13 Combustion fault

What the control is telling you

On the RH180 hybrid, the unit detects a combustion problem. Look at venting, combustion air, altitude/gas settings, the fan and the burner.

Applies to: RH180 hybrid tank-tankless (non-SENSEI) only

Likely causes

• Vent not 4 in. B-Vent or installed incorrectly
• Not enough combustion air in the room
• Altitude DIP switches set wrong
• Inlet or forced low/high manifold gas pressures out of range
• Restricted fan wheel or housing
• Clogged burner orifices, debris in the burner, or fouled heat exchanger fins

Test and repair steps

1. Make sure the vent is 4 in. B-Vent installed per the manufacturer's requirements.
2. Inspect the whole vent inside and out clearances, approved materials, sections fully seated, and joints sealed so they cannot pull apart.
3. Check that the room has enough combustion air for all gas appliances in it. If the unit runs with a door left open, recalculate combustion air for the space.
4. Check the altitude DIP switches (SW2/SW3 per the table on p.22 or the Tech Data Sheet).
5. Warning: Only gas-qualified technicians should do the gas pressure steps.
6. Inlet gas at full fire NG 4–10.5 in. W.C., LP 8–13.5 in. W.C. Forced low: NG 1.10 / LP 1.23 in. W.C. Forced high: NG 2.8 / LP 3.0 in. W.C.
7. Caution: Turn off power, remove the fan motor and check the wheel and housing for restrictions. Refit, restore power and see if the code returns.
8. Warning: Turn off electrical, gas and water. Then check the manifold orifices for blockage, clear debris from the burner and air chambers, and check heat exchanger fins for build-up.

Settings for these units

• RSC supply connection sizes · SENSEI
• RSC water quality limits · SENSEI
• RSC clearances to combustibles · SENSEI
• RSC temperature settings available · SENSEI
• RX supply connection sizes · SENSEI RX/CX
• RX water quality limits · SENSEI RX/CX
• RX water treatment and flushing by hardness · SENSEI RX/CX
• RX clearances to combustibles · SENSEI RX/CX