Weil-McLain LGB-20 - Manual (Page 8)

LGB-6 to LGB-20
Series 2 – Control Supplement
8 Part Number 550-141-815/1010
IV
Wiring
- continued
1. Determine right or left electrical supply wiring.
2. Attach electrical junction box(es) to inside jacket end
panel. Screws and nuts are provided. For dual base
boilers, use offset nipples (provided) to connect junction
boxes together (as at right), then hang junction boxes
by screwing top box to boiler jacket. See Figure 4.
3. Attach control transformer(s) to junction box(es).
4. Drill 1/8” hole in interior jacket panel midway between
ignition control panel and left jacket panel. Mount wire
support clip using sheet metal screw (furnished).
5. Complete wiring per diagrams, Figure 3 (pages 6 and
7) and Figure 5 (page 9). Terminate at secondary gas
valve in valve junction box with wirenuts and strain
relief provided.
Wiring procedure
1. Operating control begins startup sequence.
a. Limit control contacts are closed.
2. Pilot proving module energized.
a. Pilot solenoid opens.
b. Pilot ignition spark begins.
c. Pilot
ignites.
d. Pilot proves.
Sequence of operation
On failure to sense pilot flame, the pilot-proving module will wait 5
minutes, then retry for ignition. Upon 2 consecutive pilot flame failures,
the control will lockout and illuminate the red lockout light.
On failure to sense main flame, the main flame-proving module will
lockout and illuminate the red lockout light.
If the boiler locks out, the alarm contacts on the terminal strip (terminals
A1 and A2) close. These contacts are rated to 15 amps, 250 V. To reset
the boiler, push the red lockout button.
“Hot” side of line voltage to boiler
must be wired directly to limit
circuit, then fed to transformer
primary(ies).
Dual Base: “R” terminal of
secondaries are to supply power to
bases independently of each other.
Do not wire “R” terminals together.
Figure 4
Junction box assembly
dual base boilers
f. Main burners increase to high fire.
4. For dual base assembly - operating control energizes controls for each base assembly at the
same time. See steps 1 through 3 above.
5. Boiler shuts down when operating control satisfied.
3. Main flame proving module energized from pilot proving module.
a. Secondary gas valve opens.
b. Main gas valve opens to low fire position.
c. Main burners ignite at low fire.
d. Main flame sensor proves low fire carryover.
e. Main gas valve opens to high fire position.
6. Install pilot proving and main flame proving ground
connections as shown in Figures 1 and 2 and wiring
diagram. Route wires through wire support clip.