Greenheck DGX Installation, Operation And Maintenance Manual page 42

Winterizing Chilled Water Coils
During the winter, chilled water coils need to be protected against freezing. Greenheck recommends protecting
the coils by either blowing-out the coils or by flushing the coils.
Blowing-Out Coils
• Isolate the coil from the rest of the system by
closing the valves on both the supply and return
lines.
• Drain the coil by opening all drain valves and/or
the drain plug. Remove the vent plug to aid in
the draining process.
• Once the coil has been fully drained, a blower
can be hooked-up to the caps. The air vent and
drain plug are not suitable locations for hooking-
up the blower.
• Close the vent drain plug on the header to which
the blower is connected and open the drain
valve or cap on the other header.
• Operate the blower for 45 minutes and then
check if the coil is dry. A mirror placed in the
discharge will become fogged if moisture is
present. Repeat this procedure until the coil is
dry and no fog appears on the mirror.
• Let the coil stand for several minutes then blow
it out again. If water comes out, repeat the
blowing operation.
• Leave all plugs out and drains open until the
threat of freezing has passed.
Maintenance - Fall
Flushing Coils
Greenheck recommends the use of inhibited glycol
designed for HVAC applications for corrosion
protection. The use of uninhibited glycol can
produced formicary corrosion in copper tubing.
The complete filling of water coils with an inhibited
glycol solution for freeze protection can be expensive,
but in some instances it is more cost effective.
Residual glycol fluid can be left in the coil without the
threat of freeze damage, provided the correct
concentration of inhibited glycol is used. The
recovered fluid can then be used to flush other coils.
It is important to select an inhibited glycol solution
that will protect the coil from the lowest possible
temperature that may be experienced over the cold
season. See the following table for concentration
recommendations.
42
% Ethylene Glycol
By Volume
0
10
20
30
40
50
60
% Propylene Glycol
By Volume
0
10
20
30
40
50
60
Freeze Point
(°F)
32
25
16
3
-13
-34
-55
Freeze Point
(°F)
32
26
19
8
-7
-28
-60