Submittal Sheet

Job __________________________
Designer ______________________
Contact _______________________
www.tekmarcontrols.com  of 2 © 20 C 257 - 0/
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0/
Setpoint Replaces: New

The DHW Control 257 is designed to operate multiple boilers for volume water heating. It can be used in hotels, apartments, and
laundromats to control multiple boilers and provide quick recovery for domestic hot water. This control regulates a single hot water
temperature through DHW control. It is capable of controlling up to 2 on/off boilers using a sensor to maintain a tank setpoint
temperature.

N / A
 --------------------------
Boiler Rotation
Cumulative boiler run time hours
Proportional or PID staging
2 Stage control
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•
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 -----------------------------------------------------
Two Stage
Literature D257, A257, D00, D070
Control Microprocessor control. This is not a safety (limit) control
Packaged weight 0.8 lb. (360 g)
Dimensions 4-3/4” H x 2-7/8” W x 7/8” D (20 x 74 x 22 mm)
Enclosure White PVC plastic, NEMA  rated
Approvals CSA C US, meets class B: ICES & FCC Part 5
Ambient conditions
Indoor use only, -20 to 20°F (-30 to 50°C), RH ≤90% Non-
condensing
Power supply 24 V (ac) ±0%, 50/60 Hz, 3 VA
Relay 240 V (ac) 0 A max, /3 hp
Sensors NTC thermistor, 0 kΩ @ 77°F (25°C ±0.2°C) ß=3892
–Included Universal Sensor 082
–Optional tekmar type #: 078
Warranty Limited 3 Year (See D257 for full warranty)
Front View
DHW Control 257
Two Stage
Item
Date Code
Power: 24 V ±10% 50/60 Hz 3 VA
Relays: 240 V (ac) 10 A 1/3 hp
tektra 906-11
Meets Class B:
Canadian ICES
FCC Part 15
Stage Mode Delay
Target DHW
DifferentialDHW
1 2 3 4
C R
7
Com
Sen
8
DHW
Sen
No Power
Signal wiring
must be rated
at least 300V
Made in Canada
Power Heat 1
5 6
H3014B
Heat 2
Rotate
On
Off
2–7/8”
(74 mm)
4–3/4”
(120 mm)
Side View
7/8”
(22 mm)
Cover O
Item
1–3/8”
(37 mm)
6/8”
(18 mm)
6/8”
(18 mm)
DHW Control 257
Two Stage
Item
Date Code
Power: 24 V ±10% 50/60 Hz 3 VA
Relays: 240 V (ac) 10 A 1/3 hp
tektra 906-11
Meets Class B:
Canadian ICES
FCC Part 15
Stage Mode Delay
Target DHW
DierentialDHW
 2 3 4
C R
7
Com
Sen
8
DHW
Sen
No Power
Signal wiring
must be rated
at least 300V
Made in Canada
Power Heat 
5 6
H3014B
Heat 2
Rotate
On
O