What happens if the primary control is set incorrectly?

expert EXPERT April 26, 2007

The set point on most controls can be adjusted easily. The set point can be either too high or too low. Set points are sometimes changed season to season, or are tied directly to the outdoor temperature.

There are different implications to different improper settings. If the primary control is set too high, the boiler water may be near the high temperature limit. Keeping water at over 200F in the boiler is inefficient at best, and may overheat the boiler, shortening its life. Setting the control too low may mean a long wait for heat when the thermostat calls.

Some primary controls have at their lower end the setting described as Summer. Rather than a temperature setting, this a setting allows the homeowner or service person to ensure that the boiler won't come on during the warm summer months.

If the water temperature on the gauge is over 200F when the boiler is at rest, you may suspect the primary control is set too high. You can usually look at the setting and determine this. In some cases, the setting indicated is not accurate. When the boiler temperature is over 200F, you should probably get it serviced.

If the primary control is set too low, the burner may not come on, no matter what you do with the thermostat. If the operating control is set to the Summer position, the burner won't fire because it thinks the water is warm enough.