Arrived onsite to investigate intermittent heat issues on a Viessmann boiler that has faulted 4–5 times over the past month with an F4 (no flame signal) error code. We were onsite last month and replaced the igniter. I inspected the igniter wiring and found it to be within specifications. I checked the gas pressure and found it at the low end of the acceptable range at 10 in/wc, (specification is 10–14 in/wc.) I adjusted the gas pressure at the 2nd stage regulator to 13 in/wc. Performed an annual tune-up, including cleaning the burner, heat exchanger, igniter, neutralizer and condensate trap. Inspected the expansion tank, relief valve, combustion, venting, and overall hydronic system operation. Bubble-tested the gas line and checked carbon monoxide levels; no leaks were found. Verified proper operation, and the system is working correctly at this time.
