34
Modulating Gas System
The second system, the
modulating gas system,
consists of a temperature selector dial, a discharge air
sensor, an amplifier, and a modulating gas valve. The two types of modulating gas systems used are the
Maxitrol 14 or RTC Solutions controls and the Maxitrol 44 series. The Maxitrol 14/RTC utilizes a discharge
air sensor and modulates the Maxitrol gas valve to provide discharge air to match the selected
temperature on the temperature selector. The Maxitrol 44 utilizes a room temperature sensor to control
room temperature as well as a discharge air sensor in order to control the discharge air temperature. The
modulating gas valve controls the amount of gas flow to the burner based on the temperature rise needed.
When the modulating gas valve is all the way open and achieving the maximum BTUs and temperature
rise of the unit, it is called “high fire”.
Figure 22 - Maxitrol 14 Amplifier
High Temperature Limit
One of the backup safety devices is the
high temperature limit
switch. This switch is a mechanical
thermostat that measures the temperature inside the unit downstream of the burner. If the factory-set
temperature of
180°F
is exceeded, it will signal the FSC to turn off the burner. This requires a manual reset
of the high temperature limit. This ensures that the discharge does not exceed 185°F.
Figure 23 - High Temperature Limit Control
DECREASE
INCREASE
DO
NOT
TAMPER
SENSITIVITY
FACTORY CALIBRATED
1
3
2
1. Temperature Setting
2. Adjustment Screw
3. Manual Reset Button
Содержание D76
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