A.O. Smith SGS-28, Installation, User And Service Manual

Page: 74 / 126

If there is nothing else you need to check or adjust, you can put the covers back on
the appliance.
7.9.3 Procedure for checking the gas control valve pressure
The procedure for checking the gas control valve pressure is only applicable to appliances
that have a pressure-reducing valve. If the appliance does not have a reducing valve,
continue from adjusting the CO
2
value (see section 7.9.4).
To check the gas control valve pressure, proceed as follows:
Isolate the appliance from the power supply (see section 4.2.2).
Carefully remove the covers from the appliance.
The electrical section is now visible.
The gas control valve has a test nipple that can be used for measuring the gas
control valve pressure. This test nipple has a sealing screw. Loosen the sealing screw
by a few turns. Do not completely loosen it as it can be difficult to retighten.
Open the gas supply.
Connect a pressure gauge to the test nipple.
Switch on the power to the appliance using the isolator on the appliance.
Switch the controller ON by setting the 0/I switch to position I .
The display will now show INTERNAL CHECK for about 10 seconds, and will then go
to the main menu.
7.9.3.1 Procedure for checking the gas control valve pressure
Select SERVICE OPERATION, FULL LOAD from the service menu.
Confirm with [ENTER].
The display shown here will appear.
The appliance is now in PARTIAL LOAD mode and will ignite.
You must wait about 1 minute after the display shows the text RUNNING before
reading the dynamic pressures (the fan needs this time to get up to full speed, so
that a reliable reading can be obtained).
Use the pressure gauge to read the pressure and compare it against the value from
the gas table (see section 12.3).
If necessary, adjust the gas control valve pressure using the reducing valve's
adjuster screw (2) until the value is within the range listed in the table.
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74 Installation, Maintenance and Service part