PLUS LINE
C 
Gas) continued
ON STEAM BOILER APPLICATIONS ONLY — You must replace the automatic air vent supplied with the water heater with a manual air vent. Failure to do so could result in severe personal injury, death or substantial property damage.
Connecting water heater to steam boiler
When designing steam and domestic hot water sys- tems, there are some key issues that must be taken into consideration during the initial design phase. By designing the system properly from the start, you can avoid problems and have a hot water loop in a steam boiler system.
Special considerations:
•Keep the loop temperature below the flash point. Flashing can result in noise and circulator damage or shortened life.
•Be sure the loop is completely closed, with no au- tomatic air vents or anything that could allow air to enter the system when the pump shuts off. Use manual air vents only to prevent the possibility of flooding the boiler.
•Pipe supply from one side of the boiler, return to the opposite side.
•Supply from a tapping that is high enough to prevent introducing sediment into the piping and circulator yet still positions the circulator below the water line. Avoid the mud leg of the boiler.
•Use an all bronze circulator (avoid wet rotor circula- tors). This will reduce clogging and will resist the corrosion potential from the steam condensate.
•Make sure the circulator is properly sized. If the pump runs too far out on the curve, cavitation potential increases significantly.
•Return piping should be dedicated domestic re- turn.
•Use (2) flow/check valves as shown to reduce the potential for gravity circulation. Do not use spring- loaded check valves in place of the flow/check valves shown in Figure 29 on page 45.
Installation and
See Figure 29, page 45, for suggested piping schematic. Pipe the domestic water connections to the water heater per Section A of this manual.
•Boiler connections for the water heater must be below the water line.
•For steam piping, refer to the boiler manual.
•Replace the automatic air vent furnished with the water heater with a manual air vent.
•Wire the water heater and circulator to the boiler per suggested wiring in Figure 29.
To fill the boiler and water heater:
•Close isolation valves 5 and 6 (Figure 29) to isolate the boiler.
•Fill the boiler to the recommended water level per the boiler manual. Fill the domestic side of the water heater per Section A of this manual.
•To fill the water heater outer tank with boiler water, isolation valves 5 and 6 must remain closed. Valves 1 and 2 should be fully opened. Drain valves 3 and 4 should also be fully opened.
•Open the water heater manual air vent to bleed the system of air.
Open the water heater manual air vent one turn only.
•Fill the boiler/water heater system through drain valve 3 until a steady stream of water flows through drain valve 4, initially purging the system of air.
•Continue to fill the boiler/water heater system while closing drain valve 4.
•When drain valve 4 is fully closed and a steady stream of water is exiting at the air vent, close the manual air vent tightly. Drain valve 3 can now be closed.
Water may spray from the manual air vent.
•Open isolation valve 5 (at the front of the boiler). Then open valve 6.
•Start the boiler per instructions given in the boiler manual.
44 | Part Number |
