Weil McLain SERIES 2 LGB 20 User Manual
Gas–fired boiler  
LGB  
Control Supplement  
Series 2 – Propane gas  
Universal Control System  
U.S. and Canada  
Contents  
I. New installation ........... 2  
II. Existing installation ..... 4  
III. Gas piping ..................... 5  
IV. Wiring............................ 5  
Sequence of operation ..... 8  
Wiring procedure .............. 8  
V. Operating instructions . 9  
VI. Parts list – U.S. ........... 10  
VII.Parts list – Canadian ... 11  
Indicates presence of hazards that can cause severe personal injury,death or  
substantial property damage.  
These terms are used throughout this  
manual to bring attention to the  
presence of hazards of various risk  
levels or to important information  
concerning the life of the product.  
Indicates special instructions on installation, operation or maintenance that  
are important but not related to personal injury or property damage.  
This Control Supplement must only be used by a qualified installer/service  
technician. Read these instructions completely before beginning the  
installation. Failure to follow these instructions can cause severe personal  
injury, death or substantial property damage.  
Part Number 550-141-797/0798  
 
UniversalControlSystem–Propanegas  
I
New installation  
– continued  
10-32 x 5/16“  
Machine Screws(2)  
Igniter  
UCS Pilot  
Burner  
Figure 1  
Sensor  
Pilot burner assembly, typical  
Locating Slot  
Ground Leadwire:  
Connect to Pilot  
Proving Module  
24 V (GND) terminal  
Pilot Mounting  
Bracket  
Burner Support Bar  
Pilot Line Tubing  
Sensor Lead  
10-32 x 1/4“  
Machine Screws (2)  
Main Burner  
(with Pilot  
Mounting  
Bracket)  
Compression  
Union  
Igniter Lead  
LGB-A84-B  
6-32 x 5/16“ Type ”F”  
Self Tapping Screws(2)  
Figure 2  
Flame  
Sensor  
Main flame sensor assembly  
Locating Slot  
10-32 x 5/16“  
Machine Screws(2)  
Ground Leadwire:  
Connect to Main Flame  
Proving Module  
24 V (GND) terminal  
Burner Support Bar  
Flame Sensor  
Mounting Bracket  
Sensor Lead  
Main Burner  
(with Pilot  
Mounting  
Bracket)  
LGB-A85  
Part Number 550-141-797/0798  
3
LGB-6 to LGB-23 Series 2 – Control Supplement  
II  
Existing installation Conversion from natural gas to propane gas  
This conversion is to be installed by a Weil-McLain distributor or other  
qualified agency in accordance with the manufacturer’s instructions and all  
codes and requirements of the authority having jurisdiction. Failure to  
follow instructions could result in serious injury or property damage. The  
qualified agency performing this work assumes responsibility for this  
conversion.  
For your safety, turn off electrical power supply before making any electrical  
connections to avoid possible electrical shock hazard.  
1. These instructions are for use with Propane Control Cartons as listed in Gas Control  
Arrangement, Table 2 (page 2).  
2. Remove jacket door(s) and access panel(s).  
3. Disconnect wiring and tubing from existing pilot burner and main flame sensor.  
4. Remove all burners. Remove 3.95 mm natural gas main burner orifices in manifold. Install  
2.40 mm propane gas main burner orifices. Use pipe dope sparingly only on male ends.  
Use pipe dope compatible with propane gases. Do not overtighten orifices.  
5. Remove and discard existing electronic pilot burner from pilot burner tube. Replace with  
electronic pilot burner in carton.  
6. Attach Q327 standing pilot to burner tube in kit. Connect pilot tubing and thermocouple  
to pilot.  
7. Re-install burners. See Table 1 (page 2) for location of pilot burners and flame sensor(s).  
8. Attach pilot switch box to jacket. See Figure 5 (page 10) or Figure 6 (page 11). Connect  
thermocouple to pilot switch box. Cut 60” pilot tubing into 2 pieces to make connections  
from tee in pilot line to pilot switch box and from pilot switch box to standing pilot.  
9. Remove natural gas valve train.  
10. Install propane gas valve train and fittings from carton (See page 5, section III, paragraph  
4 of this Supplement).  
11. Re-install access panel(s).  
12. See Figure 5 (page 10) or Figure 6 (page 11), for propane piping.  
13. Wire per wiring diagram, Figure 3 (pages 6 and 7). Add splices as needed.  
14. Attach:  
a. 550-223-710 label at boiler operating instruction label. Place so that this label reads  
first.  
b. 550-223-796 label at rating label.  
c. Wiring diagram over diagram on door (one on each base).  
15. To place in operation, follow instructions on constant burner pilot light-up label and  
boiler operating label.  
16. Replace jacket doors.  
4
Part Number 550-141-797/0798  
 
UniversalControlSystem–Propanegas  
III  
Gas piping  
1. Contact gas supplier to size pipes, tanks and regulator.  
a. Inlet gas pressure to manual main shut-off gas valve —  
minimum 11”W.C., maximum 13”W.C.  
b. If pressure to gas valve exceeds 13”W.C., install 100% lock-up gas pressure regulator  
upstream of hand valve.  
2. Remove gas supply knockout disc from jacket panel.  
3. Follow good piping practices.  
4. Pipe joint compound (pipe dope) must be resistant to corrosive action of liquefied  
petroleum gases. Apply sparingly only to male threads of pipe joints.  
5. Install drip leg at inlet of gas connection to boiler. Where local utility requires, extend drip  
leg to floor.  
6. Install ground joint union when required for servicing.  
7. Support piping by hangers, not by boiler or its accessories.  
8. Purge all air from supply piping.  
9. Before operating boiler, check boiler and its gas connections for leaks.  
Do not check for gas leaks with an open flame – BUBBLE TEST. Failure to  
use bubble test or test for leaks can cause severe personal injury, death or  
substantial property damage.  
a. Close manual main shut-off valve during any pressure testing at less than 13”W.C.  
b. Disconnect boiler and gas valve from gas supply piping during any pressure test  
greater than 13”W.C.  
10. Set gas pressure switch as follows or to local inspector’s requirements (LGB-21 through  
LGB-23 only):  
a. High – 14”W.C.  
11. Canada only - manual main shut-off valve must be identifed by installer.  
Wiring  
IV  
For your safety, turn off electrical power supply before making any  
electrical connections to avoid possible electrical shock hazard.  
1. All wiring must be installed in accordance with the requirements of the National Electrical  
Code and any additional national, state or local code requirements having jurisdiction. All  
wiring must be N.E.C. Class 1.  
2. The boiler must be electrically grounded in accordance with the National Electrical Code,  
ANSI/NFPA No. 70-latest edition. Use 105 °C. thermoplastic wire, or equivalent, if any of  
the original wire must be replaced (except for pilot spark, sense and ground wires).  
3. Canadian installations must conform to CSA C22.1 Canadian Electrical Code Part 1 and  
any local or provincial codes.  
4. Supply wiring to the boiler must be No. 14 gauge or heavier. Install in conduit.  
5. A separate electrical circuit with a fused disconnect switch (15 amp. recommended) should  
be used for the boiler.  
Part Number 550-141-797/0798  
5
 
LGB-6 to LGB-23 Series 2 – Control Supplement  
UniversalControlSystem–Propanegas  
Figure 3  
Wiring diagram  
6
Part Number 550-141-797/0798  
Part Number 550-141-797/0798  
7
LGB-6 to LGB-23 Series 2 – Control Supplement  
IV  
Wiring  
– continued  
Sequence of operation  
1. Operating control begins start-up sequence.  
a. Limit control contacts are closed.  
2. Pilot-proving module energized.  
On failure to sense pilot flame or main flame, control will wait 5 minutes  
then retry for ignition.  
a. Pilot solenoid opens.  
b. Pilot ignition spark begins.  
c. Pilot ignites.  
d. Pilot proves.  
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.  
f. Main burners increase to high fire.  
4. Dual base assembly (LGB-13 through LGB-23) - operating control energizes the controls  
for both base assemblies at the same time. See steps 1 through 3 above.  
5. Boiler shuts down when the operating control is satisfied.  
Wiring Procedure  
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 juction boxes together, then hang junction  
boxes by screwing top box to boiler jacket. See  
Figure 4.  
Figure 4  
Junction box assembly  
dual base boilers  
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 wiring diagram, Figure 3,  
pages 6 and 7. Terminate at secondary gas valve in  
valve junction box with wirenuts and strain relief  
provided.  
“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.  
6. Install pilot proving and main flame proving  
ground connections as shown in Figures 1, 2 and  
3. Route wires through wire support clip.  
7. Canada only - attach chain between junction  
box(es) and transformer with S-hooks.  
8
Part Number 550-141-797/0798  
 
UniversalControlSystem–Propanegas  
V
Operating instructions  
A. This boiler is equipped with a pilot which must be lighted by hand. When lighting the  
pilot, follow these instructions exactly. The gas supply to this pilot is controlled by Pilot  
switch box. This boiler is also equipped with an ignition device which automatically lights a  
second pilot. The gas supply to this pilot is controlled by the Gas control. Do not try to  
light this pilot by hand.  
B. BEFORE OPERATING THE MANUAL PILOT, smell all around the appliance area for gas.  
Be sure to smell next to the floor because some gas is heavier than air and will settle on the  
floor.  
WHAT TO DO IFYOU SMELL GAS  
•
•
•
Do not try to light any appliance.  
Do not touch any electric switch; do not use any phone in your building.  
Immediately call your gas supplier from a neighbor’s phone. Follow the gas  
supplier’s instructions.  
•
If you cannot reach your gas supplier, call the fire department.  
C. Do not use this appliance if any part has been under water. Immediately call a qualified  
service technician to inspect the appliance and to replace any part of the control system  
and any gas control, which has been under water.  
This document is intended only as a supplement to the LGB Gas-Fired Boiler Manual. Follow  
all instructions in the Manual, including those regarding start-up (found in Section VIII,  
“Placing boiler in operation”).  
Starting  
boiler  
1. STOP! Read the safety information above.  
2. Set the Operating control to lowest setting.  
3. Turn off all electrical power to the appliance.  
4. Remove the Base access shield.  
5. Close Pilot shut-off valve connected to Manual main shut-off valve. Close  
Manual main shut-off valve.  
6. Wait five (5) minutes to clear out any gas. Then smell for gas, including  
near the floor. If you smell gas,STOP! Follow“B”in the safety information  
above. If you don’t smell gas, go to the next step.  
7. Open Pilot shut-off valve.  
8. Press and hold the reset lever on the Pilot switch box. Manually light the  
pilot while holding the lever down. Air in the gas supply line will have to  
purge through the line before sufficient gas will reach the pilot.  
9. After purging all air, hold thePilot switch box lever for about 1 minute to  
heat the thermocouple.  
10. Release the Pilot switch box lever. The pilot should remain lit.  
11. Open the Manual main shut-off valve and follow the sequence below.  
12. This appliance is also equipped with an ignition device which automatically  
lights the second pilot. Do not try to light this pilot by hand.  
13. Turn on all electric power to the appliance.  
14. Set Operating control to desired setting.  
15. If the appliance will not operate, turn off gas to the appliance by closing  
the Manual main shut-off valve and Pilot shut-off valve. Call your service  
technician or gas supplier.  
16. Replace Base access shield and Front panel.  
Part Number 550-141-797/0798  
9
 
LGB-6 to LGB-23 Series 2 – Control Supplement  
VI  
Parts list - U.S. boilers  
Figure 5  
U.S. parts  
drawing  
Ref. No. Description  
Size  
Vendor/Part Number  
Weil-McLain Part Number  
1
2
Main flame sensor  
Main burner with pilot bracket  
Main flame sensor bracket  
Honeywell 392956  
Weil-McLain  
Weil-McLain  
Kinco-Balon 500  
Kinco-Balon 600  
Honeywell V8943A1003  
Honeywell V8943A1111  
Honeywell V8944L1033  
Honeywell V8944L1041  
Weil-McLain  
511-724-274  
512-200-055  
423-300-420  
511-246-325  
511-246-330  
511-044-191  
511-044-192  
511-044-346  
511-044-218  
383-300-410  
383-300-411  
512-200-055  
460-005-624  
1"  
1 ¼"  
1"  
1 ¼"  
1"  
3
4
5
Manual main shut-off valve  
Secondary gas valve  
Main gas valve  
1 ¼"  
6
7
Pilot burner, standing-repair kit propane  
Pilot burner, electronic-repair kit propane  
Main burner with pilot bracket  
Pilot burner bracket  
UCS control module  
(2 per control panel)  
Weil-McLain  
Weil-McLain  
Weil-McLain  
8
Honeywell S8620C1003  
United Technologies 1003-511  
Honeywell V8046C1014  
Johnson Controls H91ABG  
Kinco-Balon P2R  
Johnson Controls L62GB-3C  
Honeywell Q309A  
Honeywell C645B1013  
9
511-330-097  
10  
Pilot solenoid  
511-044-039  
11  
12  
13  
14  
15  
16  
17  
Pilot shut-off valve  
Pilot switch box  
Thermocouple  
High gas pressure switch  
Pilot tubing, alum. ¼ O.D. x .032-20" long  
Pilot tubing, alum. ¼ O.D. x .032-60" long  
Pressure switch tubing, alum. ¼ O.D. x .032-100" long  
511-246-340  
511-330-229  
511-724-245  
511-624-555  
48"  
Available at Local Supply House  
*Contact local Weil-McLain distributor/agent for current replacement part and order number.  
10  
Part Number 550-141-797/0798  
 
UniversalControlSystem–Propanegas  
VII  
Parts list - Canadian boilers  
Figure 6  
Canadian  
parts  
drawing  
Ref. No. Description  
Size  
Vendor/Part Number*  
1
Main flame sensor  
Main burner with pilot bracket  
Main flame sensor bracket  
Honeywell 392956  
2
Weil-McLain  
1"  
1 ¼"  
1"  
1 ¼"  
1"  
Kinco-Balon 500  
Kinco-Balon 600  
Honeywell V8943A1003  
Honeywell V8943A1111  
Honeywell V8944N1053  
Honeywell V8944N1061  
3
4
Manual main shut-off valve  
Secondary gas valve  
Main gas valve  
5
1 ¼"  
Pilot burner, standing  
Pilot orifice, LP, standing  
Pilot burner, electronic  
Pilot orifice, LP, electronic  
Main burner with pilot bracket  
Pilot burner bracket  
Honeywell Q327A1642  
Honeywell K14  
Johnson Controls Q90GE-1 or Beckett Gas E48A1  
Johnson Controls Y90AA4712 or Beckett Gas 31400  
6
7
8
Weil-McLain  
UCS control module  
Honeywell S8620C1003  
United Technologies 1003-511  
Honeywell V8046C1014  
Johnson Controls H91ABG  
Conbraco 53-103-01  
Johnson Controls L62GB-3C  
Honeywell Q309A2010  
Honeywell C645B1013  
9
(2 per control panel)  
10  
Pilot solenoid  
11  
12  
13  
14  
15  
16  
17  
Pilot shut-off valve  
Pilot switch box  
Thermocouple  
High gas pressure switch  
Pilot tubing, alum. ¼ O.D. x .032-20" long  
Pilot tubing, alum. ¼ O.D. x .032-60" long  
Available at Local Supply House  
Pressure switch tubing, alum. ¼ O.D. x .032-100" long  
1"  
1 ¼"  
1 ½"  
Watts FBV3-06  
Watts FBV3-07  
Watts FBV3-08  
18  
Firing valve  
*Contact local Weil-McLain distributor/agent for current replacement part and order number.  
Part Number 550-141-797/0798  
11  
 
LGB-6 to LGB-23 Series 2 – Control Supplement  
Weil-McLain  
500 Blaine Street  
Michigan City, IN 46360-2388  
http://www.weil-mclain.com  
12  
Part Number 550-141-797/0798  

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