...

• Waterproof Digital Temperature Temp Sensor Probe DS18b20
• a 1/2″ male NPT x 1/4″ compression fitting
• 2 1/4" o-rings

• 3/4" male NTP to 1/2" female NTP adaptor

• teflon tape

Put the temperature sensor, reducer and compression fitting together using teflon tape where needed.

<ADD PIC OF ASSEMBLED TEMP SENSOR>

We can add one to the outlet (see f in diagram below). You may have a different setup, check your owner's manual for details.

Image Removed

Since the header Type 'B' has a 3/4", we will need a 3/4" male NTP to 1/2" female NTP adaptor.

...

a temperature sensor to the heater's header using the following procedure:

• Remove drain plug from header and allow all water to drain from heat exchanger.

Image Added

• Locate the threaded boss on the outlet port of the header, and find the dimple at the center.

• Use the dimple to center the drill bit. For header type A: Drill a 1/4 in (6.4 mm) diameter hole through the boss. For header type B: Drill a 3/8 in (9.5 mm) diameter hole through the boss. Take care not to damage the plastic threads. TIP: Drilling a 1/8 in (3 mm) diameter hole first will help prevent thread damage.

Image Added

• Each male connection should be first wrapped in 5-6 turns of PTFE (Teflon) tape.
• Install the temperature sensor assembled with any required reducers at the heater header. Make sure to get a sung fit. Do not overtighten.

References

...