Refrigeration System; Refrigerant; Compressor Oil; Servicing Systems On Roofs With Synthetic Materials - Carrier 25VNA Service Manual

REFRIGERATION SYSTEM

Refrigerant

WARNING
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could result in personal injury
or equipment damage.
Puronr refrigerant which has higher pressures than R- -22 and
other refrigerants. No other refrigerant may be used in this
system. Gauge set, hoses, and recovery system must be
designed to handle Puronr. If you are unsure consult the
equipment manufacturer.
In an air conditioning and heat pump system, refrigerant transfers
heat from one replace to another. The condenser is the outdoor coil
in the cooling mode and the evaporator is the indoor coil.
In a heat pump, the condenser is the indoor coil in the heating
mode and the evaporator is the outdoor coil.
In the typical air conditioning mode, compressed hot gas leaves the
compressor and enters the condensing coil. As gas passes through
the condenser coil, it rejects heat and condenses into liquid. The
liquid leaves condensing unit through liquid line and enters
metering device at evaporator coil. As it passes through metering
device, it becomes a gas- -liquid mixture. As it passes through
indoor coil, it absorbs heat and the refrigerant moves to the
compressor and is again compressed to hot gas, and cycle repeats.

Compressor Oil

CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
The compressor in a Puronr system uses a polyol ester
(POE) oil. This oil is extremely hygroscopic, meaning it
absorbs water readily. POE oils can absorb 15 times as much
water as other oils designed for HCFC and CFC refrigerants.
Take all necessary precautions to avoid exposure of the oil to
the atmosphere.
Servicing Systems on Roofs With Synthetic
Materials
POE (polyol ester) compressor lubricants are known to cause long
term damage to some synthetic roofing materials. Exposure, even if
immediately cleaned up, may cause embrittlement (leading to
cracking) to occur in one year or more. When performing any
service which may risk exposure of compressor oil to the roof, take
appropriate precautions to protect roofing. Procedures which risk
oil leakage include but are not limited to compressor replacement,
repairing refrigerants leaks, replacing refrigerant components such
as filter drier, pressure switch, metering device, coil, accumulator,
or reversing valve.
Synthetic Roof Precautionary Procedure
1. Cover extended roof working area with an impermeable
polyethylene (plastic) drop cloth or tarp. Cover an
approximate 10 x 10 ft area.
2. Cover area in front of the unit service panel with a terry
cloth shop towel to absorb lubricant spills and prevent
run- -offs, and protect drop cloth from tears caused by tools
or components.
3. Place terry cloth shop towel inside unit immediately under
component(s) to be serviced and prevent lubricant run- -offs
through the louvered openings in the base pan.
4. Perform required service.
5. Remove and dispose of any oil contaminated material per
local codes.

Brazing

This section on brazing is not intended to teach a technician how to
braze. There are books and classes which teach and refine brazing
techniques. The basic points below are listed only as a reminder.
Definition: The joining and sealing of metals using a nonferrous
metal having a melting point over 800_F/426.6_C.
Flux: A cleaning solution applied to tubing or wire before it is
brazed. Flux improves the strength of the brazed connection.
When brazing is required in the refrigeration system, certain basics
should be remembered. The following are a few of the basic rules.
1. Clean joints make the best joints. To clean:
⎯ Remove all oxidation from surfaces to a shiny
finish before brazing.
⎯ Remove all flux residue with brush and water while
material is still hot.
2. Silver brazing alloy
copper- -to- -steel, or copper- -to- -copper. Flux is required
when using silver brazing alloy. Do not use low temperature
solder.
3. Fluxes should be used carefully. Avoid excessive
application and do not allow fluxes to enter into the system.
4. Brazing temperature of copper is proper when it is heated to
a minimum temperature of 800_F and it is a dull red color
in appearance.
33
is used on copper- -to- -brass,