Assessments - 3, GPA: 4.7
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Facilidade de uso
w.c.) CFM Size 4 Size 5 Modulating Gas System The second system, the Maxitrol modulating gas system, consists of a temperature selector dial, a discharge air sensor, an amplifier, and a Maxitrol 14 modulating gas valve. The two types of Maxitrol systems used are the Maxitrol Amplifier14 series or the Maxitrol 44 series. The Maxitrol 14 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”. High Temperature Limit One of the back up safety device is the high temperature limit switch. High Temperature Limit This switch is a mechanical thermostat that measures the temperature inside the unit downstream of the burner. If the factory-set temperature of 170°F is exceeded, it will signal the FSC to turn off the burner. This requires a manual reset of the high temperature limit. This insures that the discharge does not exceed 185°F. Operation Summary • With the blower already running and the airflow switch proven; • The outside air temperature falls below the setting of intake air thermostat or • The optional remote panel is set to “Manual” and “Heat” mode • The FSC in energized and the following occurs; • FSC indicates that it has power by illuminating the OPR CTRL LED • FSC verifies proper Airflow 16 • Begins Pilot Trial For Ignition and turns on PTFI LED • The pilot gas solenoid valve is opened, the spark igniter begins sparking, and the flamerod sensor watches for flame initiation • When flame is established, the FLAME LED is illuminated and main valve opens and the FSC powers the Maxitrol system and gas flow begins modulating • The FSC monitors the flame while the Maxitrol system adjusts to the selected temperature • The Maxitrol system checks the discharge air temperature (and the room temperature for the Maxitrol 44) and regulates the gas going to the burner to satisfy the temperature setting. The Maxitrol system will modulate the main burner gas from 100% down to 5% as needed. Optional Remote Panel Circuit Power Supply From Heater "Power" Light Off On No Power to Panel Panel is Powered Blower Switch Nothing Happens No Power is Sent to Heater "Off" Position (3-Position Panels Only) "Manual" "Auto" Power is Sent to Heater to Open Damper (if provided) and Start Blower "Blower On" Light Off On Intake Air is Warmer Than Thermostat Set-Point Intake Air Thermstat is Powered Intake Air is Cooler Than Thermostat Set-Point Nothing Happens Heat Circuit is Energized Heat Circuit is Energized "Burner On" Light Illuminates with "Burner On" Light Illuminates with proper flame. proper flame. "Flame Failure" Light illuminates "Flame Failure" Light illuminates if proper flame is not established if proper flame is not established Damper is not Open or Freeze- Stat has Detected Low Temperature Operation Blower Operates Cooling Circuit is Energized Power is Sent to Heater to Open Damper (if provided) and Start Blower "Blower On" Light Off On "Cool" Temperature Control Switch "Vent" Position Damper is not Open or Freeze- Stat has Detected Low Temperature Operation Blower Operates Heat Does not Operate Position (if provided) "Heat" Position 17 Components The following image and list outlines the typical direct fired heater components and their functions. 4 3 2 8 10 15 16 20 22 23 12 14 19 18 9 21 13 5 7 6 17 1 11 1. Gas Inlet – Main gas supply connection 2. Motor Starter – Contactor with overload protection to start and protect motor. 3. Freeze-Stat Thermostat (Optional) – De-energizes blower motor if the discharge air temperature falls below the set point. 4. Cooling Interlock Relay (Optional) – Energizes power to cooling circuit on call for cooling. 5. Inlet Gas Pressure Tap – Inlet gas pressure should be measured here. 6. Combination Gas Valve - A combination of redundant solenoid valves, pilot valve and gas regulator built into one unit. 7. Pilot Tubing – Pilot tube connection to combination gas valve. 8. Manual Reset High Temperature Limit – Safety device that prevents the heater from overheating. 9. Maxitrol Modulating Amplifier - Regulates temperature by modulating gas valve 10. Power Transformer – Installed when motor voltage > 120V. Used to provide 120V service to controls. 11. Circuit Breaker – Protects electrical components from high current spikes. 12. Terminal Strip – Central location to terminate control wiring. Should be used for troubleshooting. 13. Control Transformer – 120V primary; 24V secondary control transformer. 14. Low Pressure Airflow Probe – Measures profile pressure downstream of burner. 15. High P...