Pump Control On/Off Conditions - A.O. Smith T-M50 ASME Service Manual

12-11. Pump control ON/OFF Conditions

To run circulation pumps efficiently and effectively, the T-M50 offers four different modes of pump
control. The following table shows the pump control ON/OFF conditions for different modes. To change
pump control modes, see section 12-7 for dipswitch settings.
"Normal mode" and "Storage tank circulation mode"
There are no specific ON/OFF conditions for these two modes. The circulation pump will receive a
constant "ON" signal from the pump terminal on the central computer board, and will run
continuously.
"Re-circulation mode" and "Energy conserving re-circulation mode"
These functions enable the re-circulation pump to be controlled by the following conditions.
ON/OFF Conditions
Conditions that activate
the pump
Conditions that
deactivate the pump
*The computer records the inlet temperature and the flow rate of the pump during the final minute of
its previous operation when calculating the BTU requirement.
Re-circulation mode
The BTU requirement is more than
14,880 BTU/h*
OR
30 minutes have elapsed after
previous operation
When the central computer board detects the following conditions, it will stop
The BTU requirement is less than 5,950 BTU/h
Inlet temperature is higher than the set temperature
The water flow rate is less than 0.4 GPM
T-M50 / T-M50 ASME Service Manual
Energy conserving re-circulation mode
Inlet water temperature is less than
95°F(35°C) and flow rate is less than
0.8GPM
20 minutes have elapsed after
previous operation
the pump 60 sec. after detection.
OR
OR
Outlet temperature is over 194°F
OR
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CONFIDENTIAL
Ver. 1.05
OR