Any HVAC techs on here that can help me out?

[BigAir]

The gas control valve on my old A.O. Smith boiler needs replaced. It is an Essex CC-251, that is no longer made and no one can find a direct replacement for. It is a standing pilot for a 100k BTU boiler. The weird thing is it has 3 connections for the pilot instead of just the normal gas line and thermocouple. I can't figure out what the third does. I have disconnected it and both the pilot and main burner still operate normally. Can anyone tell me what it does? I have attached pics and have more if they would help.

 

[Hawkster]

Disconnect what ? Another pair of wires ? If so than it's a thermopile , burner will not ignite if it is and is bad , pilot will stay lit also .

Hold on , they also make a gas thermopile

 

[05rmksteve]

On some of the older valves the second line was a gas valve vent line. You should be able to replace it with a standard 24v standing pilot gas valve and a new pilot burner. One would have to determine if the existing valve is a slow opening or fast opening valve and figure out what direction the pilot burner hood needs to be to properly light the main burners.

 

[plumberdood]

Maybe it’s time to consider replacing the boiler.

 

[CB_Rob]

Maybe it’s time to consider replacing the boiler.

Yep..
You can get a pretty sweet high efficiency mod con boiler for about 2500.00 nowadays

 

[BigAir]

Yep..
You can get a pretty sweet high efficiency mod con boiler for about 2500.00 nowadays

Thanks for the help guys. I replaced the gas valve with a Honeywell VR8200A2132 and with a 90 degree outlet flange it was a direct replacement. Boiler is working good again. It definitely is past time to replace it though, since it will literally be 50 years old next year (manufactured 1972). Any suggestions on best brand for replacement? How much does install normally run just connecting boiler to existing plumbing? Thanks again.

 

[05rmksteve]

For wall hung high efficiency I install the Navien brand for standard units Slant-Fin. Price all depends on what all needs to be replaced, piping, venting, gas line, pumps, controller ect.

 

[CB_Rob]

Thanks for the help guys. I replaced the gas valve with a Honeywell VR8200A2132 and with a 90 degree outlet flange it was a direct replacement. Boiler is working good again. It definitely is past time to replace it though, since it will literally be 50 years old next year (manufactured 1972). Any suggestions on best brand for replacement? How much does install normally run just connecting boiler to existing plumbing? Thanks again.

Ive been installing triangle tube instinct boilers for home heating and snow melt systems.
Very affordable when it ordered from supplyhouse.com