Adding a Fuse Spur on to a Consumer Unit Circuit

[RDB85]

I’ve had a disagreement with one of the Engineers in work. So we are doing an install. Installing an Intruder Alarm. Rather than go with my suggestion of coming off a Socket and adding in the Fuse Spur as he’s been doing it 15 years it’s now going next to the Consumer Unit. Which at a guess is 20 years old. He said it’s fine to just add in a circuit to an existing circuit.

Myself personally I’m dead against it. He’s not a qualified electrician. Thoughts?

 

[davesparks]

What do you mean by adding a new circuit to an existing circuit?

If you mean installing a new circuit (ie adding a new OCPD) from the CU then that's fine.

If you mean installing a spur from the OCPD of an existing power circuit then that is also fine, unless it is a ring and a spur has already been taken from that point.

 

[RDB85]

What do you mean by adding a new circuit to an existing circuit?

If you mean installing a new circuit (ie adding a new OCPD) from the CU then that's fine.

If you mean installing a spur from the OCPD of an existing power circuit then that is also fine, unless it is a ring and a spur has already been taken from that point.

Sorry for the Alarm Panel we use flex from the FCU to the Panel and the man add 2.5mm T&E to the circuit. So we are okay to add a new circuit to the consumer unit. But what if that circuit is already in use? You can’t then add our circuit into that can we?

 

[davesparks]

But what if that circuit is already in use? You can’t then add our circuit into that can we?

You can spur directly from the OCPD of an existing circuit exactly the same as you can any other point on that circuit.

If there is already a circuit there then you are not adding another circuit to it you are adding your new wiring to an existing circuit.

 

[DPG]

Sorry for the Alarm Panel we use flex from the FCU to the Panel and the man add 2.5mm T&E to the circuit. So we are okay to add a new circuit to the consumer unit. But what if that circuit is already in use? You can’t then add our circuit into that can we?

How can it already be in use if it's a new circuit? I think I may have misunderstood

 

[RDB85]

How can it already be in use if it's a new circuit? I think I may have misunderstood

Sorry I mean if we add our new circuit to say a 16amp MCB that already has a circuit on it? Your having an affect on the diversity?

 

[davesparks]

Sorry I mean if we add our new circuit to say a 16amp MCB that already has a circuit on it? Your having an affect on the diversity?

Then you are not adding a new circuit, you are altering an existing circuit.

You will have not have an effect on diversity.

 

[James]

Assuming you have a standard type of ring circuit for your existing sockets, you can add a spur at any point in the ring, including the circuit breaker that feeds it.

this is also true for a radial circuit, I am not sure I fully understand why you are concerned about adding the "small" load of an intruder alarm to any point of an existing circuit.

 

[RDB85]

Then you are not adding a new circuit, you are altering an existing circuit.

You will have not have an effect on diversity.

Okay thanks. I thought I better check as I’ve also made the assumption. But that’s good to know. I must have go something wrong somewhere. Thanks for the clarification.

 

[RDB85]

Assuming you have a standard type of ring circuit for your existing sockets, you can add a spur at any point in the ring, including the circuit breaker that feeds it.

this is also true for a radial circuit, I am not sure I fully understand why you are concerned about adding the "small" load of an intruder alarm to any point of an existing circuit.

It’s not going on the ring circuit. It’s going directly on to a circuit on the consumer unit. It is only a small load though. It’s fused down to 3amp. As long as he doesn’t add it into the lighting circuit or the ring main circuit.

 

[davesparks]

It’s not going on the ring circuit. It’s going directly on to a circuit on the consumer unit. It is only a small load though. It’s fused down to 3amp. As long as he doesn’t add it into the lighting circuit or the ring main circuit.

I agree it shouldn't be added to a lighting circuit but why do you say not a ring circuit?

 

[RDB85]

I agree it shouldn't be added to a lighting circuit but why do you say not a ring circuit?

It could do. But as it’s such a small load. I thought put it on a lower rated MCB.

 

[James]

I’ve had a disagreement with one of the Engineers in work. So we are doing an install. Installing an Intruder Alarm. Rather than go with my suggestion of coming off a Socket and adding in the Fuse Spur as he’s been doing it 15 years it’s now going next to the Consumer Unit. Which at a guess is 20 years old. He said it’s fine to just add in a circuit to an existing circuit.

Myself personally I’m dead against it. He’s not a qualified electrician. Thoughts?

So as you say neither of you are qualified electricians.

you are doing an electrical installation of a new circuit or maybe an alteration to an existing circuit.

If you are doing this for reward, i.e. it is a paid job, how on earth have you got insurance to trade doing work that you cant show competence in?

Who fills out the installation certificate?
how do you show compliance with the regs and how do you test and document it?

 

[DPG]

It’s not going on the ring circuit. It’s going directly on to a circuit on the consumer unit. It is only a small load though. It’s fused down to 3amp. As long as he doesn’t add it into the lighting circuit or the ring main circuit.

It can be added to the ring final via a fused spur, or from the origin (ie. MCB/RCBO) of the ring final. As above, it could even by added to the lighting circuit in a similar way to a TV aerial amplifier (someone slated me for saying that before but I'm not bothered!)

The current draw is only going to be a few tens of mA.

 

[RDB85]

So as you say neither of you are qualified electricians.

you are doing an electrical installation of a new circuit or maybe an alteration to an existing circuit.

If you are doing this for reward, i.e. it is a paid job, how on earth have you got insurance to trade doing work that you cant show competence in?

Who fills out the installation certificate?
how do you show compliance with the regs and how do you test and document it?

Exactly. That’s my point. I’ve my level 2 and 3 2365. But that doesn’t mean I’m qualified. But our place don’t care.