Immersion heater - elements wired the wrong way around?

[Spark123]

Yep - the supplementary bonding didn't need to be carried out in the cupboard - that was just one option available to the sparky.
Are the pipes in the bathroom copper?
If they are copper are there any pipe clamps on the pipework in the bathroom or nearby with "BS951 Safety electrical connection do not remove" tags on them?

 

[st07]

I've never looked, but I will certainly check the next time I'm around there.

On another note. is anyone else shocked by the shoddy design of the heating element cover? Ours doesn't appear to have any kind of cable grip so the strain is put on the three cores. Also, the stranded cable seems to become 'shredded' by the screwing action of the element connectors, reducing current carrying capacity and presumably causing the 'burn' marks on the live cable.

Is there any better way of securing the cable and indeed, would it be recommended to use some solid core cable such as T&E?

 

[RF Lighting]

No you mustn't use T&E.

Immersion heaters get hot, and you must use a heat resistant cable such as butyl sheathed flex.

Normally there is a cable grip built into the heater or the cover. Maybe yours has become damaged or discarded?

The screws shouldn't damage the strands of the flex. If it is really bad you could terminate the flex into a ring crimp, and then screw through that, but you would need a pair of ratchet crimpers to fit these.

 

[st07]

Interesting. I may purchase some better cable then. I wouldn't use a ratchet crimp as I don't really like crimps What are your views on bending cable over insulation, then screwing in? I'd imagine it would give the cable a bit more 'strength' in the terminal, reducing the strain which may be causing the strand damage?

Both covers show no signs of ever having a cable grip I'll have to sort out a grip of some sort though, not really happy with the cord dangling by the three cores only.

 

[RF Lighting]

What are your views on bending cable over insulation, then screwing in?

I'm not really sure what you mean by that.

 

[st07]

Strip a cable, then bend the copper core backwards over the sheath, then place the sheath/core in to a terminal.

 

[RF Lighting]

Ohh no no no no.

This will give you a high resistance joint, which will overheat and burn up the wire, and ultimately fail.

It is especially bad in something like an imm. heater as it is a reasonably heavy load, and will often be drawing power for a good few hours which will rapidly destroy a bad joint.

Could you post a picture off the imm. heater with its cover off. I'm not sure why you are having problems. I'm wondering if there is something missing. There is normally a sort of square washer with two bent over ends, and sometimes a spring washer on the element terminals.

It should be in this order:

Screwhead, spring washer, square washer, wire, element (the threaded flat bit which the screw goes into)

 

[st07]

Cool, I'll get a picture for you the next time I'm over there, most likely Friday

 

[plugwash]

Strip a cable, then bend the copper core backwards over the sheath, then place the sheath/core in to a terminal.

bad idea, likely to lead to a high resistance joint if there is any movement (and high resistance joints lead to stuff burning up)

Some strand damage is normal with screw terminals. One way to reduce it is to tin the end of the wire with solder first.

 

[Adam_151]

solder in a screwed joint is a bit of a no no as well though isn't it?

 

[Taylortwocities]

Why is that? Much the same as a ferrule, I would have thought.

 

[Adam_151]

The constant pressure of the screwed joint will cause the solder to slowly creep at room temperatures over the years (remember that 60/40 melts at somewhere around 200 degress celsius if memory serves) leading to a bad connection over time

 

[st07]

Right then, I've decided to replace the 'boost' switch with a timed boost switch, the Horstmann E30 to be precise.

I take it I can't simply replace the existing switch with the E30 as the E30 has no switch or whatever to disconnect the two poles. Would it be OK to take a feed from the existing switch, up to the E30, mounted in a patress box above, then from E30 to immersion heater?

Many thanks!

 

[Taylortwocities]

I guess you are going to use that just as a boost on the 24hour immersion?

You'll still need to keep the DP switch/ You'd be better using the one I recommended previously - gives you controls for both off peak and boost.
Its up to you if you dont want to spend the extra £30......

Re timing. have a look at one of these. made for the job
http://www.tlc-direct.co.uk/Products/HOELEC7.html[/QUOTE]