CB
Built Like A Tank With Laser Precision
Page
10
of 24
H. T-stat, Controls, Overriding Timer Relay
A second thermostat needs to be installed to operate your existing blower for forced air or your
circulation pump for radiant heat and needs to be set higher that your original thermostat so your
existing furnace will automatically take over to maintain your household temperature if your boiler is
not running. Please see page 18 for an example wiring layout.
The GT-220 uses a hot water thermostat (aquastat) with a thermocouple that is inserted into a
brass drywell for sensing the water temperature of the unit. When the temperature falls below the
differential setting on the aquastat, the blower turns on and the damper actuator opens, feeding
oxygen to build a hotter fire and remains on until the water temperature in the boiler reaches the set
point of the aquastat. Temperature may be set up to a maximum of 190F. Do not set above this as the
refractory bricks continue heating the water to around 200F after shutdown. When heating your home
through a radiant system, the recommended (and maximum) setting is 190. When heating with a
forced air system, the recommended (and minimum) setting is 170. The aquastat also has a
temperature differential that is adjustable. Recommended setting is 3 degrees which provides for
shorter idle times resulting in less creosote buildup. See aquastat manual for details on programming.
If there is difficulty in achieving gasification, the timer relay (TR1) in the control box can be used to
override the aquastat and force the boiler to run, keeping the firebrick hot enough. Recommended timing is
3 hours off, 5 minutes on. Unplug the relay if not needed. See timer relay manual for details on adjusting.