Littelfuse-ALT115-S

Protection Relays  

Alternating Relays  

ALT SERIES  

8-pin Plug-in Alternating Relay  

Description  

The ALT series alternating relays are used to alternate between  

two loads. The A

L

T

i

s commonly used in duplex pumping  

applications to balance the runtime of both pumps.  

The

A

L

T

–

S

is used in single high-level float applications. When  

the float switch opens, the alternating relay changes state,  

forcing the other pump to run the next time the float closes.  

All A

L

T

r

elays have a built-in debounce feature that prevents  

the relay from changing state if the switch or float contact  

bounces momentarily.  

The

A

L

T

–

X

has an internal cross-connected relay and is used  

in dual high-level float applications. These floats are commonly  

referred to as lead and lag floats.  

Wiring Diagram  

The pumps alternate as in the A

L

T

–

S version but the cross-  

connected relay configuration allows both pumps to run  

simultaneously when both the lead and lag floats are closed.  

TYPICAL WIRING DIAGRAM FO

R

T

HE A

L

T

–

S  

These relays are also available with a built-in switch (SW option)  

that is used to manually force one of the pumps to run every  

time the float switch is closed. This is helpful when a pump has  

been removed for repair or for test purposes. In the case of the  

A

L

T

–

X-SW,

the switch essentially forces one pump to be the  

lead pump, while still allowing the second to run when both  

floats are closed.  

Must use the OT08PC socket for UL Rating!  

*Note: Manufacturer’s recommended screw terminal torque for the OT series  

Octal Sockets is 12 in.-lbs.  

TYPICAL WIRING DIAGRAM FOR THE A

L

T

–

X (CROSS CONNECTED)  

ALTERNATING RELAY  

S1  

F1  

Features & Benefits  

L1  

L2  

2

7

3

6

1

8

4

5

FEATURES  

BENEFITS  

F2  

S2  

Prevents nuisance actuating causes by waves or  

spashing in the tank  

F1 – F2:  

Debounce time delay  

1-2A TYPICAL SIZE  

FOR CONTACTOR COILS  

Built-in manual/  

auto switch  

Force lead pump operation when a pump is  

removed for repair or testing (on select models)  

F3  

F4  

L1  

L2  

PUMP  

#1  

Ordering Information  

F3 – F6:  

SIZE FOR INDIVIDUAL  

PUMP APPLICATION  

F5  

MODEL  

ALT024-S

†  

LINE VOLTAGE  

DESCRIPTION  

MAGNETIC CONTACTORS  

20-26 V ac or V dc  

For single high-level float applications  

For single high-level float applications  

with built in manual switch  

L1  

L2  

ALT024-S-SW

†  

ALT115-S  

20-26 V ac or V dc  

95-125 V ac  

PUMP  

#2  

F6  

For single high-level float applications  

For single high-level float applications  

with built in manual switch  

95-125 V ac  

ALT115-S-SW  

For dual high-level (lead and lag) float  

applications  

For dual high-level (lead and lag) float  

applications with built in manual switch  

For single high-level float applications  

For single high-level float applications  

with built in manual switch  

95-125 V ac  

ALT115-X  

Accessories  

OT08PC Octal 8-pin Socket  

95-125 V ac  

195-250 V ac  

195-250 V ac  

ALT115-X-SW  

ALT230-S  

8-pin 35 mm DIN rail or surface mount. Rated at  

10 A @ 600 V ac. Surface mounted with two #6  

screws or snaps onto a 35 mm DIN rail.  

ALT230-S-SW  

For dual high-level (lead and lag) float  

applications  

For dual high-level (lead and lag) float  

applications with built in manual switch  

195-250 V ac  

195-250 V ac  

ALT230-X  

ALT230-X-SW  

© 2019 Littelfuse, Inc.  

Rev: 2-C-043019  

Protection Relays  

Alternating Relays  

ALT SERIES  

General Characteristics  

Temperature Range  

Maximum Input Power  

Safety Marks  

UL (OT08PC octal  

socket required)  

CSA  

Specifications  

-40 °C to 50 °C (-40 °F to 122 °F)  

5 W  

Input Characteristics  

Supply Current  

40 mA  

Functional Characteristics  

Debounce Time Delay  

Control Input Impedance (min)  

24  

115  

230  

0.5 second  

UL 508 (File #E68520)  

C22.2 No. 14 (File #46510)  

H

44.45 mm (1.75”);

W

60.33 mm (2.375”);  

D

104.78 mm (4.125”)  

0.38 lb. (6.08 oz., 172.67 g)  

DIN rail or surface mount  

(plug into OT08PC socket)  

OT08PC (UL Rating 600 V)  

10 kΩ  

56 kΩ  

100 kΩ  

Dimensions (with socket)  

Weight  

Mounting Method  

Output Characteristics  

Output Contact Rating  

480 VA @ 240 V ac  

Socket Available  

The 600 V socket can be surface mounted or installed on DIN rail.  

Disclaimer Notice –

Information furnished is believed to be accurate and reliable. However, users should independently evaluate the suitability of and test each product selected for their own  

applications. Littelfuse products are not designed for, and may not be used in, all applications. Read complete Disclaimer Notice at

© 2019 Littelfuse, Inc.  

Rev: 2-C-043019