LAARS Mighty Therm VW-PW (Sizes 175-400) - Installation, Operation and Maintenance Instructions - Manual (Page 23)

Mighty Therm Volume Water Heaters
Page 23
If the gas valve is found to be defective, replace
it by following these instructions.
1. Turn off electrical power to the heater.
2. Turn off the main gas supply at the manual gas
cock outside the heater jacket or at the meter.
3. Remove the front access door on the heater.
4. Disconnect the service union in the gas line, and
unscrew the main gas pipe from the gas valve
(see Figure 30).
5. Remove the two screws that fastens the anti-
rotation bracket on the left side of the gas valve
(see Figure 30), and the three screws attached to
heater.
6. Remove the pilot gas tube and copper
thermocouple shield, if present, from the gas
valve.
Caution
Label all wires prior to disconnection. Wiring errors
can cause improper and dangerous operation.
7. Tag and remove all wires from the gas valve
terminals.
8. Pull the burner tray out of the heater (see
Figure 30).
9. Screw the new gas valve onto the manifold pipe.
Make sure the arrow on the bottom of the gas
valve that indicates the direction of gas flow is in
the proper direction. Also make sure the brass
fitting is on the right side.
10. Connect the pilot gas tube to the pilot assembly
and thermocouple to the gas valve.
NOTE: Due to sharp edges on the metal burners, wear
protective gloves for the next steps.
11. Hold the gas burner or pilot burner firmly, and
push it away from the manifold until it is clear of
the orifice. Slide the burner to be replaced out of
the burner tray (see Figure 31).
12. To replace the gas burner, insert the burner into
the slot at the rear of the burner tray, line it up
with the proper orifice and snap it into position.
13. To replace the pilot burner, install the pilot
assembly on the new pilot burner and install it in
the burner tray.
14. Slide the burner tray back into the heater and
fasten it with two screws.
15. Install the anti-rotation bracket to the inner panel
and fasten with two screws (see Figure 30), and
the three screws to heater.
16. Connect the service union in the gas line, and
screw the main gas pipe to the gas valve (see
Figure 30).
17. Turn on gas valve following the lighting
instructions found on the inside of the heater.
18. Turn on the main gas supply at the manual gas
cock or the meter.
19. Check the system for leaks using a soap solution.
Caution
Since some leak test solutions (including soap and
water) may cause corrosion or stress cracking, rinse
the piping with water after testing.
20. Reconnect the electrical wires to the gas valve in
accordance with the wiring diagram found on the
inside of the heater.
21. Install the front access door on the heater.
22. Turn all electrical power to the heater on.
Figure 33. Heat exchanger tube cleaning.
Notes:
1.
When pressure relief valve is used, it must be removed and the hole plugged, as shown.
2. Remove the plug before reinstalling the heat exchanger.
City
Water
Supply
400-500 RPM
Drill Motor