Boiler Piping Connections; Recommended Piping - Weil-McLain PFG 7 Series Installation & Operation Manual

PFG S 7 G
erieS aS
Boiler piping connections to the heating
system
(refer to piping diagrams, Page 7)
Failure to properly pipe the boiler may result in
improper operation and damage to the boiler or
building.
These boilers are provided with built-in air elimination sys-
tems.
1. Install relief valve vertically in top ¾" tapping in right end section.
See WARNING following.
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 possible 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 thread-
ed, with a material serviceable for temperatures of
375 °F or greater.
• Do not pipe the discharge to any place where freez-
ing could occur.
• No shutoff valve shall be installed between 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 guidelines could
result in failure of the relief valve to operate, result-
ing in possibility of severe personal injury, death or
substantial property damage.
• Test the operation of the valve after filling and pres-
surizing 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.
. Install pressure-temperature gauge in tapping provided in left end
section.
3. This boiler is for forced hot water circulation only. The circulator and
expansion tank must be selected and sized according to the design
requirements of the system.
a) Size and install circulator. Can be installed on supply or return
piping
b) Size expansion tank to handle the volume of water in the sys-
tem.
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4. Expansion tank installations.
a) Closed type expansion tanks - connect from the ¾" N.P.T.
expansion tank tapping on the left end section (located just
behind the supply outlet tapping) to the expansion tank using
¾" N.P.T. piping. Any horizontal expansion tank piping must
pitch upward toward the tank at least 1 inch for each 5 feet of
piping.
b) Diaphragm type expansion tank - may be located anywhere in
the system, preferably near the boiler.
A manual or automatic type air vent must be
installed in the ¾" N.P.T. tapping when a diaphragm
type tank is used.
The most common cause of lime deposits in boilers is inadequate
expansion tank volume. If the expansion tank is too small, system
water is lost from the relief valve and make-up water is added
through the fill valve. Eventual section failure will result.
5. Connect the system supply piping to the supply outlet tapping on
the left end of the boiler. See Figure a for minimum pipe size.
6. Connect the system return piping to the return tapping on the right
end of the boiler. See Figure a for minimum pipe size.
7. Install drain valve provided with boiler on left side. The installer
must provide a drain cock to drain the right (return) side of the
boiler and its connecting piping. The drain cock on the left side of
the boiler will not fully drain the right side.
8. Low water cut off:
a) Must be installed on any PFG boiler if the boiler is located above
radiation level.
b) Must be installed on all PFG-8 boilers to meet ASME specifica-
tions (low water cut-off not supplied by Weil-McLain).
c) May be required by certain state, local or territorial codes or
insurance companies.
If a low water cut-off is required, use a control designed especially
for water installations. An electrode probe type low water cut-off
may be located in a tee in the supply line above the boiler.
9. If the system is to be ASME inspected and approved, an additional
high temperature limit is needed. Purchase and install the control
in the supply outlet piping to the boiler.
Figure 2a Minimum recommended pipe sizes
(Supply and return sizes refer to minimum size of
pipe connected to the boiler for 20°F temperature
drop between supply and return.)
Part Number 550-110-641/0605