JOHNSON CONTROLS
126
FORM 161.01-OM1
ISSUE DATE: 6/8/2018
SECTION 5 - MAINTENANCE
1. The condenser tubes should be cleaned annually
or earlier if conditions warrant. If the temperature
difference between the water off the condenser
and the condenser liquid temperature is more than
4°F (2°C) greater than the difference recorded on
a new unit, it is a good indication that the con-
denser tubes require cleaning.
See
orator and Condenser Tubes on page 126
in this
section for condenser tube cleaning instructions.
2. The evaporator tubes under normal circumstances
will not require cleaning. If the temperature dif-
ference between the refrigerant and the chilled
water increases slowly over the operating season,
it is an indication that the evaporator tubes may be
fouling or that there may be a water bypass in the
water box requiring gasket replacement or refrig-
erant may have leaked from the chiller.
Chemical Water Treatment
Since the mineral content of the water circulated
through evaporators and condensers varies with almost
every source of supply, it is possible that the water be-
ing used may corrode the tubes or deposit heat resistant
scale in them. Reliable water treatment companies are
available in most larger cities to supply a water treat-
ing process which will greatly reduce the corrosive and
scale forming properties of almost any type of water.
As a preventive measure against scale and corrosion
and to prolong the life of evaporator and condenser
tubes, a chemical analysis of the water should be made
preferably before the system is installed. A reliable wa-
ter treatment company can be consulted to determine
whether water treatment is necessary, and if so, to fur-
nish the proper treatment for the particular water con-
dition.
Cleaning Evaporator and Condenser Tubes
Evaporator
It is difficult to determine by any particular test wheth-
er possible lack of performance of the evaporator is
due to fouled tubes alone or due to a combination of
troubles. Trouble which may be due to fouled tubes is
indicated when, over a period of time, the cooling ca-
pacity decreases and the split (temperature difference
between water leaving the evaporator and the refriger-
ant temperature in the evaporator) increases. A gradual
drop-off in cooling capacity can also be caused by a
gradual leak of refrigerant from the system or by a
combination of fouled tubes and shortage of refriger-
ant charge.
Condenser
In a condenser, trouble due to fouled tubes is usually
indicated by a steady rise in head pressure, over a pe-
riod of time, accompanied by a steady rise in condens-
ing temperature.
Tube Fouling
Fouling of the tubes can be due to deposits of two types
as follows:
1.
Rust or sludge – which finds its way into the tubes
and accumulates there. This material usually does
not build up on the inner tube surfaces as scale,
but does interfere with the heat transfer. Rust or
sludge can generally be removed from the tubes
by a thorough brushing process.
2. Scale – due to mineral deposits. These deposits,
even though very thin and scarcely detectable
upon physical inspection, are highly resistant to
heat transfer. They can be removed most effec-
tively by circulating an acid solution through the
tubes using skilled experts as described below.
Tube Cleaning Procedures
Brush Cleaning of Tubes
If the tube consists of dirt and sludge, it can usually be
removed by means of the brushing process. Drain the
water sides of the circuit to be cleaned (cooling wa-
ter or chilled water) remove the heads and thoroughly
clean each tube with a soft bristle nylon brush. DO
NOT USE A STEEL BRISTLE BRUSH. A steel brush
may damage the tubes.
Improved results can be obtained by admitting water
into the tube during the cleaning process. This can be
done by mounting the brush on a suitable length of 1/8"
pipe with a few small holes at the brush end and con-
necting the other end by means of a hose to the water
supply.
The tubes should always be brush cleaned before acid
cleaning.
Acid Cleaning of Tubes
If the tubes are fouled with a hard scale deposit, they
may require acid cleaning. It is important that before
acid cleaning, the tubes be cleaned by the brushing
process described above. If the relatively loose foreign
material is removed before the acid cleaning, the acid
solution will have less material to dissolve and flush
Summary of Contents for YZ MODEL A
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