Carrier 30XA080-500 Controls, Start-Up, Operation, Service And Troubleshooting Instructions page 57

1. Cable
2. Glass Seal
3. Motor Housing
4. Stepper Motor
5. Bearing
6. Lead Screw
7. Insert
8. Valve Piston
9. Valve Seat
10. Valve Port
8\
9,
10\
5 4 3 2 1
, \
,, \
\\ \\ , \\
1
2
i
7_. \
Fig. 31 -- Cutaway Views of the Electronic Expansion Valve
ECONOM[ZER EXV CONTROL -- The economizer EXV
is controlled by the circuit EXV bomd. There is an economizer
gas temperature thermistor and economizer pressure transducer
located in the line, which runs from the economizer assembly to
the compressol: The economizer pressure is converted to satu-
rated temperature and is used to c_dculate economizer supeflleat.
Economizer superheat equals economizer temperature minus
saturated economizer tempelature. The economizer EXV only
operates during normal conditions when the capacity of the
circuit is approximately 75% plus or minus 5% capacity. Once
the capacity of the circuit is greater than 75% the MBB will stmt
controlling the economizer EXV to maintain economizer super-
heat set point, which is approximately 8 ° to 12 ° F (4.4 ° to
6.7 ° C). If the circuit capacity is less than 75%, the economizer
EXV will be closed.
The economizer EXV has one override. If the dischmge gas
temperature exceeds 195 F (90.6 C) the economizer EXV will
start to open. The EXV will be controlled to maintain discharge
gas temperature at approximately 195 F (90.6 C).
If it appears that main EXV or economizer EXV is not
properly controlling circuit operation to maintain correct super-
heat, there are a number of dlecks that can be made using test
functions and initialization features built into the microproces-
sor control. See the Service Test section to test EXVs.
EXV TROUBLESHOOTING PROCEDURE-- There are
two different economizer EXVs. Both of the economizer
EXVs have a total of 2785 steps. There are three different main
EXVs, which _11have a toted of 3690 steps. The EXV motor
moves at 150 steps per second. Commanding the valve to
either 0% or 100% will add an additiomfl 160 steps to the
move, to ensure the valve is open or closed completely.
Follow the steps below to diagnose and correct EXV prob-
lems. Check EXV motor operation first. Switch the Enable/
Off/Remote (EOR) Contact switch to the Off position. Press
on the Navigator
TM
module until the highest operat-
ing level is displayed. Use the rerow keys to select the Service
Test mode and press -- ----_ . The display will read TEST.
Use the arrow keys until display shows QUIC. Press
(password entry may be required) and use [] or [] to
change OFF to ON. The Quick Test sub-mode is now enabled.
Move the arrow down to the appropriate circuit EXV. Circuit A
EXV % Open (Service Test-cQUIC--_EXV.A), Circuit B EXV
% Open (Service Test-)QUIC-+EXV.B), or Circuit C EXV %
Open (Service Test--)QUIC-+EXV.C), and press _.
The current v_lue of 0 will be displayed. Press _ and
the value will be flashing. Using the [] increase the EXV
position to select 100% valve position (hold [] for quick
movement) and press _. The actuator should be felt
moving through the EXV. Press _ again twice if neces-
sary to confirm this has occurred. This will attempt to force the
EXV to 100% again. To close the valve, press _, select
0% with [] and press _. The actuator should knock
when it reaches the bottom of its stroke. See Table 31 for a list
of EXV modes and submodes.
Table 31 -- EXV Modes and Submodes
EXV TYPE AND CIRCUIT NAVIGATOR
TM
PATH
EXV, Circuit A Service Test Mode--_QUIC--_EXV.A
EXV, Circuit B Service Test Mode--_QUIC--_EXV.B
EXV, Circuit C Service Test Mode--_QUIC--_EXVC
Economizer EXV, Circuit A Service Test Mode--_QUIC--_ECO.A
Economizer EXV, Circuit B Service Test Mode--_QUIC--_ECO.B
Economizer EXV, Circuit C Service Test Mode--_QUIC--_ECO.C
If the valve is not working properly, continue with the fol-
lowing test procedure:
Check the 8-position DIP switch on the board for the proper
address (see page 9). Check the EXV output signals at appro-
priate terminals on the EXV module. For 30XA080 units,
connect the positive test lead to EXV-J2A terminal 5 for Circuit
A and to EXV-J2B terminal 5 for Circuit B.
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