Bryant Base Series Application Manual And Service Manual page 28

Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual
Reversing Valve
In heat pumps, changeover between heating and cooling modes is
accomplished with a valve that reverses flow of refrigerant between the
two coils. This reversing valve device is easy to troubleshoot and
replace. The reversing valve solenoid can be checked with power off
with an ohmmeter. Check for continuity and shorting to ground. With
control circuit (24v) power on, check for correct voltage at solenoid coil.
Check for overheated solenoid.
With unit operating, other items can be checked, such as frost or
condensate water on refrigerant lines.
The sound made by a reversing valve as it begins or ends defrost is a
"whooshing" sound, as the valve reverses and pressures in system
equalize. An experienced service technician detects this sound and uses
it as a valuable troubleshooting tool.
Using a remote measuring device, check inlet and outlet line
temperatures. DO NOT touch lines. If reversing valve is operating
normally, inlet and outlet temperatures on appropriate lines should be
close to each other. Any difference would be due to heat loss or gain
across valve body. Temperatures are best checked with a remote reading
electronic-type thermometer with multiple probes. Route thermocouple
leads to inside of coil area through service valve mounting plate area
underneath coil. Fig. 22 and Fig. 23
valve for recording temperatures. Insulate points for more accurate
reading.
Fig. 22 – Reversing Valve
(Cooling Mode or Defrost Mode, Solenoid Energized)
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
show test points (TP) on reversing
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If valve is defective:
1. Shut off all power to unit and remove charge from system.
2. Remove solenoid coil from valve body. Remove valve by cutting it
from system with tubing cutter. Repair person should cut in such a
way that stubs can be easily re-brazed back into system. Do not use
hacksaw. This introduces chips into system that cause failure. After
defective valve is removed, wrap it in wet rag and carefully unbraze
stubs. Save stubs for future use. Because defective valve is not
overheated, it can be analyzed for cause of failure when it is
returned.
3. Braze new valve onto used stubs. Keep stubs oriented correctly.
Scratch corresponding matching marks on old valve and stubs and
on new valve body to aid in lining up new valve properly. When
brazing stubs into valve, protect valve body with wet rag to prevent
overheating.
4. Use slip couplings to install new valve with stubs back into system.
Even if stubs are long, wrap valve with a wet rag to prevent
overheating.
5. After valve is brazed in, check for leaks. Evacuate and charge
system. Operate system in both modes several times to be sure
valve functions properly.
Fig. 23 – Reversing Valve
(Heating Mode, Solenoid De-Energized)
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