Advanced Manual For Multiple Boiler Systems; Expansion Tank Location; Diaphragm- Or Bladder-Type Tank - Weil-McLain Evergreen EVG 70 Manual

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Primary/Secondary System Piping -
See Advanced Manual for Multiple Boiler Systems

Expansion tank location

Figure 49 and Figure 50 show typical installation of the
system expansion tank. It is highly recommended that you
locate the air separator and expansion tank as shown in the
suggested piping drawings on pages 49 - 51 .
Ensure that the expansion tank size will handle boiler
and system water volume and temperature. See tank
manufacturer's instructions and ratings for details.
Additional tanks may be added to the system if needed
to handle the expansion. These tanks may be installed by
connecting to tees in the system piping.
Undersized expansion tanks cause system
water to be lost from the relief valve and
makeup water to be added through the fi ll
valve. Eventual boiler failure can result due
to excessive make-up water addition. Always
locate the cold-water fi ll connection at the
expansion tank. Never locate this elsewhere.

Diaphragm- or bladder-type tank:

Refer to Figure 49 for suggested piping when using a
diaphragm- or bladder-type expansion tank.
Diaphragm- or bladder-type expansion
tank—Control fi ll pressure with the tank air
charge pressure. Always check pressure and
charge tank with tank removed from system
to be sure reading is accurate. Boiler relief
valve is set for 30 PSIG. Operating pressure
of system, after temperature expansion above
cold fi ll pressure, should not exceed 24 PSIG
to avoid weeping of relief valve.
Install an automatic air vent on top of the air separator, per
separator manufacturer's instructions.
Part number 550-100-191/0917
as-fired water boiler —
70/110/155
Single Boiler System
Figure 49 Piping to diaphragm (or bladder) expansion tank
Boiler Manual
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