tekmar 275 Boiler Control - Manual (Page 12)

© 2012 275_D - 11/12 12 of 48
Mode 1 - DHW in Parallel with No Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) turns on. The primary pump can operate
when a Boiler Demand is present. It is assumed that the
DHW pump will provide adequate flow through the heat
exchanger and the boiler. Heating zones are unaffected
by DHW operation.
Mode = 1
DHW
Pump
Primary
Pump
Mode 2 - DHW in Parallel with Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) turns on. The primary pump can operate
when a Boiler Demand is present. If the boilers are unable
to maintain the boiler target temperature, space heating
zones are shut off sequentially using tN4 communication
in order to provide priority to the DHW tank. For non-tN4
systems, the primary pump shuts off to provide priority. It
is assumed that the DHW pump will provide adequate flow
through the heat exchanger and the boiler.
Mode = 2
DHW
Pump
Primary
Pump
OFF
Mode 3 - DHW in Primary/Secondary with No Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) and Primary Pump relay (terminal 24) turn
on. Heating zones are unaffected by DHW operation. This
mode can be used if the DHW tank is piped in parallel and
a DHW valve is installed (need to use an external relay to
power the valve with 24 V (ac) since the DHW pump output
is a 120 V (ac) powered output).
Mode = 3
DHW
Pump
Primary
Pump
Mode 4 - DHW in Primary/Secondary with Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) and Primary Pump relay (terminal 24) turn
on. If the boilers are unable to maintain the boiler target
temperature, space heating zones are shut off sequentially
using tN4 communication in order to provide priority to the
DHW tank. For non-tN4 systems, priority requires the use
of an external relay to force the heating zones off.
Mode = 4
OFF
DHW
Pump
Primary
Pump
Mode 5 - DHW in Parallel / Last Boiler with Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) turns on and boiler pump 4 turns off. The
control uses the DHW Exchange Supply Sensor in order
to measure the boiler supply temperature supplied to the
indirect tank. There are two boiler target temperatures, one
for the heating system (BOIL TARGET) and one for the
indirect DHW system (BOIL DHW TARGET). In this mode,
the DHW Demand can only be provided from an External
Powered Demand or tN4 Setpoint Control in DHW mode.
All boilers are used for space heating requirements
Boiler 4 is used for DHW when there is a DHW demand
The dedicated DHW boiler is always boiler 4 (relay 4),
even if there are less than 4 boilers.
If boiler 4 is disabled and mode 5 is selected then the
dedicated DHW boiler (boiler 4) will not operate.
Mode = 5
OFF
ON
DHW Pump
Primary
Pump
Boiler
Supply
Sensor
DHW Exchange
Supply Sensor
•
•
•
•