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Operation and Maintenance
Flushing Coils
McQuay recommends the use of inhibited glycol designed
1
for HVAC applications for corrosion protection. The use of
uninhibited glycol has produced formicary corrosion in
copper tubing. The complete filling of water coils with an
inhibited glycol solution for freeze protection can be
expensive. In some instances, it is more cost effective to
flush the coils with an appropriate concentration of
inhibited glycol solution. Residual fluid can be left in the
coil without the threat of freeze damage provided the
correct concentration of inhibited glycol was used. The
recovered fluid can then be used to flush other coils. Select
an inhibited glycol solution that will protect the coil from
the lowest possible temperatures that can occur at the
particular coil's locality.
Estimate the volume of the coil in gallons. For 5/8" tubes
2
(1.5" face tube spacing) (finned height in inches) x (finned
length in inches) x (# of rows) x 0.0011 = gallons.
Isolate the coil from the rest of the system by closing the
3
valves on both the supply and return lines (gate valves in
Figure 5 and Figure 6).
Drain the coil by opening all drain valves and/or the drain
4
plug. Remove the vent plug to aid the draining process.
Figure 9: Flushing System
8
Close the drain valve(s) and drain plug.
5
Connect the flushing system to the coil. A typical system is
6
shown in Figure 9.
With the throttling valve closed, start the pump and operate
7
until the air is vented from the coil. After venting, close the
air vent.
Open the throttling valve about halfway and circulate the
8
fluid through the coil for 15 minutes. Check the strength of
the fluid. A hydrometer or test kit from the fluid
manufacturer is suitable for this application.
Adjust the solution strength as needed and circulate the
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fluid for another 15 minutes.
Repeat steps 8 and 9 until the desired concentration is
10
reached.
Shut the pump down and drain the inhibited glycol from the
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coil.
The recaptured fluid can be used to flush other coils.
12
Note: Follow the manufactures' recommendations before
utilizing any glycol based antifreeze solution.
Additional fluid will be required for the pump,
connected piping, and fluid reservoir. Formulae are
for estimation purposes only.
McQuay IM 900
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