All three systems use
the thermal storage principle, whereby large mass heat-retaining mate-
rial heated during the off-peak period and allowed emit the stored heat
throughout the day. See Fig.Electrical installations and wiring systems
295
See the section supplementary equipotential bonding later this chap-
ter and Fig. 14. 14. Heating appliances where the
heating element can touched must have switch which disconnects
all conductors.19.
Electric space heating circuits
Electrical heating systems can broadly divided into two categories:
unrestricted local heating and off-peak heating. The final circuits all off-peak heating installations must
be fed from separate supply controlled electricity board time clock.
Ducted warm air systems have centrally sited thermal storage heater with
a high storage capacity. Fixed heaters that
are wall mounted inset must connected through fused connection
and incorporate local switch, either the heater itself part the
fuse connecting unit, shown Fig. 14. 14.
. This requirement includes radiators which have element
inside silica-glass sheath. Each radiator must have a
20A means isolation adjacent the heater and the final connection
should via flex outlet.
Off-peak heating systems may provide central heating from storage radia-
tors, ducted warm air underfloor heating elements.15.17
Immersion heater wiring.4kW at
each point. The unit charged during the off-peak period, and
a fan drives the stored heat the form warm air through large air ducts
to outlet grilles the various rooms.
DP switch for
functional switching
DP switch for local
isolation during maintenance
Heat resistant
flexible cord
Supplementary
bonding
Water vessel
15A switch fuse
or 15A fuse in
consumer’s unit
FIGURE 14. The wiring arrangements for this type
of heating are shown Fig. This will allow the radiator changed future time with
the minimum disturbance the installation.18 for wiring arrangements.
Unrestricted local heating may provided portable electric radiators
which plug into the socket outlets the installation.64.
When calculating the size cable required supply single-storage
radiator, good practice assume current demand equal 3
