LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 34)

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Service Manual - NeoTherm 500
Removing and Replacing the Flow Switch
The switch assembly includes two parts: a set of paddles that extend into the
water pipe, and a control box. See Fig. B9-1.
Figure B9-2 shows the paddles that extend into the piping to detect the water
flow.
The paddles are sized to match the amount of water flowing through the
system, so a flow switch installed in a smaller system, with a smaller pipe,
will have smaller paddles, and a switch in a larger system will have larger
paddles. Keep this in mind if you need to replace one of these switches.
Tools and equipment required:
• Medium-sized pipe wrench
• Sheet-metal shears - use a type that can make a curved cut
• 100-grit sandpaper
• Pipe dope or Teflon® tape
Procedure:
1. Turn off power to the system. Use the main disconnect switch mounted
above the front panel.
2. Isolate the boiler. Turn off the water shutoff valves located upstream and
downstream of the unit.
3. Drain the boiler. The drain valve is located xx.
4. Remove the cover from the control box for the switch. Note the positions
of the wiring connections, then disconnect the wires.
5. Now you can use the pipe wrench to remove the whole switch assembly.
6. When you receive the new switch, it will include four paddles. These will
be longer than necessary for your installation, so you will need to trim
these paddles to the correct sizes. The best way to do this is to copy the
sizes of the paddles in the old switch. Make a smooth curve at the end
of each paddle, as shown in Fig. B9-2. Remove any burrs from the cut
end of the paddle using 100-grit sandpaper.
B10