Thermo King MD-MT, Operator'S Manual

Page: 125 / 192

Refrigeration Service Operations
125
R-404A
Refrigerant R-404A is classified as a Hydrofluoro
carbon (H.F.C.) because it contains hydrogen
fluorine and carbon. It does not contain chlorine.
R-404A was developed as a replacement for
R-502. R-502 contains chlorine that presents a
hazard to the environment.
The pressure temperature relationship of R-404A
is similar to that of R-502. The capacities of this
new refrigerant is similar for box temperatures
above 0 F (-18 C). At temperatures below 0 F
(-18 C), H.F.C. refrigerant capacities are slightly
less than CFC refrigerants.
Unit Identification
Units charged with R-404A are identified by the
following methods:
1. HFC-404A will be stamped on the unit’s serial
plate.
2. “HFC” may be incorporated in the model
designation on the sides of the unit such as
“MD-MT HFC”.
3. Decals will be applied to unit as shown below:
Figure 68: R-404A Decal
Availability
Refrigerant 404A is available from wholesalers.
The price will depend upon the quantity
purchased. Thirty (30), 50 and 125 containers are
available. When purchasing R-404A in 30 pound
or 50 pound containers, specify industrial
containers with 1/4 inch flare fittings to receiver
containers with 1/4 inch flare fittings for use with
Thermo King truck unit applications.
Leak Detection
Leaks can be detected by a Halogen leak detector
such as the G.E. H10G (TK No. 204-712) or
portable leak detector (TK No. 204-854). See
Truck and Trailer Service Bulletin T&T 048 for
additional details.
Compressor Oil
Thermo King Corporation has chosen to use a
compressor oil called Polyol Ester (POE)—also
called ester based oil. POE oil is compatible with
R-404A and can be used in low temperature
applications. This oil is available from service
parts TK No. 203-513.
Compressors Shipped with R-404A
The MD-MT compressors are Thermo King
compressors and are charged with Polyol Ester oil
(POE) (TK No. 203-513). All gauge fittings are
1/4 inch fittings.
Because Polyol Ester has an affinity for moisture,
it must be kept in capped containers. In addition,
it should be added as the last step in system repair.
Rubber gloves are recommended when handling
Polyol Ester because it may cause skin irritation.
CAUTION: POLYOL ESTER (POE) IS
THE ONLY OIL FOR USE WITH
THERMO KING UNITS USING R-404A.
IT SHOULD NOT BE ADDED TO
STANDARD THERMO KING UNITS,
NOR SHOULD THE STANDARD OR
SYNTHETIC OIL BE ADDED TO
SYSTEMS CONTAINING R-134a AND
R-404A. COMBINING THE TWO OILS
COULD RESULT IN DAMAGE TO THE
SYSTEM.