Xylem MM 802F Model TC-4 Test-N-Check Valves For Hot Water Boilers - Manual (Page 2)

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Simplify Testing of Low Water Cut-offs on Hot Water Boilers
TEST-N-CHECK ® VALVES
IMPORTANT:
• When using tape sealant or thread joint compound on pipe or fittings with external threads follow
manufacturer’s instructions. Do not use tape sealant or thread joint compound on first thread.
To prevent serious personal injury from steam pipe blow down, connect a
drain pipe to the control opening to avoid exposure to steam discharge.
If vacuum breaker stem is accidentally depressed, hot water could be dis-
charged causing burns.
Failure to follow this caution could cause personal injury.
! CAUTION
TEST-N-CHECK VALVES
SIMPLIFY TESTING OF LOW WATER CUT-OFFS
ON HOT WATER BOILERS
Good operating practice requires installation of a low
water cut-off on a hot water boiler and that it be
checked regularly to make certain the control will
function properly in the event of a low water condition.
Boiler owners and installers need a quick and efficient
way to test a low water cut-off on a hot water boiler.
Simply opening a blow-off valve below the float
chamber may not serve as a valid test and is excessively
wasteful of boiler water and fuel. The water
level in the float chamber, and the float, must drop far
enough to start the control through its cycle of operation.
However, water flowing in through the equalizing
piping may replenish the level in the float chamber fast
enough to delay the necessary float drop, or prevent it
altogether.
McDONNELL & MILLER Test-N-Check Valves have
been specially designed for such installations. In normal
operation, they allow free circulation of water through
the equalizing piping and float chamber. But any sudden
onrush of water, such as caused by opening the blowoff,
snaps shut a damper in each valve to restrict flow
to the float chamber. Water level in the float chamber
falls quickly to start the control through its operating
cycle, with a minimum loss of boiler water. When
blow-off is closed, dampers return to normally open
position.
McDONNELL & MILLER Test-N-Check Valves simply
replace the crosses above and below the control in the
equalizing lines. Valves have the same dimensions as
standard crosses and nipple in the horizontal leg, and
allow normal rod clean-out of pipe in both directions.
Connections are 1" NPT female tappings.
Upper and lower valves are identical, except that the
upper valve has vacuum breaker built in to allow for
rapid evacuation of the float chamber. They are furnished
in sets-one upper and one lower valve, to
equip one equalizing line. They can be used with all
McDONNELL & MILLER Low Water Cut-Offs for hot
water boilers.
LWCO
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