Given that on Xmas Eve was called out to yet another example of an electric shower isolator burning off it's neutral at the terminal, is it time to cease fitting isolators for the likes of ovens and showers?
Can we not just isolate in the consumer unit instead?
From what I have seen, there isn't an isolator of sufficient quality on today's market which is capable of carrying out it's function without burning out during normal service.
Compliments of the Season to one and all.
Good point about the risk of losing one half of a duel rcd board in the event of a dead neutral and cpc coming together at the shower end.
The actual isolator took some finding, it being sited low down and behind a heavy wardrobe on the wall dividing the bathroom from the bedroom!
This is not uncommon, with cooker isolators buried in kitchen cupboards behind jars and plates, or not even fitted at all.
In terms of improved accessory quality? I would say that this is well beyond our scope of control as installers. You can only tiddle with the willy you've been given!
Maybe this is where the various doyens of the BS7671 committees should be directing their ire. A new resolution is required. "The committees JPLE64/BS7671/IEC et al shall cease the practice of treating symptoms and instead shall focus upon detecting and remedying root causes".
I've had a lot of experience with this, having worked for a Social Housing provider for a year. Yes, burnt out shower pull switches are common. I'd say 20+ per year in the area I worked in. That'd be around 4000 houses total, around 50% had electric showers, so the percentage is low, around 1%, but that is higher than I would expect.
At first, I put it down to poor installation when fitted, but that changed when I got called back, after 3 months, to one I had fitted. It was burnt at the neutral.I gave them a really good twist when tightening the screws, but subsequent experiments with a loose piece of 10mm T+E and a switch showed that the cable was twisting slightly when the plate was tightened to the box, and the cable was coming loose. The cables are so stiff that they cause the problem, in that it is difficult to tighten them enough to counteract the twisting/crushing motion when fixing it onto the backbox.
The switches with 2 screws on the terminals are far better. The round Cradtree ones are a better, slightly larger, unit, though cannot be used close to walls, so not suitable for many existing cables.
Cooker switches - very few of the wall mounted switches (40A+) ever got changed, Their internal profile makes them very similar to the 45A shower pull switches, but, I think the main point, they dont get turned on/off as much. The majority of shower switches were turned off when not in use.This adds in vibration each time the switch is used, so could add to the loosening.
Another accessory that was a regular 'burn out' was washer and dryer outlets. Usually an unswitched single socket outlet below the worktop. I almost always put this down to poor quality plug tops on the appliance. The Line feed would always burn, melting the plug top and ruining the socket outlet. Of course, the Tenants would always blame the socket, as their washer was only 6 months old!
Usually an unswitched single socket outlet below the worktop. I almost always put this down to poor quality plug tops on the appliance. The Line feed would always burn, melting the plug top and ruining the socket outlet.
Definitely not a new thing with socket-outlets directly behind appliances (and hence I have none located there in my kitchen). I think in this case, if the appliance being pushed up against the back of the plug, there's not enough room for the heat that builds up in the fuse to escape, so this overheats the line pin in the plug, and/or the socket-outlet. (Neither the plug nor the socket-outlet are tested with an appliance butted up against the plug).
If my assertion as to overheating is correct, the "root cause" could be considered to be one of the following:
(I have not listed a problem with the tests in BS 1363 product standards, given that the appliance manufacturer's instructions noted in 1. is a valid argument for the product standard.)
Should a shower isolator have a pull cord? Surely just a switch attached to the ceiling or on the wall near the ceiling would be better? Accessible enough for a plumber, inaccessible enough not to be turned back on by accident (e.g. by someone thinking it's the light switch). And it would disabuse householders of the notion that they're supposed to turn it off after each shower use. And once RCBOs become more-or-less universally double-pole switching, perhaps shower switches can be consigned to the annals of history?
Should a shower isolator have a pull cord? Surely just a switch attached to the ceiling or on the wall near the ceiling would be better?
That depends who the intended user of the isolator is. If it's the user of the shower, rather than the plumber, then not really.
The instructions often, however, tell users to make sure the shower is switched off at the isolator when not in use (as well as requiring one is installed). In which case, it's not really a BS 7671 issue and would have to be taken up with the manufacturer.
The instructions often, however, tell users to make sure the shower is switched off at the isolator when not in use (as well as requiring one is installed). In which case, it's not really a BS 7671 issue and would have to be taken up with the manufacturer.
Then perhaps the shower manufacturers should supply a suitably robust isolator as part of their kit?
Then perhaps the shower manufacturers should supply a suitably robust isolator as part of their kit?
That does, of course, assume that the isolator is always the cause (rather than the symptom).
If it's something else other than the isolator, then the a symptom could be moved somewhere else (cable damage, or damage to other products ... possibly fire) - even if we over-rate or over-test the isolator.
Given that shower isolators are prevalent and a handy means of switching at the bathroom; there are probably many that give satisfactory service, I suggest that the problem is with limp wristed installers or the switch location being covered up with excess, thermal insulation. The ones that simply switch pressure pumps are probably most troublefree, having a lower current rating.
Jaymack
Well, I went to CEF (only buggers open this week) and picked up a Click isolator - no 2 screw option though, only a single screw for each terminal. I fitted the thing but am forecasting that it won't be long before I have to go back and fit another. Shower is a Mira jobbie but I couldn't find the KW rating label on it anywhere. All I know is that it was fitted roughly 9 months ago.
A resistance measurement of the elements might have given a fair indication. There does seem to be some corelation on the few I`ve tested, enough to hint at an estimation anyway.
In fact I did the measurements of a couple of 3 element types and noted some kind of corelation as being "within the parish" sort o` speak. The reason I was doing it was to calculate a reconfig to put elements in series to get an idea of the likely resulting KW for a lower power in line water heater jobby.
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