T-M50 / T-M50 ASME Service Manual
Ver. 1.05
79
CONFIDENTIAL
12-22. Freeze protection for recirculation systems
<Function and Purpose>
The T-M50 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 central computer board in
the T-M50. When the central computer board detects the potential of the system freezing, the pump in
the system starts automatically.
To use this function in an Easy-link system, the pump must be connected to the pump
control port in the central computer board of the Parent unit. Refer to Section 12-14 for
details.
< While recirculation system freeze protection is in operation>
While this freeze protection is operating, the central computer board will display “P” on its
7-seg LED, however, the remote controllers will not display anything on its screen.
In order to detect the temperature of the system accurately, The central computer board
makes the pump work every two minutes during the freeze protection operation
A. Activation conditions (all 3 conditions must occur):
1. The T-M50 is in non-operation (no call for hot water).
2. Dipswitch No.6 (the upper bank) on the central computer board of the Parent unit is set to the “ON”
position.
3. The central computer board (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).
When T-M50 is NOT connected to the remote controller, Change the dipswitch No.4 (the
lower bank) on the central computer board to the “OFF” position.
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 central
computer board (of the Parent unit) will actively
measure water temperature. Pump will
deactivate if temperatures remain above 50°F
(10°C) continuously for 10 minutes.
Central computer board
The banks of dipswitches
