Confessions of an Electrician...

Well, there are many thousands of water heaters in domestic use in the UK that use an un-insulated element in direct contact with the water flowing through them and considered to be the best brand you could buy.........................


Regards


BOD

really ? I'm not aware of any where a  live element contacts the water Ive only seen designs with earthed metal sheaths in the UK.. 

Direct contact won't work with an RCD.

Yes I was thinking that. Except perhaps the old Dolphin showers - string pullcord switching a toggle switch inside the shower unit?

Alasdair Anderson:

Denis McMahon:

Thanks, Alasdair.......could you quote the text of 554.2.1 please?

Denis,

All it says is:
554.2.1 Every heater for liquid or other substance shall incorporate or be provided with an automatic device to prevent a dangerous rise in temperature.

As you can see there is nothing about electrical protection or isolation.

Alasdair

 

Thanks Alasdair. I have played through the "suicide shower" video again. It seems that the shower contacts are pressure operated through the diaphragm. I am concerned that if there were air bubbles in the water supply a situation could arise whereby the shower was under pressure but the heating elements were surrounded by air, which would not readily escape downwards, hence overheating.


The instructions specify resistivity of the water. I am not impressed. It would take more than a simple test meter to check this. It would need laboratory equipment whereby current was passed through a tube of water of specified length and uniform cross-section area. And is the water in South America quality assured for resistivity? I don't think it is in the UK; I've never seen any reference to resistivity on my water account.


The use of a bare earthed wire to keep the water output at earth potential seems woefully inadequate. I could have hoped, at least for something like an earthed coarse wire net filter through which the water passed.

There used to be an electric shower manufacturer here in  Worcester that made electric showers that were not electrically insulated, hence the old practice of running a main earthing conductor to the shower as well as the circuit protective conductor.


As Bod passed comment the requirement to install a RCD finished off that type of shower, though I still occasionally see them in old bathrooms that have not been updated for many years.


You may be surprised to see some of the old electrical equipment that is still in use or still in place awaiting replacement.


Andy Betteridge

We had a Dolphin electric shower at my old house it was protected by a 30 amp switch fuse and yes they ran an extra earth wire to it. We thought we were so posh! I don't remember if they updated the supply company's fuse  or not but guess they must have

really ? I'm not aware of any where a  live element contacts the water Ive only seen designs with earthed metal sheaths in the UK.. 


As posted above, Dolphin showers used to be of this type and 15th edition 554-28 to -30 stipulated additional wiring requirements.


The design had the "live" end of the bare immersed heating element connected to the incoming water and the neutral to the heating element at the exit end.


Regards


BOD

The Dolphin were a great big case. As I mentioned a toggle switch operated via a string type cord to push/pull and a great big perspex block that had a long coil in it - that was the heating element. They were big numb things even back then but quite popular and not cheap.

 30A jobby and it was often discovered some were wired into an adjacent 13A socket in the nearest bedroom. Ohh dear - but they worked and probably went on like that for years.


I once ordered a replacement element for one. A few days later a "rep" turned up with one to my business premises asking about a very large electrical contracting company = me (I was not in and I shared my humble workshop with a couple of furniture manufacture/repair guys).

Halicon days, I must have impressed the tec guy when I ordered the spare. LOL.

Immersion heaters with failed insulation don’t pack up immediately, if there isn’t an RCD they will carry on working until after the has been a major insulation failure.


Andy B

Quick confession as this post slips down the forum.


Last week a job I was going to do in West Wales was postponed, but I had already booked a guest house at the back of Tenby as it was too far to go to do the job and get back home in a day.


So we went to the guest house anyway and tagged the rest of the weekend on as well at hotel in the town itself, rather than losing half the money I had paid for the guest house and trying to fit another two days work in.


Sometimes it's just easier to let life happen rather than planning it meticulously.