I have under 200 foot of baseboard with a size 60 expansion tank and the pressure is riding up to 29# causing the relief valve to drip. The fill valve is new and started out @12# cold. ???
The boiler manufacturers instructions should tell you the capacity of the expansion vessel fitted to the boiler and then you would need to know how much water there is actually in your system to compare the two. Are you sure its not the vessel thats faulty/needs repressurising.
