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17 ZONES WITH INDIVIDUALLY PUMPED ZONES (3 zones shown)
18 ZONES WITH SPRING-RETURN MOTORISED VALVES
IMPORTANT
Terminal L2 may control the appropriate
pump(s) directly, provided that the total
running or starting current does not exceed
6A (resistive or inductive): if this rating would
be exceeded then appropriate switchgear
must be used to control the pumps indirectly.
Three zones are illustrated but the principles
may be extended as required, provided the
above conditions are met. Only one relay is
required, irrespective of the number of zones.
Overrun
During overrun and dormant periods, Zone
Valve 1 is held open. This zone, therefore,
MUST satisfy the conditions in the foregoing
paragraphs and Graph 2.
Normal operation
During a call for heat on Zone 1 only, the
boiler is energised via Zone 1 thermostat and
the normally closed contacts of the relay.
During a call for heat on other zone(s), the
relay will be energised by the auxiliary switch
on the zone valves. This provides power to
energise the boiler. If, in addition, Zone 1 now
calls for heat, its thermostat will open Zone 1
valve via the normally open contacts of the
relay.
Concord CXC -
Installation
INSTALLATION
When the clock period ends, Zone valve 1 will (stay) open via normally
closed relay contacts to achieve pump overrun.
Water circulation system - refer to page 7
IMPORTANT
Terminal L2 may control the appropriate
pump(s) directly, provided that the total running
or starting current does not exceed 6A (resistive
or inductive): if this rating would be exceeded
then appropriate switchgear must be used to
control the pumps indirectly.
Three zones are illustrated but the principles
may be extended as required, provided the
above conditions are met. For each zone
(except Zone 1) a relay with 2 C/O contacts is
required.
Overrun
During overrun periods, Zone 1 pump performs
the overrun facility; this zone, therefore, must
satisfy the conditions in the foregoing
paragraphs and Graph 2.
Normal operation
During a call for heat on Zone 1 only, Zone 1
thermostat energises the boiler, which in turn
energises Zone 1 pump from terminal L2.
During a call for heat on other zones, the
appropriate relay directs power to L1 to
energise the boiler, at the same time ensuring
that Zone 1 pump is controlled by Zone 1
thermostat.
Water circulation system - refer to page 7
17
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