PREMIX SYSTEMS
pressure variable or different from furnace room pressure
control valve
Mixer
-2 osi
built-in Limiting Orifice
EFFECT OF PRESSURE OR SUCTION IN COMBUSTION CHAMBER ON CONTROL WITH A ZERO OR ATMOSPHERIC SYSTEM With the lower side of diaphragm open to atmosphere (without line A), a suction in the furnace is transmitted along the dashed line to the upper side of the control of the system. Similarly, a positive combustion chamber pressure will add a closing force and upset control of the system Addition of dotted line (A) compensates for variable combustion chamber pressure or balances any combustion chamber pressure higher or lower than the room pressure adjacent to the regulator. Line (A) will not cause trouble if installed where not required, so if in doubt about combustion chamber pressure, install it. * * See page 9, regarding location of combustion chamber pressure tap.
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