Install Instructions

AQUA PLUS indirect-fired water heaters — Product Manual
Connecting to a low-pressure steam boiler
Special considerations
When designing steam and domestic hot water systems, there are some
key issues that must be taken into consideration during the initial de-
sign phase. By designing the system properly from the start, you can
avoid problems and have a hot water loop in a steam boiler system.
• The domestic water demand should preferably not exceed 1/3
of the steam boiler capacity. Larger demand may cause difficulty
obtaining steam as needed.
• 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 automatic or manual
air vents, or anything that could allow air to enter the system when
the pump shuts off.
• Pipe supply from one side of the boiler, return to the opposite
side as shown.
• Supply from a tapping that is high enough to prevent introducing
sediment into the piping and circulator yet still below the water
line. Avoid the mud leg of the boiler.
• Use an all bronze circulator.
• Avoid wet rotor circulators. Select a circulator with a large
volute, such as a typical 3-piece circulator.
• This will reduce clogging and will resist the corrosion potential
from the steam condensate.
• Make sure the circulator is properly sized. If the circulator runs too
far out on its curve, cavitation potential increases significantly.
• 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 16, page 19.
Installation and start-up of water heaters
connected to steam boilers
1. See Figure 16, page 19, for suggested piping schematic.
2. Pipe the domestic water connections to the water heater per “Do-
mestic water piping,” page 6.
Boiler connections for the water heater must be below
the water line. DO NOT use the gauge glass tapping or a
low water cut-off tapping if a LWCO is installed there.
For steam piping, refer to the steam boiler manual.
DO NOT install an air vent anywhere in the piping. The
piping must be air tight.
3. Wire the water heater and circulator to the boiler per suggested
wiring in Figure 15. The water heater must be wired and ready to
operate before proceeding. Note that the L4006A aquastat is located
in the boiler and sets a boiler operating temperature when there is
no call for steam heating.
To fill the boiler and water heater:
1. Follow the procedure given in Figure 16, page 19 to fill the water
heater piping.
2. Follow the boiler manual instructions to fill the steam boiler.
Figure 15 Typical wiring for connection to low-
pressure steam boiler
Install the Honeywell L4006A aquastat in the boiler, be-
low the water line. Set for a temperature of 180 to 190°F
to control boiler temperature when there is no call for
steam heating.
Valve 7, the memory stop valve, must
be supplied, piped and adjusted as in-
structed. This valve allows cooler return
water to mix with the hot water from
the steam boiler. The valve is set to yield
approximately 180°F water entering the
circulator. Higher temperature water
could cause cavitation in the circulator,
damaging the impeller and shortening
circulator life.
DO NOT connect the piping to the boil-
er’s mud leg. This would probably cause
excessive sediment to enter the water
heater piping, damaging the circulator.
The strainer in the circulator suction line
must be serviced regularly. NOTE that
noise from the circulator is a likely sign
that the strainer is restricting circulator
flow, causing cavitation.
Part number GL-E223-ADOC 0311
18