Gas Valve "Buzzing"

SpeyFitter

A buddies parents have a newer (2-3 years old) raypak type H raytherm boiler (model 0090B - 90,000 BTUH input). Now I"m not a service guy per se, but I do know my way around these things a little bit. So their complaint which I verified is there is this buzzing sound that to me sounds like it comes from the gas valve. The Gas valve is a Robertshaw 7200. The boiler seems to fire fine, pilot works properly, thermocouple in good shape. Not a burner expert but it looks like it should according to the instructins, however I did check the inlet and outlet pressures with a manometer and there was about 6.5" going in, 5.5" going out. Now most spec 3.5" but I'm told that's not gospel, and the burner looks like it's running fine. Just looking for opinions before I throw parts at it (I'm a ticketed gas fitter btw but just don't know which part is making the buzzing sound - it only happens when the main gas valve opens and lets gas to the burner).

Tim McElwain

What does the rating

plate on the boiler say the pressure should be?



Did you clock the burner to see what the boiler is burning for input?



Make sure polarity is correct.



As a quick check remove the wires from the gas valve and connect the multimeter in place of the valve, is there still a noise (could be the transformer) then what is the voltage, typically should be around 24 to 25 volts. If the noise stops and the input is correct and the valve is still buzzing replace the valve.