User's Manual
Installation Manual    ASCO 3ATS, 3ADTS, 3NTS, 3NDTS 
381333-406  ASCO Power Technologies  Page 3 
maintenance 
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Clockwise DOWN closes 
the Normal source 
contacts (lower) and 
opens the Emergency 
source contacts (upper) 
Counterclockwise DOWN 
closes the Emergency 
source contacts (upper) 
and opens the Normal 
source contacts (lower) 
Clockwise DOWN CLOSES
the contacts 
Pull out
 shaft to close 
Emergency source contacts 
(upper) 
Push in
 shaft to close 
Normal source contacts 
(lower) 
Counterclockwise DOWN 
OPENS the contacts 
Pull out
 shaft to open 
Emergency source contacts 
(upper) 
Push in
shaft to open Normal 
source contacts (lower) 
maintenance handle 
insert handle into 
hole in hub 
slide hub onto shaft 
and insert the pin
Functional Test 
The functional test consists of three checks: manual 
operation, voltage checks, and electrical operation. 
Do these checks in the order presented to avoid 
damaging the transfer switch. 
1 – Manual Operation 
A maintenance handle is provided on the transfer switch for 
maintenance purposes only. Manual operation of the transfer 
switch should be checked before it is energized (operated 
electrically). 
Do not manually operate the transfer switch until 
both power sources are disconnected: open both 
circuit breakers. 
1.  After deenergizing both power sources, open the enclosure 
door. Locate and remove the maintenance handle from the 
clip on the left side of the transfer switch. See Figures 3, 4, 
and 5. See Figure 2 for the contact position indicators. 
2.  Install the handle into the hole in the molded hub. Move 
the handle up or down as shown to manually operate the 
transfer switch. It should operate smoothly without any 
binding. If it does not, check for shipping damage or 
construction debris. 
3.  3ADTS and 3NTS have two contact shaft hubs. See 
Figure 5. 
4.  Return the transfer switch to the Normal position. 
Note: If Normal and Emergency connections are reversed this 
operation is also reversed. 
Figure 3. Maintenance handle on 3ATS & 3NTS. 
Figure 4. Maintenance handle operation on 3ATS & 
3NTS. 
Figure 5. Maintenance handle on 3ADTS & 3NDTS. 
NOTIC
E
 WARNING 
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