2
Caution
Improper installation and operation of this control could result in damage to the equipment and possibly even personal
injury. It is your responsibility to ensure that this control is safely installed according to all applicable codes and
standards. This electronic control is not intended for use as a primary limit control. Other controls that are intended
and certified as safety limits must be placed into the control circuit.
Step One
Getting ready
Check the contents of this package. If any of the contents listed are missing or damaged, please refer to the Limited Warranty
and Product Return Procedure on the back of this brochure and contact your wholesaler or tekmar sales agent for assistance.
Type 255 includes:
• One Two Stage Boiler Control 255 • One Outdoor Sensor 070 • One Supply Sensor 071
• One Data Brochure D 255 • One Data Brochure D 001 • Application Brochures A 255
Other information available:
• Essay E 000 • Essay E 200
Read Application Brochures A 255 and select the correct Application for your job.
Note:
Carefully read the details of the Application, and the Sequence of Operation section in this brochure to ensure that you have
chosen the proper control, and understand its functions within the operational requirements of your system.
Step Two
Mounting
The control is mounted in accordance with the instructions in the Data Brochure D 001.
Step Three
Rough-in wiring
All electrical wiring terminates in the two wiring chambers at the bottom front of the control. If the control is to be mounted on
an electrical box, the wiring can be roughed-in at the electrical box prior to installation of the control (see Brochure D 001).
Standard 18 AWG solid wire is recommended for all low voltage wiring to this control.
Caution: Power should not be applied to any of the wires during this rough-in wiring stage.
• Install the Outdoor Sensor 070 and the Supply Sensor 071 according to the instructions in Data Brochure D 001 and run the
wiring back to the control.
• Install a 24 V ac Class II transformer with a minimum 5 VA rating and run the wiring from the transformer to the control.
A Class
II transformer must be used. Do not connect any of the transformer terminals to ground.
• Install the wiring from the boiler(s) and pump circuits to the control.
Step Four
Testing and connecting the wiring
Caution
These tests are to be performed using standard testing practices and procedures and should only be carried out by a properly
trained and experienced person. A good quality electrical test meter, capable of reading from at least 0 — 200 Volts ac and at
least 0 — 2,000,000 Ohms, is essential to properly test this control. At no time should voltages in excess of 28 V ac be measured
at any of the wires connected to the control.
Warm Weather Shut Down (WWSD)
This control shuts off the boiler(s) when the outdoor temperature is above the WWSD point and heat is no longer needed. When
the correct WWSD point has been selected, overheating is prevented and comfort and energy savings are increased. When the
outdoor temperature cools off again, the heating system is turned on at the WWSD point to start delivering heat. The WWSD point
is usually the desired room temperature in the building, however internal heat gains (from appliances, people, etc.) can change
heat requirements and a lower WWSD point may be selected through trial and error.
• When the system is operating near the WWSD point and the building is too cold, the WWSD point should be raised.
• When the system is operating near the WWSD point and the building is too warm, the WWSD point should be lowered.
Installation
Test the sensors
These tests must be performed
before power is applied to the control and before the sensors are connected to the terminal strip.
Test both sensors according to the instructions printed in the Data Brochure D 001.
Test the power supply
• Ensure that the wires from the power supply transformer are not touching each other, any other wires or ground. Turn on the
power, and using an AC voltmeter, you should measure between 20 and 28 volts at the secondary side of the transformer.
• Turn off the power and complete the electrical connections to the terminal strips of the control.
24 V Only
No Power
24Vac
power
supply
Closes to
operate Boiler
#1
Closes to
operate pump
or Boiler #2
DIP
Switch
1
C
2
R
3
4
10A
10A
Boiler 1
Pump /
Boiler 2
5
6
7
Com
Sen
Sup
Sen
Out
Sen
8
9
Supply
Sensor
#1 (071)
Outdoor
Sensor
#2 (071)
Power
2
1
Nº of boilers
Power and output connections Caution, Maximum 24 Volts
Connect the transformer to terminals
Power C—R (1 and 2).
Connect the boiler #1 circuit to terminals
Boiler 1 (3 and 4)
• If two boilers (stages) are to be operated, slide the DIP switch to the "2"
position and wire boiler #2 to terminals
Pump / Boiler 2 (5 and 6). For
single boiler operation, slide the DIP switch to the "1" position and wire
the system pump circuit to terminals
Pump / Boiler 2 (5 and 6).
Sensor connections Caution, never apply power to these terminals.
Connect the Outdoor Sensor 070 to terminals
Com Sen — Out Sen (7 and 9).
Connect the Supply Sensor 071 to terminals
Com Sen — Sup Sen (7 and 8).