Boiler upgrade no earthing present

[Lee85]

Hi All,

Had a job today to connect an upgraded boiler and replace existing controls. Installed bonding as none present.
No earth coming from supply cable and no earth rod.
3036 board and no RCD any where.
Normally I would recommend installing an earth rod, fitting a small garage unit with an RCD main switch and say 16a mcb and running a new circuit in for the boiler and controls. Then issuing an EIC stating that consideration should be given at the earliest oppurtunity to RCD protect the rest of the house.
On this one though the boiler is on its own 15a radial and the FCU is adjacent to the board (as is the programmer). I have already fitted a second isolator for mechanical maintenance next to the boiler which is elswhere.
Rather than messing about fitting a second DB do you guys think it would be ok to just replace the FCU with an RCD type and stick a rod in? Obviously the same recommendation regarding the rest of the installation would be recorded on the cert. I can't really see a problem with it as everything I have worked on/installed is RCD protected and it is only the short bit of 2.5 from the board to the supply side of the FCU that isn't any way.
Any advice welcome.

 

[Welchyboy1]

The circuit you have worked on has no effective fault protection before your rcd, and the basic tt system is not considered compliant with no upfront rcd protection(unless you have a REALLY low ra value) so you cant really issue a compliant cert can you!

Can you not install an upfront 100mA for the whole board, if only for the time being, then get the system upgraded to a pme if availiable?

your other option of installing an additional cu with an rcd and new circuit is also a bit of a cop out IMO and i would still opt to protect the existing board with a 100ma rcd and rod instead

 

[Richard Burns]

When you say there is no earth coming from the supply cable does this mean the supply cable has no earth capability or that there is no measurable earth connection.
If it is the latter then the DNO need calling to repair their earth.
If it is the former then you cannot work on the installation without ensuring that the earthing and bonding are adequate.
Before you start work you need to inform the customer that there is no means of earth protection on the installation and that this needs to be addressed before electrical work can be undertaken.
The hazards of not having any earth protection should also be advised.

However you must ensure that you have your information correct before this so that you are not missing an old earth rod / rcd connection that has become disconnected.

 

[Lee85]

Thanks for the replies lads.
Richard, No, there is no earth rod or rcd at the minute.
There is no earth coming from the service head or sheathing. The DNO just give there usual response: If an earth is provided we will maintain it free of charge but if there isn't one we will charge. Alternatively the customer can install an earth rod and RCD.
Welchyboy; agreed in an ideal world I would rod and fit an 100mA RCD to cover the whole installation. I am just anticipating the N-E fault on one of the other circuits that will inevitably be there. I think I will do a quick L&N together to earth at 250v and see if there are any shorts, if so put in a second DB for my circuit only as stated in my OP.
Regarding my original question. Yes, I know not a great idea I suppose, was a bit late last night and I was looking for an easy out! Just got to thinking: What is the difference between 6 inches of 25mm tails feeding a DB that aren't RCD protected and six inches of 2.5mm feeding an RCD FCU!!

 

[telectrix]

difference is about 6" of 22.5sq.mm.

 

[wiganspark]

so youve done the install of these controls and the property has been left with no earth?

 

[Des 56]

so youve done the install of these controls and the property has been left with no earth?

No,I would say
It appears he has upgraded controls to an existing circuit and whilst testing the modification,he has become aware of earthing problems that he is now addressing

He is seeking opinion on the best course of action to remedy the existing deficiencies (which admittedly)he would have been best to check initially,but how many times are we caught by the £30 job requiring us to insist on a £300 job to actually carry it out

 

[Lee85]

Actually as soon as I arrived on site I saw that it was without an effective means of earthing, testing confirmed this. This was the first time I had seen the existing installation and up to that point had no other information about it.
The controls were dead when I arrived on site; the gas engineer had removed the 3a fuse from the FCU so he could safely strip out and replace the boiler.
I have replaced the controls and connected up the boiler ready to energize and complete testing and certification once this issue re earthing has been resolved.
I won't be livening anything up that I have installed until I am happy it safe to do so.

 

[Lee85]

difference is about 6" of 22.5sq.mm.

hahaha!!