Caravan air conditioning the options?..

[Jim_374334401]

Just had an exciting day at the NEC and ordered a new Coachman VIP. Then we had an interesting conversation about the fitting of an air conditioning unit. I had expected to have a roof mounted domestic unit fitted, however was advised by the Coachman Rep that the roof mounted unit was unsuitable for the VIP as it hasn't got the necessary roof structure or positioning for the unit. I was steered towards an under locker unit which would have the cold air ducted through one of the wardrobes. Has anyone any experience of using an in locker unit and what are the pros and cons?

 

[ProfJohnL]

Hello Jim,

Whichever system you choose it’s going to be a quite expensive option. Bearing in mind that the number of days its likely to be used will depend on where you are, but in the UK is relatively few.

A simple (not the most accurate) but reasonable way of indicating the potential capability of an AC system is to take the volume of the space to be cooled by the power input to run the AC unit. IF we can show you the effectives of the caravan compared to another system that you will be familiar with – such as your car , you will be in a better position to consider your choices.

Comparing a car and caravan is a practical and reasonably good choice as both collect a lot of solar heat gain, have low thermal mass, which means they respond quickly to changes in ambient conditions. There are other factors that might make a 20% error or so in the comparisons but as I think you will see the outcome is still quite dramatic.

You don’t tell us which VIP model you have chosen but based on the smallest model (460/2) the manufacturers specification tells internal length 4.75M width 2.1M and height 1.9 (all round down a little) gives an approx volume of 18.9 cubic meters. With a maximum power input of 3Kw that gives Kw/m3 = 0.3. or 300W per M3.

I note your stated car is a Ford Kuga. The internal volume of the Kuga will be about 2m3, and the cars AC unit will probably draw 10HP or 7.5Kw of engine power. Apply the same effectiveness calculation and you will get 3.75kw/m3

That is 12 times as much capability than the caravans systems! Even allowing for the estimated 20% margin of the caravan system will still have significantly less capability than the system your familiar with in the car.

So you cannot expect the same level of cooling in the caravan as you get in your car.

Now ceiling or floor mounted. The ceiling versions will only work on room in which its mounted. The floor mount versions with ducting can be made to work in more remote or divided rooms such as bedrooms.

Surprisingly we did used to manage without AC (a bit like mobile phones) and often almost as much comfort can be derived for a fraction of the cost from a simple air fan.

Armed with this perception you can perhaps re- evaluate the desire for AC in the caravan.

 

[Jim_374334401]

Thanks for your reply John. I perhaps should have added that we spend a number of weeks each year in the hotter regions of Europe. We have tried several fans which give little comfort, especially in the Evening when a good night sleep becomes a premium. After over 20 years and with healthier finances we have decided it would be a luxury worth having but are respectful of the advice given by Coachman not to have a roof mounted unit at the structure is not designed to support such a unit. Your comparisons to car units are interesting and I would be interested to know of anyone who have had an under locker unit fitted.

Thanks again
Jim

 

[ProfJohnL]

Hello again Jim,

Of course its entirely up to you if you want one or not, so I'm not telling not to have one, just that you need to be circumspect about how effective it might be.

Its a good idea to ask for personal experiences and I hope you do get some replies. Mighty I also suggest that if you know anyone who uses a caravan with an AC unit , ask if you can visit them on a hot day to experience the unit at work spend some time and be aware of the temperature, air movement (too much or too little) and noise.

A company I worked for (20 years ago) was considering producing an AC unit for caravans, and I was involved with testing some prototypes developed with a major manufacturer of AC units for the armed forces and specialist vehicles. We did comparisons with the established overhead and underbed models and whilst we were comparable on effectiveness, we conscious of the noise, limited cooling, and the cost of purchase and running. Ultimately the project was scrapped because we didn't feel there was enough market share for such an expensive product with limited effectiveness.

We also tried some of the free standing models (available form DIY shops), and whilst they worked, again they were hamstrung by the limited input power, and the need to provide proper air external intake and exhaust for the condenser coil segregation for both the coils of the design. The advantage of these is they are relatively, and can be used at home!.

There is a model available which has separate pods for the evaporator (indoor) coil and the external condenser coil. They are joined by a relatively small pipe assembly which is easier to pass through a window or locker opening, but yet again it is limited input power that prevents it being a perfect solution - be wary of their claims of effectiveness.