I have a Burnham hot water boiler system Series 2A. I have my thermostat set at 66 at the moment. The actual temperature is 64 in the house. Why the two degree difference? I have never been off before on the thermostat until last night. Had it set at 68 was only 65 in the house and the system runs for six minutes and off for four minutes--like clockwork. Over and over and over. Runs at about 20 psi when hot and shuts off at 180* during the six minute run cycle. I have an old mercury style round Honeywell thermostat. Two wire-white and red. All the baseboards are hot and everything seems to be running correctly. Any ideas? Thanks:)

Many thermostats have a built in differential. Without that the boiler would be cycling more often than it is now. Dust/dirt also gets on the mercury bulb in the thermostat and can change it accuracy.

If your system is cycling that often it might be very cold outside but since you did not mention the temperature who knows.

Sorry, its COLD. 6* now. Its 65* in the house, turned the thermostat up to 70*--the house won't get warmer than 65* Cycles like it normally does. I know its cold out therefor the furnace will run more often than not, though shouldn't it run at 70* if that's what I set it at?

How long have you had this home?
Is this the first cold weather you have experienced in this home?

The reason for these questions is that it is possible the unit is putting out all the heat it can under the circumstances.

You said it cycled every 6 minutes. Does the pump keep running or does the entire boiler and pump shut down?

Many homes have a failure to maintain set temperature in very cold weather.

When was the last time you had your heating system serviced by a professional?

It is also possible that there is a energy savings device on the boiler causing problems but you said the temp would go to 180 degrees so that possibility is limited for a temperature differential control. It could be a timed energy saving device or it could be the control is just set at 180 and that is all the boiler can give.

This will be our 4th winter. Live in Northwest Ohio (southwest of Toledo) so winter is winter as far as cold weather goes. Its been 0* before. Cycle time=seems that everything shuts down like it normally should. Fire is out, damper closes. There is a slight hummm to it when it is "cooling down" Temp hits 165ish and furnace kicks on again. I had it service a month ago when they came to fix a water leak in a shut off valve to a register. If it seems to be a timed energy saving device, is that changeable without damaging the system? I have unhooked the thermostat and jumped the red and white wires. System runs the same. Temperature is up to 67.9 now though.

If you had the system serviced just a month ago I would ask them if they made some adjustments at that time. There is no reason your boiler will not run the same as it did last year unless a control or something else has been adjusted.

With the boiler operating to 180 the kicking back on a 165 that sounds normal with a 15 degree spread. Check to be sure all heat devices are on and that all air damper devices if equipped on the heat devices are open.

Well everything seems to be running smoothly now. Of course the temp. has gone up to 15*. Maybe it was just too cold to keep up? Thanks for your time.

I have had this same problem in the very cold weather - under 5 degrees outside temperature. I had a local repairman to the house and he showed me how to turn up the water temperature for the boiler to compensate for the unusually cold weather. We turned the water temp to 200 degrees overnight, then I set it back to 180 when the cold weather broke the next day. Some hot water boilers adjust water temp automatically depending on outside temperatures but mine does not. It can be dangerous to attempt to adjust settings without proper knowledge so I recommend to have a qualified repairman inspect your system first!

It is NEVER recommended to take a boiler past 190 degrees. Now it may have been done but it is not recommended by the manufactures.