Low water cut-off wiring (field supplied)

What is going on

Some local codes require a remote-mounted low water cut-off on top of the boiler's own protection, and the NTI TRX150, TRX199 and TRX199C allow for one. Get the wiring and placement right, because the device's job is to cut main power if the water drops. Follow local code and the cut-off's own instructions, and use a qualified installer.

Likely causes

• Local code requiring a remote low water cut-off
• Boiler's own water pressure switch only blocks the burner below 7 PSI

Check in this order

1. Mount the low water cut-off remotely and follow its manufacturer's wiring instructions
2. Do not install an isolation valve between the boiler and the low water cut-off
3. Wire the normally open contacts so they break the boiler main power supply during a low water condition
4. Note that the boiler's water pressure switch already blocks burner operation below 7 PSI
5. Test the cut-off operation after install

More general guides

• Combustion air and leak protection checks during install
• Expansion tank and air elimination
• Install and test the CH and DHW relief valves
• Primary/secondary piping and 3-way valve for heating-only use
• Removing the boiler from a common vent system
• Wall mounting the boiler