tekmar 274 Boiler Control - Manual (Page 8)

© 2012 274_D - 11/12 8 of 44
Relay Setting in Adjust Menu (C.A. Damper / Alert)
The control includes an auxiliary relay that can be used either
for a combustion damper/venting device or an Alert. Selection
is made through the Relay item in the Adjust menu. Alert
When the Relay is set to Alert, terminals 15 and 16 close
whenever a control or sensor error is detected, or when a
warning or limiting condition is detected. When the alert
contact closes, refer to the Error Messages section of this
brochure to determine the cause of the alert and how to
clear the error.
Combustion Air and Alert Settings Section D
Fixed Lead & First On / First Off
In some applications, it may be desirable to have the first
boiler fire first at all times while the firing sequence of the
remaining boilers is changed using Equal Run Time Rotation.
This rotation option is selected by setting the Fixed Lead /
Off DIP switch to the Fixed Lead position.
When using the Fixed Lead rotation option, a selection must
be made between First On / Last Off and First On / First Off
using the DIP switch.
When First On / First Off is selected, the lead boiler is always
staged on first and staged off first. This configuration is typical
of installations where the boiler plant includes similar boilers
but the first boiler is required to be the first to fire in order to
establish sufficient draft for venting.
Fixed Lead & First On / Last Off
When First On / Last Off is selected, the lead boiler is always
staged on first and staged off last. This configuration is typical
of installations where the boiler plant includes a single higher
efficient boiler with lesser efficient boilers. The lead boiler
is the high efficiency boiler, therefore it is the last boiler to
be sequenced off.
Boiler Run Time in View Menu
The running time of each boiler is logged in the view menu.
To reset the running time, select the appropriate Boiler Run
Time in the View menu and press and hold the Up and Down
buttons simultaneously until CLR is displayed.
Boiler Differential Setting in Adjust Menu
An On/Off heat source must be operated with a differential
in order to prevent short cycling. The boiler differential can
be fixed or automatically determined by the control. The Auto
Differential setting balances the amount of temperature swing
in the boiler supply temperature with boiler on times, off times,
and cycle times. This reduces potential short cycling during
light load conditions.
Manual Differential
Differential = 10°F (6°C)
Target + 1/2 Differential
Target – 1/2 Differential
Target
165°F (74°C)
160°F (71°C)
155°F (68°C)
Boiler
On
Boiler
On
Automatic Differential
Off
Differential
Time
Heating Load
On
Boiler Staging Mode - Lo/Hi or Lo/Lo in Adjust Menu
When using multi-stage boilers, a selection must be made
regarding the staging order of the boiler(s). This adjustment
is made in the ADJUST menu of the control.
Lo/Hi: If the Lo/Hi staging option is selected the control stages
in sequence all of the stages in a single boiler. Once all of the
stages are turned on, the control then stages in sequence all
of the stages of the next boiler in the rotation sequence.
Lo/Lo: If the Lo/Lo staging option is selected, the control
stages all of the Lo stage outputs in all of the boilers first.
Once all of the boilers are operating on their Lo stages, the
control then operates the second stage in each boiler in the
same order.
Boiler Fire Delay Setting in Adjust Menu
(per boiler)
The Boiler Fire Delay sets the time it takes for the boiler to
generate flame from the time the boiler turns on.
Boiler Contact Closed
Time
Fire Delay
Burner On