Re: Immersion Heater Cable
Andy Wade
> I want to replace the cable going into our standard 3 kW immersion
> heater. I understand that this cable needs to be heat resistant. Can
> anyone tell me if HO5 V2V2 - F cable is suitable?
No, those Vs mean it's a 70 deg. rated PVC/PVC cable. What you need is
85 deg. harmonised type H07BN4-F (UK CMA code 3183TQ), 1.5 mm^2 3-core.
E.g. http://www.tlc-direct.co.uk/Products/CA1dot5TQ3slash50.html
--
Andy
NT
I've always used 2.5mm2 butyl rubber flex, its a fair bit more
capable. Not only does the flex connect to hot terminals, but it also
heats up due to current flow, both need to be taken into account.
NT
Dave Plowman (News)
<a4519c7e-a6a0-40bd...@r27g2000vbn.googlegroups.com>,
NT <meow...@care2.com> wrote:
> > No, those Vs mean it's a 70 deg. rated PVC/PVC cable. What you need is
> > 85 deg. harmonised type H07BN4-F (UK CMA code 3183TQ), 1.5 mm^2 3-core.
> >
> > E.g.http://www.tlc-direct.co.uk/Products/CA1dot5TQ3slash50.html
> I've always used 2.5mm2 butyl rubber flex, its a fair bit more
> capable. Not only does the flex connect to hot terminals, but it also
> heats up due to current flow, both need to be taken into account.
Given 1.5mm is already more than adequate at 16amps - and the run is
usually short - I'd call that overkill.
--
*Nostalgia isn't what is used to be.
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
NT
wrote:
> In article
> <a4519c7e-a6a0-40bd-938e-cbffc0241...@r27g2000vbn.googlegroups.com>,
> NT <meow2...@care2.com> wrote:
>
> > > No, those Vs mean it's a 70 deg. rated PVC/PVC cable. What you need is
> > > 85 deg. harmonised type H07BN4-F (UK CMA code 3183TQ), 1.5 mm^2 3-core.
>
> > > E.g.http://www.tlc-direct.co.uk/Products/CA1dot5TQ3slash50.html
> > I've always used 2.5mm2 butyl rubber flex, its a fair bit more
> > capable. Not only does the flex connect to hot terminals, but it also
> > heats up due to current flow, both need to be taken into account.
>
> Given 1.5mm is already more than adequate at 16amps - and the run is
> usually short - I'd call that overkill.
1.5mm2 is rated at 20A when used clipped direct. That means that it
can rise from 20C to 70C with 20A load. 16A thus gives us a temp rise
of 16/20 x 50C = 40C.
But in this case it connects to terminals we expect to run at around
60-70C, lets say 70. 70 plus a temp rise of 40C = 110C. So your 1.5mm2
cable doesnt have good long term prospects because of the combination
of the 2 heat sources.
2.5mm2 cable is rated at 27A clipped direct. 16A will increase its
temp less, giving it a bit more margin.And butyl rubber is better able
to handle such temps than pvc, hence my choice.
NT
Dave Plowman (News)
<6325909f-7ed0-4dbd...@g6g2000vbr.googlegroups.com>,
NT <meow...@care2.com> wrote:
> > Given 1.5mm is already more than adequate at 16amps - and the run is
> > usually short - I'd call that overkill.
> 1.5mm2 is rated at 20A when used clipped direct. That means that it
> can rise from 20C to 70C with 20A load. 16A thus gives us a temp rise
> of 16/20 x 50C = 40C.
> But in this case it connects to terminals we expect to run at around
> 60-70C, lets say 70. 70 plus a temp rise of 40C = 110C. So your 1.5mm2
> cable doesnt have good long term prospects because of the combination
> of the 2 heat sources.
There's a flaw in this reasoning. Can't quite put my finger on it.
> 2.5mm2 cable is rated at 27A clipped direct. 16A will increase its temp
> less, giving it a bit more margin.And butyl rubber is better able to
> handle such temps than pvc, hence my choice.
If 1.5mm butyl wasn't suitable for immersion heaters, why is it the choice?
Oh - the bit of butyl feeding the one here seems to survived some 30 odd
years without problems. ;-)
--
*The e-mail of the species is more deadly than the mail *
js.b1
Screwfix do 2.5mm butyl in 1m cut lengths for £2.83 inc VAT.
- part 16684 - 1m cut length - HO7BN4F - 3183TQ - Butyl
- 2.5mm², 3-core, heat-resistant, white flexible cable
- 240V / 20A
It is actually H07BN4F (zero-seven not ohh-seven).
H = Harmonised
07 = 450/700V rated (thicker insulation)
B = Butyl Rubber Insulation
N = Neoprene Sheath
4 = can not remember
F = Fine flexible wire (as opposed to thinner ultrafine or tinsel)
Not sure it is a neoprene sheath, I think it is butyl too.
Butyl will discolour (go yellow) in direct UV thus not for outside
usage.
Quality of termination is vital. Wire termination, more surface area
the better. Element crimps can be poor, some wobble, some undersized
crimps. Thermostat terminals can have tiny screws, low clamping force.
Andrew Gabriel
NT <meow...@care2.com> writes:
> On Aug 29, 1:56�pm, "Dave Plowman (News)" <d...@davenoise.co.uk>
> wrote:
>> In article
>> <a4519c7e-a6a0-40bd-938e-cbffc0241...@r27g2000vbn.googlegroups.com>,
>> � �NT <meow2...@care2.com> wrote:
>>
>> > > No, those Vs mean it's a 70 deg. rated PVC/PVC cable. �What you need is
>> > > 85 deg. harmonised type H07BN4-F (UK CMA code 3183TQ), 1.5 mm^2 3-core.
>>
>> > > E.g.http://www.tlc-direct.co.uk/Products/CA1dot5TQ3slash50.html
>> > I've always used 2.5mm2 butyl rubber flex, its a fair bit more
>> > capable. Not only does the flex connect to hot terminals, but it also
>> > heats up due to current flow, both need to be taken into account.
>>
>> Given 1.5mm is already more than adequate at 16amps - and the run is
>> usually short - I'd call that overkill.
> 1.5mm2 is rated at 20A when used clipped direct. That means that it
> can rise from 20C to 70C with 20A load. 16A thus gives us a temp rise
> of 16/20 x 50C = 40C.
Power loss is proportional to current squared (P = I**2 x R), so your
multiplier should be (16/20)**2, which gives
(16/20)**2 x 50C = 32C.
However, most rubber cables have max operating temperature > 70C.
I don't have any current capacity tables on me, but they're probably
rated at a higher current rating as a result.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
NT
wrote:
> In article
> <6325909f-7ed0-4dbd-9f30-87942e54c...@g6g2000vbr.googlegroups.com>,
> NT <meow2...@care2.com> wrote:
> If 1.5mm butyl wasn't suitable for immersion heaters, why is it the choice?
presumably because its cheaper and is usually ok for many years. But
it does disintegrate at the ends sometimes.
NT
Andy Wade
> Power loss is proportional to current squared (P = I**2 x R), so your
> multiplier should be (16/20)**2, which gives
> (16/20)**2 x 50C = 32C.
Quite. Also NT is starting from ratings for non-flexible fixed wiring
cables. Table 4F3A of BS 7671 (flexible cords, non-armoured, copper
conductors) is probably a better place to start:
1.5 mm^2 - 16 A
2.5 mm^2 - 25 A
Then apply the given deratings for 90 deg. thermoplastic or
thermosetting cords:
Ambient temp Factor
------------ ------
35 - 50 deg. 1.00
55 deg. 0.96
60 deg. 0.83
65 deg. 0.67
70 deg. 0.47
Which suggests that for a 3 kW heater (13 A) you're OK up to about 60
deg. ambient. How hot do the terminals get? I don't know, but the
terminal box cover is supposed to be left uninsulated (thermally).
Maybe 1.5 is a bit marginal, but 99.9% of the nation's immersion heaters
are wired up with that size and I can't say I've seen many problems with
the insulation crumbling (except where a completely inappropriate cable
type has been used).
> However, most rubber cables have max operating temperature > 70C.
Careful - ordinary rubber flexes (H0xRRF etc.) and old rubber fixed
wiring cables like TRS are/were only rated at 60 deg. conductor temperature.
--
Andy
Andy Wade
> H = Harmonised
> 07 = 450/700V rated (thicker insulation)
> B = Butyl Rubber Insulation
> N = Neoprene Sheath
> 4 = can not remember
N4 is 'CSP' - chlorosufonated polyethylene, see
http://www.eland.co.uk/cable-genius/1/an-introduction-to-harmonised-cables.html
for example. That's similar to neoprene, I think - any chemists around?
> Not sure it is a neoprene sheath, I think it is butyl too.
The insulation (B) is EPR (ethylene-propylene rubber and the sheath (N4)
is CSP.
--
Andy
Dave Plowman (News)
<d47af3aa-af66-4b80...@z34g2000vbl.googlegroups.com>,
NT <meow...@care2.com> wrote:
> > If 1.5mm butyl wasn't suitable for immersion heaters, why is it the
> > choice?
> presumably because its cheaper and is usually ok for many years. But
> it does disintegrate at the ends sometimes.
So does PVC into a socket etc if the connection isn't properly made.
--
*Why is it that doctors call what they do "practice"?