®
Series 3
WATER
BOILER
— Boiler Manual
General piping information:
ASME or Canadian requirements
• If installation is to comply with ASME or Canadian
requirements, an additional high temperature limit is
needed. Install control in supply piping between boiler
and isolation valve. Set control to a minimum of 20 °F
above set point of the boiler limit temperature sensor.
Maximum allowable set point is 220 °F. Wire control
as shown on wiring diagram (page 20 & 21).
Low water cutoff devices
• The Hydrostat 3250 control has an integrated LWCO
device. The probe for the control is inserted into the
well located on the top off the boiler. Ensure the probe
is fully inserted into the well.
Backfl ow prevention
• Use
backfl ow check valve in cold water supply as re-
quired by local codes.
Install piping:
Pipe sizing
• See Table 3 for pipe sizing for near-boiler piping and
single-zone piping.
Near-boiler piping
(with diaphragm expansion tank)
•
See Figure 6, page 15.
Near-boiler piping
(with closed expansion tank)
•
See Figure 7, page 15.
Multiple-zone piping
•
See page 16.
Low-temperature system piping
•
See page 17.
Chiller system piping
•
See page 18.
For multiple-boiler piping
• Refer to Weil-McLain’s “Primary/Secondary Piping
Guide.”
Relief valve
• Install relief valve vertically in elbow supplied. See
Figure 6 or 7 for location.
•
See WARNING at right.
• Also refer to tag attached to relief valve for manufac-
turer’s instructions.
Relief valve discharge piping:
To avoid water damage or scalding
due to relief valve operation:
• Discharge line must be connected to
relief valve outlet and run to a safe place
of disposal. Terminate the discharge
line to eliminate possibility of severe
burns should the valve discharge.
• Discharge line must be as short as pos-
sible and be the same size as the valve
discharge connection throughout its
entire length.
• Discharge line must pitch downward
from the valve and terminate at least
6” above the floor drain where any
discharge will be clearly visible.
• The discharge line shall terminate
plain, not threaded, with a material
serviceable for temperatures of 375 °F
or greater.
• Do not pipe the discharge to any place
where freezing could occur.
• No shutoff valve shall be installed be-
tween the relief valve and boiler, or in
the discharge line. Do not plug or place
any obstruction in the discharge line.
• Failure to comply with the above guide-
lines could result in failure of the relief
valve to operate, resulting in possibil-
ity of severe personal injury, death or
substantial property damage.
• Test the operation of the valve after
filling and pressurizing system by
lifting the lever. Make sure the valve
discharges freely. If the valve fails to
operate correctly, replace it with a new
relief valve.
Connect water piping
Table 3
Water piping sizing
Part number 550-142-182/1014
14
Model
Piping to
system
(inches)
Piping to
system
(inches)
UO-3E
1 ¼
1 ¼
UO-4E
1 ¼
1 ¼
UO-5E
1 ½
1 ½
Note: sizing based on 20° F temperature rise through boiler.