T-M50 / T-M50 ASME Service Manual
Ver. 1.05
- 71 -
CONFIDENTIAL
12-17. How to use the “External fan control”
(Only on Parent Unit
）
The external fan is needed when the air in the room is not enough for the combustion.
T-M50 external fan motor terminals are a terminal to connect to the external fan motor.
This terminal turns ON before the T-M50 start to burn.
A draft pressure switch setting is also recommended in order to check if the external fan motor
works correctly.
Note: The draft pressure switch can check the condition of the external fan motor.
With this installation, when the external fan motor failed, the “681” error code will appear.
The external fan motor will be automatically turned ON under these conditions:
When the water heater’s flow sensor detects flowing water, the external fan motor will turns ON.
When the water heater stops burning or remote controller turns OFF, the external fan motor will stop
to operate as well.
The External fan motor will be in turn OFF under these conditions:
During Storage Tank Circulation control mode, Flow adjustment valve is restricted flow rate to 2.6 GPM
by the T-M50.
When the BTU requirement is less than 14,875 BTU/h
Refer to section 12-18 about the relay in the pump connection for T-M50
Draft
pressure
switch
Power supply for
Draft Switch
120 VAC
240 VAC
Connect to this
terminal with draft
switch.
The current of electricity
Maximum is 1 A
External fan
motor
External fan motor
terminals
Draft Switch terminal
120 VAC Relay
(Locally procured parts)
(Locally procured parts)
120 VAC
