Hi I just recently found this site and I am posting on it's various forums with different issues. I have an American Standard Gas boiler It is at least 40 years old maybe older but until recently was working fine. It only heats two rooms in the house with baseboard tubing. This last winter when I started to use it made a kettling sound as it was warming up and emited a lot more noise then normal. The clanging sound reminded me of pop corn in a kettle. I had someone come and look at it and they purged the system of air but the sound remainded but it was not as loud. The rest of the rooms are heated by forced hot air with an hot/cold air system. I know it sound funny but I perfer the heat from this boiler over the new modern systems any day. Any suggestions on how to proceed. Ciao
Those are the classic symptoms of low pressure. The pressure at the boiler should be ~12psi when the burner is running which suppresses the flash-boil on the heat exchanger & subsequent sudden collapse of the bubbles as the water moves away from the heat exchanger, which is what is causing all that clanging & banging.
The expansion tank needs to be checked and charged correctly, and some water added to the system to raise the pressure to 12psi (when the system is cold/tepid) . The pressure will rise a bit when the system is at it's peak temperature, and if the expansion tank isn't properly charged it could result in the pressure relief valve letting water out. Over time the pressure becomes too low to prevent flash-boil when it initially fire.
The heat from radiators (or even fin-tube baseboard) is far more comfortable than moving hot or warm air, no surprises there.
If you've removed most of the radiation from the boiler now that most of the house is heated with the hot air system you may be short-cycling it into truly wretched efficiency. Measure the burn times and duty cycle during a continuous (and long) call for heat from the zone(s) still using the boiler, once you've fixed the kettling problem.
