© 2013
400_D - 09/13
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DHW MODE 3 - DHW in Primary / Secondary no
Priority
When a DHW Call is present, the DHW pump and the
boiler system pump is operated. Boiler temperature zones
can turn on if required.
DHW MODE 4 - DHW in Primary / Secondary with
Priority
When a DHW Call is present, the DHW pump and the
boiler system pump is operated. All boiler temperature
zones are shut off through tekmarNet
®
communication to
achieve DHW priority.
DHW Mode 5 - DHW in Near Boiler Piping with
Priority
DHW Mode 5 requires that a DHW sensor be located on
the boiler outlet pipe and a DHW call from an aquastat
inside the DHW tank. The aquastat operates the DHW
tank temperature while the DHW sensor is used to control
the boiler temperature delivered to the DHW indirect heat
exchanger.
When a DHW Call is present, the DHW pump is activated.
The boiler system pump and all boiler temperature zones
are shut off through tekmarNet
®
communication to achieve
DHW priority.
It is assumed that the DHW pump will provide adequate
flow through the heat exchanger and the boiler.
DHW Priority Override
--------------------------
--------------------------
To prevent the building from cooling off too much or the
possibility of a potential freeze up during DHW priority,
the control limits the amount of time for DHW priority
during cold weather. During warm weather the DHW
priority is 120 minutes. During cold weather the DHW
priority is 15 minutes. Once the allowed time for priority
has elapsed, the control overrides the DHW priority and
resumes space heating for 15 minutes. It will then revert
back to DHW Priority and repeat.
DHW Post Purge
------------------------------
------------------------------
After the DHW Call is removed, the control performs a purge
on the boiler. The control shuts off the boiler and continues
to operate the DHW pump and the Boiler System pump if
applicable. This purges the residual heat from the boiler
into the DHW tank. The control continues this purge for a
maximum of two minutes. The control also stops the purge
if the boiler supply temperature drops below the current
boiler target temperature.
Boiler System
Pump
DHW
Pump
Zone
Valve
ON
ON
ON Or
OFF
DHW Mode = 3
Boiler System
Pump
DHW
Pump
Zone
Valve
ON
ON
OFF
DHW Mode = 4
OFF
OFF
DHW
Sensor
ON
DHW
Pump
OFF
Zone
Valve
Boiler System
Pump
Boiler
Pump
Boiler
Sensor
DHW Mode = 5
DHW Priority Override Time
Increasing Time
Decreasing Outdoor Air Temperature
Conditional DHW Priority
----------------------
----------------------
If the boiler supply temperature is maintained at or above
the required temperature during DHW generation, this
indicates that the boiler has enough capacity for DHW
and possibly heating as well. As long as the boiler supply
temperature is maintained near the target, DHW and heating
occur simultaneously.
