replacing immersion heater

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Adam Funk

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Feb 8, 2012, 10:08:15 AM2/8/12
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I need to replace the immersion heater in a traditional hot-water
cylinder (with a cister and a coil heated by the boiler). The
existing model is labelled "HEATRAE GOLD DOT / 2.3--3 kW / 210--240 V
AC ONLY / LENGTH 27" FIXING V". (The element was installed at least
17 years ago.)

I see from googling that the Heatrae Gold Dot product in 27" size
still exists. Can I buy one, safe in the knowledge that the thread
will be the same? (In other words, I won't get a nasty surprise when
I've drained the hot water & unscrewed the old element, & am about to
try putting the one in. I'd really prefer not to have to leave
everything hanging open while I cart the old element to a shop for
comparison.)

Also, are there any tricks for getting the water level in the cylinder
below the fitting for the element? Or do I just shut off the water to
the cistern, run as much water out of the hot system as I can, and
then mop up what runs out when I unscrew the old element?

Thanks,
Adam

Tim Downie

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Feb 8, 2012, 10:24:41 AM2/8/12
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Most HW cylinders will have a drain cock tucked away at the bottom somewhere
but not always. It's a good idea to have the cylinder *full* of water
before attempting to unscrew the old element though, it may require a lot of
force and having the cylinder full of water makes it more rigid and less
prone to damage.

If you can't find a draincock I think you just have to shut off the supply,
drain what you can and have some towels handy. You could disconect the
pipework at the top and syphon water out with a hosepipe but I suspect that
is overkill (assumming the element is inserted down from the shoulder at the
top of the cylinder).

Tim

Newshound

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Feb 8, 2012, 10:34:21 AM2/8/12
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On 08/02/2012 15:08, Adam Funk wrote:
> I need to replace the immersion heater in a traditional hot-water
> cylinder (with a cister and a coil heated by the boiler). The
> existing model is labelled "HEATRAE GOLD DOT / 2.3--3 kW / 210--240 V
> AC ONLY / LENGTH 27" FIXING V". (The element was installed at least
> 17 years ago.)
>
> I see from googling that the Heatrae Gold Dot product in 27" size
> still exists. Can I buy one, safe in the knowledge that the thread
> will be the same? (In other words, I won't get a nasty surprise when
> I've drained the hot water& unscrewed the old element,& am about to
> try putting the one in. I'd really prefer not to have to leave
> everything hanging open while I cart the old element to a shop for
> comparison.)
>
> Also, are there any tricks for getting the water level in the cylinder
> below the fitting for the element? Or do I just shut off the water to
> the cistern, run as much water out of the hot system as I can, and
> then mop up what runs out when I unscrew the old element?
>
> Thanks,
> Adam

AFAIK the thread hasn't changed in a very long time. The problem with
draining is that the DHW supply normally comes from the top with the
cold feed to the bottom. Not usually much spillage with a top entry
element; you *do* have a wet and dry vacuum cleaner, don't you? If the
element is side entry at the bottom, you need to hope your plumber
fitted a drain cock on the cold feed.

TMC

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Feb 8, 2012, 11:37:18 AM2/8/12
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"Newshound" <news...@fairadsl.co.uk> wrote in message
news:9pfivp...@mid.individual.net...
> On 08/02/2012 15:08, Adam Funk wrote:
>> I need to replace the immersion heater in a traditional hot-water
>> cylinder (with a cister and a coil heated by the boiler). The
>> existing model is labelled "HEATRAE GOLD DOT / 2.3--3 kW / 210--240 V
>> AC ONLY / LENGTH 27" FIXING V". (The element was installed at least
>> 17 years ago.)
>>
>> I see from googling that the Heatrae Gold Dot product in 27" size
>> still exists. Can I buy one, safe in the knowledge that the thread
>> will be the same? (In other words, I won't get a nasty surprise when
>> I've drained the hot water& unscrewed the old element,& am about to
>> try putting the one in. I'd really prefer not to have to leave
>> everything hanging open while I cart the old element to a shop for
>> comparison.)
>>
>> Also, are there any tricks for getting the water level in the cylinder
>> below the fitting for the element? Or do I just shut off the water to
>> the cistern, run as much water out of the hot system as I can, and
>> then mop up what runs out when I unscrew the old element?
>>
>> Thanks,
>> Adam
>
Not done one of those in years

Hated the job with a passion

When I did do them getting the old ones to unscrew without trashing the tank
was the real challenge

As to getting water out after shutting the water off this can only be done
by a drain on the cold water bottom feed which was usually on the side of
the tank rather that at the front. And often the airing cupboard was built
around it afterwards

Hot water storage tanks force the hot water out of top when a tap is opened
due to the header tank being connected to the bottom

Best of luck

Regards

Syd

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Feb 8, 2012, 11:54:49 AM2/8/12
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"TMC" <an...@nowhere.co.uk> wrote in message
news:74KdnSmvprdcOa_S...@bt.com...
water off at mains, drain thro hot taps till they stop. Disconnect wiring
(safely), hammer and chisel and knock the edge of the nut of the heater till
it moves then unscrew with immersion spanner. Refitting with a small amount
of sealant on the fibre washer and nip up with spanner. Reconnect refill and
check for leaks.


harry

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Feb 8, 2012, 12:23:44 PM2/8/12
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Immersion heaters have a 2&1/4" BSP thread. With very few exceptions
they have been like this for 60 years to my knowledge. There are lots
of makes. As long as it's the same size (3Kw, 27"), it will be OK.
The stainless steel ones last longer but cost more.


The best advice is when you come to unscrew it,don't put too much
pressure on the spanner. You will ripple the tank.

Get a hacksaw blade, tape the end up for a handle and saw the big
washer through all the way round. (You will feel it skidding on the
metal when you get through.)
Clean up the face of the flange before you put the new one in. Best
put a bit of plumbers mate on the new washer.
Fill the tank before you switch on. They last about 30 seconds
without!

Michael Chare

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Feb 8, 2012, 4:10:21 PM2/8/12
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Yes, I got mine out once, but I then had to change the tank anyway, and
it was impossible to get the element out a 2nd time.


--
Michael Chare

Adam Funk

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Feb 9, 2012, 7:15:25 AM2/9/12
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On 2012-02-08, Newshound wrote:

> AFAIK the thread hasn't changed in a very long time. The problem with
> draining is that the DHW supply normally comes from the top with the
> cold feed to the bottom. Not usually much spillage with a top entry
> element; you *do* have a wet and dry vacuum cleaner, don't you?

No, but I have lots of old towels and rags. ;-) I checked and the
element's fitting is really close to the top of the cylinder, so even
if I can't find a drain cock, I don't think a lot will run out.


> If the element is side entry at the bottom, you need to hope your
> plumber fitted a drain cock on the cold feed.

I haven't found the drain cock yet, but the airing cupboard is rather
tight and I haven't rummaged thoroughly.

Adam Funk

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Feb 9, 2012, 7:16:44 AM2/9/12
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Thanks. I agree about having the cylinder mostly full to keep it
heavy and stable.

tony sayer

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Feb 9, 2012, 3:08:38 PM2/9/12
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>> If you can't find a draincock I think you just have to shut off the supply,
>> drain what you can and have some towels handy. You could disconect the
>> pipework at the top and syphon water out with a hosepipe but I suspect that
>> is overkill (assumming the element is inserted down from the shoulder at the
>> top of the cylinder).
>
>Thanks. I agree about having the cylinder mostly full to keep it
>heavy and stable.

Do go easy when you come to undoing it its very easy to rip a copper
cylinder if you apply a bit too much torque to the spanner;!!...
--
Tony Sayer

Newshound

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Feb 9, 2012, 5:22:47 PM2/9/12
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Seriously, a wet and dry vac is one of the most useful plumbing tools
you can get. The plastic Wickes / Earlex cheapie is fine.

Apart from your cylinder job, you can use them to empty gullies, catch
the water when draining a washing machine, dry up after defrosting a
freezer, empty the pan of a blocked loo, empty blocked sinks before
opening the trap, catch the muck when you need to drain a radiator, to
name but a few.

TMC

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Feb 10, 2012, 9:14:30 AM2/10/12
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"Newshound" <news...@fairadsl.co.uk> wrote in message
news:9piv9i...@mid.individual.net...
I have a George would not be without it

Adam Funk

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Feb 21, 2012, 7:53:52 AM2/21/12
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Thanks; I'll be careful...

Adam Funk

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Feb 21, 2012, 7:53:28 AM2/21/12
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On 2012-02-08, harry wrote:

> Immersion heaters have a 2&1/4" BSP thread. With very few exceptions
> they have been like this for 60 years to my knowledge. There are lots
> of makes. As long as it's the same size (3Kw, 27"), it will be OK.
> The stainless steel ones last longer but cost more.
>
>
> The best advice is when you come to unscrew it,don't put too much
> pressure on the spanner. You will ripple the tank.
>
> Get a hacksaw blade, tape the end up for a handle and saw the big
> washer through all the way round. (You will feel it skidding on the
> metal when you get through.)
> Clean up the face of the flange before you put the new one in. Best
> put a bit of plumbers mate on the new washer.
> Fill the tank before you switch on. They last about 30 seconds
> without!

Thanks very much for the advice. I'll be careful!

Ian Jackson

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Feb 21, 2012, 9:40:17 AM2/21/12
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In message <$YC8o$RGfCN...@bancom.co.uk>, tony sayer
<to...@bancom.co.uk> writes
Until you get it turning, I would suggest tapping the wrench (not too
hard, of course) rather than prolonged pulls or pushes (and grunts), and
also a bit of 'forwards and back'.
--
Ian

Adam Funk

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Feb 21, 2012, 3:19:31 PM2/21/12
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Thanks.
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