Eclipse Combustion RAH Series Manual page 4

2.0 Control System Requirements
Turndown Method
Regulator Loading Lines
Piloting
Ignition
Check Valve
Air Damper
Warning
Pressure Switch Connection
Limit Controls & Safety Equipment Limit controls and safety equipment should comply with current NFPA Standards* 86
Figure 3–Check Valve Operation
WARNING!
Do Not Install Any Valves Here!
See Section 2.0
Combustion Air
Check Valve Opens When
Gas Inlet Pressure Is at Low Fire
Input is normally controlled by a motorized butterfly valve in the gas line to the burner.
Connect the top diaphragm chambers of the main gas and pilot gas regulators to the
duct approximately 10" downstream of the burner. This will allow the regulators to
maintain a constant supply pressure to the burner regardless of varying pressures in
the duct.
Pilot gas flow is adjusted as shown in Figure 6.
Ignition voltage should be 6000 VAC.
See Figure 3. At high fire, the gas pressure at the burner inlet is higher than the air
pressure, and the check valve is closed. At low fire, gas pressure falls below the air
pressure, and the check valve opens, permitting a small amount of air to mix with the
gas. This premix at low fire stabilizes the flame and helps distribute the flame evenly
down the length of the burner.
Install an air damper at the combustion air blower inlet, or between the blower and the
burner to allow adjustment of combustion air flow.
Do not install any valve or controlling device in the gas line between the burner
and the check valve tee, Figure 3. Because this section of the gas line carries a
partial pemix at low fire, it is possible under unusual conditions for the flame to
travel back through the pipe to the tee. Devices installed in this section may be
damaged and may melt, releasing gas to the atmosphere and causing fires or
explosions.
See Figure 4 for typical connection of combustion air and circulating fan limit switches.
and 86C, and all applicable local codes and/or standards.
*Available from:
National Fire ProtectionAssociation
Batterymarch Park
Quincy, MA 02269
Tee
Gas Inlet
Manifold
4
American National Standard Institute
1430 Broadway
New York, New York 10018
Figure 4–Pressure Switch Location
P
Hi
Tube Points
Upstream
Circulating Air
Pressure Switch
Tube at
Blower Inlet
Blower
Pressure Switch
P
Burner Air Tap
Lo Hi
See Figure 7
Lo
Tube Points
Downstream