Immersion Heaters

[johnny_t]

Wasn't sure whether this was electrics or plumbing, but here's my tale...

I have a central heating / hot water system, whereby the boiler does it's stuff and heats up the water in the hot water tank. Not sure what that systems is called, but it's the old 'normal' one. Throughout last night, the boiler was continually locking out. You could restart it, and it would go for half an hour or so, and then go off again. No worries, I have 24 hour home emergency cover via Swinton. They've passed me on to Help-Link and they are ready to swing into action and come and see me urgently sometime between eight and five on Saturday.

So, in the meantime, I need hot water. My tank has an immersion heater, which goes via flex to a switch, and then there is a wire from the switch disappearing off below the floorboards. However, ever since I moved in 12 years ago, this feed to the switch has not been live. I suspect the live feed was nabbed for the shower pump, and they decided they could do without an immersion.

My plan is, to get me out of a pickle, to disconnect the flex from the switch, stick a plug on it, and plug it into an extension lead. It's not pretty, but will get me out of a hole for two days.

So, here's my questions:

1) Any obvious flaw in that plan ?
2) Assuming the immersion worked when it was disconnected, is there any inherent reason why it may have 'gone off' in the interim and no longer work ?
3) Beyond MCBs and RCDs tripping when I switch on, is there anything I should look out for when it is heating up ?
4) What's the worst that can happen ? Can I, for example, boil it all up and explode my tank or anything like that ? I might opt for periodically resetting the boiler instead if that were the case.

 

[muggles]

It'll be fine, provided your extension lead is rated to take 3000w continuously. If it isn't, things will get a bit melty. You'll almost certainly need to unwind it completely from the reel as well. As for the temperature control on it, without being able to see it it's impossible to say whether it's got a safety cut-out on it or not

 

[johnny_t]

Thanks,

I'm not at home at the moment, so am just getting the plan straight in my head for when I get there...

 

[stardanny]

Best to ask it in Electric Forum.

Mod, please can these be move to Electric Forum as I think there is the best place.

Daniel.

++++++++++++++++++++
please use the blue "report" link to request a move.

You'll be lucky if a mod happens to read every post on every thread
+++++++++++++++++++++

 

[muggles]

Nothing wrong with it being here - I've never seen an electrician fit an immersion heater!

 

[Taylortwocities]

As above. Extension reel cables have two ratings (usually writen on the reel. Wound up the rating will be not very much. The full rating can be achieved if the extension lead is fully unwound. If you do not unwind the reel it will heat up, melt, catch fire etc. I have seen it happen.

Assuming the immersion worked when it was disconnected, is there any inherent reason why it may have 'gone off' in the interim and no longer work ?

Immersion elements do degrade over time (they are immersed in water, after all.) The element can corrode but you'll find out when you turn it on. As you say, the worst that can happen is RCD tripping/fuse blowing.

Re

I suspect the live feed was nabbed for the shower pump,

The circuit should be plenty to power the pump and the immersion. You should think about re-instating it, and testing the immersion periodically. There's no point having an emergency standby system that does not work.

 

[Taylortwocities]

Nothing wrong with it being here - I've never seen an electrician fit an immersion heater!

And, Muggles, I have seen plenty immersions installed by plumbers that are a complete disaster!
Did you know that sometimes they even disconnect the immersion supply to power a shower pump!

 

[JohnD]

Nothing wrong with it being here - I've never seen an electrician fit an immersion heater!

but I think this is a question about connecting electrically, not about using the big spanner and getting wet.

 

[EFLImpudence]

I've never seen an electrician fit an immersion heater!

Of course not, why would you be there?

 

[johnny_t]

Sooo..As you'd expect with an intermittent fault, it is now working fine

I've taken the opportunity to fit the plug anyway. I measured some resistances and am getting 18 Ohms on the coil, which is good. I'm getting infinite between Live and Neutral inputs but, I'm guessing that is because the tank is hot and that will change when it cools ?

Hopefully it'll play up again before the man comes

 

[Taylortwocities]

. I'm getting infinite between Live and Neutral inputs but, I'm guessing that is because the tank is hot and that will change when it cools ?

Yes, the thermostat will open when the water reaches temperature.
The test will be to measure if there is any resistance between earth and the neutral and/or live connections on the element. You would need an Insulation Resistance tester to do this properly as you are looking at resistances in the millions of ohms. That will determine if the element casing has corroded.