Coal Stoker Holdfire Timers

The Will-Burt model 34170 Holdfire Timer provides periodic stoker operation during mild weather and other times when the system operating controller does not demand burner operation, in order to

• maintain combustion, so that the fire does not have to be frequently restarted, and
• prevent the fuel bed from burning down into, and damaging, the cast iron burner parts.

Generally utilized in residential applications, it is intended for use with 2-wire, 24 V thermostats.

Virtually identical in design and operation is the Will-Burt model 20350 Holdfire Timer, which fulfills the same function as the 34170 while working in conjunction with a boiler limit control.
The Will-Burt model 34170 Holdfire Timer provides periodic stoker operation during mild weather and other times when the system operating controller does not demand burner operation, in order to maintain combustion, so that the fire does not have to be frequently restarted, and

34170/20350 Timer Interval Adjustment

Operating Interval 30 Minutes: 1-5 Minute Adjustable “On” Period
Operating Interval 60 Minutes: 1-10 Minute Adjustable “On” Period

Approximate 34170/20350 Timer Dimensions

Timer Case: 5″ X 4-3/8/” X 4-5/8″ High
Timer Cover: 5-1/16″ X 4-3/8/” X 4-5/8″ High

Specifications