Heating Help

Anyone Know?

I recently encountered a oil fired hot water boiler, expansion tank has been replaced less than one year ago and appears to still be doing its job. However 3/4 blowoff valve gushing water every time i attempt to add water to boiler (1-3 psi on gauge on front of boiler at most.) Am i making this harder than it has to be ? Replace valve should solve problem or is there more to this than meets the eye? Any and all help greatly apprciated.Also flocheck valve near exp. tank piped on riser in closed position does this have anything to do with press. problems in the past, vents on baseboards appear not to have benn touched in quite sometime????

is

the expansion tank between a flow check and zone valves? Sounds like that's the case. If so, open the flow check. The zone valves will stop the natural convection. 

anyone know 2

no zone valves in the equation

Could just be a bad tridicator.

I don't trust these tridicators nowadays. They are making them cheaper and cheaper. Rig up a gauge with a boiler drain and verify that the tridicator is showing the correct pressure.

pt.3

 im watching gauge needle move each time i attempt to add water from fill valve

xxxxxxx

Watching it move  and/or knowing its bad are not the same thing. You must test pressure in boiler . Get a hose x 1/4" adaptor and 100 psi  gauge and put it on working draw off and see what pressure is. now you have a place to start. not the same or very close then you know if gauge is bad. now you are ready to trouble shoot. ED N.Y.C.

Have you checked

the pressure in the tank?

If not, you will have to de-pressurize the system side of the tank all the way to zero. Then use a tire pressure gauge to check the pressure at the Schrader valve on the bottom of the tank. The pressure should match the system's initial fill pressure.

Thank you all

Thanks to everyone who offered any insight on dilemma. Much appreciated
turned out to be blowoff valve, didnt have to replace the boiler fill or expansion tank
 however leak on cold water inlet to coil was a pain right along with the replacement of the tripple Aquastat withe the burned out board just below that leak. did i mention the T&P gauge just top left of that singed control,  stem snapped in threads of coil luckily there was an EZ out  just right for the job.
tthanks again