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Setpoint
TEMP
Actual
TIME
Supply
PRGM
Target
Supply
USE
258 indicator lights
Menu
Item
There are eighteen lights on the front of the control that will aid in testing and troubleshooting. During normal operation, these
lights indicate the following functions:
"Power" light on
"Setpoint" light on
"Actual Supply" light on
"Target Supply" light on
"Heat Demand" light on
Dem (5 and 6)
"WWSD" light on
"Minimum" light on
"System pump" light on
"Comb. air" light on
"Stage 1 to 8" lights on
"Test" light on/flashing
Sequence of Operation
When the Eight Stage Boiler Control 258 is powered-up, the "Power" light will come on and the full display along with all of the red
temperature indicator lights are switched on for approximately 5 seconds. The Display will then default to show the "ACTUAL SUPPLY"
fixed display mode and the control will enter the operating mode. A "fixed display" is one which will show its information continuously,
and the four fixed displays available to the user are illustrated on the previous page. More information on access to displays and on
programming is available in the "Programming" section, starting on page 15.
Once in operating mode, the control uses the Outdoor Sensor 070 to continually monitor the outdoor temperature, and the Universal
Sensor 071 to continually monitor the system supply water temperature.
Indoor temperature can be monitored through the use of a tekmar 10K Zone Control (Optional; must be ordered separately)
While monitoring these temperatures, the control recognizes a variety of conditions and inputs, and will operate the system as described
below. During operation, the lights on the front of the control – illustrated above – will indicate how the system is operating.
By reading this sequence of operation section and comparing it to what the indicator lights and the L.C.D. display actually show; installers,
end users and maintainance personnel can easily confirm proper system and control operation in the field and make the right corrective
adjustments when necessary.
Heating Operation
The 258 control must have the Reset/Stpnt selector switch set for "Reset", and must
receive a Heat Demand signal before it can operate in the heating mode.
ROOM
OUTSIDE
1
2
AMPM
UNOCC
S
M T W T F S
• the 24Vac power supply has been connected to terminals Power C – R (1 and 2), and is energized.
• the Display is showing the programmed setpoint temperature.
• the Display is showing the current supply sensor temperature.
• the Display is showing the control's calculated target supply temperature.
• the control is receiving a 24Vac external Heat/Setpoint Demand signal at terminals Heat
or the Heat/Setpoint Demand selector switch is in the "Permanent" position or a 10K Zone Control
is connected and is creating a Heat Demand.
• the control is in the "Reset" mode, the outdoor temperature is above the WWSD point and the
control has shut the heating system off.
• the control has calculated that it must operate the boiler(s) to maintain the Minimum Supply
temperature until the outdoor temperature is cold enough to allow Heating Curve operation.
• the system pump relay is on, closing the contacts between terminals System Pmp (3 & 4).
• the combustion air relay is on, closing the contacts between terminals Comb. air (7 & 8).
• a boiler relay is on, closing the contacts between terminals Stage 1 (9 & 10) , Stage 2 (11 & 12), etc.
• the control is going through the programmed test routine/is halted in test routine.
F C
OVR
Override
4
WWSD
Power
Heat
Minimum
Demand
Pump
Comb. Air
Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
Stage 6
Stage 7
Stage 8
Fixed lead
Stage
Rotate
1 2 3 4 5 6 7 8
Auto
Stpnt
1
2
3
4
5
6
7
8
9
1
Off
Reset
T est
Lo-Hi fire
Fixed last
Int. timer
Perm.
Demand
External
2
3
4
5
6
Off
Demand
Ext. timer
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