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water boiler
Connect water piping
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 0 °F above set point of the boiler aquastat. Maxi-
mum allowable set point is 0 °F. Wire control as
shown on wiring diagram (page 0).
Low water cutoff devices
• Use a low water cutoff device when:
• Boiler is installed above radiation level.
• Required by certain state or local codes or insurance
companies.
• Use a low water cutoff designed for water installa-
tions.
• Probe-type is recommended.
• Purchase and install in tee in supply line above
boiler. Wire per wiring diagram, page 0.
Backflow prevention
• Use backflow check valve in cold water supply as
required by local codes.
Install piping:
Pipe sizing
• See Table for pipe sizing for near-boiler piping and
single-zone piping.
Near-boiler piping
(with diaphragm expansion tank)
• See Figure 6, page 14.
Near-boiler piping
(with closed expansion tank)
• See Figure 7, page 14.
Multiple-zone piping
• See page 1.
Low-temperature system piping
• See page 16.
Chiller system piping
• See page 17.
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 manu-
facturer's instructions.
Part number 550-141-986/1005
— Boiler Manual
Table 3
Water piping sizing
Piping to
Model
system
(inches)
UO-3
1¼
UO-4
1¼
UO-5
1½
Note: sizing based on 20°F temperature rise through boiler.
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 7 °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.
Piping from
system
(inches)
1¼
1¼
1½
1
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