Hi , we just had a new boiler put in ( Carrier). The new system works great with one exception. when boiler temp is down and a zone calls for heat and the boiler temp starts to rise there is a loud snap like a piezo lighter or mouse trap coming from within the boiler. It doesn't seem to be a switch as you can have a hand on the switches and feel nothing . It seems to come within the casting, I don't know if its expansion but there will be LOUD snaps at maybe 10 second or 5 sec intervals . The snapping decreases as the temp gets up to 140 or so then may snap once at 170 as its shutting down . The snaping isn't consistant but seems to be temp related. As the temp starts to rise you can bump the casting with the heal of your hand and cause it to snap then wait a bit before bumping it again to get it to snap . The system is great and the installation looks good. Just wondering if anyone has run into this situation. Thanks