Specifications

JOHNSON CONTROLS
67
SECTION 5 – MAINTENANCE
FORM 160.81-NOM2
ISSUE DATE: 2/29/2012
5
pumps are stopped. The level should be at the center of
the upper sight glass.
Charge the refrigerant in accordance with the method
shown under “Refrigerant Charging.” The refrigerant
level should be observed and the level recorded after
initial charging.
HANDLING REFRIGERANT FOR DISMANTLING
AND REPAIRS
If it becomes necessary to open any part of the refriger-
ant system for repairs, it will be necessary to remove
the charge before opening any part of the unit.
Condenser – In a condenser, trouble due to fouled tubes
is usually indicated by a steady rise in head pressure,
over a period of time, accompanied by a steady rise
in condensing temperature, and noisy operation. These
symptoms may also be due to foul gas buildup. Purging
will remove the foul gas revealing the effect of fouling.
Tube Fouling
Fouling of the tubes can be due to deposits of two types
as follows:
1. Rust or sludge – which nds 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.
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 thorough-
ly clean each tube with a soft bristle bronze or 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
connecting the other end by means of a hose to the wa-
ter 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 from the tubes with the result that
a more satisfactory cleaning job will be accomplished
with a probable saving of time.
COMMERCIAL ACID CLEANING
In many major cities, commercial organizations now
offer a specialized service of acid cleaning evaporators
and condensers. If acid cleaning is required, Johnson
Controls recommends the use of this type of organiza-
tion. The Dow Industries Service Division of the Dow
Chemical Company, Tulsa, Oklahoma, with branches
in principal cities is one of the most reliable of these
companies.
TESTING FOR EVAPORATOR AND
CONDENSER TUBE LEAKS
Evaporator and condenser tube leaks in R-134a sys-
tems may result in refrigerant leaking into the water
circuit, or water leaking into the shell depending on the
pressure levels. If refrigerant is leaking into the water,
it can be detected at the liquid head vents after a period
of shutdown. If water is leaking into the refrigerant,
frequent purging will be necessary and system capacity
and efficiency will drop off sharply. If a tube is leak-
ing and water has entered the system, the evaporator
and condenser should be valved off from the rest of
the water circuit and drained immediately to prevent
severe rusting and corrosion. If a tube leak is indicated,
the exact location of the leak may be determined as
follows:
1. Allow the system to warm up until a substantial
pressure is reached for testing. Dry nitrogen (pres-
sure not to exceed 12 PSIG (83kPa)) may be ad-
mitted to the unit to increase pressure in the shell.
Remove the heads and listen at each section of
tubes for a hissing sound that would indicate gas
leakage. This will assist in locating the section of
tubes to be further investigated. If the probable
location of the leaky tubes has been determined,
treat that section in the following manner (if the