Commissioning: Tankless Water Heater tips

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

Calibrate the water valves (PA water actuator)

Bosch · Greentherm T9800 SE 160/199 and T9900 SE 160/199 tankless water heaters

Needed after replacing the main or bypass valve or the electronic control unit; takes several minutes and needs hot water flowing (bypass calibration needs 0.80 to 1.80 gpm).

1. Enter AU Technical Settings, then open PA
2. Select MF main valve or BP bypass valve and touch OK
3. Open a hot water tap and do not interfere until completion shows

Run gas and air auto adjust (UC)

Bosch · Greentherm T9800 SE 160/199 and T9900 SE 160/199 tankless water heaters

Automatic gas and air adjustment inside the combustion adjust menu; takes about 15 minutes. Needed after an LPG conversion, repeated unresolved errors, or replacing the control unit, fan or gas valve.

1. Enter AU Technical Settings and open the combustion adjust menu
2. Select UC Auto Adjust
3. Open hot water taps when Open Taps shows
4. Wait for the green check mark

Set up a cascade (assign main and sub units)

Navien · NPN-160U/180U/199U, NPN-120E/160E/180E/199E

Two heaters are paired from their front panels; the main unit shows MA.00 and the sub unit SL.01.

1. Main unit: hold Diagnostic + Up (+) for more than 5 s; MA.00 appears.
2. Sub unit: hold Diagnostic + Down (-) for more than 2 s; SL.01 appears.
3. Main unit: hold Diagnostic + Up (+) for 5 s again; displays return to temperature.

Set up a cascade (assign sub unit IDs)

Navien · NPE-A2, NPE-S2

Cascade units are linked with Ready-Link cables and the main unit hands out the sub unit IDs.

1. Wire the cascade with Ready-Link cables and switch all units on.
2. Main unit: hold Menu + Back 3 s, open 2. Cascade Status and Set > 3. Cascade System Setting, press OK at START.
3. Sub unit: hold OK for 3 seconds; the panel shows 'ID 1. Allocated!' when the ID is received.

First power-up setup: gas type and indoor/outdoor (RX/CX)

Rinnai · Rinnai SENSEI RX/CX tankless (RX, RXP, CX, CXP)

At first power-up the controller asks for gas type then installation location; gas type can also be changed later with parameter 10, only within 20 minutes after power is supplied.

1. At first power-up SEt shows and the Priority LED blinks. Press Priority: nG appears.
2. Press On/Off to confirm natural gas. For propane, press Up or Down to change to LPG, then On/Off.
3. To redo, press Up to go back to the first step; to accept, press Priority.
4. The gas type can also be changed later with parameter 10, but only within 20 minutes after power is supplied.
5. Press On/Off to confirm indoor.
6. For an outdoor installation with the Versa-Vent outdoor vent cap, press Up or Down to change to Out first.
7. From the In screen press Up or Down: Out appears.
8. Press On/Off to confirm outdoor.