tekmar 268 Boiler Control - Manual (Page 5)

5 of 32 © 2010 D 268 - 11/10
SETBACK (UNOCCUPIED)
To provide greater energy savings, the control has a setback feature. With setback, the
supply water temperature in the system is reduced when the building is unoccupied. By
reducing the supply water temperature, the air temperature in the space may be reduced
even when thermostat(s) are not turned down. Any time the UnO Sw (5) and the Com – (1) are
shorted together, the control operates in the UnOccupied mode. When in the UnOccupied
mode, the UNOCC segment is displayed in the LCD. The control adjusts the supply water
temperature based on the UNOCC settings made in the control. This feature has no effect
when the control is used in the External Input mode.
1
Com
2
Boil
Sup
3
Boil
Ret
4
Out
5
UnO
Sw
Timer Switch
1 2 3
3 2 1
720 hours 690 hours 672 hours
672 hours 690 hours 720 hours
ROTATION
The control’s Equal Run Time Rotation function is fixed at 48 hours. The
firing order of the boilers changes whenever one boiler accumulates 48
hours more running time than any other boiler. After each rotation, the
boiler with the least running hours is the first to fire and the boiler with
the most running hours is the last to fire. This function ensures that all of
the boilers that are being rotated receive equal amounts of use. When
the Rotate / Off DIP switch is set to the Off position, the firing sequence
always begins with lowest boiler to the highest boiler.
Fixed Lead Rotation
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.
First On / Last Off or First On / First Off
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 / Last Off is selected, the lead boiler is always staged on first and staged off last. When
First On / First Off is selected, the lead boiler is always staged on first and staged off first. This DIP switch is only read by the
control when the Fixed Lead / Off DIP switch is set to Fixed Lead.
Fixed Last
In some applications, it may be desirable to have the last boiler fire last 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 Last / Off DIP switch to
Fixed Last. With a fixed last rotation, the last boiler is the last to stage on and the first to stage off.
Resetting the Rotation Sequence
To reset the rotation sequence, set the Rotate / Off DIP switch to the Off setting for 5 seconds and then return the DIP switch to
the Rotate setting.
COMBUSTION AIR OR ALERT CONTACT
The control has an isolated contact that can be used as either a combustion air damper contact or an alert contact. This selection
is made using the C. A. / Alert DIP switch.
Combustion Air (C. A.)
When the DIP switch is set to C. A., terminals 12 and 13 can be used as a switch to operate a combustion air damper. This contact
closes prior to the first stage operating on the control. The amount of time that the contact closes prior to the first stage operating
is set using the combustion delay setting.
The combustion air contact remains closed for a minimum of 15 seconds after the last stage is turned off.
Alert
When the DIP switch is set to Alert, terminals 12 and 13 can be used as a switch to operate an alert circuit. This contact closes
whenever an error message is present on the control. When the alert contact is activated, refer to the Error Messages section of
this brochure to determine the cause of the alert. Once the fault has been fixed, the alert can be cleared by pressing either the
Menu, Item,
▲
or
▼
button.
Boiler Alert
The control can monitor the boiler supply temperature and provide an alert if the temperature does not increase within a certain
amount of time. The amount of time can be set using the Boiler Alert setting. This alert can be used to determine if the boilers
have failed to fire. To reset the alert, press and hold the
▲
and
▼
buttons for 5 seconds while in the VIEW menu.