Watlow SDA Card Shorted Solid State Relay Detector User Manual

There is concern that if a solid state relay fails, it will
most likely fail in a shorted condition. To alleviate this
concern, Watlow Controls has designed a low-cost card
(Watlow P/N 08-5386) that provides a shorted SSR
alarm. It is designed to be used with DC input SSRs,
rated 10 to 40 Amps on either a single phase or two-leg,
three-phase system. In addition to the SDA card, we
strongly recommend semiconductor fuses to protect the
SSR, and a high limit cutout to protect the thermal
system from any runaway conditions.

The SDA card mounts directly on the solid state relay
and takes its power from the current flowing through the
current transformer. If there is no input command signal
from the temperature control to the SSR, and there is
current flow to the load, the alarm becomes energized.
The alarm circuit’s output is a triac rated for 300mA @
120 or 240V~ (ac). This can be wired through a
customer supplied latching relay and alarm to 120 or
240 volts.

Watlow Controls

1241 Bundy Blvd., P.O. Box 5580

Winona, MN 55987-5580

Phone: [phone], Fax: [phone]

SDA Card

Shorted Solid State Relay Detector

Data Sheet

0600-0028-0004 Rev C (1278) Made in the U.S.A.

January, 1998 Printed on Recycled Paper

10% Postconsumer Waste

Figure 1 - SDA Card Dimensions (08-5386)

NOTE: Mount with two 6-32 screws 5/8”
long. (Included with the SDA card.)

To Heater

TB1

2 1

(See below for wiring.)

Load

Line

Fuse

L1
L2

Load Number of Passes of Load Wire

Current Through Current Transformer

2 to 3 Amps 5
3 to 4 Amps 4
4 to 5 Amps 3

5 to 10 Amps 2

10 to 40 Amps 1

Figure 3 - SDA Card Wiring

Table 1 - Application of 16-0231 Current Transformer

Figure 2 - Three Dimensional View of Wiring

NOTE: The triac connection
between connector TB1 pins
1 and 2 is closed when a
shorted SSR condition is
detected. This output is rated
24 to 240V~ (ac), 300mA @
25°C, 125mA @ 80°C.

L2

AC Line

Voltage

L1

Semiconductor

Fuse

Output

Load

DC Input

Solid State Relay

DC

-

Input

+

Signal

- +

Input

TB1

2 1

Current

Transformer

30A to 20mA

- +

SDA Board

08-5386

120 V~ (ac)

T o Alarm

or Contactor

Customer Supplied Relay

(Philips ECG PIY 1055 or equivalent)