The Boiler Control 256 has a built-in test routine which is used to test the boiler function. The 256 continually monitors the sensors,
and displays an error message whenever a fault is found. See the following pages for a list of the 256’s error messages and possible
causes. When the button is pressed, the
Boiler
relay closes and the control displays the burner segment. Once the button is
released, the
Boiler
relay returns to normal operation.
When troubleshooting any heating system, it is always a good idea to establish a set routine to follow. By following a consistent
routine, many hours of potential headaches can be avoided. Below is an example of a sequence that can be used when diagnosing
or troubleshooting problems in a hydronic heating system.
Establish the problem. Get as much information from the customer as possible about the problem. Is there
too much heat, not enough heat, or no heat? Is the problem only in one particular zone or area of the
building, or does the problem affect the entire system? Is this a consistent problem or only intermittent?
How long has the problem existed for? This information is critical in correctly diagnosing the problem.
Understand the sequence of operation of the system. If a particular zone is not receiving enough heat,
which pumps or valves in the system must operate in order to deliver heat to the affected zone? If the
zone is receiving too much heat, which pumps, valves or check valves must operate in order to stop the
delivery of heat?
Sketch the piping of the system. This is a relatively simple step that tends to be overlooked, however, it
can often save hours of time in troubleshooting a system. Note flow directions in the system, paying close
attention to the location of pumps, check valves, pressure bypass valves, and mixing valves. Ensure correct
flow direction on all pumps. This is also a very useful step if additional assistance is required.
Document the control for future reference. Before making any adjustments to the control, note down all
of the items that the control is currently displaying. This includes items such as error messages, current
temperatures and settings, and which devices should be operating as indicated by the LCD. This infor-
mation is an essential step if additional assistance is required to diagnose the problem.
Isolate the problem between the control and the system. Now that the sequence of operation is known
and the system is sketched, is the control operating the proper pumps and valves at the correct times?
Is the control receiving the correct signals from the system as to when it should be operating? Are the
proper items selected in the menus of the control for the device that is to be operated?
Test the contacts, voltages and sensors. Using a multimeter, ensure that the control is receiving adequate
voltage to the power terminals and the demand terminals as noted in the technical data. Use the multimeter
to determine if the internal contacts on the control are opening and closing correctly. Follow the instructions
in the Testing the Wiring section to simulate closed contacts on the terminal blocks as required. Test the
sensors and their wiring as described in the Testing section.
Testing the Control
Troubleshooting
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© 2019 tekmar 256_D - 09/19
Establish the
Problem
Understand the
Sequence of
Operation
Sketch the
Piping in the
System
Document the
Control
Isolate the
Problem
Test the Contacts
Voltages &
Sensors
