p.i.r report

[betty swollocks]

previous customer informs me that two new properties he has bought and had tests on have failed because of

1) no rcd protection for ground floor s/o - code 1

2) bs3036 fuses installed with 3.15KA psc - code 1

3) main earth conductor 10mmcsa - code 2

4) main supply tails 10mmcsa - code 2

5) equipotential bonding in 6mm - code 2

6) no mains smoke alarms installed - code 2

numerous code 4's, usual stuff, green cpc, etc

remedial work each house -

 

[Clouseau]

I would agree, a lot of sparks (perhaps less confident?) opt for code 1 & 2 when code 4 is more appropriate. It can be a bit like crying wolf, how do you differentiate between a live wire sticking out the wall and no rcd protection if they are both code 1?

Maybe work creation or maybe over the top niceic guidance, but customers deserve better.

 

[norv]

This might help a bit

Recommendation codes for the Periodic Inspection Report (PIR)

Code Observation

1 Requires urgent attention

 

[cheggers]

A very good post Norv

 

[Admin1]

Indeed it is a very good post - Thanks Norv.

 

[The Godfather]

This might help a bitRecommendation codes for the Periodic Inspection Report (PIR)

Code Observation

1 Requires urgent attention

 

[The Godfather]

Code 1 faults should be a real danger to the safety of an installation.

The lack of bonding is hardly a danger, especially when almost 35% of homes have none.

By default homes with boilers and immersion will bond the water and gas pipes (if the main bonds are not in place), this is not ideal because it relies on the cpc of the supplying conductors. How ever it does provide some protection.

(Where Ze and Zs on all circuits is well within limits, as per BS7671 tables)

The Godfather

 

[kme]

Though I understand your position on this GF, I have a similar list here, and I have always marked main bonds as a code 1.

Maybe if we all did that, 35% of those houses might have main bonds in place now?????

 

[The Godfather]

Though I understand your position on this GF, I have a similar list here, and I have always marked main bonds as a code 1.Maybe if we all did that, 35% of those houses might have main bonds in place now?????

Thank you KME.

It does look like we will differ on this point of view.

The Electrical Safety Council document on PIR codes also marks this a 2.

(I might also add, that this document is a collaboration of 7 organizations)

Don

 

[kme]

Thank you KME.It does look like we will differ on this point of view.

The Electrical Safety Council document on PIR codes also marks this a 2.

Don

Thank you.

The NICEIC insp, test & cert book (17th) gives it a code 1.

FYI

 

[The Godfather]

Thank you.The NICEIC insp, test & cert book (17th) gives it a code 1.

FYI

Who also contribute to the Electrical Safety Council document:

Periodic Inspection Reporting.

The Godfather

 

[steptoe]

tend to agree with the godfather on this,

NO main bonds isnt a code 1, it DOESNT produce a danger,

only if another fault should appear is it a danger, bit like a 6mm earth conductor,

NOT an immediate danger, tho requires improvement.

NO rcd is not a 1 either, it is only a danger if another fault arises.

code 1 is for an immediate danger, NOT if another fault arises to make the original observation dangerous.

 

[The Godfather]

tend to agree with the godfather on this,NO main bonds isnt a code 1, it DOESNT produce a danger,

only if another fault should appear is it a danger, bit like a 6mm earth conductor,

NOT an immediate danger, tho requires improvement.

NO rcd is not a 1 either, it is only a danger if another fault arises.

code 1 is for an immediate danger, NOT if another fault arises to make the original observation dangerous.

Thank you Steptoe.

My boys could only mark this a code 1 if other faults conspired to cause the lack of bonding to be a dangerous situation.

Don

 

[davetheglitz]

Very much in accord with the Don here. However perhaps someone can help me out with my understanding of bonding.

Main bonding is to ensure all metal parts stay equipotential if a fault outside the property introduces a potential into the house which could supply a high current (digger cutting through a supply cable and water main for example). Hence large conductor size. In principal a rare event and only in place until the supply fuse goes - hence no long line of bodies due to 35% having no bonding. As an aside this will also protect for internal faults like putting a nail through a cable and touching a pipe.

As the Don points out - any house with a boiler will be most likely cross bonded - so will provide the same level of protection as the main bonding for the more common internal fault.

Why then is it that when a service comes into the house in plastic, but then changes to metal we have to install main bonding with large conductors? There must be an electrical reason - but I can't see it myself!

 

[The Godfather]

Very much in accord with the Don here. However perhaps someone can help me out with my understanding of bonding....Why then is it that when a service comes into the house in plastic, but then changes to metal we have to install main bonding with large conductors? There must be an electrical reason - but I can't see it myself!

Well as far as TN systems go, 6mm main bonding is considered the mimumum size acceptable, any less should be replaced.

Dave don't forget we want to keep all pipwork at less than 0.05 ohms with respect to the incoiming earth, we also want to ensure that all heating and gas pipwork is at earth (cpc) potential.

ADS (automatic disconnection of supply, formerly eebads) relies on this somewhat.

As for the size of the cables, one must consider the high (short term) faults currents that can occur, prior to the removal of fault current.

The Godfather

 

[davetheglitz]

Well as far as TN systems go, 6mm main bonding is considered the mimumum size acceptable, any less should be replaced.Dave don't forget we want to keep all pipwork at less than 0.05 ohms with respect to the incoiming earth, we also want to ensure that all heating and gas pipwork is at earth (cpc) potential.

ADS (automatic disconnection of supply, formerly eebads) relies on this somewhat.

As for the size of the cables, one must consider the high (short term) faults currents that can occur, prior to the removal of fault current.

The Godfather

A appreciate what you are saying here with the 0.05 ohms - but consider this another way. If the incoming pipe is plastic then potential cannot be introduced from outside - so we are only concerned with a fault within the house.

In a domestic situation the worst case fault would be from the shower cable to a pipe at say 50A. The concern now is that that the 50A breaker would trip within the required time. We are now looking at R1 + R2 at the fault do decide the switch off time. This is no different to a line to earth fault at the shower. So if the cpc in the shower cable was adequate to cause the breaker to trip - then the bonding from a substantial copper pipe to the earth terminal only needs to be as large as the largest cpc to give the same effect - i.e much smaller than the main bonding recommended.

We are only looking at very small fault currents in this case - whereas an outside fault could be in the kA range.

 

[The Godfather]

A appreciate what you are saying here with the 0.05 ohms - but consider this another way. If the incoming pipe is plastic then potential cannot be introduced from outside - so we are only concerned with a fault within the house.... ..We are only looking at very small fault currents in this case - whereas an outside fault could be in the kA range.

Good points Dave,

But Main Bonding works both ways (internal & external) and we cannot rely on the CPC alone.

Consider a fault scenario, where the CPC is broken (over time, bad workmanship etc) and the copper pipework (plastic incoming) is not bonded.

And for arguments sake is 10 ohms wrt to the MET.

Under a serious fault condition where the copper pipework becomes live, there will be a considerable Voltage rise and worst the MCB supplying the fault may not trip in a 'reasonable time' if at all (in this example).

We know have the potential for electrocution on all pipework

Don

 

[kme]

Good points Dave,But Main Bonding works both ways (internal & external) and we cannot rely on the CPC alone.

Consider a fault scenario, where the CPC is broken (over time, bad workmanship etc) and the copper pipework (plastic incoming) is not bonded.

And for arguments sake is 10 ohms wrt to the MET.

Under a serious fault condition where the copper pipework becomes live, there will be a considerable Voltage rise and worst the MCB supplying the fault may not trip in a 'reasonable time' if at all (in this example).

We know have the potential for electrocution on all pipework

Don

Further, it may also be worth noting that, while a plastic pipe does not introduce an external potential;

THE SUBSTANCE WITHIN THE PIPE MAY DO!

i.e. water, the resistance of which varies around the country, according to hardness, alkalinity etc.

 

[davetheglitz]

Hi Martyn,

I don't know what they pipe into your house - but i sure as hell hope it doesn't conduct to any extent as it will be undrinkable - but you never know!

 

[steptoe]

DIGGERS CUTTING THROUGH CABLES??????

unthinkable, it just NEVER happens?!!!!!

does it????

re my previous posts on the dangers of PME.....

code 1s are still onl;y applicable if the observation constitutes a danger WITHOUT any external/other influence.

NOT purely on its own.

you could almost say NO earth only makes 'requires improvement' as on its own there is no danger until a fault occurs.(?)

discuss......