Got a head scratcher here. Four yo high eff Lennox boiler. Pumping away from cushion tank, water feed T'd there as well. Issue is pressure climbs to 24psi (eventually hits 30 and blows P/T), reg set to 18. Three story home with cast iron rads. Originally had too small of a cushion tank installed, replaced with honeywell tk300-60 (as per manufacturer's spec). The confusing part is when the boiler is off and feed is open, pressure stays put at 18psi. When boiler fires up pressure increases, even with feed closed. Previous boiler (older mid) never had pressure issues. Any suggestions are welcomed. TIA.

Posted by Deleted (aad2bacd) at 2021-02-23 18:58:09 UTC