Boiler circuit 16A MCB

[Michaelwgroves]

I'm following a spark who used an existing Panel Heater circuit, for new gas boiler circuit 6 months ago. The panel heaters were removed, so it's now a dedicated boiler circuit. I'm doing an EICR.
I've found a number of faults;
1. No grommet in Consumer unit knock out, used for gas bonding (It's a recessed consumer unit)
2. Stranded cable does not have ferrules
3. Unfused Boiler switch
4. 16A MCB (2.5mm T&E)
5. Gas not bonded, bonding taken to central heating pipe only

Most of these are black and white very poor work. I've had to fix all of these so the EICR is a pass, but I have a dilemma.
#4, the MCB is way too big for a boiler. I now have a switched fuse with 3A fuse, so the boiler is now protected. It's a 2.5mm T&E cable so the 16A MCB is protecting the cable. Nothing is unsafe. If it were a new circuit, I'm sure he would have purchased a 6A MCB, but as it's not he's just used existing 16A. I'm going to need to do 16 EICR's following these guys. I'm sure this will be a theme. Is there a reg I can quote for wrong sized MCB, or is this just poor workmanship ?

 

[James]

Mcb is not wrong.
up to20A is normally ok for 2.5mm
3A fuse protects fly lead to boiler and associated control cables.
you make no statement about rcd protection, if the cable is buried then it is probably required.

 

[Risteard]

Also you mention stranded conductors without a ferrule. Are these stranded, fine stranded or very fine stranded?

 

[Michaelwgroves]

Mcb is not wrong.
up to20A is normally ok for 2.5mm
3A fuse protects fly lead to boiler and associated control cables.
you make no statement about rcd protection, if the cable is buried then it is probably required.

Thanks for your thoughts, it's 17th edition board, this circuit has RCD.

 

[Michaelwgroves]

Also you mention stranded conductors without a ferrule. Are these stranded, fine stranded or very fine stranded?

In all honesty, I don't know. What is the technical difference ?

 

[Rockingit]

In all honesty, I don't know. What is the technical difference ?

Respectfully - if you don't know and understand what you're inspecting, should you be inspecting?

 

[Michaelwgroves]

Respectfully - if you don't know and understand what you're inspecting, should you be inspecting?

Helpful............

 

[timhoward]

1. No grommet in Consumer unit knock out, used for gas bonding (It's a recessed consumer unit)

Are you particularly worried about a bonding conductor touching the frame of a metal consumer unit? Do you feel that is potentially dangerous?

Simpler to add a fused spur (as you did) than mess around changing an MCB for the boiler.
I don't lose sleep about simple fixes, I do them and move on. It's usually quicker than filling out the observations section!

 

[loz2754]

While I sympathise with the OP, I would tend to agree with @Rockingit. Anyone involved in periodic inspection and testing of existing installations should be very familiar with the type of installation that they're inspecting and testing.
Of course, no one person can be expected to know everything. But it boils down to the difference between knowledge and experience. Such experience is often picked up on the job whilst working alongside more experienced colleagues.
What though if a person doesn't have the benefit of being able to work with such a mentor?
I suppose the next best thing is this forum...

 

[timhoward]

Stranded cable does not have ferrules

Explain a bit more - cable for what, terminated where and how?

 

[Michaelwgroves]

Are you particularly worried about a bonding conductor touching the frame of a metal consumer unit? Do you feel that is potentially dangerous?

Simpler to add a fused spur (as you did) than mess around changing an MCB for the boiler.
I don't lose sleep about simple fixes, I do them and move on. It's usually quicker than filling out the observations section!

My concern was protection against fire, the consumer unit is now open to the cavity. Any internal fire within the consumer unit could now travel freely in the cavity. A blind grommet would have easily resolved this.

 

[davesparks]

My concern was protection against fire, the consumer unit is now open to the cavity. Any internal fire within the consumer unit could now travel freely in the cavity. A blind grommet would have easily resolved this.

No it won't, a blind grommet will not stop the spread of fire.

 

[davesparks]

Is there a reg I can quote for wrong sized MCB, or is this just poor workmanship ?

It's not the wrong size MCB and it's not poor workmanship.

16A 2.5mm radial has been the generally accepted standard supply for any small appliance such as a boiler for a long time.

Using a smaller MCB would be unusual and would be unlikely to give any selectivity with the 3A fuse for the boiler.

 

[davesparks]

In all honesty, I don't know. What is the technical difference ?

Coarse stranded conductors do not need ferrules, fine stranded conductors do need ferrules or other suitable treatment at the end.

It is important to remember that the regulations do not require the use of ferrules, they require fine stranded cables to be suitably treated at their terminations. This can be achieved by using ferrules but this is not the only way.

 

[JgMaan]

My concern was protection against fire, the consumer unit is now open to the cavity. Any internal fire within the consumer unit could now travel freely in the cavity. A blind grommet would have easily resolved this.

A rubber blind grommet wont stop any sort of fire, and regardless this is outside the scope of an EICR.

You are pulling up things that relate to workmanship (gas bond excluded) and adherence to BS7671. An EICR is solely to give an engineering view on whether an installation is safe for continued use.

 

[Michaelwgroves]

Explain a bit more - cable for what, terminated where and how?

Its a 1mm cable from FCU to boiler. 526.9.1 requires suitable terminals. I'm now curious on the definition of fine wire & very fine wire. I'd say 1mm would come under this regulation. Any multiwire cable below 2.5mm I put a feral on. But I'm not aware of the physical difference.

 

[Michaelwgroves]

A rubber blind grommet wont stop any sort of fire, and regardless this is outside the scope of an EICR.

You are pulling up things that relate to workmanship (gas bond excluded) and adherence to BS7671. An EICR is solely to give an engineering view on whether an installation is safe for continued use.

For clarity, I am referring to 'Wylex Fire Retardant Membrane Cable Entry'

 

[davesparks]

For clarity, I am referring to 'Wylex Fire Retardant Membrane Cable Entry'

That still won't stop the spread of fire!

Fire retardent does not mean the same thing as fire proof!

 

[Michaelwgroves]

It's not the wrong size MCB and it's not poor workmanship.

16A 2.5mm radial has been the generally accepted standard supply for any small appliance such as a boiler for a long time.

Using a smaller MCB would be unusual and would be unlikely to give any selectivity with the 3A fuse for the boiler.

I'd not thought about, Selectivity, this is a good point. Saving myself doing the maths, what size MCB do you put on boiler circuit to achieve selectivity?

 

[Michaelwgroves]

Coarse stranded conductors do not need ferrules, fine stranded conductors do need ferrules or other suitable treatment at the end.

It is important to remember that the regulations do not require the use of ferrules, they require fine stranded cables to be suitably treated at their terminations. This can be achieved by using ferrules but this is not the only way.

I agree with your comments, but what is fine wire and very fine wire ?