As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.

On 29/09/2020 16:36, John Smith wrote:
As we have no working boiler only an electric shower and while I wait to
see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.

While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 29 Sep 2020 16:36:04 +0100, John Smith
wrote:

As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.
At about 4amps/Kw that's 12 amps for the immersion heater plus ? for
the shower could be getting on for 18-20 amps. It depends how the
shower is wired, might just be on it's own 15 amp supply, which
wouldn't take the extra load.

On 2020-09-29 15:59:08 +0000, Davidm said:

On Tue, 29 Sep 2020 16:36:04 +0100, John Smith
wrote:

As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.
At about 4amps/Kw that's 12 amps for the immersion heater plus ? for
the shower could be getting on for 18-20 amps. It depends how the
shower is wired, might just be on it's own 15 amp supply, which
wouldn't take the extra load.

Shower is upstairs and not on the circuit under stairs.

On 29/09/2020 16:36, John Smith wrote:
As we have no working boiler only an electric shower and while I wait to
see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.

Boilers are (typically) powered by a five amp fused spur off an existing
ring main. So that wiring is unlikely to be man enough for the job.

As a *really* temporary fix I suppose you could run it off a 13 amp plug
and socket. You must use adequate cable, it *should* be heat resistant
cable close to the heater but you might get away with it for a month or
two, especially if it is in free air (and not, for example, covered with
extra thermal insulation).

Even high quality plugs and sockets such as MK don't like being wired up
to immersion heaters for too long. I know because a mate of mine had
this arrangement in his brewery, at one time.

I think that running it off a proper 13A switched and fused spur is
within the regs (but John or Adam will be along in a minute to correct me).

On 2020-09-29 15:57:09 +0000, John Rumm said:

On 29/09/2020 16:36, John Smith wrote:
As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.

While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.

Thanks. I guess the key is whether there are other things on the
heating controls circuit. Controls are off anyway. I'm trying to read
the scawled legends on the CU - think I'll have to find a magnifying
glass....

On Tue, 29 Sep 2020 16:57:09 +0100, John Rumm wrote:

While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.

Agreed but 3 KW is 13 A. The heating circuit *may* have a 6 A MCB,
worth a check.

--
Cheers
Dave.

On Tue, 29 Sep 2020 17:16:02 +0100, newshound wrote:

As a *really* temporary fix I suppose you could run it off a 13 amp plug
and socket.
snip
I think that running it off a proper 13A switched and fused spur is
within the regs (but John or Adam will be along in a minute to correct
me).

I'd try and avoid the 13 A fuse, passing 13 A for a reasonable amount
of time it's going to get warm if not hot... A 20 A DP switched
connection unit and 2.5 mm fixed and flexiable wiring through out
with a 16 A MCB would be fine and if a radial from the CU how it
ought to be installed anyway.

--
Cheers
Dave.

John Rumm explained :
While normally placed on their own circuit, sharing with the heating controls
sounds fine as well since they are unlikely to be more than a couple of amp
at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.

On 29/09/2020 17:16, newshound wrote:

As a *really* temporary fix I suppose you could run it off a 13 amp plug
and socket. You must use adequate cable, it *should* be heat resistant
cable close to the heater but you might get away with it for a month or
two, especially if it is in free air (and not, for example, covered with
extra thermal insulation).

Even high quality plugs and sockets such as MK don't like being wired up
to immersion heaters for too long. I know because a mate of mine had
this arrangement in his brewery, at one time.

I think that running it off a proper 13A switched and fused spur is
within the regs (but John or Adam will be along in a minute to correct me).

As a temp supply I would use your suggestion and just plug it into the
nearest socket.

Although the OP might find that the immersion does not work. So he would
certainly be better off trying your suggestion to find out if it works
before buggering about with 20A DP switches etc..

I did this last year in a hard water area. There was a massive bang and
then the sound of lumps of limescale dropping down the inside of the
cylinder. Probably a 30 year old element that had never had a volt
across it.

Cheers

--
Adam

On 29/09/2020 19:27, ARW wrote:
On 29/09/2020 17:16, newshound wrote:

As a *really* temporary fix I suppose you could run it off a 13 amp
plug and socket. You must use adequate cable, it *should* be heat
resistant cable close to the heater but you might get away with it for
a month or two, especially if it is in free air (and not, for example,
covered with extra thermal insulation).

Even high quality plugs and sockets such as MK don't like being wired
up to immersion heaters for too long. I know because a mate of mine
had this arrangement in his brewery, at one time.

I think that running it off a proper 13A switched and fused spur is
within the regs (but John or Adam will be along in a minute to correct
me).

As a temp supply I would use your suggestion and just plug it into the
nearest socket.

Although the OP might find that the immersion does not work. So he would
certainly be better off trying your suggestion to find out if it works
before buggering about with 20A DP switches etc..

I did this last year in a hard water area. There was a massive bang and
then the sound of lumps of limescale dropping down the inside of the
cylinder. Probably a 30 year old element that had never had a volt
across it.

Cheers

Good point. I usually fish out the megger before connecting something
new......but not always :-)

On 29/09/2020 20:02, newshound wrote:
On 29/09/2020 19:27, ARW wrote:
On 29/09/2020 17:16, newshound wrote:

As a *really* temporary fix I suppose you could run it off a 13 amp
plug and socket. You must use adequate cable, it *should* be heat
resistant cable close to the heater but you might get away with it
for a month or two, especially if it is in free air (and not, for
example, covered with extra thermal insulation).

Even high quality plugs and sockets such as MK don't like being wired
up to immersion heaters for too long. I know because a mate of mine
had this arrangement in his brewery, at one time.

I think that running it off a proper 13A switched and fused spur is
within the regs (but John or Adam will be along in a minute to
correct me).

As a temp supply I would use your suggestion and just plug it into the
nearest socket.

Although the OP might find that the immersion does not work. So he
would certainly be better off trying your suggestion to find out if it
works before buggering about with 20A DP switches etc..

I did this last year in a hard water area. There was a massive bang
and then the sound of lumps of limescale dropping down the inside of
the cylinder. Probably a 30 year old element that had never had a volt
across it.

Cheers

Good point. I usually fish out the megger before connecting something
new......but not always :-)

And I suppose I should also have said make sure the heater has a
thermostat in series! With a "not installed" system it is not beyond the
bounds of possibility that the thermostat is missing, and that an
inexperienced person might just try connecting mains to the heater element.

On 29/09/2020 20:06, newshound wrote:


And I suppose I should also have said make sure the heater has a
thermostat in series! With a "not installed" system it is not beyond the
bounds of possibility that the thermostat is missing, and that an
inexperienced person might just try connecting mains to the heater element.

Good point.

It's now supposed to be two thermostats in series.

But the OP should INHO test the element before buggering about with the
stat(s). 230V should do the test:-)



--
Adam

"ARW" wrote in message
...

Cheers

--
Adam

Glad to see you back. How's the er....

shuffles feet....


michael adams

....

On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......

On 29/09/2020 20:13, michael adams wrote:
"ARW" wrote in message
...

Cheers

--
Adam

Glad to see you back. How's the er....

shuffles feet....


Had the dry cough and aches, took the day off work.

The aches were probably because I am getting too old to build and climb
a tower scaffold and lump up light fittings and then the cough turned
into a cold.

So I am not bothering with a test.


--
Adam

On 29/09/2020 20:58, No Name wrote:
On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than
a couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......


It's 230V (give or take +10/-6%) in the UK.

A 13A BS1362 (plug fuse) will not trip at 20A for a long time.





--
Adam

No Name wrote :
you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that makes
I = 13.63A......

....and supposing it is a 240v element running on a 240v supply?

"ARW" wrote in message
...
On 29/09/2020 20:13, michael adams wrote:
"ARW" wrote in message
...

Cheers

--
Adam

Glad to see you back. How's the er....

shuffles feet....


Had the dry cough and aches, took the day off work.

The aches were probably because I am getting too old to build and climb a tower
scaffold and lump up light fittings and then the cough turned into a cold.

So I am not bothering with a test.


Good to hear it. Its probably only when you get a high temperature and lose the
sense of smell or taste* that it's time to take a test. Unless you're feeling
really rough. In which case you probably wouldn't want to get out of bed in
the first place.

I take every precaution but I've had a mild cold for weeks, which I'm keeping
to myself.


michael adams


*other symptoms are available

On Tue, 29 Sep 2020 20:58:34 +0100, No Name wrote:

3kw immersion heater = 12.5amps !

you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......

Except that it wouldn't as the resistance of the element doesn't
change.

240 V and P = 3000 R = V^2/P = 19.2 ohms

220 V and 19.2 ohms I = V/R = 11.45 A and P has also dropped to
2520 W

--
Cheers
Dave.

On 2020-09-29 18:27:29 +0000, ARW said:

I did this last year in a hard water area. There was a massive bang and
then the sound of lumps of limescale dropping down the inside of the
cylinder. Probably a 30 year old element that had never had a volt
across it.

Arrgh - the cylinder was installed about 17 years ago and in London
it's hard water. Maybe this is not such a good idea...

On 29 Sep 2020 at 20:58:34 BST, "No Name" wrote:

On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......

You might think that, but usually UK sold immersion heaters are 3kW at 240V.
This is a few pence cheaper for the maker, and in practice we stiil have 240V.
Although it is harmonised to be a nominal 230 plus or minus a tolerance this
is actually so far a paper exercise only.

--
Roger Hayter

On Wednesday, 30 September 2020 00:29:15 UTC+1, Roger Hayter wrote:
On 29 Sep 2020 at 20:58:34 BST, "No Name" wrote:

On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......

You might think that, but usually UK sold immersion heaters are 3kW at 240V.
This is a few pence cheaper for the maker, and in practice we stiil have 240V.
Although it is harmonised to be a nominal 230 plus or minus a tolerance this
is actually so far a paper exercise only.

A lot of people don't seem to realise that while the harmonised spec is nominally 230v, part of the plan was, and still is, to keep France 220v and UK 240v for the benefit of old appliances. 220 & 240 are within the new 230v spec. If you're in the habit of measuring mains voltages it won't take long to realise the current UK target voltage is 240 not 230.

And fwiw there is no such thing as 230v versus 240v immersion heaters. All marked either voltage can run on the other. Some old ones have a list of voltage versus power on them, sometimes covering everything from 200v to 250v..


NT

On Tuesday, 29 September 2020 16:36:09 UTC+1, John Smith wrote:
As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.

The circuit might be on a 5A or 6A fuse/mcb, but it's the cable rating that matters, fuses & MCBs can be changed. The wiki gives the ampacity of the usual cables.

If you use a mains plug, beware that some really can not handle 13A continuous for a long time.


NT

On 29/09/2020 20:58, No Name wrote:
On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than
a couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......


Generally they are rated 3kw @ 240v. Lower voltage and you get less out
and they stay under 13amps

Dave

On 29/09/2020 23:10, John Smith wrote:
On 2020-09-29 18:27:29 +0000, ARW said:

I did this last year in a hard water area. There was a massive bang
and then the sound of lumps of limescale dropping down the inside of
the cylinder. Probably a 30 year old element that had never had a volt
across it.

Arrgh - the cylinder was installed about 17 years ago and in London it's
hard water. Maybe this is not such a good idea...


You could install a new one, but getting the old one out without
distorting the tank might be fun. My tank had a blanking plate and I
installed a heater.

Dave

In article 2020092916360490695-nospam@nospamcom,
John Smith wrote:
As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.

Boiler etc controls don't take much current. If they are fed off a ring
via an FCU, check the size of the cable used. Most would use lighting
cable.

--
*I'm already visualizing the duct tape over your mouth

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

On 29/09/2020 22:01, michael adams wrote:
Good to hear it. Its probably only when you get a high temperature and lose the
sense of smell or taste* that it's time to take a test. Unless you're feeling
really rough. In which case you probably wouldn't want to get out of bed in
the first place.

I take every precaution but I've had a mild cold for weeks, which I'm keeping
to myself.

I caught a mild cough on a 'plane on the way back from California in
February. I still have it.

Andy
--
It so happens I had a chest x-ray for something else, and nothing
showed. So it is just a cough.

On 29/09/2020 20:58, No Name wrote:
On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than
a couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......

A couple of points to keep in mind. The EU wide voltage spec is 230V
+10%/-6% a loose spec that includes all the common generation voltages
used in the EU states.

However our generation voltage has *not actually changed*, and is still
240V. But 240V is within the allowable spec of 216V - 253V

For design purposes however we use 230V

Lastly for a resistive load, lowering the voltage does not result in it
drawing more current to compensate for the lower voltage to maintain a
given power output. If its actual power output at 240V is 3kW, reducing
the voltage to 216V will drop the power output to ~2.4kW, at 253V it
would rise to ~3.3kW.

(the heaters documentation will normally specify at what voltage the
output was calculated)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 29 Sep 2020 16:36:04 +0100, John Smith
wrote:


As we have no working boiler only an electric shower and while I wait
to see if the boiler can be fixed or needs replacing, I notice we have
immersion heater in the hot water tank but it's never been connected.

I assume this is a 3kW heater - does it have to have its own circuit by
regulation or can it be powered from a nearby circuit already powering
the heater controls. This would only be temporary and be a backup to
when the boiler is fixed.


My immersion heater is 3kW and plugged into a 13A socket via a
clockwork timer.
--
Dave W