16
CHAPTER 4
CHAPTER 4 - BOILER PIPING
4.8. Expansion Tank and Makeup Water
Ensure the expansion tank is properly sized for the boiler
volume, (3 gallons [12 L] for the PRESTIGE Solo 80/110,
5 gallons [19 L] for the PRESTIGE Solo 155/175/250, 7
gallons [26 L] for PRESTIGE Solo 299/399), the system
water volume, and the system water temperature.
Undersized expansion tanks will cause system
water to be lost through the pressure relief
valve and cause additional makeup water to be
added to the system. Eventual boiler heat ex-
changer failure can result due to this excessive
makeup water addition.
The expansion tank must be located as shown in Fig.
7 on page 15 and Fig. 8 below, when using a prima-
ry/secondary piping arrangement or as per recognized
design methods. Refer to the expansion tank manufac-
turer for additional installation details.
Connect the expansion tank to an air separator only if
the air separator is located on the suction side (inlet)
of the system circulator. Always locate and install the
system ll connection at the same location as the ex-
pansion tank connection to the system.
CAUTION
4.8.1 Diaphragm Expansion Tank
Always install an automatic air vent on top of the air
separator to remove residual air from the system.
4.8.2 Closed-Type Expansion Tank
It is recommended to pitch any horizontal piping up-
wards toward the expansion tank 1 inch per 5 feet of
piping. Use 3/4” piping to the expansion tank to allow
air within the system to rise.
DO NOT install automatic air vents on a closed-
type expansion tank system. Air must remain
in the system and be returned to the expansion
tank to provide an air cushion. An automatic
air vent would cause air to be vented from the
system resulting in a water-logged expansion
tank.
NOTICE
Boiler
Supply
Boiler
Return
System
Supply
Cold
Water
Fill
System
Return
12"
Max.
Minimum
¾” Piping
Fig. 8 - Near Boiler Piping - Closed Type Expansion Tank
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