(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

"Tim Watts" wrote in message
...
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.


I would expect the cable could be at 40C at that load.

However if you suspect that the switch is getting hotter than the cable then
swap the switch [1] as it is only a few quid and see what happens.

[1] A Yorkshireman can spend other peoples money:-)

--
Adam

On 18/12/15 19:32, ARW wrote:

I would expect the cable could be at 40C at that load.

However if you suspect that the switch is getting hotter than the cable
then swap the switch [1] as it is only a few quid and see what happens.

[1] A Yorkshireman can spend other peoples money:-)


Thank you Adam. Did not think to check the cable. IIRC I used 10mm2 for
that one.

Thinking P=I^2 x R, even if the switch has a contact resistance of
0.01 Ohms, that, for I=40A, would be 1600 x 0.01 = 16W developed across
the contacts. In a fully plastic enclosure, I guess that is actually
quite a bit of heat. Could be reasonable I suppose...

Yeah - I'll get a new switch of the same make (for same terminal layout)
next time I'm up TLC in a week or two.

On Friday, 18 December 2015 19:43:47 UTC, Tim Watts wrote:
Thinking P=I^2 x R, even if the switch has a contact resistance of
0.01 Ohms, that, for I=40A, would be 1600 x 0.01 = 16W developed across
the contacts. In a fully plastic enclosure, I guess that is actually
quite a bit of heat. Could be reasonable I suppose...

Maybe Amendment 4 will require all switches 16A to be in non-combustible enclosures.

Owain

On Fri, 18 Dec 2015 19:10:46 +0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim


It's difficult to be certain. For fairly modern stuff it's "not hot
enough to cause damage to the contacts or operating mechanism"! You'd
really need to look at the manufacturers data sheet as that will indicate
stuff like derating due to ambient temperature.

In article om,
mick writes:
On Fri, 18 Dec 2015 19:10:46 +0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim


It's difficult to be certain. For fairly modern stuff it's "not hot
enough to cause damage to the contacts or operating mechanism"! You'd
really need to look at the manufacturers data sheet as that will indicate
stuff like derating due to ambient temperature.

Yep - datasheet (at least for professional quality parts) will tell you,
because the heat from a breaker running at full load reduces the overload
trip rating of the adjacent breakers. Hence there is sometimes a requirement
to space out breakers expected to run at full load for long periods, so
they don't overheat or take themselves or adjacent breakers too far from
the rating plate.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 18/12/15 20:57, Andrew Gabriel wrote:

Yep - datasheet (at least for professional quality parts) will tell you,
because the heat from a breaker running at full load reduces the overload
trip rating of the adjacent breakers. Hence there is sometimes a requirement
to space out breakers expected to run at full load for long periods, so
they don't overheat or take themselves or adjacent breakers too far from
the rating plate.


Just to clarify, this is an isolator - not the MCB/RCBO (which runs
stone cold BTW).

I lied about it being a GET - it's an MK:

http://www.screwfix.com/p/mk-2-gang-...on-white/15973

Which is odd as all my other stuff is GET. Not much on the datasheet -
nothing useful like contact resistance or derating

On Fri, 18 Dec 2015 19:43:41 +0000, Tim Watts wrote:

Yeah - I'll get a new switch of the same make (for same terminal layout)
next time I'm up TLC in a week or two.

Hum, a plain switch running hot when the associated MCB/RCBO is cold.
Bear in mind that MCBs have a thermal part...I think I'd be down the
shops tommorow or not use what ever it is until the switch has been
replaced.

Why is terminal layout so critical? OK 10 mm2 isn't the most bendy
stuff but the switch will be on a 47 mm deep box won't it to give
room. Take a drawing of the layout with you so you can get something
close.

--
Cheers
Dave.

On 19/12/15 00:35, Dave Liquorice wrote:
On Fri, 18 Dec 2015 19:43:41 +0000, Tim Watts wrote:

Yeah - I'll get a new switch of the same make (for same terminal layout)
next time I'm up TLC in a week or two.

Hum, a plain switch running hot when the associated MCB/RCBO is cold.
Bear in mind that MCBs have a thermal part...I think I'd be down the
shops tommorow or not use what ever it is until the switch has been
replaced.

Well, even I'm not going to panic quite that much This is only used
when people are around.


Why is terminal layout so critical?

There's not much slack...

OK 10 mm2 isn't the most bendy
stuff but the switch will be on a 47 mm deep box won't it to give
room. Take a drawing of the layout with you so you can get something
close.

On Friday, 18 December 2015 19:10:54 UTC, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

If the terminals are tight, change the switch.
The contacts must be burnt/defective
A shower is only run for a few minutes, there's no way it should get even warm.

On 18/12/2015 19:43, Tim Watts wrote:
On 18/12/15 19:32, ARW wrote:

I would expect the cable could be at 40C at that load.

However if you suspect that the switch is getting hotter than the cable
then swap the switch [1] as it is only a few quid and see what happens.

[1] A Yorkshireman can spend other peoples money:-)


Thank you Adam. Did not think to check the cable. IIRC I used 10mm2 for
that one.

Thinking P=I^2 x R, even if the switch has a contact resistance of
0.01 Ohms, that, for I=40A, would be 1600 x 0.01 = 16W developed across
the contacts. In a fully plastic enclosure, I guess that is actually
quite a bit of heat. Could be reasonable I suppose...

Yeah - I'll get a new switch of the same make (for same terminal layout)
next time I'm up TLC in a week or two.

One other thing to think about is to uprate the switch to say a 60A,
that will give you more headroom between the actual current flow and the
maximum current rating of the switch, that hopefully would reduce I2R
losses across the switch and hence reduce the overheating effect?

On 19/12/15 08:09, I love spam wrote:

One other thing to think about is to uprate the switch to say a 60A,
that will give you more headroom between the actual current flow and the
maximum current rating of the switch, that hopefully would reduce I2R
losses across the switch and hence reduce the overheating effect?

I'm not aware anyone makes a 60A shower isolator?

Crabtree make a 50A one

http://www.screwfix.com/p/crabtree-2...on-white/99780

Richard

Lap make a 50A pull switch

http://www.screwfix.com/p/lap-50a-dp...ch-white/7251g

Richard

harry Wrote in message:
On Friday, 18 December 2015 19:10:54 UTC, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

If the terminals are tight, change the switch.
The contacts must be burnt/defective
A shower is only run for a few minutes, there's no way it should get even warm.

it's not a shower, it's a water heater.

--
--
Chris French


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On 18/12/15 19:10, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

Well - I had a mate round (not a sparks) and I said: "touch that" (we
use highly scientific testing methodologies in this household!)

"Bloody hell, that's hot" he said.

At which point I wandered off to B&Q (being open late on a Saturday).

Interesting point - bought a Crabtree 50A unit to replace - the Crabtree
has twin screw terminals (except earths) +1.
It seems to have a ceramic switch unit mounted to a plastic body +another1
It says: "50A" on the back and the packet.

The MK one (identical to the current one) is in a box on the shelves
where the box and the packet say "50A" but it has "45A" printed on the
plastic. -10 for lying. The terminals are the same single screw type
mine is and the neon still has 2 weedly exposed wires that get pushed
around by the 10mm2 going into the terminals.

Conclusion: MK is not the brand it used to be.

I will attempt to disassemble the old one and see if there's any
interesting tell tales of overheating inside...

In article ,
Tim Watts wrote:
On 18/12/15 19:10, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

Well - I had a mate round (not a sparks) and I said: "touch that" (we
use highly scientific testing methodologies in this household!)

"Bloody hell, that's hot" he said.

At which point I wandered off to B&Q (being open late on a Saturday).

Interesting point - bought a Crabtree 50A unit to replace - the Crabtree
has twin screw terminals (except earths) +1.
It seems to have a ceramic switch unit mounted to a plastic body +another1
It says: "50A" on the back and the packet.

The MK one (identical to the current one) is in a box on the shelves
where the box and the packet say "50A" but it has "45A" printed on the
plastic. -10 for lying. The terminals are the same single screw type
mine is and the neon still has 2 weedly exposed wires that get pushed
around by the 10mm2 going into the terminals.

Conclusion: MK is not the brand it used to be.

Having looked at Wiki to check that I was right about the current owner
ship of the company. I noticed that there is a "product recall" of certain
switches. Could the one you have be affected?

I will attempt to disassemble the old one and see if there's any
interesting tell tales of overheating inside...

--
Please note new email address:

On 19/12/15 19:09, charles wrote:

Having looked at Wiki to check that I was right about the current owner
ship of the company. I noticed that there is a "product recall" of certain
switches. Could the one you have be affected?

That's a CU main isolator, so anyone with an MK CU would be well advised
to check it. Good mention.

Not my part though - which is a K5215.

So Honeywell own them now... Hmm.

On Saturday, 19 December 2015 12:18:37 UTC, Chris French wrote:
harry Wrote in message:
On Friday, 18 December 2015 19:10:54 UTC, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

If the terminals are tight, change the switch.
The contacts must be burnt/defective
A shower is only run for a few minutes, there's no way it should get even warm.


it's not a shower, it's a water heater.

That's some water heater that needs 45A
10Kw?

On Sat, 19 Dec 2015 07:16:44 +0000, Tim Watts wrote:

Yeah - I'll get a new switch of the same make (for same terminal
layout) next time I'm up TLC in a week or two.

Hum, a plain switch running hot when the associated MCB/RCBO is
cold.
Bear in mind that MCBs have a thermal part...I think I'd be down
the
shops tommorow or not use what ever it is until the switch has
been
replaced.

Well, even I'm not going to panic quite that much This is only used
when people are around.

But you still did when your mate came round and commented. B-)

Why is terminal layout so critical?

There's not much slack...

OK 10 mm2 isn't the most bendy stuff but the switch will be on a
47 mm
deep box won't it to give room.

Tricky I know to leave slack with heavy cables, shallow boxes don't
help.

--
Cheers
Dave.

On 20/12/15 11:12, Dave Liquorice wrote:
On Sat, 19 Dec 2015 07:16:44 +0000, Tim Watts wrote:

Yeah - I'll get a new switch of the same make (for same terminal
layout) next time I'm up TLC in a week or two.

Hum, a plain switch running hot when the associated MCB/RCBO is
cold.
Bear in mind that MCBs have a thermal part...I think I'd be down
the
shops tommorow or not use what ever it is until the switch has
been
replaced.

Well, even I'm not going to panic quite that much This is only used
when people are around.

But you still did when your mate came round and commented. B-)

Yes - sometimes it helps when some else agrees on the spot
My sense of temperature by feel is not a well calibrated instrument - it
helps to have a second opinion.

Why is terminal layout so critical?

There's not much slack...

OK 10 mm2 isn't the most bendy stuff but the switch will be on a
47 mm
deep box won't it to give room.


Tricky I know to leave slack with heavy cables, shallow boxes don't
help.


Yes it is - and I used a 47mm box (of course - I'm not that stupid), but
I did not leave much slack. So I will move the new box back a bit and
replace the short run to the heater. That'll give me more room to get to
the screws at the wall end.

I slapped the thing in a hurry some years ago - none of it was
optimal... Will do it a bit better this time.

On 18/12/15 19:10, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

Well, replaced after some hours with a Crabtree 50A isolator - and after
filling a bath, it is virtually stone cold. The rocker has a hint of
warmth, but you'd be hard pressed to tell.

So the ultimate answer to the subject is "hardly at all".


Apparently according to a sparky I was talking too (not Adam) have have
also been making a mistake of twisting the strands in 10mm2 cable -
something my dad always did....

On Sunday, 20 December 2015 17:22:53 UTC, Tim Watts wrote:
On 18/12/15 19:10, Tim Watts wrote:
(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim

Well, replaced after some hours with a Crabtree 50A isolator - and after
filling a bath, it is virtually stone cold. The rocker has a hint of
warmth, but you'd be hard pressed to tell.

So the ultimate answer to the subject is "hardly at all".


Apparently according to a sparky I was talking too (not Adam) have have
also been making a mistake of twisting the strands in 10mm2 cable -
something my dad always did....

The terminal should ideally be as full of copper as possible before tightening the screws.
So so, back off the terminal screws fully, twist up the cable if stranded and double over if necessary.

On very large cables, the end should be bound with copper wire.
Rarely seen these days.

The object is to make sure the screw nips the cable rather than going between the strands.

On Fri, 18 Dec 2015 19:10:46 -0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

My parents' one gets hot. It's a 15A switch running a 3kW immersion heater. the front plate (plastic) gets to about 40C. When I looked inside there was nothing loose or otherwise untoward, so I bought a brand new decent (MK?) one. It got equally warm, so we decided to just ignore it.

--
Why does the law society prohibit sex between lawyers and their clients?
To prevent clients from being billed twice for essentially the same service.

On 20/12/15 19:31, Mr Macaw wrote:
On Fri, 18 Dec 2015 19:10:46 -0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

My parents' one gets hot. It's a 15A switch running a 3kW immersion
heater. the front plate (plastic) gets to about 40C. When I looked
inside there was nothing loose or otherwise untoward, so I bought a
brand new decent (MK?) one. It got equally warm, so we decided to just
ignore it.


I've concluded MK are no longer decent - they are on my blacklist now.

I did take the old one apart - nothing obviously wrong so I am assuming
it is either a poor contact pad or a weak spring.

On Sun, 20 Dec 2015 20:59:05 -0000, Tim Watts wrote:

On 20/12/15 19:31, Mr Macaw wrote:
On Fri, 18 Dec 2015 19:10:46 -0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

My parents' one gets hot. It's a 15A switch running a 3kW immersion
heater. the front plate (plastic) gets to about 40C. When I looked
inside there was nothing loose or otherwise untoward, so I bought a
brand new decent (MK?) one. It got equally warm, so we decided to just
ignore it.


I've concluded MK are no longer decent - they are on my blacklist now.

I did take the old one apart - nothing obviously wrong so I am assuming
it is either a poor contact pad or a weak spring.

All these regulations and nothing to test things to stay at a decent temperature.

--
A man walks into a bar with a slab of asphalt under his arm and says, "A beer please, and one for the road."

On Sunday, 20 December 2015 19:31:48 UTC, Mr Macaw wrote:
On Fri, 18 Dec 2015 19:10:46 -0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

My parents' one gets hot. It's a 15A switch running a 3kW immersion heater. the front plate (plastic) gets to about 40C. When I looked inside there was nothing loose or otherwise untoward, so I bought a brand new decent (MK?) one. It got equally warm, so we decided to just ignore it.

The temperature it gets to depends on the ambient temperature.
You must make sure the cables are properly "nipped by the terminal screws. Some terminals are too big.

Lots of electrical stuff is **** now thanks to the EUSSR and "harmonisation".
Standards have definitely fallen.

On Mon, 21 Dec 2015 07:16:56 -0000, harry wrote:

On Sunday, 20 December 2015 19:31:48 UTC, Mr Macaw wrote:
On Fri, 18 Dec 2015 19:10:46 -0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

My parents' one gets hot. It's a 15A switch running a 3kW immersion heater. the front plate (plastic) gets to about 40C. When I looked inside there was nothing loose or otherwise untoward, so I bought a brand new decent (MK?) one. It got equally warm, so we decided to just ignore it.

The temperature it gets to depends on the ambient temperature.
You must make sure the cables are properly "nipped by the terminal screws. Some terminals are too big.

Lots of electrical stuff is **** now thanks to the EUSSR and "harmonisation".
Standards have definitely fallen.

The correct wiring was used and it was firmly in the terminals, I can't see there being unnecessary resistance there. I think it was coming from the switch part.

--
101 Dalmatians and Peter Pan are the only two Disney animated features in which both the parents are present and don't die throughout the movie.