I'm working on a 250K btu pool heater. I use to have an old millivolt meter that told how low your reading could be and still hold in a 750 mv valve. The meter is long gone, I installed a new power pile and get around 590 to 600 mv when connected to the valve, but the pilot goes out when trying to energize the valve. I am going to change the valve, how low can the mv's be and still hold the valve in?
Been awhile since I've done a millivolt system. Thanks.
I thought it was pretty low, like 200mv. But I may be way wrong. It might also depend on the valve it's self. It may have trouble opening.
My first instinct says resistance somewhere. Try disconnecting all the wires from the gas valve except the PG and than using 2 jumpers jump the 2 middle terminals and than the 2 opposite the PG. Meaning one of the middle terminals will have 2 jumpers. The middle jumpers are acting like a buss. These last 2 are acting like the t'stat. If the valve fires off than you know the problem is elswhere. These problems normally are corrected using a meter unless you get lucky. Most millivolt valves will dropout around 60 mv. Do not confuse the the dropout in a millivolt gas valve with that of a power unit (magnet) in a 24 volt valve or a water heater control.