On a 3‑story 1928 gravity‑conversion with a Taco 007e and an Extrol 30 precharged to 18 psi, I’m setting 18–20 psi cold to cover about 40 ft of static head, but seeing 26–28 psi hot and the 30 psi ASME relief starts to weep. Are you dialing the fill lower or upsizing the tank to keep it under 25 while staying within code and maintaining top‑floor pressure?
, on big gravity conversions an Extrol 30 is usually too small — “26–28 psi hot” screams undersized tank or a bad PONPC. Swap to a #60 or add a second 30 and tie the tank in at the circulator suction (pump away), then try a 16–18 psi cold fill to keep it under about 25 hot. Dan Holohan breaks it down here: https://heatinghelp.com/systems-help-center/pumping-away/. Did you set the tank precharge to your cold fill with the system at zero pressure?
It sounds like your charge is definitely pushing the limits of that Extrol 30. From experience, I’ve had better luck with a larger tank or even two smaller ones to manage temp swings without hitting that relief valve. Have you checked the precharge lately?