Dunkirk boiler circulator cutting off and on

wenbee

last year , before heating season, I did some maintenance on a friends system. Dunkirk PWX-4ent2. Specifically added a valve on the boiler feed pipe, new feed regulator, and new relief valve. The original relief valve leaking constantly. System ran good all winter. The system was restarted a couple of days ago and boiler pressure is causing valve to release. What I noticed:

The boiler calls for heat, Circulator pump starts up, Boiler kicks on As temps start to rise, the circulator pump begins a stop & start dance. When the circulator stops (boiler still running) the boiler temps and pressure start to rise. When circulator starts running again, boiler temps reduce drastically. It does this stop and start until temps are over 210 and eventually relief valve lets go. I’m thinking the pump is going bad. Could the aquastat cause this issue also? But also wondering why the boiler isn’t shutting off once it hits the hi-temp set point. I’m not close enough to have immediate access to the boiler.

HVACNUT

What circulator? Internal? External? What controls the circulator?

pecmsg

Why isn't the aquastat shutting it down?

What's the amperage on the circulator?

Ironman

It’s mostly likely the circulator, particularly if there’s any air in it: it’s bearings are water lubricated.

The only way to know for certain is to have voltage meter connected to it to see if power is constant while it’s attempting to run.