not another earthing question

josey · 6 Dec 2004

sorry i know....but

i've just fitted a chrome "ladder" type towel rad, i cant find any specific earth clamps to attach to the rad itself,( and they would like a **** anyway), is it acceptable to just bond to the two pipes supplying it.

JerryD · 7 Dec 2004

It would be unlikely that the towel rail wasn't earthed if the pipes are supplementary bonded as the rad valves connect the pipes to the rad and there is metel to metal contact here.

So in answer to your question, I would not earth the rad other than through the pipes (purely for appearance sake). Whether or not this complies with regs is a debatable point. Look in the OSG page 30, it shows bathroom supplementary bonding which obviously includes the heating pipes but the rad is quite clearly not separately earthed.

It is assumed that your house has all the normal earthing and bonding too.

ban-all-sheds · 7 Dec 2004

PTFE tape?

josey · 8 Dec 2004

why the remark ban, are you suggesting the use of ptfe tape on the fittings would remove the continuity from the pipes to the rad ?

andy · 8 Dec 2004

josey said:
are you suggesting the use of ptfe tape on the fittings would remove the continuity from the pipes to the rad ?

yes

plugwash · 9 Dec 2004

can the radiator introduce a dangerous potential into the special location?

if the radiator is fed by metal pipes which are bonded then the answer to that is obviously no even if the radiator doesn't have a good connection to the pipes

therefore there is no more reason to bond it than there is to bond a metal tap with a plastic connector

JerryD · 9 Dec 2004

Yes, you can't have it both ways, either the pipes do create an earth to the rad through the valve connection threads, in which case the rad is bonded.

But if you're saying the ptfe stops the rad from being earthed then surely this ptfe is also isolating the rad, stopping it from introducing a potential.

You can't have one without the other.

ban-all-sheds · 9 Dec 2004

But what if a layer or two of PTFE tape, forced into the threads, creates a partial connection. Not a good one, and not isolated, either, but a low enough resistance for it to be capable of introducing a potential?

As I sit here, the plumber is clattering and humming away in the bathroom, and I'm thinking - what shall I do about bonding my new towel rail? It's dual fuel, and the electric element is Class I, so I think I'll call it's cpc the bonding conductor. I sure as **** don't want a bit of g/y clamped to it.....

kendor · 9 Dec 2004

I still question the answer made by others that the water inside the pipes cannot introduce a hazard, I don't believe that the water is pure enough not to be conductive and therefore a potntial difference can occur and therefore to gain an equipotential zone one must bond all extraneous metalwork, i'm sure others would disagree but as far as i'm concerned if all metalwork is at the same potential in the zone then you are less likely to get a hazard as there will be no potential difference for current to flow. an earth taken behind and crimped to the supporting plate of the rail would be hidden behind rather like the hidden earth in the back of a switch.
proof of the pudding possibly? //www.diynot.com/forums/viewtopic.php?t=17796

ban-all-sheds · 9 Dec 2004

kendor said:
I still question the answer made by others that the water inside the pipes cannot introduce a hazard, I don't believe that the water is pure enough not to be conductive and therefore a potntial difference can occur

Well if you read the research done you'll see that even water with a double-dose of inhibitor has a resistance of over 20kOhms/m (15mm²). If we assume a worst case resistance for a body of 250 ohms, and a maximum current of 10mA, we need the water to drop 227.5V at that current, i.e. a resistance of 22.75kOhms. IMHO anything over, say 1.5m is good enough isolation. Less than that? - take a sample of your CH water and measure it.

an earth taken behind and crimped to the supporting plate of the rail would be hidden behind rather like the hidden earth in the back of a switch.

Most towel rails are of fairly open construction and are mounted on spacers away from the wall. No concealed brackets. e.g.

BTW - I do like the magic invisible pipes and valves that they've used...

brown-nought · 9 Dec 2004

I thought you were going to tell us that's your new remodelled bathroom B-A-S.

ban-all-sheds · 9 Dec 2004

No - but I am having one of those towel rails (a bit shorter though). But the pipes and valves will show.

And I can just get the FCU for the electric element into Zone 3....

andy · 9 Dec 2004

JerryD said:
But if you're saying the ptfe stops the rad from being earthed then surely this ptfe is also isolating the rad, stopping it from introducing a potential.

may i remind you of the shelf which killed a MP's daughter

plugwash · 9 Dec 2004

isolated metal objects drilled into live cables are supposed to be prevented at the design stage........

if you consider the remote possibility of drilling into a badly placed cable to be nessacery they you would be bonding everyw single bit of isolated metalwork in the room

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not another earthing question

josey

josey

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