Hi guys

Back thinking on the good old' not enough hot water' thing.

I think I'm going to try replacing the standard, immersion heater
mounted thermostat with an externally mounted one. Reason being that I
suspect the thermostat switches off a bit earlier than it should, as
the water at the top of the tank is roasting, whilst the water further
down the tank isn't.

I've been told it needs to be at least 15 or 16amp rated. Will this
one be Ok?

http://www.screwfix.com/app/sfd/cat/...56303&ts=19795

I don't really understand what SPDT means?

Can someone advise how far down the tank I should fit this - about half
way at a guess? Any problems with fixing it a bit lower?

Obviously the water at the top of the cylinder will get really hot if
the water at the centre is to be heater to 60 degrees - I dont' have a
problem with the hot water coming out really hot, but are there any
other problems I should be aware of?

I'm also not sure on how it'd be wired up, just 2 wires as the existing
thermstat is?

Thanks for your time

In an earlier contribution to this discussion,
Russ wrote:

Hi guys

Back thinking on the good old' not enough hot water' thing.

I think I'm going to try replacing the standard, immersion heater
mounted thermostat with an externally mounted one. Reason being that I
suspect the thermostat switches off a bit earlier than it should, as
the water at the top of the tank is roasting, whilst the water further
down the tank isn't.

I've been told it needs to be at least 15 or 16amp rated. Will this
one be Ok?

http://www.screwfix.com/app/sfd/cat/...56303&ts=19795

I don't really understand what SPDT means?

It means "Single Pole Double Throw" - in other words a change-over switch
which connects a 'Common' terminal to one or other of two additional
terminals when it switches. Have a look at
http://www.kpsec.freeuk.com/components/switch.htm for some diagrams.


Can someone advise how far down the tank I should fit this - about
half way at a guess? Any problems with fixing it a bit lower?

Obviously the water at the top of the cylinder will get really hot if
the water at the centre is to be heater to 60 degrees - I dont' have a
problem with the hot water coming out really hot, but are there any
other problems I should be aware of?

I'm also not sure on how it'd be wired up, just 2 wires as the
existing thermstat is?

To have the desired effect, it would have to be wired in parallel with - or
even instead of - the built-in stat. [If wired in series, the heater will go
off when the original stat switches, even if the external stat is still
calling for heat].

There are safety considerations, though! Current regs require immersion
heaters to have an additional over-heat stat - which has to be manually
reset if it trips. This is to prevent a potentially dangerous situation of
the tank boiling if the primary stat fails 'on'. Whatever happens, you
*musn't* bypass the safety stat.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but is disposable in the event of excessive
spam.

On 13 Feb 2006 00:47:03 -0800, "Russ"
wrote:

Hi guys

Back thinking on the good old' not enough hot water' thing.

I think I'm going to try replacing the standard, immersion heater
mounted thermostat with an externally mounted one. Reason being that I
suspect the thermostat switches off a bit earlier than it should, as
the water at the top of the tank is roasting, whilst the water further
down the tank isn't.

I've been told it needs to be at least 15 or 16amp rated. Will this
one be Ok?

http://www.screwfix.com/app/sfd/cat/...56303&ts=19795

I don't really understand what SPDT means?

Can someone advise how far down the tank I should fit this - about half
way at a guess? Any problems with fixing it a bit lower?

Obviously the water at the top of the cylinder will get really hot if
the water at the centre is to be heater to 60 degrees - I dont' have a
problem with the hot water coming out really hot, but are there any
other problems I should be aware of?

SPDT = (S)ingle (P)ole (D)ouble (T)hrow

meaning there is a single contact which moves between two contacts
which are known as NC Normally closed and NO Normally open
and yes that one will do.

Your two wires needs to be connected across the NC part so that the
Immersion heater initially gets hot, then at the correct temperature,
the contact opens and disconnects the element.

I would say 1/3 of the way up is best and the water at the top will
not get too hot. That is the way all thermostats function. Personally
I prefer 55 but it's a matter of experimentation really as I doubt
all stats are that closely calibrated anyway.

Andy



I'm also not sure on how it'd be wired up, just 2 wires as the existing
thermstat is?

Thanks for your time

"There are safety considerations, though! Current regs require
immersion
heaters to have an additional over-heat stat - which has to be manually

reset if it trips. This is to prevent a potentially dangerous situation
of
the tank boiling if the primary stat fails 'on'. Whatever happens, you
*musn't* bypass the safety stat."

This is what I don't get. My old thermsotat that I only replaced
recently didn't have this safety stat. and it'd been working merrily
for years and years.

What exactly is the danger people keep mentioning, other than the water
at the top getting hot?

The whole system operates on a timer, so if the thermostat did get
stuck on the power would go off after a few hours anyway?

I presume these external ones don't have a separate overheat trip like
the regular thermostats?

Russ wrote:
"There are safety considerations, though! Current regs require
immersion
heaters to have an additional over-heat stat - which has to be manually

reset if it trips. This is to prevent a potentially dangerous situation
of
the tank boiling if the primary stat fails 'on'. Whatever happens, you
*musn't* bypass the safety stat."

This is what I don't get. My old thermsotat that I only replaced
recently didn't have this safety stat. and it'd been working merrily
for years and years.

What exactly is the danger people keep mentioning, other than the water
at the top getting hot?

The whole system operates on a timer, so if the thermostat did get
stuck on the power would go off after a few hours anyway?

That's assuming the timer doesn't fail, or even you don't have a timer.

We never ever use our immersion heater as our boiler heats the water
fine. I've never even looked at it to be sure it works fine.

However, the immersion heater runs off a flex and mains plug. We never
plug it in. However, after using the socket in the airing cupboard for
something else, we plugged the bedside light back in.

3-4 hours later, came back to find water dripping from the light fitting.

After looking around, it turns out we'd plugged the immersion heater
back in, and steam/boiling water had been venting into the loft,
splashing off the badly placed insulation jacket and onto the loft
floor. From here it found a conveniently placed light fitting to drip
through.

I've no idea what the thermostat setting was on the immersion heater, or
whether it was working, or whether it tripped any safety mechanism (it
wasn't venting when I turned it off).

Basically these safety devices are for when the normal switching devices
fail, or a user does something stupid.

D

In article . com,
Russ wrote:
I think I'm going to try replacing the standard, immersion heater
mounted thermostat with an externally mounted one. Reason being that I
suspect the thermostat switches off a bit earlier than it should, as
the water at the top of the tank is roasting, whilst the water further
down the tank isn't.

Are you certain the actual immersion is long enough? Plumbers may just use
one they had in stock as a replacement, and they come in several lengths.

I've been told it needs to be at least 15 or 16amp rated. Will this
one be Ok?

http://www.screwfix.com/app/sfd/cat/...56303&ts=19795

It doesn't give a current rating and most of this type aren't meant to
switch heaters but merely pumps so don't have a 15 amp rating.

I don't really understand what SPDT means?

Single pole double throw. Basically a changeover switch which has three
terminals and can be either off or on at 'rest'.

--
*I love cats...they taste just like chicken.

Dave Plowman London SW
To e-mail, change noise into sound.

"Russ" wrote in message
ups.com...
Hi guys

Back thinking on the good old' not enough hot water' thing.

I think I'm going to try replacing the standard, immersion heater
mounted thermostat with an externally mounted one. Reason being that I
suspect the thermostat switches off a bit earlier than it should, as
the water at the top of the tank is roasting, whilst the water further
down the tank isn't.

I've been told it needs to be at least 15 or 16amp rated. Will this
one be Ok?

http://www.screwfix.com/app/sfd/cat/...56303&ts=19795


I think that you would do better to make sure that the length of your existing
immersion heater is appropriate for the size of tank that you have. Assumming
the heater is mounted on the top, you might want to choose one long enough to
heat the water near the bottom of the tank.

Further some immersion heaters use thermostats which are a separate internal
component and where you can adjust the temperature to suit you needs.

In your proposed solution you risk causing the water at the top of the tank to
boil, which may scald you.


--

Michael Chare

guys, as per my loads of other post on this poxy hot water system that
only seems to be playing up since old bits have been replaced (by me)
with new bits with 'safety' features - the immersion heater is a 36" -
which is the longest one I could find. Seems daft though as the
thermostat is only 18" (standard, it seems).

In article .com,
Russ wrote:
guys, as per my loads of other post on this poxy hot water system that
only seems to be playing up since old bits have been replaced (by me)
with new bits with 'safety' features - the immersion heater is a 36" -
which is the longest one I could find. Seems daft though as the
thermostat is only 18" (standard, it seems).

No - hot water rises to the top so all you need to do is measure it near
there.

--
*A fool and his money are soon partying *

Dave Plowman London SW
To e-mail, change noise into sound.

In an earlier contribution to this discussion,
Russ wrote:

"There are safety considerations, though! Current regs require
immersion
heaters to have an additional over-heat stat - which has to be
manually

reset if it trips. This is to prevent a potentially dangerous
situation of
the tank boiling if the primary stat fails 'on'. Whatever happens, you
*musn't* bypass the safety stat."

This is what I don't get. My old thermsotat that I only replaced
recently didn't have this safety stat. and it'd been working merrily
for years and years.

What exactly is the danger people keep mentioning, other than the
water at the top getting hot?


There have been one or two high profile cases involving fatalities - causing
the water not only in the cylinder but also in the cold header tank in the
attic to boil. In one case, the plastic header tank collapsed due to the
heat and dumped 50 gallons of scalding water on the people sleeping below.

It obviously needs a particular set of circumstances for the consequences to
be as dire as that - but in the knowledge that it *can* happen, it's as well
to take precautions.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but is disposable in the event of excessive
spam.

Hi,

Is the immersion heater boss perpendicular so the element is vertical
in the tank, or is tilted to one side, so the element is off vertical?

Also, have you bought a thermometer yet?

cheers,
Pete.

On 13 Feb 2006 00:47:03 -0800, "Russ"
wrote:

Hi guys

Back thinking on the good old' not enough hot water' thing.

I think I'm going to try replacing the standard, immersion heater
mounted thermostat with an externally mounted one. Reason being that I
suspect the thermostat switches off a bit earlier than it should, as
the water at the top of the tank is roasting, whilst the water further
down the tank isn't.

I've been told it needs to be at least 15 or 16amp rated. Will this
one be Ok?

http://www.screwfix.com/app/sfd/cat/...56303&ts=19795

I don't really understand what SPDT means?

Can someone advise how far down the tank I should fit this - about half
way at a guess? Any problems with fixing it a bit lower?

Obviously the water at the top of the cylinder will get really hot if
the water at the centre is to be heater to 60 degrees - I dont' have a
problem with the hot water coming out really hot, but are there any
other problems I should be aware of?

I'm also not sure on how it'd be wired up, just 2 wires as the existing
thermstat is?

Thanks for your time

tilted/off vertical Pete, and no, I've not bought a thermometer?

No - hot water rises to the top so all you need to do is measure it near
there.

But it is the temperature near the bottom that should be measured, to ensure
that the entire tank has been heated through. As you say, the hot water
rises to the top. If you measure there, it will satisfied almost
immediately, even when the majority of the cylinder is stone cold.

Christian.

In article ,
Christian McArdle wrote:
No - hot water rises to the top so all you need to do is measure it
near there.

But it is the temperature near the bottom that should be measured, to
ensure that the entire tank has been heated through. As you say, the hot
water rises to the top. If you measure there, it will satisfied almost
immediately, even when the majority of the cylinder is stone cold.

Looking at the TLC site, 11 and 18 inch elements have dedicated stats,
while the 27,30 and 36 inch share the same one.

--
*Time flies like an arrow. Fruit flies like a banana.*

Dave Plowman London SW
To e-mail, change noise into sound.

Looking at the TLC site, 11 and 18 inch elements have dedicated stats,
while the 27,30 and 36 inch share the same one.

Which is why long top mounted stats don't work well. They don't heat all the
cylinder as the stat clicks off when it is only hot halfway down.

Christian.

In article ,
Christian McArdle wrote:
Looking at the TLC site, 11 and 18 inch elements have dedicated stats,
while the 27,30 and 36 inch share the same one.

Which is why long top mounted stats don't work well. They don't heat all
the cylinder as the stat clicks off when it is only hot halfway down.

Could be - I've got one of those tall slim cylinders so probably the worse
scenario but have only once used the immersion. And it certainly provided
enough for a decent shower and general hot water over the couple of days
when I had the boiler in bits to fix a leak.

--
*Income tax service - We‘ve got what it takes to take what you've got.

Dave Plowman London SW
To e-mail, change noise into sound.

On 14 Feb 2006 00:19:34 -0800, "Russ"
wrote:

tilted/off vertical Pete,

Hi,

Is the thermostat hole/'pocket' towards the outside of the cylinder or
the middle?

If the latter then the thermostat might be above the tilted element,
so warm water rising off the element could make it switch off before
the rest of the cylinder is up to temp.

I'd try and fit the heater so the pocket is towards the _outside_ of
the cylinder, eg by using an extra washer or two under the immersion
heater fitting. Then it will be below the element so should only
switch off when the water in the cylinder is up to temp, as warm water
will rise off the element and away from it.

Ideally there should be a spacer towards the end of the thermostat
pocket to hold it away from the element.

and no, I've not bought a thermometer?

If you had one you could heat the thermostat in a pan of water to see
what temp it opens, which would be useful to know.

Also to measure the water temp at the basin, if it can go above 60C
there are precautions you must take.

cheers,
Pete.