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MUA-SVX004B-EN
Controls
•
Electronic modulating gas firing is available from the factory on natural and propane gas
units.
•
Do not use a thermostatic fan control switch when either two-stage firing or modulated gas
controls are used. A fan time delay switch can be used, however, and is available as an option
on outdoor duct furnaces.
•
All controls are located on the access side of the unit.
•
Chart 5 lists orifice sizes for outdoor duct furnaces.
Operating High Limit Control
•
The operating limit control is a factory installed component surface mounted in the inlet air
stream end of the heat exchanger. This surface mounted safety device must have adequate
contact to the rear header plate of the heat exchanger to insure its function.
•
When the temperature reaches the limit set point, all heat is shutoff. The limit control has a
built in auto-reset that comes on when the equipment is sufficiently cooled down. Reference
the unit's wiring diagram.
Pilot Control
Intermittent pilot ignition is standard on all outdoor unit sizes. Intermittent pilot ignition contains
a solid state ignition control system that ignites the pilot by spark for each cycle of operation.
When the pilot flame is proven, the main burner valve opens to allow gas flow to the burners.
Both the pilot and burners are extinguished during the off cycle.
High Gas Line Pressure Regulator (Natural Gas Only)
•
The pressure regulator is a field installed component located external of the unit and as close
as possible to where the gas line inlet enters the unit.
•
The pressure regulator reduces the main gas line pressure to a minimum of seven inches WC
(1.74 kPa).
