--99.225.xx.xxx

I suggest using a 24volt test light or LED on the terminals of the gas valve, there may be power coming from another source, the switch turned off may only be water feeder, be sure you don't run this boiler low on water --76.188.xxx.xx

Some apartment buildings are still using the old fashion indoor outdoor control to control the heat not a very efficient set up. The boiler should shut off when the power is shut off. Most boiler use a 24 VAC gas valve. The best option is to get rid of the old fashion indoor outdoor control then install a Tekmar electronic boiler control which is much more precise with temperature control. It is possible to get control which can operate a indirect hot water tank which is much more efficient then the direct fired hot water tank which lose 7 to 12 degrees per hour. Less one degree heat loss per hour has a considerable energy saving. For the radiators Danfoss or Honeywell Braukman locking non electric thermostatic radiator valves will reduce the entire building heating water temperature. Most boilers have a website where can get a wiring diagram along with technical information. The worst case is a gas valve is required. Desco sells boilers, gas valves. Have a licensed gas fitter install a new gas valve. Insulating all the heating and hot water pipes in the boiler room will produce a energy saving over the winter and all year round. --147.194.xxx.xxx

I guess the main switch isn't working and it sounds like someone put a tool across the electrical connections to start it up when it wasn't running. Maybe one of the tenants did that to get more heat. This happened in one of my duplexes when I had the heater serviced. This was an oil hot air heater. The technician jumped it to make sure it ran rather than going into the tenant's unit and upping the thermostat. Then the technician left and the screwdriver he used to jump it was still there. I got a call and went over and the doorknobs upstairs were hot. I found the tool and removed it after shutting off the power to the heater. The tenant in that unit was a heavily medicated Vietnam Vet and he didn't even realize it was approaching a hundred degrees in his apartment. It was obvious that he was unsafe alone there so his family got the VA to house him. --73.33.xxx.xxx

Sounds like a thermostat problem or a problem with the limit switch. Both are simple repairs. Usually Boilers stops firing when they reach the high temperature limit, setting went up to 210 on a Weil Mcclain Boiler I used to service, but you can adjusted to the recommended settings. Thermostat sounds most likely the problem, and maybe you have a 750 millivolt system if it works in the off position. --108.176.xxx.xxx

Thanks for the replies. The problem has not repeated itself, so the cause hasnt been found. Im guessing gas valve or aquastat thermostat. I will see about having both replaced. Tech wasnt helpful. --65.94.xxx.xxx