tekmar 557 Thermostat Installation - Manual (Page 35)

© 2014 557_D - 09/14
35 of 52 A Watts Water Technologies Company
Backup W2 Differential ----------------------------------------------- -----------------------------------------------
The backup heat source operated by W2 has an adjustable differential. The differential
is relative to the previous heating stage.
No radiant floor heating, no heat pump (no W1, no Y1, no Y2)
The W2 relay’s differential is ±1°F (0.5°C) centered around Set Heat.
Radiant floor heating, no heat pump (W1, no Y1, no Y2)
The W2 relay turns on at Set Heat - Backup Differential.
Single Stage Heat Pump (W1, Y1, no Y2)
The W2 relay turns on at Set Heat - 1°F (0.5°C) - Backup Differential.
Two Stage Heat Pump (W1, Y1, Y2)
The W2 relay turns on at Set Heat - 1°F (0.5°C) - Y2 Differential - Backup Differential.
Freeze Protection ---------------------------------------------------- ----------------------------------------------------
The thermostat operates the heat whenever the room or floor temperature falls below
40°F (4.5°C) even when the mode is set to off.