Expansion Tank Location; Diaphragm- Or Bladder-Type Tank - Weil-McLain ECO 70 Manual

TM -
G
AS FIRED WATER BOILER
Primary/Secondary System Piping
Closed-type expansion tank:
DO NOT use a closed-type tank if connect-
ing to a water heater that is equipped with an
automatic air vent.
Figure 47, page 43 shows suggested piping when
using a closed-t y p e expansion tank, in which
the air is directly in contact w ith tank water.
Connect piping (½" or ¾") from the air separator outlet to
the tank fitting. Slope any horizontal piping a minimum of
1 inch per 5 feet of horizontal pipe.
Always use a tank fitting such as the B&G Tank-trol or Taco
Taco-trol (shown). The fitting reduces gravity flow of water
in the piping to the tank, avoids air bubbling through the
tank water, and provides the proper fill height in the tank
Correct all leaks in the system or tank piping.
Leaks allow air to escape from the system and
will cause water-logging of the tank. This will
result in water loss through the boiler relief
valve due to over-pressurization. NEVER use
an automatic air vent in a system equipped with
a closed-type expansion tank. The air removed
from the system will cause water-logging of the
expansion tank.
Closed-type expansion tank—Follow tank
manufacturer's instructions for filling the tank.
Typical tank sizing provides for approximately
12 PSIG when the tank is filled to the normal
level and system water is cold. Note that boiler
relief valve is set for 30 PSIG. Operation pressure
of system, after temperature expansion above
cold fill pressure, should not exceed 24 PSIG to
avoid weeping of relieve valve.
Part number 550-142-122/0513
— Boiler Manual
Piping to closed-type expansion tank
43