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Old January 13th 05, 10:04 AM
Dane Koekoek
 
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Default Immersion heater problem

I had to replace the thermostat on the immersion heater on the water water
tank at my parents' house recently as the thermostat decided that it didn't
wish to switch off anymore, continuously heating the hot water to very hot
levels.

The tank is a very old large one with an immersion heater mounted right at
the very top facing downwards. I replaced the thermostat like for like with
what was there before and now they have hot water without having to keep
turning it on and off at the switch!

The cap on the immersion heater cover claims the element is 27" in length,
but the thermostat that was already there was only 18" in length. Would this
be right, or should the thermostat not be 27" also? That is assuming that the
cap is correct and the element is actually 27" long... Don't know without
removing the whole element from the tank - not something I want to do as it's
actually working.

The problem is that although they now have hot water there is not much of it.
The system used to be heated by a gas boiler which has since been condemed!
That's why they since used the immersion heater as they have no desire to
replace the gas boiler (as it only heats the water). The problem is that with
gas heating (via coil inside tank) there was enough hot water for two baths,
now there is barely enough for one full bath.

Any suggestions? Would I be able to just change the thermostat to a longer
one, or would it not physically fit?

--
Dane Koekoek


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Old January 13th 05, 10:20 AM
Christian McArdle
 
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Any suggestions? Would I be able to just change the thermostat to a longer
one, or would it not physically fit?


I think 18" is the standard length for the thermostat.

Perhaps you have a fancy dual element heater and are using the short
element?

Before the thermostat was fixed, did it produce enough water on electric
heating?

Christian.


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Old January 13th 05, 11:22 AM
Dane Koekoek
 
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Default

In message t
"Christian McArdle" wrote:

Any suggestions? Would I be able to just change the thermostat to a
longer one, or would it not physically fit?


I think 18" is the standard length for the thermostat.

Perhaps you have a fancy dual element heater and are using the short
element?


Only one set of electrical connections to the element, so I doubt it. Looked
fairly standard when I had the cover off.


Before the thermostat was fixed, did it produce enough water on electric
heating?


Simple question, but I've asked that to my mum before, but she can't answer
that! The element was replaced without my knowledge about a year or so ago at
some exhorbitant cost by some electrical/plumbing firm when the old one went
short circuit and tripped the MCB.

My parents both belong a health club where they go swimming and use the
showers there virtually every day, so (bizarrely) hardly ever have a bath or
shower at home! Mum says she thinks it worked okay before the element was
changed, but can't say whether it's worked fine since due to lack of use
other than for washing dishes or hands!

The tank is an old copper one with a lagging jacket (no foam insulation
here!) You can certainly feel that only the top small portion of the tank is
actually being heated. How can I improve on this? I know they should heat it
by the coil inside the tank as this will heat the whole tank, but they don't
want to go down this route - they say it's too much hassle replacing the old
boiler!


--
Dane Koekoek

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Old January 13th 05, 11:33 AM
Christian McArdle
 
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Default

Simple question, but I've asked that to my mum before, but she can't
answer
that! The element was replaced without my knowledge about a year or so ago

at
some exhorbitant cost by some electrical/plumbing firm when the old one

went
short circuit and tripped the MCB.


Perhaps the installers were cretinous and replaced with a short element,
although the fact that the thermostat was 18" might suggest otherwise.

However, the amount heated by a top mounted element is never likely to be
good. I would recommend installing a new side entry element near the bottom
of the tank.

Christian.


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Old January 13th 05, 11:41 AM
Dane Koekoek
 
Posts: n/a
Default

In message t
"Christian McArdle" wrote:

Simple question, but I've asked that to my mum before, but she can't
answer that! The element was replaced without my knowledge about a year
or so ago at some exhorbitant cost by some electrical/plumbing firm when
the old one went short circuit and tripped the MCB.


Perhaps the installers were cretinous and replaced with a short element,
although the fact that the thermostat was 18" might suggest otherwise.


So would you say an 18" thermostat is correct for a 27" element?


However, the amount heated by a top mounted element is never likely to be
good. I would recommend installing a new side entry element near the bottom
of the tank.


Would be simple if the tank accommodated this! What's the longest element
that can be put into a tank?

--
Dane Koekoek



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Old January 13th 05, 11:47 AM
Christian McArdle
 
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Default

I would.



However, the amount heated by a top mounted element is never likely to

be
good. I would recommend installing a new side entry element near the

bottom
of the tank.


Would be simple if the tank accommodated this! What's the longest element
that can be put into a tank?

--
Dane Koekoek



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Old January 13th 05, 11:51 AM
Christian McArdle
 
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Default

So would you say an 18" thermostat is correct for a 27" element?

I would.

http://www.plumbworld.co.uk/277-14813

Would be simple if the tank accommodated this! What's the longest element
that can be put into a tank?


The problem is that top mounted ones aren't very efficient at heating the
bottom compared with a side entry. You can find longer ones, though, which
may improve matters a little.

However, you can't beat a good old side entry. Your tank will accommodate
it. You need to drain down and then drill the correct sized hole with a hole
saw. The element can then be installed. This will provide more hot water
than any top mounted device.

Christian.


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Old January 13th 05, 11:53 AM
Christian McArdle
 
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Default

snip premature reply

Sorry about this one. Don't you just hate the way Ctrl+Return always sends
immediately. I'm always accidentally hitting it...

Christian.


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Old January 13th 05, 11:59 AM
Owain
 
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Default

"Dane Koekoek" wrote
| The tank is an old copper one with a lagging jacket (no foam
| insulation here!) You can certainly feel that only the top small
| portion of the tank is actually being heated. How can I improve
| on this?

The immersion heater is only heating the water at the top of the tank
because of it's length. It might not be possible to fit a longer one, as the
coil inside may be a physical obstacle.

| I know they should heat it by the coil inside the tank as this will
| heat the whole tank, but they don't want to go down this route -
| they say it's too much hassle replacing the old boiler!

The *best* approach would probably be to replace the cylinder with a
factory-insulated one with top and bottom heaters/stats, especially if the
boiler is not to be replaced. The bottom heater can be switched on when a
bath is required, and the top heater only is used for small quantities of
hot water (washing-up etc).

An alternative would be to fit an electric boiler to the coil, on a pumped
primary loop. They're 10kW (would require new circuit from consumer unit)
and smaller than an instant shower over a bath. In some small, very well
insulated new homes, they're used for the central heating radiators.

Owain


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Old January 13th 05, 11:06 PM
Grimly Curmudgeon
 
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Default

It was somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Christian McArdle"
saying something like:

Simple question, but I've asked that to my mum before, but she can't

answer
that! The element was replaced without my knowledge about a year or so ago

at
some exhorbitant cost by some electrical/plumbing firm when the old one

went
short circuit and tripped the MCB.


Perhaps the installers were cretinous and replaced with a short element,
although the fact that the thermostat was 18" might suggest otherwise.



Likely the cretinous installers had only a dual element one with them
and used that.

The cretinous installers only wired up one element - the short one. I'd
bet the feed isn't 4core and the old switch is merely on/off with no
bath/sink.

He can connect the long element instead of the short one.
--

Dave


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