Electrical advice required for our new van

Submitted: Sunday, Mar 30, 2008 at 10:51

ThreadID: 56070 Views:4916 Replies:4 FollowUps:9

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jdbb

Hello

I hope some of the electric experts can help me make some decisions for our new van which will be built in about 6 weeks time. Our van is 21'6" internal and will be used to free camp where ever possible. It has all the goodies including 2x 120w solar with room for another panel if required.

I am not convinced that the van manufacturer will use the right materials so I have been looking at everything I can find on the net including this diagram -

.

I was thinking of using 4B&S wire and a 175A Anderson plug - are there any issues with going to the larger size?

THe diagram does not show any wiring for a fridge. I have read that one of the biggest problems with van fridges is caused by incorrect wire size. At this stage we are still deciding between a 180l Dometic 4601 or a 12v 180l vitifrigo fridge and I am thinking of using the 4B&S wire. Will this do the job?

Our van comes with 2x 100A batteries. Is there any advantage in using 1 larger battery?

Our van has halogen lights throughout. I have read about heat problems with halogens, electrical interference from flouros, and low lux levels with LED's. What type of lights should we use?

regards

John

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Reply By: MEMBER - Darian (SA) - Sunday, Mar 30, 2008 at 11:16

Sunday, Mar 30, 2008 at 11:16

That looks like Derek's diagram..............re solar.... have noted that a van maker I'm talking to stated (in round terms) that 2 x 120W panels and 2 x 120Ah batteries will be needed just to satisfy a 150L upright compressor fridge. More collection and storage would be needed for the other toys. It's a general view of course, because solar efficiency 'depends' on a lot. My plan would be to top up with a gennie, or a portable panel - a third battery is indicated but where does the weight factor stop ?

AnswerID: 295553

Follow Up By: jdbb - Sunday, Mar 30, 2008 at 11:28

Sunday, Mar 30, 2008 at 11:28

Darian

We have a 2kva honda generator to use if we need it.

We haven't made the final decision on fridge type yet. I am aware that it is impractical to run a large 12v fridge off solar.

It is difficult to work out which fridge to get. The 3 way ones have limitations in extreme heat but have the advantage of running on gas and therefore eliminate the need to take a generator. Correct installation seems to be critical with these.

The 12v compressor fridges are more efficient in hot weather but chew up the power.

I am leaning towards the dometic 4601 as we have a Waeco 50 set up in the cruiser and I'm thinking that this might get us through the times the 3 way fridge is struggling.

John

FollowupID: 561578

Follow Up By: Nomadic Navara - Sunday, Mar 30, 2008 at 12:40

Sunday, Mar 30, 2008 at 12:40

John

You did not say who the van manufacturer is so that we can advise whether they will install an absorption fridge properly or not. If you want good advice you should give full details of what you are proposing.

Host of the sad tales of Dometic fridges come from owners of small fridges and particularly the model 4401 (which was the usual one fitted for quite a few years.) There are very few sad stories of the 'T' rated fridges. These are the Dometic ones of 120 litres and bigger. The only problems with these is where the van manufacturer has fouled up the installation.

The things that manufacturers do wrong include making the hole the fridge fits in too big, spacing the back of the fridge too far from the caravan wall and installing the top vent too low & not fitting the heat shield with it. If you can get the builder to install the R500 top vent (see link) you will have the best installation possible. You will see these vents on Winebago motorhomes.

PeterD

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FollowupID: 561592

Follow Up By: MEMBER - Darian (SA) - Sunday, Mar 30, 2008 at 20:21

Sunday, Mar 30, 2008 at 20:21

Info across my desk from van makers suggests that a lot of people have been choosing compressor fridges for some years now - you are correct of course re the significant power needs, but with extra solar capacity it can work practically I think - we can assume that when we pull up to free camp somewhere the battreries will be topped up via the car's alternator - the solar is then not required to keep the batteries full necessarily, but to reduce the rate of discharge - depending on a lot of things, it will be a few days at best before we either drive again, or run the gennie.

FollowupID: 561678

Reply By: Member - David P (VIC) - Sunday, Mar 30, 2008 at 11:37

Reply By: Ray - Sunday, Mar 30, 2008 at 13:18

Sunday, Mar 30, 2008 at 13:18

Hi. I have batteries in my caravan (2x75amphr). I have used 4awg cable through a 175amp Anderson plug to charge them ( via a solenoid and fuse of cause)
My 3 way fridge is powered from the caravan batteries but only when they are being charged from the vehicle. When the ignition is turned off the fridge does not draw power from the batteries. This isolation is controlled by a solenoid from the ignition. Between the batteries and the fridge I have used 8awg wire.
Regarding the fridge there are certain things to be considered. Baffles new the heat exchangers are quite important and airflow must be concentrated over them. Any open areas around the sides and top of the fridge must be sealed off. I also have a 4" computer fan installed to help the air circulation and if the weather is exceptionally hot or if the sun is shinning on the air vents I use a shade cloth screen to eliminate this.
Be careful where you buy the wire for these jobs as there does not seem to be recognised standards for auto wire. I purchased my wire from JAYCAR

AnswerID: 295577

Follow Up By: Nomadic Navara - Sunday, Mar 30, 2008 at 15:22

Sunday, Mar 30, 2008 at 15:22

"Be careful where you buy the wire for these jobs as there does not seem to be recognised standards for auto wire."

The big problem seems to be there is a de facto standard for auto wire that looks similar to the Australian standards for wire and cable. The de facto auto standard measures the overall insulation diameter (hole size you can push it through) and not the copper that is in the wire. The Australian standard requires you to state the cross-section of the coper in the wire in square mm. The AWG sizes you used (or any other wire gauge) should not be quoted - unless you state the Australian size first.

Another problem with specifying the correct wire size is some people look at and use the current carrying capacity of the wire. The current carrying capacity is the current that will cause the insulation to become soft (or melt.) If you are drawing that much current through a wire your voltage drop will be excessive and your system will not work properly.

For further discussion see this link It gives you the formula to work out your wire size.

PeterD

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FollowupID: 561618

Follow Up By: Dunaruna - Sunday, Mar 30, 2008 at 17:33

Sunday, Mar 30, 2008 at 17:33

Another problem that confuses the hell out of aussie consumers is the B&S table (Brown & Sharpe, AKA AWG), Narva sell a range of Battery & Starter cable which is listed in their catalogue as B&S.

FollowupID: 561636