Tekmar DHW Control 257 Manual
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Tekmar DHW Control 257 Manual

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- Data Brochure
DHW Control 257
The DHW Control 257 is used for dedicated domestic hot water systems. The control operates two on/off boilers, or one
two-stage boiler to maintain the DHW Target temperature at the DHW Sensor. The control can operate in Proportional (P)
mode, or Proportional, Integral, Derivative (PID) mode.
Additional functions include:
•
Boiler rotation
•
Cumulative boiler run time hours
•
P or PID staging modes of operation
•
CSA and UL certified for use in the USA and Canada
Power Supply
Meets Class B:
Canadian ICES
FCC Part 15
Made in Canada
tektra 906-11
Stage Mode
Item
DHW Control 257
Two Stage
1 2 3 4
On
Power
Heat 1
C
R
Off
Input
24 V (ac)
Output
Boiler
Power: 24 V ±10% 50/60 Hz 2 VA
Relays: 240 V (ac) 10 A 1/3 hp
pilot duty 240 VA
Delay
DHW
Differential
Target DHW
No Power
Signal wiring
5 6
7
8
must be rated
Heat 2
Com
DHW
at least 300V
Sen
Sen
Output
Boiler
1 of 12
D 257
Input
Universal Sensor
Included
© 2008
D 257 - 03/08
03/08

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Summary of Contents for Tekmar DHW Control 257

  • Page 1 03/08 The DHW Control 257 is used for dedicated domestic hot water systems. The control operates two on/off boilers, or one two-stage boiler to maintain the DHW Target temperature at the DHW Sensor. The control can operate in Proportional (P) mode, or Proportional, Integral, Derivative (PID) mode.

  • Page 2: Table Of Contents

    How to Use the Data Brochure This brochure is organized into three main sections. The Control Settings section of this brochure describes the various items that are adjusted and displayed by the They are: 1) Sequence of Operation, 2) Installation, and control.

  • Page 3: Display And Symbol Description

    Display Number Field Menu Field Displays the current value Displays the of the selected item current menu Status Field Displays the current status Item Field of the control’s inputs, Displays the current Stage Mode Delay Differential outputs and operation item selected. Target DHW Buttons Selects Menus, Items...

  • Page 4: Sequence Of Operation

    Sequence of Operation Powering Up the Control When the DHW Control 257 is powered up all LCD segments into the normal operating mode and the LCD defaults to are displayed for 2 seconds followed by the version number displaying the current DHW temperature.

  • Page 5: Rotation

    Rotation This function rotates the firing sequence of the two boilers Relay Run Times based on the accumulated running hours of each stage. The The control logs the number of run time hours for the HEAT HEAT 1 and HEAT 2 items in the default menu display the 1 and HEAT 2 relay in the default menu.

  • Page 6: Installation

    Operation to ensure that you have chosen the proper wholesaler or tekmar sales representative for assistance. control for your application. Type 257 includes: One DHW Control 257, One Universal Sensor 071, Data Brochures D 257, D 070, D 001, Application Brochure A 257.

  • Page 7: Electrical Connections To The Control

    Test the Power Supply Test the Outputs Make sure exposed wires and bare terminals are not in Heat 1 and Heat 2 contact with other wires or grounded surfaces. Make sure power is off to the boiler circuits and connect the TT contacts on the boilers to the Heat 1 and Heat 2 If a 24 V (ac) transformer is used, make sure the voltmeter is set to AC.

  • Page 8: Control Settings

    The Off | On – Rotate DIP switch is used to turn boiler rotation on or off. When using a single boiler with two DHW Control 257 stages, the DIP switch should be in the off (down) position. Two Stage...

  • Page 9: Default Menu

    Default Menu View Next Item The Default menu items display current operating temperatures and system status information. Use the Item button to view items in this menu. Item Item Field Range Description DHW TEMPERATURE -60 to 255°F The current DHW temperature as measured by the DHW sensor.

  • Page 10: Program Menu

    Program Menu Enter Program Menu Next Item Change Value The Program menu items are the programmable settings used to operate the system. Press and hold all three buttons simultaneously to enter the Program menu. Item Item Item Field Range Description Actual Setting 70 to 190°F TARGET DHW...

  • Page 11: Field Test

    Field Test To test the control, push and hold the up button for 3 seconds while in the default menu. While in Field Test “tSt” is displayed. Step 1: Heat 1 relay will close and Heat 2 relay will open for 10 seconds Stage Mode Delay...

  • Page 12: Technical Data

    Any representations or warranties about the Products made by Purchaser ited. The Purchaser, by taking receipt of any tekmar product (“Prod- to its customers which are different from or in excess of the tekmar Lim- uct”), acknowledges the terms of the Limited Warranty in effect at ited Warranty are the Purchaser’s sole responsibility and obligation.

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