tekmar 274 Boiler Control User Manual

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Flow Proof Delay Setting in Adjust Menu
The control waits a period of time to receive a flow proof
demand from the time the primary pump turns on. If the
control does not receive a flow proof demand within that
period of time, the primary pump turns off and the stand-by
primary pump (if active) turns on. The control then waits
that period of time again for the stand-by primary pump to
prove flow. If flow is not proven, the stand-by pump turns
off. The period of time is set through the Proof Demand
‘Pump’ DLY item in the Adjust menu and it is adjustable
between 10 seconds and 3 minutes.

Flow Proof Demand Test
The control includes a flow proof demand test in order to
determine if the flow/pressure device has failed. A flow
proof failure is detected if a flow proof is present after the
pumps have been shut off for more than four minutes. This
can occur if the flow proof device sticks in the on position
even when flow has stopped in the system. A proof demand
error will latch when this condition exists.

Primary Pump Rotation Setting in Adjust Menu
The control rotates the pumps based on the Rotate item
in the Adjust menu. Frequency of Rotation is based on the
running time of the pumps. Rotation is done when the lead
pump is off. If the lead pump runs continuously, the rotation
is delayed for up to 12 hours. If the pump runs continuously
and rotation is required, the control shuts off the lead pump
and 1 second later the stand-by pump is turned on. This
eliminates overloading the pump electrical circuit. Upon
turning on the stand-by pump the flow proof input is checked
after the flow proof demand delay time.

Primary Pump Purge
After the last valid demand is removed, the primary pump
is operated for an additional purging time of at least 20
seconds. If the last demand came from a tN4 zone, the
control sends out a purge message to override the zone
open for the duration of the boiler purge. At the end of
the purge, the zone override is removed so the zone is
allowed to close and turn off the primary pump. If the last
demand came from a non-tN4 zone, the purge period for
the primary pump is adjustable between 10 seconds and
19:55 minutes.

Boiler Pump Operation
The control can operate individual boiler pumps when set
to Mode 2, 4 or 5. Refer to the Boiler Operation section for
more information about the mode settings.

A pre-purge operates the respective boiler pump for a period
of time before the boiler is ignited in order to purge potential
residual heat out of the boiler.

The pre-purge time is determined from the boiler mass
setting. As the boiler mass setting is increased, the boiler
pump pre-purge time is also increased. The pre-purge time
is fixed at 4 seconds whenever a DHW / Setpoint demand
is provided in order to reduce boiler pick-up times.

The control includes a boiler pump post-purge feature that
operates the respective boiler pump for a period of time
after the boiler is turned off. This feature will purge heat out
of the boiler and aid in reducing “kettling”. The amount of
time for the boiler pump post purge is adjustable between
10 seconds and 19:55 minutes. See the boiler pump purge
setting in the adjust menu.

The control will exercise the Combustion Air Damper, all
pumps, and tN4 zones (zone valves and zone pumps) for
10 seconds every three days of inactivity to prevent seizure.

To enable exercising, switch the Exercise / Off DIP to the
Exercise position.

Exercising

Section I

The control has a built-in time clock to allow the control to
operate on a schedule. A battery-less backup allows the
control to keep time for up to 4 hours without power. The
time clock supports automatic adjustment for Daylight
Saving Time (DST) once the day, month, and year are
entered. Use the Time menu to set the correct time, day,
month, and year.

Note: The Setback / Off DIP Switch must be set to Setback
before the Time menu can be accessed.

Time Clock

Section J

Daylight Savings Time Modes

Mode

DST Start

DST End

1st Sunday in April

Last Sunday in October

2nd Sunday in March

1st Sunday in November