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Blowing-Out Coils
Isolate the coil from the rest of the system by closing the
1
valves on both the supply and return lines (see gate valves
in Figure 5 and Figure 6).
Drain the coil by opening all drain valves and/or the drain
2
plug. Remove the vent plug to aid the draining process.
Once the coil has been fully drained, the blower
3
compressed air can be hooked-up. Caps installed in the
piping on straight runs going to the supply and return
connections are ideal points to hook-up the blower. The air
vent and drain plug are not suitable locations for hooking
up the blower.
The blower operator must take precautions to insure that water
does not come into contact with any of the electrical
components of the blower. Failure to do so will result in damage
to the equipment and serious injury.
Close the vent or drain plug on the header that the blower is
4
connected and open the drain valve or cap on the other
header.
Operate the blower for 45 minutes and then check the coil
5
to see if it is dry. A mirror placed in the discharge will
become fogged if moisture is present. Repeat this
procedure until the coil is dry.
Let the coil stand for several minutes then blow it out
6
again. If water comes out, repeat the blowout operation.
Leave all plugs out and drains open until the threat of
7
freezing has passed.
Figure 6: Horizontal Air Flow
McQuay IM 900
DANGER
Operation and Maintenance
Figure 7: Vertical Air Flow
Air Vent
Side Vent
Plug
Gate
Supply
Valve
Return
Tee
Dirt Leg
Cap
Freeze Protection Fittings
During the winter, chilled water coils need to be protected
against freezing. Factory installed and tested freeze protection
fittings are brazed onto water and steam coil headers, return
bends and tube stubs (as necessary) as part of the factory
assembly process. Freeze relief caps are then screwed onto
each fitting. All coils are leak tested at 315 psi air pressure
before shipping. The relief caps are designed to burst at 650
psig, relieving pressure before coil damage occurs. When
freeze damage occurs, simply unscrew the ruptured relief caps
and screw in replacement caps.
Figure 8: Freeze Protection Fittings
Air Flow
Side Drain Plug
Union
Drain Valve
7
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