T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
87
CONFIDENTIAL
12-20. Freeze protection for recirculation systems
The T-H2-DV or T-H2-OS has the freeze protection function for a re-circulation system by using a pump
installed in the system. Basically, this function is only ON / OFF control of the pump from the computer in
the T-H2-DV or T-H2-OS. When the computer detects the potential of the system freezing, the pump in
the system starts automatically.
To use this feature in an Easy-link system, the pump must be connected to the T-H2-DV or
T-H2-OS pump control port in the Parent unit. Refer to Section 12-15 for details.
< While recirculation system freeze protection is in operation>
While this freeze protection is operating, the T-H2-DV/T-H2-OS will display “P” on its three
7-seg LED, however, the TM-RE30 remote controllers will not display anything on its screen.
In order to detect the temperature of the system accurately, The computer makes the pump
work every two minutes during the freeze protection operation
A. Activation conditions (all 3 conditions must occur):
1. Please follow the procedure on the next page.
2. The T-H2-DV/T-H2-OS is in non-operation (no call for hot water).
3. The computer (of the parent unit) detects water temperature 50°F (10°C) or below (the computer
will activate the pump every two minutes to properly measure water temperatures throughout the
recirculation line).
B. Deactivation condition:
After pump has been activated for freeze protection, the pump is set to run for at least 1 hour.
After 1 hour has elapsed, the computer (of the parent unit) will actively measure water temperature.
Pump will deactivate if temperatures remain above 50°F (10°C) continuously for 10 minutes.
