Unstable or noisy readings may be symptomatic of a contaminated flow system. Hydrocarbon contamination can occur in multiple areas: external components, like the fuel or air supplies, external frits and filters, regulators or supply tubing; internal flow components, such as pressure regulators and gauges; and finally, with water or condensation infiltration of the burner itself.
Contamination issues can be mitigated with intensive cleaning of the suspect components, or with their replacement.
Keywords: Rosemount 400A troubleshooting