Freeze Protection For Recirculation Systems - A.O. Smith 710 ASME Service Manual

12-18. Freeze protection for recirculation systems

<Function and Purpose>
The 710 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 710. When
the computer detects the potential of the system freezing, the pump in the system starts automatically.
To use this function in Easy-link system, the pump must be connected to the pump control
port in the computer board of the Parent unit. Refer to Section 12-17 for details.
< While recirculation system freeze protection is in operation>
While this freeze protection is operating, the computer 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 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 710 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).
When 710 is NOT connected to the remote controller, Change the dipswitch No.4 (the left
bank) on the 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 computer
(of the parent unit) will actively measure water
temperature.
temperatures remain
continuously for 10 minutes.
Pump will deactivate
above 50°F
if
(10°C)
Left bank of dipswitches
72
CONFIDENTIAL
710 / 710 ASME Service Manual
Computer board
Ver. 1.00