161 High DHW outgoing water temperature

What the control is telling you

Triggered when the system sees domestic hot water above 203°F (95°C).

Applies to: I-Series Plus boilers — 150K BTU and smaller and 175K BTU and higher (Combi)

Likely causes

• Damaged DHW outlet sensor wiring
• Scaled or faulty DHW outlet thermistor
• Wrong gas type supplied or wrong A0 setting
• Wrong gas orifice (175K+)
• Faulty gas valve assembly

Test and repair steps

1. Inspect the DHW outlet temperature sensor wiring for damage.
2. Compare Performance Data #7 (DHW temperature) with the actual tap temperature, or check Performance Data 8 (inlet) with DHW off and then flowing; see the install instructions for entering performance data mode.
3. Pull the DHW sensor and wipe off any scale.
4. With domestic supply off, remove the outlet thermistor and measure on a 20K ohm range; it should fall when warmed by hand, rise on ice. 150K and smaller: CN7 pins 6–12 and 4–14. 175K and higher: CN7 pins 12–14 and 4–6.
5. Compare against Appendix A Water Temperatures in the source manual; replace the sensor if more than 5°F off.
6. 175K and higher confirm the correct gas orifice is fitted in the gas valve, groove side out (grey = propane, black = natural gas, white = natural gas high altitude above 2000 ft).
7. Confirm the gas supply matches the rating plate and Parameter A0 is set correctly (A = Natural Gas, b = Propane).
8. Replace the gas valve assembly if the fault remains.