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How do you size a surge protective device?
What is the correct way to determine which size of SPD to use in a system? SPDs are not one-size-fits-all devices, nor do the size of their kA rating (the surge rating) go hand-in-hand with the size of the panel. In other words, do not select an SPD with a maximum kA rating just because the panel is large.
Does an SPD need an MCB?
Also as an SPD is a voltage detection device, it does not have a short circuit withstand capacity, such as an MCB, so does not require type testing to any specific manufacturer.
What type of SPD do I need?
The Type 1 SPD is recommended in the specific case of service-sector and industrial buildings, protected by a lightning protection system or a meshed cage. Type 1 SPD is characterized by a 10/350 µs current wave. Type 2 SPD. The Type 2 SPD is the main protection system for all low voltage electrical installations.
How do I specify SPD?
Specifying the SPD requires identifying and understanding the ratings associated with its application. Performance values and ratings associated with an SPD include maximum continuous operating voltage (MCOV), voltage protection rating (VPR), nominal discharge current (In), and short circuit current rating (SCCR).
What size MCB for an SPD?
For a type 1 SPD, minimum CSA is 16mm2 for the earth and 6mm2 for the supply conductors.
Do I need to fit a SPD?
Electrical installations in single dwelling units are not required to have SPDs installed, but their use is not precluded and it may be that in discussion with a client such devices are installed, reducing significantly risks associated with transient over-voltages.
When to install a surge protection device ( SPD )?
If the distance between that surge protective device and the protected equipment exceeds 30 metres, an additional surge protective device (Type 2 or Type 3) should be installed near the equipment.
When to use a Type 3 surge protection device?
Type 3 SPD is used for local protection for sensitive loads. These SPDs have a low discharge capacity. They must therefore only be installed as a supplement to Type 2 SPD and in the vicinity of sensitive loads. They are widely available as hard-wired’ devices (frequently combined with Type 2 SPDs for use in fixed installations).
How are surge protection devices chosen for a switchboard?
Finally, the protection device associated with the surge protective device (circuit breaker or fuse) will be chosen according to the short-circuit current at the place of installation. In other words, for a residential electrical switchboard, a protection device with an I SC < 6 kA will be chosen.
What happens if a SPD is the wrong size?
When a person uses a surge protection device (SPD) that is the incorrect size for their system, they waste money on an unnecessarily high level of surge protection (which is the best-case scenario), or they waste money on a device that will provide inadequate protection and also have a short lifespan.