IDEC RSS Series Application Information
Relays & Sockets
RSS Series
Recommended Loads
Transformer Loads
Transformer loads sometimes result in severe inrush current when the transformer saturates during the fi rst cycle. Use a relay rated for this surge, which
has a 1/2 cycle surge current greater than the maximum applied line voltage; the
transformer’s primary resistance (approximately 10x rated current).
Recommended Loads
SSR Rating at 120V AC at 240V AC
10A 500VA 1KVA
25A 1KVA 2KVA
50A 2KVA 4KVA
Heater Loads
When using solid state relays for driving heaters where the load is switched on
and off rapidly and continuously, severe thermal stress will result. In such cases,
use an SSR relay at no more than 75% of the rating.
Recommended Loads
SSR Rating at 120V AC at 240V AC
10A 1KW 2KW
25A 2KW 4KW
50A 3KW 6KW
Switches & Pilot Lights Display Lights Relays & Sockets Timers Terminal Blocks
UL Motor Load Ratings (HP Ratings)
Part Number 120V 240V 480V
10A 1/2 3/4 3/4
25A 1/2 3/4 3/4
50A 3/4 1 1/2 1 1/2
75A 3/4 5 5
90A 3/4 5 5
Lamp Loads
Zero voltage switching is ideal for driving incandescent lamps, since the cold
fi lament will not be subjected to a large inrush current. Using a zero-switched
SSR will reduce inrush current and prolong lamp life.
Recommended Loads
SSR Rating at 120V AC at 240V AC
10A 1KW 2KW
25A 2KW 4KW
50A 3KW 6KW
Internal Circuit Block Diagram
Solenoid Valves and Contactors
RSS relays use high-noise immunity circuitry with a built-in snubber to handle
the electrical noise generated by inductive loads.
Recommended Loads
SSR Rating at 120V AC at 240V AC
10A 900W 1,800W
25A 2,100W 4,200W
50A 3,800W 7,500W
RSS series relays provide a highly reliable means of switching AC loads when
applied properly. Read the technical notes on the following page prior to installing solid state relays.
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RSS Series
Relays & Sockets
Technical Notes
Environment
Do not install SSRs near sources of excessive heat. Make sure applications are dry and well ventilated.
If SSRs must be installed in an environment subject to high temperatures or poor ventilation, or if SSRs are mounted collectively, reduce the load current so that it
does not approach the ambient temperature-load current recommendation. (See the Temperature Derating Curves on the following page.)
When SSRs are used with inductive loads, suppress the inrush current to half of the peak surge current.
Switches & Pilot LightsDisplay LightsRelays & SocketsTimersTerminal Blocks
Heat Sinks
Heat sinks are recommended for all solid state relays depending on ambient temperature and mounting position. The recommended heat sink dimensions and material are shown in the table:
Output Rating Dimensions Material
10A 12” x 12” x 1/8” Aluminum (black anodized)
25A 12” x 12” x 1/8” (DC/AC) Aluminum (black anodized)
25A 15” x 15” x 1/8” (AC/AC) Aluminum (black anodized)
50A 15” x 15” x 1/8” Aluminum (black anodized)
75A 17” x 17” x 1/8” Aluminum (black anodized)
90A 17” x 17” x 1/8” Aluminum (black anodized)
Using a thermal compound between the base of the SSR and the heat sink for heat dissipation is recommended.
Wiring
Locate SSRs as far from motor leads as possible to prevent malfunction from induced current.
Use shielded wires for input leads when they are exposed to a source of induced current.
Mounting
Provide suffi cient ventilation.
Use #6 – 32 screws, fl at washers, and lock washers to secure mounting on heat sinks.
Vertical mounting is recommended to allow air to fl ow unimpeded. Horizontal or inverted mounting is possible, but the SSR must be derated according to the derating
curves on the following page.
Additional Information
Do not exceed the load voltage and current specifi cations.
A small-capacity load may not turn off due to the leakage current present after the SSR has turned off. If this is the case, use a resistor in parallel with the load to
shunt the leakage current.
Observe the polarity of input terminals. Failure to do so may cause damage to the SSR.
When the SSR output is subjected to a higher than rated voltage, a varistor or other element should be connected to the output terminals to absorb the over-voltage.
When the input signal contains a ripple voltage, the lowest ripple amplitude should exceed the minimum pick-up voltage of 4V.
Over 4V
0V
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