15. 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. 14.
Electric space heating circuits
Electrical heating systems can broadly divided into two categories:
unrestricted local heating and off-peak heating.19.
Ducted warm air systems have centrally sited thermal storage heater with
a high storage capacity.64. 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. See Fig.
When calculating the size cable required supply single-storage
radiator, good practice assume current demand equal 3. The final circuits all off-peak heating installations must
be fed from separate supply controlled electricity board time clock. 14.
. This requirement includes radiators which have element
inside silica-glass sheath.Electrical installations and wiring systems
295
See the section supplementary equipotential bonding later this chap-
ter and Fig. The wiring arrangements for this type
of heating are shown Fig.18 for wiring arrangements.17
Immersion heater wiring.
Unrestricted local heating may provided portable electric radiators
which plug into the socket outlets the installation. Heating appliances where the
heating element can touched must have switch which disconnects
all conductors.4kW at
each point. Each radiator must have a
20A means isolation adjacent the heater and the final connection
should via flex outlet. 14. 14. This will allow the radiator changed future time with
the minimum disturbance the installation.
Off-peak heating systems may provide central heating from storage radia-
tors, ducted warm air underfloor heating elements.
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. 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
