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Better ask twice than lose your
way once – Danish
Proverb
Q. Is it risky to free-camp? If so, how can risks be reduced?
A. Although it’s rare, one can be hassled by bored and/or drunken
hoons. They are generally harmless but are always disconcerting. Physical
attacks are extremely rare – but have happened. General experience
is that such problems are mainly limited to a 30-40 km radius of large
towns, and particularly on Friday/ Saturday nights. Keeping 40-50 km
away generally solves the problem. We personally prefer to minimise risk
by camping out of sight of the road – easy for us as we have 4WD
vehicles. If you see others in a promising but exposed situation, stop
and ask if they would not object to company. Most welcome it.
Q. We intend to travel indefinitely, but would still like to vote. Is
this possible?
A. Absolutely! In fact you are legally obliged to. Visit any Electoral
Office (Telstra White Pages) and have them pre-register you as ‘itinerant
voters’. This enables you to cast your votes at any polling booth – no
matter where you are.
Q. I have heard that you have recently changed your published advice
re the effectiveness of vitamin B1 as a mosquito repellent.
A. Whilst vitamin B1-based mosquito products remain on the market, a
recently published study indicates that vitamin B1 may simply reduce
the effect of the subsequent itching and swelling. I feel it is better
to be cautious until further studies are published.
Q. I have spent ages trying to locate a leak in my motorhome. Is there
any trick to this?
A. Not so much a trick as a logical method. Ideally with one person inside,
place a fine spray hose on the outside – but starting low and
slowly working upward (most people do the opposite). This way will indicate
the level at which water is entering – knowing that, it’s
easier to trace the cause.
Q. Is there any absolutely sure way of knowing
whether I have a crook fridge – or a crook fridge installation?
A. Most fridge problems are fridge installation problems but a virtually
100% way to tell is to remove the fridge and see how it performs standing
alone in a garage at much the same temperature as before. If electric,
then cable size and length must be identical.
Q. You have stated many times that most fridges are connected by cable
that is far too small. How come the errors (if indeed they are errors)
are still perpetuated?
A. They are still perpetuated! The problem is caused by ongoing silliness
in cable ratings. When specifying connecting cable, makers of 12/24-volt
electrical stuff worldwide either quote the cross-sectional area (in
square millimetres), or if American, AWG or B&S – and identical
for all practical purposes. That is, the makers specify the size of the
copper conductor that carries the current – or (with AWG and B&S)
the commercially-rated cable nomenclature. But, for reasons that totally
defy sanity, auto cable makers use similar ‘numbers’ (eg,
4 mm, 6 mm) but rate their cable sizes totally differently. Their ‘4
mm’ is not 4.0 sq mm – but the overall diameter of the cable
including its insulation. That rating is simply the size hole you can
push the cable through! Worse, because insulation thickness and type
varies from maker to maker, no exact conversion is possible.
In practice most ‘4 mm’ auto cable is 1.8-2.0 sq mm, most
6 mm auto cable is 4.6 sq mm. The reason why so many installations are
affected is that 4 mm and 6 mm cable are the two sizes most commonly
used. With the former the voltage drop is more than doubled (often to
a volt or more). With the latter the resultant excess voltage drop is
still far from good. When people ask for (say) 4 mm cable what they are
almost always sold is 1.8-2 sq mm auto cable. Many people fall into this
trap.
Q. My three-way fridge draws about 10-amps. It is connected to the battery
via eight metres (total for twin conductor) of 35-amp cable. A friend
has one of your books and says that the cable is still not heavy enough.
How can this possibly be – it’s already three and a half
times the necessary current rating!
A. This is yet another problem caused by ‘ratings’ being
misunderstood. The ‘current rating’ of cable is almost meaningless.
It relates only to the current the cable can carry before the insulation
begins to melt: i.e. it is a fire rating, and has absolutely nothing
to with voltage drop. It also varies hugely with insulation type. The
most commonly used ’35-amp’ cable is 4 mm auto cable (1.8
sq mm). Eight metres of this introduces no less than 0.75 volt drop.
The minimum size you need is 6 sq mm.
Q. I have two 12-volt 100 amp-hour batteries connected in parallel. If
I connect them in series will I get twice the power?
A. No. In the first case you have 12-volts at 200 amp-hours (equals 2400
watthours). In the second case you have 24-volts at 100 amp-hours (also
equals 2400 watt-hours). Some years back I met a CMCA Member who had
totally refitted his bus, from 12-volts to 24-volts, on quite the wrong
assumption that he would thus gain twice the energy from the same batteries.
Q. Is it true that I should not parallel two batteries of different size
(i.e. capacity)?
A. The batteries must be of the same voltage, type (and preferably age),
but their relative capacities do not matter. Each battery will draw whatever
it needs, and will supply current to the load in proportion to battery
size. Each will reach full charge in much the same length of time. You
can take this to extremes if necessary – an electrical engineer
colleague has been routinely parallel charging a 12 Ah battery and a
350 Ah battery for many years.
Q. How can I tell if the 240-volt wiring in my new motorhome has been
competently done?
A. Most requirements need some level of expertise to check but here are
some you can check visually. If any do not meet the Standard’s
requirements (as set out here), it is possible/probable that other requirements
are not met either. These checks relate to new or recently rewired vehicles
only. All relate to the relevant Australian Standard AS/NZS 3001:2001,
and are required in all Australian States and NZ. (The annotation in
brackets at the end of each item are the relevant AS/NZS 3001:2001 references).
Cable Inlet Socket: must be mounted such that the earthing pin (the largest
of them) is not in the uppermost position relative to the other pins
(3.2.1 (i).) If this inlet socket is mounted on the same face of the
vehicle as any entry door (including those to the driving cab . . .but
not loading or service hatches) then the inlet socket must be not less
than 1.5 metres from any such doors. (3.2.1 – general).
Circuit Breakers and Residual Current Devices: These must have clear
markings on or adjacent to them that indicate the electrical equipment,
or section of the installation, that they protect. (3.3.1.2 (b). Wiring:
Where wiring passes through any conductive material (eg. metal cladding),
the holes must be flared to protect the wiring – or the wiring
protected by means of suitable bushings or grommets. (3.4.2) Unenclosed
cables must be securely fixed at intervals of not more than 300 mm … in
enclosed spaces the fixings may be at 500 mm and supported on a horizontal
surface such as a ceiling or frame member (3.4.3 (b). 12-Volt Outlets:
Must have the voltage rating conspicuously marked adjacent to them and
must be of a form such that their corresponding plugs cannot be inserted
into mains-voltage socket outlets. (3.6.3.3). Please note that this article,
as with all Collyn Rivers’ published writing, is fully protected
by the Commonwealth Copyright Act.
Collyn Rivers, W8054.
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