,
,
5
'
Electri€al Safety
95
The question of earthing has caused a lot of
amongstu, ,
aquasts beCause'it is very difcult to apply a suitable method to
aquaria. 'The principle behind the idea of earthing electrical appli—
ances
is that if a fault develops Which, for instance, results in the
metal casing of an electric iron becoming live,,then if that casing is
effectively connected to the earth of the supply systema—glarg'e
current will flow from the live terminal to the earth with the result
that
the
fuses blow out immediately to make everything safe.
Various difficulties are encountered in aquaria,
the problem is
'
not really capable of solution and it is instructive to consider why
this is so,
'
The usual aquarium construction, whereby the water is contained
Within glass, putty, plastics, glass fibre and other materials, which_
are
all electrical ihsulators, means that sh0uld the water become
‘
live,
instance through a cracked heatèr tube, there is no con- ,
ducting “material in direct contact with the water to which
wire can be attached. The only usable, efficient Conducting materials
»
are
metals, usually copper, but even if the aquarium frame were
made of copper it would still be insulated wholly or partially, from
the water, by the glass and putty. Thus the only effective earth
a
terminal actually in thewater itself, but this is not ‘ :Â_
possible because of the toxic effects of submerged metals on small
_
living creatur€s. It is well known for instance, that particles"—
new
copper watefpiping in extremely loW_ concentrations Willklll
fishes easily. Theref0re the onlyposSible effective earthing method
is ruled out:
.
.
__
,
,
,
'
Fortünatelÿ water is not one of…the
and if the _aquarist puts his handintQ
and is su1tably
insulated by shoes,
are dry he“ Will not
_
usuallÿÆeceive a Shock
the full
of the supply
behind it, although it will" still’be unpl'easant (Figure 38), However,
if he
hand
in a live aquarium and thentouchesan,
earth terminal, "such as’ a
connectedtothesupplÿ
earth but insu—lated from the live water by
glass and putty,then
the full current available
flow through his body on1tswayt
tha—t earth (Figure 38), with probably fatal reSultsÏ
’
It Would
seem that the aquaristmustnskanySh0Cks
_
WhiCh _' may Come along and must minimise theuposs1bleeffect
reliablç-installationan—d wiring;and,dl”Y-Ç60nd1üonsÏt15bettert°
,
5
'
Electri€al Safety
95
The question of earthing has caused a lot of
amongstu, ,
aquasts beCause'it is very difcult to apply a suitable method to
aquaria. 'The principle behind the idea of earthing electrical appli—
ances
is that if a fault develops Which, for instance, results in the
metal casing of an electric iron becoming live,,then if that casing is
effectively connected to the earth of the supply systema—glarg'e
current will flow from the live terminal to the earth with the result
that
the
fuses blow out immediately to make everything safe.
Various difficulties are encountered in aquaria,
the problem is
'
not really capable of solution and it is instructive to consider why
this is so,
'
The usual aquarium construction, whereby the water is contained
Within glass, putty, plastics, glass fibre and other materials, which_
are
all electrical ihsulators, means that sh0uld the water become
‘
live,
instance through a cracked heatèr tube, there is no con- ,
ducting “material in direct contact with the water to which
wire can be attached. The only usable, efficient Conducting materials
»
are
metals, usually copper, but even if the aquarium frame were
made of copper it would still be insulated wholly or partially, from
the water, by the glass and putty. Thus the only effective earth
a
terminal actually in thewater itself, but this is not ‘ :Â_
possible because of the toxic effects of submerged metals on small
_
living creatur€s. It is well known for instance, that particles"—
new
copper watefpiping in extremely loW_ concentrations Willklll
fishes easily. Theref0re the onlyposSible effective earthing method
is ruled out:
.
.
__
,
,
,
'
Fortünatelÿ water is not one of…the
and if the _aquarist puts his handintQ
and is su1tably
insulated by shoes,
are dry he“ Will not
_
usuallÿÆeceive a Shock
the full
of the supply
behind it, although it will" still’be unpl'easant (Figure 38), However,
if he
hand
in a live aquarium and thentouchesan,
earth terminal, "such as’ a
connectedtothesupplÿ
earth but insu—lated from the live water by
glass and putty,then
the full current available
flow through his body on1tswayt
tha—t earth (Figure 38), with probably fatal reSultsÏ
’
It Would
seem that the aquaristmustnskanySh0Cks
_
WhiCh _' may Come along and must minimise theuposs1bleeffect
reliablç-installationan—d wiring;and,dl”Y-Ç60nd1üonsÏt15bettert°