Queries on main bonding

[Welsh_sparky_21]

Just want to know everyone’s approach to testing bonding within houses. I do a lot of EICRs, and I would say more times than not I can never get access to the water bond as the stopcock isn’t accessible. Now in this instance what I’ve been taught since my times been out is to test at any exposed copper, normally at the boiler. I would test from MET to the pipework and note my reading then I would disconnect the 10mm from the MET (with the power off) and the reading should go higher. There has been times but I’ve maybe had a reading of 0.12 ohms for example when doing the long lead test to exposed copper and then disconnected the 10mm which I’m assuming goes to the water from the MET and there’s been no change in the reading. When I’ve spoke with my boss he’s told me that it must be bonded as im getting this reading of 0.12, but is that right? Because surely if it was bonded when I disconnected the 10mm the reading would change? Just want to fully understand the ins and outs of bonding

 

[buzzlightyear]

 

[Vortigern]

At the boiler normally the water and gas all go together through a metal plate. In the old days you often used to see the pipes all bonded together for some unknown reason as they are "bonded" at the entry point into the boiler. Meaning, that if you disconnect what you assume to be the water bond, you will still have the gas bond connected via a paralell earth. I suppose the readings would be the clue as the resistivity of 10mm² is known and the length can be estimated. Which would at least give some clue as to what you are reading against the calculated ohms of the run. Dunno if that helps. If you disconnected the gas bond and measured then the water bond again you might get a better idea. This is assuming you are working in the dark so to speak as you cannot access the water bond? Then again you could always disconnect the earth at the boiler supply and get further clues. But a bit messy for an untimately unknown that you cannot confirm. If I get to the point that I cannot confidently say that the water is bonded then it is N/V which may give rise to F.I. If I don''t do that and there is a problem down the line then I am in trouble!
Just recently rewiring a refurb Victorian three bed the floow down was tiles through to the front. An concrete was under that with the old earth bond bare earth wire. The builders had to dig up the concrete and find the lead pipe coming in and put a hatch by the front door to access the clamp for the future. I appreciate that is not possible invariably.

 

[Joemile]

Just want to know everyone’s approach to testing bonding within houses. I do a lot of EICRs, and I would say more times than not I can never get access to the water bond as the stopcock isn’t accessible. Now in this instance what I’ve been taught since my times been out is to test at any exposed copper, normally at the boiler. I would test from MET to the pipework and note my reading then I would disconnect the 10mm from the MET (with the power off) and the reading should go higher. There has been times but I’ve maybe had a reading of 0.12 ohms for example when doing the long lead test to exposed copper and then disconnected the 10mm which I’m assuming goes to the water from the MET and there’s been no change in the reading. When I’ve spoke with my boss he’s told me that it must be bonded as im getting this reading of 0.12, but is that right? Because surely if it was bonded when I disconnected the 10mm the reading would change? Just want to fully understand the ins and outs of bonding

From my experience you are supposed to physically inspect both the gas & water bonding clamps to make sure they are correctly labeled with a warning tag and to make sure there is a 10mm cpc connected within at least 600mm of the stopcock/gas meter.

The reason your still getting a reading after disconnecting the 10mm could be that there is an older 4mm cpc present that you can't see, 8/10 times when I change a consumer unit there is an old 4-6mm bonding cable present in the property.

 

[Welsh_sparky_21]

At the boiler normally the water and gas all go together through a metal plate. In the old days you often used to see the pipes all bonded together for some unknown reason as they are "bonded" at the entry point into the boiler. Meaning, that if you disconnect what you assume to be the water bond, you will still have the gas bond connected via a paralell earth. I suppose the readings would be the clue as the resistivity of 10mm² is known and the length can be estimated. Which would at least give some clue as to what you are reading against the calculated ohms of the run. Dunno if that helps. If you disconnected the gas bond and measured then the water bond again you might get a better idea. This is assuming you are working in the dark so to speak as you cannot access the water bond? Then again you could always disconnect the earth at the boiler supply and get further clues. But a bit messy for an untimately unknown that you cannot confirm. If I get to the point that I cannot confidently say that the water is bonded then it is N/V which may give rise to F.I. If I don''t do that and there is a problem down the line then I am in trouble!
Just recently rewiring a refurb Victorian three bed the floow down was tiles through to the front. An concrete was under that with the old earth bond bare earth wire. The builders had to dig up the concrete and find the lead pipe coming in and put a hatch by the front door to access the clamp for the future. I appreciate that is not possible invariably.

Yeah that makes sense,

At the boiler normally the water and gas all go together through a metal plate. In the old days you often used to see the pipes all bonded together for some unknown reason as they are "bonded" at the entry point into the boiler. Meaning, that if you disconnect what you assume to be the water bond, you will still have the gas bond connected via a paralell earth. I suppose the readings would be the clue as the resistivity of 10mm² is known and the length can be estimated. Which would at least give some clue as to what you are reading against the calculated ohms of the run. Dunno if that helps. If you disconnected the gas bond and measured then the water bond again you might get a better idea. This is assuming you are working in the dark so to speak as you cannot access the water bond? Then again you could always disconnect the earth at the boiler supply and get further clues. But a bit messy for an untimately unknown that you cannot confirm. If I get to the point that I cannot confidently say that the water is bonded then it is N/V which may give rise to F.I. If I don''t do that and there is a problem down the line then I am in trouble!
Just recently rewiring a refurb Victorian three bed the floow down was tiles through to the front. An concrete was under that with the old earth bond bare earth wire. The builders had to dig up the concrete and find the lead pipe coming in and put a hatch by the front door to access the clamp for the future. I appreciate that is not possible invariably.

yeah that makes sense, I’d say more times than not I’ve never got access to the water bond, And im reluctant to start taking apart peoples bathrooms/kitchens to try find an earth clamp.

 

[Welsh_sparky_21]

From my experience you are supposed to physically inspect both the gas & water bonding clamps to make sure they are correctly labeled with a warning tag and to make sure there is a 10mm cpc connected within at least 600mm of the stopcock/gas meter.

The reason your still getting a reading after disconnecting the 10mm could be that there is an older 4mm cpc present that you can't see, 8/10 times when I change a consumer unit there is an old 4-6mm bonding cable present in the property.

Yeah I’ve seen that before