Violent hammering in second zone

Hi all -- I have a gas-fired boiler with two zones - basement and main living floor (its a ranch). Whenever I turn up the stat in the basement, there is some pretty violent hammering until the pressure relief valve on the boiler blows - at this point I usually just turn down the stat so the system shuts off. I have tried bleeding the basement radiators but this appears to have no effect. Any idea what might be causing this? Reason it is becoming such an issue now, is temps have been really low the past few days, and from what I can tell they are lower than the lowest stat setting causing the basement heat to kick on, in turn causing the violent hammering - of course this all happens at 4am waking me up from what is otherwise a very enjoyable sleep.

Any advice would be appreciated - thanks

You have air in the system and the high limit is set too high, the boiler is making steam.

thanks for the reply -- is the high limit setting something I can adjust relatively easily or is it best to call in a pro?

thanks

Your expansion tank may be toast. If you knock on it, it should sound hollow. If you momentarily open the Schrader valve to the bladder (same as a tire valve), it should have air verses water. If you have a primary/secondary loop for the boiler, the primary loop circulator could be shot. The pump must be on when the burner is on or there's nothing to move the water across the heat exchanger, and the water will boil in the heat exchanger. If there's only one circulator, is it actually running? What is the system pressure? It should be around 14-18 pounds or so (designs vary a little).

thanks for the replies - considering I'm neck-deep in a kitchen/bath/living room renovation that is taking longer than my significant other had expected - I think I'll call in a pro to check it out. The problem is only coming from the basement baseboard zone - so I can just leave that off until the problem is addressed. Thanks anyway