I have a 30 year old Slant Fin cast iron boiler heating system. The heat is split into two zones in the house. Yesterday we turned on the heat for the first time this season and after testing it out turned it back off. The heat kept coming from the pipes so we tried switching the thermometers to cool (they're both Hunter digital thermometers) and that didn't work either. I've also tried disconnecting both thermometers, but that doesn't work either. I've turned it off at the breaker, but every time I turn it back on the heat comes back on in both zones and remains on. Looking for possible suggestions on anything I might be able to do myself or if I should just call a technician.

Thank you,
Noodlz

Something is calling for heat to be produced or a relay/control device is defective doing the same thing as calling for heat. If you know how to trouble shoot these type of items go for it but if not better to call a pro. Usually I recommend a boiler be serviced every year especially with fuel costs being so high. So they can do your annual service and fix the problem all at the same time.

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Originally Posted by hvac1000

Something is calling for heat to be produced or a relay/control device is defective doing the same thing as calling for heat. If you know how to trouble shoot these type of items go for it but if not better to call a pro. Usually I recommend a boiler be serviced every year especially with fuel costs being so high. So they can do your annual service and fix the problem all at the same time.

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Thanks for the response. Called the service technician. Turned out it was an extremely simple fix. When it was last serviced the technician left the valves open. He found the problem right away, closed both valves, problem solved.

Well that should have been a free bee.