I had to have a new boiler installed this past winter. It was expensive but I’m glad it’s out of the way. However, now that warm weather has arrived, there’s a problem. The boiler keeps kicking on*, even thought the upstairs thermostat (a Honeywell mercury wall bump, circa 1958-1987) is backed off to it’s lowest peg. These are cast iron radiators, fwiw. They’re a bit warm to the touch which sucks since it’s a little over 80 in here and I’m trying to delay using the AC.
The circulator isn’t turning on when the boiler fires and the fire turns off after a short time. It seems to be simply keeping the water within the boiler at a ready-to-go temperature. I happened to be looking at it when it fired up right at 110 and stopped at 135 which seems like something programmed in.
This is likely a property of the boiler controller which is a Hydrostat 3200 Plus: pdf manual. However, I’m uncertain which setting this is or if it’s something else altogether. The Circulator Hold Off (pg 9) seems the most likely culprit but I’m hoping someone has specific advice. There’s a switch that I can use to kill power to the entire thing but I’d rather understand what it’s doing.
How do I program my boiler controller?
*I first noticed it while laying in bed during a quiet weekday morning. I can just barely hear the flue open and then the whoomp of the boiler firing down in the basement. During warmer weather like this, the my gas meter makes a tiny squeaking sound every few seconds, almost the same as the birds outside but now, I listen for it and can tell when the thing is running.
I have 3 zones on my boiler and if there is no call for heat on any zones the boiler does not fire. If the outside temperature is above the cut off on the Outdoor Reset controller, the boiler does not fire. If there is a call on any zone and the outdoor temp is below the cutoff, the boiler heats to the cutoff temp which ranges from 90 to 120 based on the outdoor sensor.
Could the economy dial be set to off?
Otherwise, I would just kill power to the system. It can’t hurt anything.
In the meantime, I’ve flipped the switch to power the whole thing down but I’m still curious to know how to program this controller. Its really hot in here, over 80 F, and I’d like to get this figured out.
Recap: Why does my boiler fire when it gets gets below 110, regardless of thermostat input.
I know nothing about boilers, but I know a little bit about hot water.
Modern hot water systems are required to cycle up to a temperature hot enough to kill legionella once a day. The manufacturer of your heating system may have found a similar regulatory requirement somewhere?
When we first had our furnace looked at, the repairman said he could set things up two ways: The boiler stayed warm all the time, for quicker response when you needed heat; or the boiler gets cold when there’s no need for heat. It sounds like yours is set up the first way.
I got the impression that changing it (on our 1960s-era system) was a matter of rewiring inside the control box. YMMV, of course; but at least that indicates that the option probably exists on your system.