Air con - how cold should it be?

I got back to the campsite after Chatsworth flower show yesterday and was rather hot and bothered, as it was really sunny all day. Great day, despite no Monty Don.

I decided to try the air con in the habitation, but it wasn’t that impressive. I wondered how cold/effective it should be. It certainly didn’t get the van cold, although there was a nice powerful breeze from the vents.  If anyone uses theirs and can give me some guidelines, I can check it out when I next use the van (not for a month or so unfortunately) and decide if it needs looking at. 

Many thanks
Sally
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I've not really used ours except to check it works. The thing with air con is it's no good if you have any window or door open as all you do is try to cool the outside. I did switch it on this afternoon as we've just moved to a CL with electric and I set it to 19 degrees. The air from the vents was pretty cold and if rooflights and door were shut, I'm pretty sure it would soon cool the inside down to that 19 degrees.

Paulmold wrote:I've not really used ours except to check it works. The thing with air con is it's no good if you have any window or door open as all you do is try to cool the outside. I did switch it on this afternoon as we've just moved to a CL with electric and I set it to 19 degrees. The air from the vents was pretty cold and if rooflights and door were shut, I'm pretty sure it would soon cool the inside down to that 19 degrees.

Hi Paul

Hmm, I’m not sure it would have cooled it down.  The first thing I noticed is that it came on in auto mode set at 20 degrees, with a powerful fan, but I couldn’t change it to a different mode, or reduce the 20. I know that may be in the settings, but I thought I should have been able to change the mode. 

It’s under warranty so it won’t be a problem, but I want to be sure it’s genuinely faulty first. Would you say you could sit in the van on a sunny day and get it cool enough to want to switch it off?  I’m just trying to think of a way of gauging if it’s working as it should. 

Thanks for your reply
Sally
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I can certainly change the mode by pressing the fan symbol and temp by pressing the + and -. I would probably always leave it on auto.

Looks like somethings not right somewhere.

We have the old fashioned AC never lets us down never have a problem we just open the window

chrisk wrote:We have the old fashioned AC never lets us down never have a problem we just open the window

You can’t beat the old fashioned methods. But mine came with it as standard fitting, and now I’ve got it, I want it.    

Sally
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When I turn on my hab AC, it is clear it is working. The air is dry and is much cooler than outside (after an hour or so) . I don't mean when directly in the blast of air, because any direct flow of air will feel cold on your skin even if it is not getting refrigerated.
PS I have a Warwick Duo with a Truma Comfort fitted on the roof, not a Sussex Duo.

The only objective test I can think of is to use a thermometer to measure the air temperature.
Also the AC should remove humidity from the air as well as cooling it.

Opening a window can only get you as cool as it is outside in still air plus the heat retained in the van. AC is better if you have EHU if you want to get some sleep in hot and/or humid conditions.

Allowing for Dons comment that that moving air should feel colder the outlet should feel significantly colder than that. The target temperature is for the space itself and the only way the aircon can achieve that is by being significantly colder than that target. In fact all things being equal the cooled exchanger temp won't change only the airflow rate.

The only thing to watch out for is with some systems setting too low a temp. It should be configured not to do it automatically but with one system we had we could not set it below 19 degrees as if we did the exchanger would freeze up. Because no air could flow it got warmer.

Hi The current setting is defaulted to 20 degrees, on automatic mode. For some reason I’m unable to change to a different mode, or the temperature (I think it went up but not down).  The handbook suggests it should be able to go as low as 17, but I’m no technician or engineer 

I must admit I didn’t leave it as long as an hour.  I was comparing it to the air con in my MX5 which gets cold quickly.  I’ll have to check it out in my next trip but unfortunately it won’t be for another 6 weeks now. 

Many thanks for the help so far
Sally
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This comment is more for the people who understand a/c rather than Sally.

It is recommended that a/c in cars is used frequently to ensure seals are kept lubricated etc.. is the same true of habitation a/c in a motorhome?

The only real  engineering difference between the car A/C and Hab A/C is the former can use an engine driven pump whereas a stand alone A/C has an electrically driven pump to circulate the refrigerant. It is claimed that aircons should be activated regularly to keep seals etc. lubricated so why is it more of an issue with cars than domestic systems that may be off for the best part of half a year?

I don't know if it has been statistically proven that there is a need but given the cost of auto aircon pumps who wants to find out? Even in winter aircons will dehumidify air so there is at least some benefit in running car aircon all year round, you don't get that benefit with domestic installations.

Car A/C has an open drive compressor with a shaft seal. The reason you run Car A/C frequently is to keep the shaft seal lubricated.Habitation van A/C is a sealed system.

Sally if you have a thermometer you can check the difference between the air on and air off temperature of your unit. when running on cooling mode you will see a delta T of at least 5 deg C. I.E. Air being sucked into the unit is warmer than air being blown out of the unit.  Paul Mold is correct with closing all doors windows and vents. As you wouldn't run your fridge with the door open, same principle applies to the van A/C.
Be mindful that if the air being sucked into the unit is at or below your set point temperature no cooling will take place.

And don't forget -- you are trying to cool an area a lot bigger than the inside of the MX5.

Paulmold wrote:And don't forget -- you are trying to cool an area a lot bigger than the inside of the MX5.

I must admit that thought occurred to me when I mentioned the MX5 

I’ll give it a long test of an hour the next time I’m out on hook up. I’ll see if I can get a thermometer as well. I still think there’s something not quite right as I can’t change the modes, it’s stuck on auto at 20 degrees, and the air coming out of the vents didn’t seem really cold. 

I’ve got a 12 month warranty so everything is covered, but it would be so much easier if it was a simple setting or just needs servicing. I assume that these air con units should be serviced?  That’s the downfall of secure storage, I can’t pop out to check things. 

Unfortunately, it’s yet another thing that wasn’t checked correctly during the pre delivery inspection checks and handover.  Perhaps it explains why they don’t provide a checklist or any documentation for the promised habitation check. My faith in large dealers continues on its downward spiral; I naively thought that you paid more but had peace of mind. Apparently not. 

But at the end of the day there are many people far worse off than me, who have real problems.  Mine are minor issues that are all solveable; I’m extremely lucky and already looking forward to my next trip.

Sally
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Paul O wrote:Car A/C has an open drive compressor with a shaft seal. The reason you run Car A/C frequently is to keep the shaft seal lubricated.Habitation van A/C is a sealed system.

Sally if you have a thermometer you can check the difference between the air on and air off temperature of your unit. when running on cooling mode you will see a delta T of at least 5 deg C. I.E. Air being sucked into the unit is warmer than air being blown out of the unit.  Paul Mold is correct with closing all doors windows and vents. As you wouldn't run your fridge with the door open, same principle applies to the van A/C.
Be mindful that if the air being sucked into the unit is at or below your set point temperature no cooling will take place.

Delta T 

Can I ask you a couple of quick questions, just out of interest, as I love learning new things. 

Firstly, does both a car dash air con and a van habitation air con pull air from outside and cool it and push it into the vehicle. Or do they both take air from inside and cool it and put it inside. Or do they work differently.

Secondly, when you say use a thermometer, do you mean a fancy one, like the gun things I’ve seen workmen have, or do you mean just a normal one from Boots etc.?  Would I just hold it up to the vents?

I’m only asking as I’m interested in learning, and doing a bit of hands on. Watch out, girl with spanner! 

Sally
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Paul O wrote:Car A/C has an open drive compressor with a shaft seal. The reason you run Car A/C frequently is to keep the shaft seal lubricated.Habitation van A/C is a sealed system.

Paul, thank you for the clarification. As my instructions didn't appear to mention periodic running I assumed the systems were fundamentally different.

Sally, the only bit of your question I can answer quickly is - delta t = change in temperature.

The other thing I was going to say is that I don't know about regular servicing but my Truma unit had dust filters that should be changed once a year. Part of the housing is pulled away and the filter could then be replaced. Perhaps another question for your dealer.

Two related points worth mentioning perhaps, for those who want the most efficient cooling from their cab aircon.

It's best to switch the air intake away from outside, and set it to re-circulate. Then once the air in the van has cooled a bit, you are cooling it further, rather than continuously cooling hot air from the outside. This has to be a lot more effective!

Secondly, some members have installed a curtain rail behind the cab seats, and pull across a curtain to isolate the cab area. This means the aircon is only cooling the cab, not the rest of the van which is a comparatively massive volume. The curtain itself can be fairly flimsy - it's not there to insulate but just to contain the cooled air in the cab.

(Not much can be seen through the rear view mirror, so blocking the view is not a significant problem.)

Hope this is useful.

Sally
Car aircon can pull air from outside or you can recirculate it from inside the vehicle. Unable to clarify if your habitation air con pulls air from outside or just recirculates the air from inside the van as i am not familiar with that unit.

Delta T is the temperature difference between air on temperature  and air off temperature on the A/C unit. (supply air and return air) 

Thermometer wise an air probe type is best in my view. 
Unless you know about thermography and Emisifity settings, infrared thermometers are rather more complicated and can give you inaccurate measurements.

As Dave says filters are probably 95% of the service requirement given the A/C unit will have such a small amount of refrigerant in it. Any engineer with good knowledge should diagnose any cooling fault if it is refrigerant related by suction and discharge pipe temperatures, NOT pressures. Amperage readings off the compressor also indicate how efficient the unit is running. Amperage is power drawn by the unit. (sorry but it does get too technical to put in words without writing a chapter on it)

Paul

Aircon is still something of an oddity in motorhomes. I can't think why as cars for UK market have come with aircon as a standard fitment for donkeys years now....but the m/h market lags behind.

Fair enough if most of your touring is in UK you probably wouldn't miss it apart from two or three days a year, but for me where i tour it's not a luxury.....i consider it an essential. Driving through Germany and Austria the past couple of weeks, temps have been as high as 35c in my van. That's with driver window open, one of the rear sliders, fan on all vents plus another fan i mounted on the screen pillar.

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Cab aircon is more important to me than habitation as the latter can easily be solved...and very cheaply too. But i continue to be astonished at the number of later model vans which have no cab a/c.

We’re into our third week in the south of France and our air con is working great. 
I bought a stand-alone unit from Argos which sits between the cab chairs and blows cool air into the hab. A vent takes the extract air out the side window and a drain let’s liquid run out to outside. 
The only thing of note is that the van heats up very quickly, even at night if we switch the A/C off. I put this down to poor insulation of the van at build.

StewPotch wrote:We’re into our third week in the south of France and our air con is working great. 
I bought a stand-alone unit from Argos which sits between the cab chairs and blows cool air into the hab. A vent takes the extract air out the side window and a drain let’s liquid run out to outside. 
The only thing of note is that the van heats up very quickly, even at night if we switch the A/C off. I put this down to poor insulation of the van at build.

Insulation on PVC's is notably poor, i suspect due in part to the limited space available. When i replaced my roof aerial i was shocked at the thin layer of insulation under the roof lining. They may as well not bothered! Some friends of mine have an old A class (can't remember the make) and their van is noticeably warmer inside even without heating on. Good insulation not only keeps cold out, it helps keep heat from the sun out too.

My "aircon" is a table fan i bought from Morrisons for £9! Obviously only works when on ehu but had it running the whole night a few days back as van temp was 28c at night.

Remember the "cab" is primarily a business product and the number of company buyers that would fork out for AirCon for their plebs is rather limited (I'll bet their company car has it fitted though).

Just checked on the Ford Transit price list, only the basic manual air conditioning is available and that is £600 plus VAT. I suspect other base vehicles would be much the same.

MH builders have to pre specify their requirements and I suspect would not want to bump the price up that much. After all buyers can add Hab Aircon to their purchase.

Not just for MH's but I NEVER switch off the air con in the car or the Warwick, the front end that is, we don;t have a roof mounted a/c on the Warwick.

Two reasons.............I can find ZERO difference in MPG with it on or off................The most important thing it does apart from cooling is drying, so the inside of the vehicle is bone dry and doesn't smell like a damp dog.