I could not find the OEM specification gude part # 6711 I have this burner and it now seems to run for hours before it shuts off. This is used in a steam system. Although this is a low steam appication the pressure needle does not come off its post. I believe when it was first installed that as it was running it to got up to two pounds of pressure. I am wondering if when it was last cleaned if they put a smaller nozzle in the burner thus causing it to make steam but not enough to push it to the varisous radiators. I can;t find in the manual what size nozzle to use. It does give the recommended spray angles. Can you help me?