Spd supplied of exsisting mcb

Evening , been to look a job this evening for an additional socket in kitchen . When checking out board an spd has been fitted but the supply is is coming off an 20amp mcb that looks like it is feeding a small radial circuit . Is this a total no no . I think it is and I have explained to customer that he needs it changed etc. I can see why it has been down as it is an old board with GE ep61 mcb which are difficult to get hold off . Just wondered what people thought are on this

 

[PS Electrics]

A stand-alone or dedicated circuit breaker for surge protector performs the following functions:

• Allows power to the surge protector to be removed without interrupting power to other loads.
• If a component fails inside the protector, only the circuit breaker will trip, and the power of any other load will not be disturbed.

So if the client is happy with the above restrictions then I don't think it is a problem. The MCB is only to protect the electronics of the SPD is my understanding but stand to be corrected.

The other consideration is that it is not advised to do Insulation Resistance testing on installed SPDs (NICEIC Guidance). I guess not being on its own breaker could mean the SPD is included in a IR test if it was not noticed that it is supplied from the circuit supplying the radial.

Guidance here

Regulation 643.3.2 permits the following actions when items of equipment such as SPDs are likely to influence the results of an insulation resistance test or may suffer damage as a result of an applied test voltage of 500 V DC:

● Wherever possible the equipment should be disconnected prior to carrying out the test. In many cases, this is a practical option as the SPD will be installed in parallel and a means of isolation should have been provided to facilitate inspection and replacement of either component parts or the device. This is not such a practical proposition where an installation contains multiple SPDs incorporated into socket-outlets, for example. Once testing is complete it is essential that all disconnected SPDs are re-connected.

The other thing of course is, is it installed to manufacturers instructions? MCB is of the correct rating for the SPD etc

 

[mainline]

A stand-alone or dedicated circuit breaker for surge protector performs the following functions:

• Allows power to the surge protector to be removed without interrupting power to other loads.
• If a component fails inside the protector, only the circuit breaker will trip, and the power of any other load will not be disturbed.

So if the client is happy with the above restrictions then I don't think it is a problem. The MCB is only to protect the electronics of the SPD is my understanding but stand to be corrected.

The other consideration is that it is not advised to do Insulation Resistance testing on installed SPDs (NICEIC Guidance). I guess not being on its own breaker could mean the SPD is included in a IR test if it was not noticed that it is supplied from the circuit supplying the radial.

Guidance here

Regulation 643.3.2 permits the following actions when items of equipment such as SPDs are likely to influence the results of an insulation resistance test or may suffer damage as a result of an applied test voltage of 500 V DC:

● Wherever possible the equipment should be disconnected prior to carrying out the test. In many cases, this is a practical option as the SPD will be installed in parallel and a means of isolation should have been provided to facilitate inspection and replacement of either component parts or the device. This is not such a practical proposition where an installation contains multiple SPDs incorporated into socket-outlets, for example. Once testing is complete it is essential that all disconnected SPDs are re-connected.

The other thing of course is, is it installed to manufacturers instructions? MCB is of the correct rating for the SPD etc

Some Spd,s have internal protection and therefore doesn't have an external Mcb.

 

[Rockomuir]

Yes some don’t require mcb, but the one fitted is fusebox. I reckon because the mcb does not match buster they just come off existing

 

[mainline]

Yes some don’t require mcb, but the one fitted is fusebox. I reckon because the mcb does not match buster they just come off existing

The mcb used will be sized for the spd cable.