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Safety Control Operation - Standing Pilot and Intermittent Ignition
Hydrolevel CG400A Low Water Cut-off - Interrupts burner operation if the water in the boiler drops below a safe level. As the
water drops past the cut-off point, the amber lamp on the CG400 will glow. The CG400 will interrupt power to the burners 15
seconds after the water level drops past the cut-off point. This feature prevents short cycling of the burners due to a bouncing
water line. The burners will then remain off until 30 seconds after the water level has been raised above the cut-off point.
The CG400 is also equipped with a feature which will shut down the burners after they have been firing for 10 minutes, regardless
of the water level status. The CG400 then keeps the burners off for 90 seconds, allowing the water level and any foam which is
present to settle. During this 90 second interval, the green LED on the CG400 will glow. If the water level is still above the cut-off
line at the end of this 90 second interval, the CG400 will restart the burners.
The vent damper will close when the low water cut-off interrupts burner operation.
McDonnell & Miller #67 Low Water Cut-off - Interrupts burner operation if the water in the boiler drops below a safe level.
Burner operation is restored when the water level in the boiler is raised above the cut-off point.
The vent damper will close when the low water cut-off interrupts burner operation.
Pressure Limit Control - Interrupts burner operation when the pressure in the boiler exceeds the “Cut-in” setting plus the
differential setting. The “Cut-in” setting is shown on the outside of the control and is adjusted using the screw on the top of the
control. The differential is adjusted using the white thumb wheel on the inside of the control. Burner operation is restored when
the pressure in the boiler drops to the “Cut-in” pressure.
The vent damper will close when the pressure limit control interrupts burner operation.
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FIGURE 18: WIRING DIAGRAM, INTERMITTENT IGNITION AND HYDROLEVEL CG-400A LOW WATER CUTOFF
“BURNER”
“BURNER”
TH
TR
+
ROBERTSHAW
7000DERHC
GASVALVE
(BSI379)
HONEYWELL
VR8204/VR8304
SERIESGASVALVES
(BSI069-345)
VENTDAMPER(NOTE2)
NOTE3
LESSVENT
DAMPER
2.VENTDAMPERREQUIREDONBSI069-BSI276,OPTIONALONBSI310-BSI379
3.ONBOILERSLESSVENTDAMPER,DAMPERHARNESSNOTUSED.REDANDBLUE
LEADSAREJUMPEDTOGETHERUSINGREDJUMPERWIRE.