Should my boiler (hot water system) cycle on (burners fire and refire) when my THERMOSTAT is set in the OFF position? These are my symptoms:1,THE RADIATORS STAY HOT WHEN THERMOSTAT IS IN OFF POSITION! 2, LOUD BANGING NOISES IN PIPES. The only way I stop these symptoms is to shut off the entire system at the main switch. It just seems to me that the BURNERS should stay off until the thermostat is switch ON and calls for heat! It has a L8124A aquastat and AT72D transformer both by honeywell

AL

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:confused:

No a boiler should shut off when there is no call for heat, unless it is wired incorrectly. If there is banging, it could be a restricted boiler, low flow, dead recirc pump etc. Need more info on type of boiler install, maybe pictures could help

Looks like the aquastat (L8124A) has a high and LOW SETTING. Its seems like the LOW setting is designed to keep the water temp at the LOW setting temp no matter what the thermostat is set to! Similar to a hot water tank. DOES THIS SOUND PLAUSIBLE?

AL

Check the sticky at the top of the forum and see if your thermostat follows the same wire colors. Also, gas or electric? Do you have zone valves closing off different sections of the house. To get heat to a radiator, the thermostat needs to activate the burners, start the pump, and open any zone valve. Everything is controlled by relays which can stick. If a zone valve sticks open, it may continue to call for the pump and burner to be on. Look over your system and get back to us with more info.

Sometimes, boilers are hooked up this way. It was a popular way in the 1950's to late 60's. They called it something like, heat ready, an older timer than me would remember. The thinking was the core would stay hot, the burner ran on limit, and when the thermostat came on, it only turned on the pump. Often these where changed over to other configurations because of the perculation noises. Also if you didn't turn off the wall switch it would stay hot all summer or when not needed.