Tekmar 257 - Control Description 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 using solar collectors or a wood boiler as a heat source.
Literature—D 257, A 257, D 001, D 070
Control—Microprocessor control; This is not a safety (limit) control
Packaged Weight—0.78 lb. (355 g)
—Enclosure C, White PVC plastic
Dimensions—4-3/4" H x 2-7/8" W x 7/8" D (120 x 74 x 22 mm)
Approvals—CSA certified to CSA C22.2 #24 and UL # 508
Ambient Conditions—Indoor use only, 32 to 122°F (0 to 50°C), < 90% RH non-condensing
Power Supply—24 V +/- 10% 50/60 Hz 2 VA
Relay—240 V (ac) 10 A 1/3 hp, pilot duty 240 VA
Sensors Included—NTC thermistor, 10 kΩ @ 77°F (25°C +/- 0.2°C) ß=3892 One Universal Sensor 071
Optional—tekmar type #078,082
