Carlin 702GAS Inst Manual - Manual (Page 4)

Model 702GAS Advanced gas burners — Instruction manual
Carlin part number MN702G Rev. 03/14/11 – 4 –
Where appliance instructions differ from this manual, follow the appliance instructions.
702GAS overview
The Model 702GAS gas burner is a low-high-low (step modulating) burner
that utilizes a damper motor and butterfly valve to control air (and gas fuel
rate).
The burner operates on either natural gas or propane.
See the next page for gas train component locations.
Operation
Ignition for main flame is accomplished by a proved gas pilot of approxi-
mately 280,000 Btuh. Pilot gas is introduced at the main burner flame re-
tention ring, and is ignited by a Carlin 14,000-volt electronic ignitor wired
to the two electrodes.
After the pilot flame is proven, the two main gas safety valves open. The
pilot gas valve closes after a time delay to allow main flame to establish.
Flame is monitored both for pilot flame and main flame with a UV scanner
mounted to the under side of the burner combustion head assembly.
The burner main flame begins at low fire. If additional input is required,
the damper motor opens the gas butterfly valve and air damper to their
high fire positions.
Gas is introduced into the burner through a manifold around the air tube. The
gas then circulates through a set of four orifice spuds into the air stream,
ahead of the retention ring. The spin of the air flow at the retention ring
thoroughly mixes the gas/air before it reaches the combustion zone.
Firing rate adjustment
• See the “Starting and operating” section of this manual for the complete
description of the adjustment process. The following is a brief summary
only.
• High-fire air is set by adjusting the combustion head position (to control air
flow through and around the retention ring).
• Low-fire air is then adjusted by fine-tuning the position of the low fire
adjusting screw.
• Pilot gas flow is set for a smooth light-off. Then gas inputs are adjusted for
good combustion at low and high-fire air settings.
Gas pressure requirements
The 702GAS burner requires 3.4” w.c. minimum pressure at the butterfly
valve during high fire. Select a gas train that has a pressure drop no more
than the available pressure at the gas train inlet minus the 3.4” needed
at the butterfly valve.
See page 13 for gas train pressure drop information. The burner is equipped
with a 1” gas train unless a larger gas train is ordered.
Example:
A boiler has an input rating of 1,300,000 Btuh. Gas pressure available at
the gas train entrance is 6.0” w.c. Subtract 3.4” from the available 6.0”
w.c. The gas train pressure drop must be 2.6” or less. A 1” gas train has
a pressure drop of 3.3” w.c., and cannot be used. Select a 1¼” RV-61
regulator gas train, which has a pressure drop of 0.87” w.c.
1. The Carlin Model 702GAS gas burner
LEGEND for page 5
1 Cast aluminum burner housing
2 Air tube (with gas manifold)
3 Burner flange
4 Burner motor
5 Primary control, Honeywell RM7897C
6 Carlin EZ-Contactor (burner motor contactor)
7 Ignitor (Carlin 41000)
8 Damper motor
9 Air damper & low fire adjusting screw
10 Air damper linkage
11 Air flow switch
12 Junction box (connection for 120
vac
power and 120
vac
control and
limit circuit input from boiler)
13 ON/OFF switch
14 Low fire hold switch (LFS)
28 Pilot orifice nipple
29 Gas manifold
30 Gas spuds (4 required)
31 Gas butterfly valve
32 Butterfly valve linkage
33 Union
34 Gas shut-off valve (with 2 test tappings)
35 Automatic gas valve (diaphragm type)
36 Automatic gas valve
37 Gas train junction box
38 Gas pressure regulator
39 Manual gas valve (with two test tappings)
40 Gas entrance connection
41 Pressure tap & bleed port
42 Pilot gas line manual valve
(with 2 test tappings)
43 Combination pilot gas valve
60 Head position indicator scale
61 Head position adjustment screw
62 Support rod
63 Electrode lead wires
64 Thermal fuse
65 Electrode ceramic insulators
66 Electrodes
67 Electrode clamp
70 Retention ring assembly
71 UV scanner tube/adapter
72 UV scanner