York YR TB TB T0, Installation Operation & Maintenance

JOHNSON CONTROLS

67

SECTION 5 – MAINTENANCE

FORM 160.81-NOM1 

ISSUE DATE: 10/3/2020

5

The refrigerant charge level must be checked after the 

pressure and temperature have equalized between the 

condenser and evaporator. This would be expected 

to be 4 hours or more after the compressor and water 

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 pres-

sure, 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  finds  its  way  into  the 

tubes and accumulates there. This material usu-

ally 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 systems 

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 shut-

down. If water is leaking into the refrigerant, frequent 

purging will be necessary and system capacity and effi-

ciency will drop off sharply. If a tube is leaking and wa-

ter 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