Whenever a fault is detected in any of the sensors, the indicator lights will flash in specific ways to indicate the problem.
The following look-up table describes each error condition and shows the flashing light sequence that results.
After repairing the problem, press the test button to cycle the control through the test routine and confirm that the fault has been
repaired and that correct control action has been restored.
For detailed Sensor testing instructions see Data Brochure D 001.
Light on continually Light flashing Light off
Step Eight
Troubleshooting
As in any troubleshooting procedure, it is important to isolate a problem as much as possible before proceeding. The Error Messages
and the Test button greatly simplify troubleshooting of the 252.
If a fault occurs during operating mode or during the test routine and the control is flashing an Error Message, identify the fault from
the look-up table at the bottom of this page and then follow standard testing procedures to confirm the problem.
If you suspect a wiring fault, return to steps four and five and carefully check all external wiring and wiring connections.
Notes:
If the Outdoor Sensor develops either a short circuit or an open circuit, the control is programmed to calculate the outdoor temperature
at -8
°
F (-22
°
C) and control the supply temperature accordingly.
The control is programmed to shut the boiler(s) down before the supply temperature can reach a maximum allowable supply water
temperature of 248
°
F (120
°
C).
If the Supply Sensor develops either a short circuit or an open circuit, the control is programmed to shut down the boiler(s) and run
the System Pump to prevent overheating.
If there is an uninterrupted DHW Demand for 8 hours and the outdoor temperature is below 34
°
F(2
°
C) an error message will be given.
The control will operate in the heating mode and any DHW Demand is ignored. To remove the error message after the DHW system
fault has been corrected, the control must be powered down.
If an Indoor Sensor or RTU input becomes shorted out, the Occupied and Unoccupied dial settings will become active.
After any repair has been completed, press the Test button to allow the control to cycle through the test routine. This will allow
you to confirm that correct operation has been restored.
Step Nine
Before you leave
Install the wiring cover over the wiring chamber and secure it to the base with the two screws provided. Place the front cover on the
control to cover the setting dials and snap it into place. Install a lock if security is required.
Place this brochure, and all other brochures relating to the installation, in the protective plastic bag supplied with the control. Place
the bag in a conspicuous location near the control for future reference.
It is important to explain the operation and maintainance of this control and of the system to the end user and anyone else who may
be operating the system.
11
10K
Indoor
Sensor
short
circuit
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Supply
Sensor
short
circuit
(see
trouble-
shooting
notes)
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Outdoor
Sensor
short
circuit
(see
trouble-
shooting
notes)
DHW
Sensor
short
circuit
(see
trouble-
shooting
notes)
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1
Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Outdoor
Sensor
open
circuit
(see
trouble-
shooting
notes)
Supply
Sensor
open
circuit
(see
trouble-
shooting
notes)
2K
RTU
short
circuit
DHW System
Fault occurs
with 8 Hrs. of
continuous
DHW demand
when Outdoor
temp is less
than 34
°
F.
(see trouble-
shooting
notes)
Error Messages
Some or all of the yellow output LEDs may also
be on depending on the cause of the error.
(see troubleshooting notes)
