GeneralAire GA50A20 - Manual (Page 9)

without the transformer connected. Resistance should
read above 20K ohms with an analog meter and above
4M ohms with a digital meter. If the resistance readings
are below these values, the power board may be the
cause of the transformer failure.
Before replacing the 24 V transformer, turn OFF power to
the Air Cleaner at the source.
1. Remove power box cover.
2. Disconnect the secondary leads from the transformer
to the 24 V terminals on the power board. See Fig. 5.
3. Cut the primary leads (to the APS) close to the
transformer or disconnect leads from the APS.
4. Remove the 2 hex nuts and washers from the
transformer studs.
5. Remove the transformer.
6. Place new transformer over studs and re-install 2 star
washers and hex nuts to secure into place.
7. Connect secondary leads (white) to the 24 V
terminals on the power board (P1 & P2).
8. Wire nut primary leads from APS (cut in Step 3) to
the primary leads of the new transformer or connect
primary leads to APS terminals 1 & 4.
9. Replace power box cover.
10. Turn ON the power to the Air Cleaner and test.
Setting Voltage Of Power Board
Voltage on the power board may drop below required
level when installation area is too damp, too cold, or if
there is a leakage of water from a humidifier. Voltage on
power board may be too high when installation area is
too dry or too hot, or home is in close proximity to hydro
towers or situated in remote farm land areas. By
adjusting the HV Adj. potentiometer, the voltage can be
set to optimum level. A high voltage meter capable of
measuring 10,000 VDC is required. To test and adjust
voltage level, perform the following procedure:
1. Turn the Air Cleaner OFF.
2. Remove the power box cover.
3. Connect the ground of the high voltage meter to an
unpainted surface in the power box.
4. Turn ON the Air Cleaner and wait 5 minutes before
checking voltages to allow voltages on cells to
stabilize. The cells and ionizing wires must be clean.
5. Measure the voltages at HV1 and HV2 on the power
board.
6. Adjust the HV Adj. potentiometer until the voltage
reading matches the voltage in Table 3. Adjusting the
potentiometer clockwise decreases the voltage and
turning counter-clockwise increases the voltage.
7. Turn OFF the Air Cleaner.
8. Remove the high voltage meter.
9. Replace the power box cover.
10. Turn ON the Air Cleaner.
Setting Approximate Voltage Without High Voltage
Meter
A high voltage meter should be used to set the high
voltage. If one is not available, this method can be used.
This will only set an approximate voltage. After using this
method, the voltage should be reset with a high voltage
meter as soon as possible.
1. Remove power box cover.
2. Turn the HV Adj. potentiometer fully counter-
clockwise. The Air Cleaner may arc or snap at this
point.
3. Turn the HV Adj. potentiometer back, clockwise, until
the arrow is between 6 and 8 on the dial or on the +
side of the half way point.
4. Replace power box cover.
Testing for Voltage At The Cell
1. Open access door to Air Cleaner.
2. The cells must be in the Air Cleaner for this test and
the system fan should be on high speed.
3. Turn the Air Cleaner ON and press the safety
interlock switch lever.
4. Place a plastic handled screwdriver into the direction
arrow slot. Do not apply excessive force.
5. If there is a good snap then there is high voltage at
the cell.
Testing Cell For Bad Contacts
1. Open access door to Air Cleaner.
2. The cells must be in the Air Cleaner for this test and
the system fan should be on high speed.
3. Turn the Air Cleaner ON and press the safety
interlock switch lever.
4. Place a plastic handled screwdriver into the direction
arrow slot. Do not apply excessive force.
5. There should be an initial snap when the plates are
shorted, then no sound. If a hissing occurs, then
there is a bad contact. Look along the top of the cell,
with the short still in place. If there is a small arc
between the cell top and copper contact, then that is
the bad contact. Pull cell out and gently pull the
copper contact down.
6. If an arc is not seen and there is a bad contact, then
the problem may be an internal contact in one of the
cells.
7. Let up on safety interlock.
8. Close access door.
See below for additional testing.
Testing Cell with an Ohmmeter
To test the cell for a dead short or a bad contact an
ohmmeter can be used. Always discharge the cell with
a screw driver before testing with an ohmmeter.
Model Maximum Voltage
on Plates (KVDC)
Maximum Voltage
on Ionizer (KVDC)
GA50A14 4.8 - 5.3 (HV1) 7.2 - 8.0 (HV2)
GA50A20, GA50A22 4.8 - 5.2 (HV1) 7.2 - 7.8 (HV2)
Table 3 — Power Board Voltage Settings (with load)
The voltage will be higher without the cells in the unit.
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