16
Concord CXA/H
- Installation and Servicing
INSTALLATION
19 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 1.
Normal operation
During a call for heat on Zone 1 only, the
boiler energises 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.
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 1.
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.
When the clock period ends, Zone valve 1 will (stay) open via normally
closed relay contacts to achieve pump overrun.
18 ZONES WITH INDIVIDUALLY PUMPED ZONES (3 zones shown)
INST
ALLA
TION
Summary of Contents for Concord CXA 100/H
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