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Part number 550-110-260/0200
39
Boiler Manual
circulation of air-saturated tank water back to
the system and prevents the air from bubbling
up through the water as it returns from the
system.
•
Do not use automatic air vents in systems
with closed-type tanks.
The air will escape
from the system instead of returning to the
tank. Eventually, the tank will waterlog and no
longer control pressurization. The boiler relief
valve will weep frequently.
Diaphragm- or bladder-type — welded gas tight
with a rubber membrane to separate the tank
pressurizing air and the water. May be located at
any point in the system, but most often found near
the boiler.
• Systems with this type of expansion tank
require at least one automatic air vent,
preferably located on top of an air eliminator,
as shown in examples in manual section 3.
2. If relief valve has tended to weep frequently, the
expansion tank may be waterlogged or undersized.
Closed-type tank — tank is most likely
waterlogged. Install a tank fitting if not already
installed. Then check fill level per fitting
manufacturer’s instructions. If fill level is correct,
check tank size against manufacturer’s instructions.
Replace with a larger tank if necessary.
Diaphragm- or bladder-type — first, check tank
size to be sure it is large enough for the system. If
size is too small, add additional tank(s) as necessary
to provide sufficient expansion. If tank size is large
enough, remove tank from system and check charge
pressure (usually 12 psig for residential
applications). If tank won’t hold pressure,
membrane has been damaged. Replace tank.
Boiler relief valve
1. Inspect the relief valve and lift the lever to verify
flow as in the following warnings, excerpted from
a relief valve manufacturer’s warning label. Before
operating any relief valve, ensure that it is piped
with its discharge in a safe area to avoid severe scald
potential. Read manual section 3a before
proceeding further.
Safety relief valves should be
reinspected AT LEAST ONCE
EVERY THREE YEARS
, by a licensed plumbing
contractor or authorized inspection agency, to ensure
that the product has not been affected by corrosive
water conditions and to ensure that the valve and
❏ Check/test . . . . . . .
discharge line have not been altered or tampered with
illegally. Certain naturally occurring conditions may
corrode the valve or its components over time,
rendering the valve inoperative. Such conditions are
not detectable unless the valve and its components are
physically removed and inspected. This inspection must
only be conducted by a plumbing contractor or
authorized inspection agency — not by the owner.
Failure to reinspect the boiler relief valve as directed
could result in unsafe pressure buildup, which can
result in severe personal injury, death or substantial
property damage.
Following installation, the valve
lever must be operated AT LEAST
ONCE A YEAR to ensure that waterways are clear.
Certain naturally occurring mineral deposits may
adhere to the valve, rendering it inoperative. When
manually operating the lever, water will discharge and
precautions must be taken to avoid contact with hot
water and to avoid water damage. Before operating
lever, check to see that a discharge line is connected to
this valve directing the flow of hot water from the valve
to a proper place of disposal otherwise severe personal
injury may result. If no water flows, valve is inoperative.
Shut down boiler until a new relief valve has been
installed.
2. After following the above warning directions, if the
relief valve weeps or will not seat properly, replace
the relief valve. Ensure that the reason for relief valve
weeping is the valve and not over-pressurization
of the system due to expansion tank waterlogging
or undersizing.
Figure 23 Relief valve, typical
26032