190 Electrical grounding / short in DC circuit

What the control is telling you

Code 190 (or 120) appearing right after water flow starts, with no flame in the burner box, indicates an electrical short in a component.

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

Likely causes

• Shorted wiring harness
• Shorted water flow control or bypass valve
• Short in another component on the DC circuit

Test and repair steps

1. Confirm the code appears immediately when water flow starts and no flame is visible in the burner box.
2. Unplug one DC component at a time (harnesses, water flow control, bypass valve, etc.) and run the unit after each.
3. When the unit tries to fire without code 120/190, the short is in the circuit last unplugged; repair or replace that component.

Models that show this code

6 models in I-Series Plus 150K and smaller, I-Series Plus 175K and higher

Other codes on the same units

• 140 Overheat switch tripped (heat exchanger overheating)
• 150 Venturi control fault
• 170 Venturi blockage / position mismatch
• 180 Gas valve air/fuel adjustment limit reached
• 210 Data transfer error
• 220 Gas valve position not detected (reed switch)
• 250 Condensate pump switch tripped (accessory)
• 303 Secondary system thermistor fault