Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?
Vital! The terminals on the element run hot by conduction and ordinary
PVC goes very limp and insulation could easily be displaced.
1.5mm should be adequate for the current but not sure what the regs
might have to say.

On 21/11/2017 09:29, Bob Minchin wrote:
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?
Vital! The terminals on the element run hot by conduction and ordinary
PVC goes very limp and insulation could easily be displaced.
1.5mm should be adequate for the current but not sure what the regs
might have to say.

Thanks. How do I determine whether the existing flex is heat resistant?

In article ,
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

To the actual unit? Essential. Many fit a JB etc close to it so only need
the heat resistant flex for the last little bit.

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

1.5mm is fine for a short distance.

--
*There are two kinds of pedestrians... the quick and the dead.

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

All I can tell you that I've had one wired up since the 1970s with a short
piece of three core large flexible pvc covered wire to the switch and as
I've had the heater changed twice I know that no damage has occurred to the
wires at all. Obviously its not got hot enough to melt pvc. Now whether
there are fault scenarios that might suggest that the specs now would call
for higher temp sleaving I'd not know but certainly I've not seen any
problems, indeed even the small wires for the thermostat are pvc covered.
Brian

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This newsgroup posting comes to you directly from...
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"GB" wrote in message
news
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

Interestingly, my emersion heater terminals do not run very hot at all, and
none ever have. I suspect it depends on the type and thermostat settings. as
I say, I've seen no sign of soggy sleaving on mine since the 1970s.
Its just pvc, not ptfe.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Dave Plowman (News)" wrote in message
...
In article ,
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

To the actual unit? Essential. Many fit a JB etc close to it so only need
the heat resistant flex for the last little bit.

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

1.5mm is fine for a short distance.

--
*There are two kinds of pedestrians... the quick and the dead.

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

In article ,
Brian Gaff wrote:
Interestingly, my emersion heater terminals do not run very hot at all,
and none ever have.

They follow the temperature of the hot water. Plus any heat generated by
the terminal resistance.

--
*24 hours in a day ... 24 beers in a case ... coincidence? *

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

In article ,
GB wrote:
On 21/11/2017 09:29, Bob Minchin wrote:
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?
Vital! The terminals on the element run hot by conduction and ordinary
PVC goes very limp and insulation could easily be displaced.
1.5mm should be adequate for the current but not sure what the regs
might have to say.

Thanks. How do I determine whether the existing flex is heat resistant?

There are two common types. Butyl which has a cream sleeve and much softer
to the touch than PVC. There is also a heat resistant version of something
like PVC which is usually engraved as heat resistant. That is much less
flexible than butyl.

--
*Certain frogs can be frozen solid, then thawed, and survive *

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

On Tuesday, 21 November 2017 09:00:48 UTC, GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

PVC's temp limit is only a bit above DHW temp. Ordinary 1.5 would be fine if the terminals were cold, but they're above DHW temp, so you need heat resistant pvc plus thicker flex to minimise the temp rise in the flex due to the current it carries.

As Brian points out PVC can be run above its temp limit, but doing so is not really safe. It goes very soft, conductor migration occurs easily and only a little contact resistance sends it over the edge.


NT

In article ,
Dave Plowman (News) wrote:
In article ,
GB wrote:
On 21/11/2017 09:29, Bob Minchin wrote:
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?
Vital! The terminals on the element run hot by conduction and
ordinary PVC goes very limp and insulation could easily be
displaced. 1.5mm should be adequate for the current but not sure what
the regs might have to say.

Thanks. How do I determine whether the existing flex is heat resistant?

There are two common types. Butyl which has a cream sleeve and much softer
to the touch than PVC. There is also a heat resistant version of something
like PVC which is usually engraved as heat resistant. That is much less
flexible than butyl.

you can also get black butyl - used on theatre lanterns

--
from KT24 in Surrey, England

In article ,
wrote:
As Brian points out PVC can be run above its temp limit, but doing so is
not really safe. It goes very soft, conductor migration occurs easily
and only a little contact resistance sends it over the edge.

It will also tend to become brittle over time, and in the worst case the
insulation can fall off.

--
*Those who live by the sword get shot by those who don't*

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

On Tue, 21 Nov 2017 09:00:42 +0000, GB wrote:

Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?


If unsure - why not just replace with heat resistant 2.5 : it won't break the
bank and job done

On 21/11/2017 17:35, ranking wrote:
On Tue, 21 Nov 2017 09:00:42 +0000, GB wrote:

Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?


If unsure - why not just replace with heat resistant 2.5 : it won't break the
bank and job done


I will do. It's just a bit thick and inflexible to work with. It's got
to come out of a switched outlet, then do a sharp turn through the side
of a kitchen unit, etc.

Adam will be along in a minute to talk about 'proper' 10mm stuff, but I
don't have to deal with that and it would be a bit tricky to get in

On 21/11/2017 17:48, GB wrote:
On 21/11/2017 17:35, ranking wrote:
On Tue, 21 Nov 2017 09:00:42 +0000, GB wrote:

Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?


If unsure - why not just replace with heat resistant 2.5 : it won't
break the
bank and job done


I will do. It's just a bit thick and inflexible to work with. It's got
to come out of a switched outlet, then do a sharp turn through the side
of a kitchen unit, etc.

Adam will be along in a minute to talk about 'proper' 10mm stuff, but I
don't have to deal with that and it would be a bit tricky to get in

You could probably use 1.5mm all the way from the CU!

--
Adam

On 21/11/2017 10:04, GB wrote:
On 21/11/2017 09:29, Bob Minchin wrote:
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?
Vital! The terminals on the element run hot by conduction and ordinary
PVC goes very limp and insulation could easily be displaced.
1.5mm should be adequate for the current but not sure what the regs
might have to say.

Thanks. How do I determine whether the existing flex is heat resistant?


Any markings on it? Usually HOR etc?

--
Adam

On 21/11/2017 13:35, Dave Plowman (News) wrote:
In article ,
GB wrote:
On 21/11/2017 09:29, Bob Minchin wrote:
GB wrote:
Wiring immersion heater - how important is it to use special heat
resistant flex?

Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?
Vital! The terminals on the element run hot by conduction and ordinary
PVC goes very limp and insulation could easily be displaced.
1.5mm should be adequate for the current but not sure what the regs
might have to say.

Thanks. How do I determine whether the existing flex is heat resistant?

There are two common types. Butyl which has a cream sleeve and much softer
to the touch than PVC. There is also a heat resistant version of something
like PVC which is usually engraved as heat resistant. That is much less
flexible than butyl.


The butyl is suitable for use in contact with grease and oil and so
often seen used on cooking appliances.

It also, as you said is more flexible than the standard heat resistant
stuff.

--
Adam

On 21/11/2017 09:00, GB wrote:


Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

1.5mm heat resistant flex is the normal standard size to wire up a 3kW
immersion;-)

It's one of those myths that was started by a bloke in the pub that
"once knew an electrician" that tells you it has to be 2.5mm^2:-)

Probably the same bloke that tells you about the pike called "Pump house
terror" that once killed and ate a Jack Russell terrier that was
paddling in the local mill pond. And that is true because "a fisherman
that he once knew" told him.

Heat resistant flex would be preferred as that works up to 90 deg.



--
Adam

Dave Plowman wrote:

GB wrote:

How do I determine whether the existing flex is heat resistant?

There are two common types. Butyl which has a cream sleeve and much softer
to the touch than PVC.

It might have the cable type 3093Y printed or embossed on it for heat
resistant, or 3183Y for non-heat resist

On 21/11/2017 19:06, ARW wrote:
On 21/11/2017 09:00, GB wrote:


Also, will 1.5mm2 do for a length of just over 1m in open air, or is
2.5mm2 required?

1.5mm heat resistant flex is the normal standard size to wire up a 3kW
immersion;-)

It's one of those myths that was started by a bloke in the pub that
"once knew an electrician" that tells you it has to be 2.5mm^2:-)

Thanks. I'll check the markings on what's there.



Probably the same bloke that tells you about the pike called "Pump house
terror" that once killed and ate a Jack Russell terrier that was
paddling in the local mill pond. And that is true because "a fisherman
that he once knew" told him.

Heat resistant flex would be preferred as that works up to 90 deg.