but that cooled air then has to absorb the stored heat from the solid items throughout the vehicle, and be cooled again.....and over and over and over, until all those things have also been cooled to the same temperature as the air.

(Probably haven't explained this properly, but I hope you get the idea).

 

This is a BIG issue in hot countries. We notice it here in Spain in the summer in our car all the time.

The car has air-con, and really does balst out cold air from the vents within a minute or so of being switched on. But with outside ambient temperatures at (say) 35 degrees, and the inside temperature of the vehicle inside its glass windows become well above that, the absorbed heat inside the cars surfaces "reflects" this heat back into the air for absolutely ages as the aircon pushes cooler air through the car.

I got the air-con checked out last summer, as I thought it was failing....but the techie explained that there's nowt wrong with it, it simply ain't capable of air-cooling the volume of air inside the car when its having to fight with outside air temp, and the much higher absorbed heat of everything inside the car......maybe 60 degrees or even more, deeply absorbed over many hours.

 

He did suggest getting dark/reflective tint fitted to the rear and rear-side windows (illegal to have it on screen or front side windows here) and put one of those silver screen thingies across the inside of the screen whenever parked up. We did.

These things did/do make quite a difference, and certainly help in the fight against allowing the car to absorb heat.

 

No air-con in our MH (not even in the cab) as it is about 4 million years old, but it does have a Luton overcab, and this seems to make a HUGE difference in terms of sun heat getting absorbed into the vehicle.

I guess any "lowliner" type MH's are gonna suffer a lot more in Med-type summer heat than those with overcab Lutons.

 

If you do have a lowliner and you venture to very sunny countries, it might be a very good idea to slap your silver screen onto ther outside of your winscreen as soon as you park up, to reduce heat absorption from then until dark.

And park up in shade wherever possible.....anticipating where the sun is gonna move in the coming hours!

Many Spanish camp sites have a lot of those pitches with green mesh netting hung between trees over them. They maybe don't look the most appealing, but boy are those pitches way way cooler than others out in the full sun through the summer months.

[Pat]

Jackal - 2009-01-11 9:52 PMGas conversion???

 

Pardon my ignorance but does the air-con unit need gas, Judge?

 

We only found the nights to be a problem in Corsica, to be honest. The baby slept like a log and so did the old man. The Missus and I, just tossed and turned all night even with all the windows open and a large desk fan moving the hot air around.

 

What unit have you got, Judge?

I think Judge was referring to a small generator with a gas conversion so that if you have a fixed LPG tank you could run the generator off of that tank!Regards Pat

[Brian Kirby]

Jackal - 2009-01-11 10:03 PM Thank you Brian.

I suppose what you are saying is that the one way of ensuring a cooler vehicle of a night is to cool it down during the day.

What I suppose I'm trying to avoid is that initial struggle to get to sleep because you cannot breathe.

Surely, if the van is cooled somewhat an air-con unit might buy you a window of opportunity, Brian?

The point I was answering was yours, regarding use of the air conditioning for 10 minutes before going to bed. 

The point I was making, is that you will need to run the unit for hours, rather than minutes, since the accumulated heat within the van's structure and contents, as well as the hot internal air, all needs to be exhausted.  As I said, failure to cool the whole of the van's structure would just mean it would begin to heat up again as soon as the air conditioning was turned off.

Whether you run it day and night, or just at night, to achieve this, is a matter of choice.  However, if you want to sleep in a cool motorhome in a hot country, you will need to have the air conditioning running most, if not all, of the night.  There is no alternative: sorry.

[Guest JudgeMental]

Jackal - 2009-01-11 9:52 PMGas conversion???

 

Pardon my ignorance but does the air-con unit need gas, Judge?

 

We only found the nights to be a problem in Corsica, to be honest. The baby slept like a log and so did the old man. The Missus and I, just tossed and turned all night even with all the windows open and a large desk fan moving the hot air around.

 

What unit have you got, Judge?

As Pat said, you can convert generators to run on gas. Saves carrying explosive petrol in containers.....Cleaner, cheaper and more convenient. From memory we have a Waeco EC1500 ac/dc. (I think they have been taken over by dometic) I bought a dual voltage one based on our experiences a few years earlier when someone hit my van before the holidays and we had a hire van for a month is Spain. It was a new Fiat and the cab a/c was hopeless the kids where very uncomfortable in the back.........But my Ford based EuraMobil is a different beast, much better insulated and cab air is powerful enough to keeps things comfortable for us all. So I would probably just but a 230v one in the future.Brian is right, during the day we close up all windows and blinds. At night I give it a blast on our return from a night out then open the windows and turn it off when we go to bed.....I have been to Greece and Corsica in the summer and would run a/c day and night under those circumstances. And as Brian says if you wanna stay cool in high night time temps it needs to run all night, simply no way around it. You get used to the noise, it’s a bit like sleeping on an aeroplane lol. But pick a low noise model or you will fall out with people on site. Ours is reasonably quiet and we have never had a complaint.So we just book suitable camp sites in advance (minimum 6 amps) and forget about generators. But may get a gas one in the future when the kids stop coming and we head further afield once again.......

[Minstrel]

Perhaps the need for aircon depends partly on the amount of insulation in the motorhome. One which is good for cold weather like the Judges Euramobil (and mine) might not heat up quite to much inhot weather.

 

To be fair, we've been unlucky enough not to have really hot weather sday and night so far, so I'm not an expert. We certainly find the large over cab mostly keeps the cab comfotable when driving.

[alan k]

We've got cab aircon so can keep cool on the move, but hot sticky nights are a pain. Yes we do all we can to keep the heat off the van during the day ( silver screens whenever parked up) but if its really bad at night we have an oscillating office type fan sat on the shelf blowing air over the bed, yes I know its not cold air but even a hot breeze is beneficial.

 

Haven't quite got to the point of thinking about habitation air con yet,

 

alan

[LordThornber]

I might be talking b******s here but here goes!!

 

Two things we're going to try this year. Taking the removable carpet out, I can't believe we've never thought of that before. It must be that much cooler and another thing is opening all of the locker doors. Maybe the heat in them will disperse into the van during the day rather than just be trapped in there all night??

 

Having said that the temps we encountered last year were exceptional.

 

Brrr :D

 

Martyn

[Jackal]

Thanks for your replies, one and all.

 

It's funny how the only negative point from the whole of last summer in Corsica was the airless, breezeless nights trapped in the overcab, trying to get away from the wife (!) with a fan and the overcab windows, the only sources of "fresh" air.

 

It wasn't so much the heat to be honest, just the "dead" air. Even during the day the heat whether travelling, walking or just being in and around the van wasn't exactly the worst I've ever experienced. It was simply the lack of fresh, cooler air during the night.

 

Now whether, air-con could help this still remains a little unclear. Thanks to Brian, I'm now sure that if it's the heat that we want to get rid of then air-con all night long is the only way to go.

 

But as there is no way I'd sacrifice the wild-camping for that, then it does sound as though, I could put the money to better use. Unless of course, we stayed on hook-up on extremely hot days only...

 

 

[Brian Kirby]

Since hot air rises, the overcab will be the worst place to try to sleep on hot nights. 

This won't be much help after a day on the road, when everything gets fried, but just parking in shade, preferably under a tree, and especially shade from afternoon/evening sun, will help to reduce the build up.

Have you considered a rooflight mounted fan?  Fiamma, Omni, and Fantastic, all make replacement rooflights with variable speed and reversible fans incorporated, and I gather Omni are now making a kit fan that can be mounted in almost any make of rooflight.  All have translucent/transparent options so you don't lose the light from above, and the rooflight can still be opened for natural ventilation without running the fan.

Just the air movement will help you to cool off.  The fans are all 12V, use little current, and are all claimed to be quiet running.  You'll need to get a 12V supply to the rooflight, but apart from that, much cheaper to buy than an air con unit, and can be used whether on hook-up or not.

[Jackal]

Thanks again.

 

Our standard desk fan seems to help a bit but not the poor sod furthest away from it in the overcab!

 

A ceiling mounted fan might help and if it were 12v, even better. I did try looking for something to run off the 12v but could only come up with small 9 inch versions used by truckers on their lorry dashboards.

 

I'll have a search on the Internet for them.

 

Has anyone any ideas as to how quiet they are?

 

 

 

[Guest JudgeMental]

Jackal - 2009-01-12 9:16 PMThanks again.

 

Our standard desk fan seems to help a bit but not the poor sod furthest away from it in the overcab!

 

A ceiling mounted fan might help and if it were 12v, even better. I did try looking for something to run off the 12v but could only come up with small 9 inch versions used by truckers on their lorry dashboards.

 

I'll have a search on the Internet for them.

 

Has anyone any ideas as to how quiet they are?

 

 

12v fans are hopeless...we managed for years with two desk top fans before getting the a/c. But would not be without a/c nowre your overcab, have you windows at each end? if not no wonder you bake!lol We had to specify an extra window as standard van had only one. Our over cab is latgest in class, well insulated and airy with two windows and Heki next to it as well. the kids never conplain (we sleep in bed over garage)your chioces are simple: and vary from high to low cost avoid the far south and extreme heat in high season. Get a/c and book suitable sites. look at either the new style Efoy fuel cells or the latest gas running version just coming out..... a conventional petrol genny preferably with a gas conversion (last probably cheapest option after staying on sites)

[Jackal]

We have two windows which open to 90 degrees at either side and a large heki right next to us.

 

Even with a large desk fan, another smaller heki open and the two large side windows open ajar, depending on the perceived security situation, the air circulation was not good, even by the sea.

 

Of course, at about 5am each morning the van and ambient temperature usually left us clambering for the sheet but in my experience, it was the "dead" air situation that grated the most, not the heat.

 

As for the heat during the day, as I said it really didn't bother us so I can't really see that forking out for air-con, just to cool us during the day would really be worth it, unless it enabled us to make the nights more bearable.

 

I have no intention of giving up the far South though!