Button combinations: Tankless Water Heater tips

Short, practical technician tips on button combinations for tankless water heater. Check each one against the manual for your exact model before acting.

Lock or unlock the controller (key symbol)

Rinnai · Rinnai SENSEI tankless (RU, RUR, RSC, CU) and SENSEI RX/CX (RX, RXP, CX, CXP)

While locked, the set temperature cannot be changed; RX/CX outdoor units lock themselves after 30 minutes without use.

1. To lock: press and hold Priority, then press Up as well until a beep sounds (about 5 seconds), and let go of both together.
2. To unlock: repeat the same steps.

Lock or unlock the KCM controller (LOC)

Rinnai · Rinnai KCM tankless with MC-601-US controller

Locking one controller locks every controller in the system.

1. To lock: press Priority and Up together for 5 seconds; a beep confirms it.
2. To unlock: press Priority and Up together for 5 seconds again.

Performance data readout (items 01 to 24)

Rinnai · SENSEI RX and CX series tankless

Live and lifetime values: flow, temperatures, run hours, cycles, fan frequency, as numbered items on the controller.

1. Hold the down arrow; after about 2 s also hold On/Off until 01 shows
2. Scroll with up / down to the item wanted
3. See the Performance data table under Settings for the item list

Show live flow and outlet temperature on the KCM controller

Rinnai · Rinnai KCM tankless (RUCS65i/75i, RUS65e/75e)

Information mode on the MC-601-US shows water flow and outgoing temperature.

1. Press and hold Down for 2 seconds and, without letting go, press On/Off. Repeat the same press to leave.
2. Press Up or Down until 01 shows: the water flow follows in 0.1 gal/min (58 means 5.8 gal/min).
3. Press Up or Down until 02 shows: the outgoing water temperature follows in °F.

Show the last 9 stored codes (diagnostic history)

Rinnai · SENSEI RX and CX series tankless

The controller plays back the nine most recent maintenance codes one after another. LC shows as 00 in this list.

1. Switch the heater off with On/Off
2. Hold On/Off 2 s, then press the up arrow while still holding
3. The codes flash in sequence
4. Repeat the same hold to leave, then switch back on