IET logo
 
IET
Decrease font size
Increase font size
Locked Topic Locked
Topic Title: Immersion Heater Supply Question.
Topic Summary: Opinions Invited Please.
Created On: 04 August 2017 04:56 PM
Status: Read Only
Linear : Threading : Single : Branch
<< 6 7 8 9 10 Previous Next Last unread
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 10 August 2017 02:10 PM
User is offline View Users Profile Print this message



rocknroll

Posts: 9534
Joined: 03 October 2005

A lot of you new breed and the reg preachers including the two handbag bashers Zup and Lec would probably benefit from watching some of John Ward's videos for some common sense, he is UK from Poole.

Here

Regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 10 August 2017 04:17 PM
User is online View Users Profile Print this message



potential

Posts: 1616
Joined: 01 February 2007

Interesting to see the wago connector actually burst into flames when the wire failed..... presumably because the wire had been repeatably bent, either in assemble or after, and the crystal structure of the hardened copper when bent caused minute crazing in the wire's metallic structure hence the failure?
 10 August 2017 04:49 PM
User is offline View Users Profile Print this message



weirdbeard

Posts: 3078
Joined: 26 September 2011

Originally posted by: Zoomup

An example of a real mess after an airing cupboard fire. Cause unknown. ">http://windowcleaningf....co.....527c6e6c2b8




That pic is inside a window cleaners van:

http://windowcleaningforums.co.uk/topic/3994-using-immersion-heater/

-------------------------
:beer)

Edited: 10 August 2017 at 05:22 PM by weirdbeard
 10 August 2017 05:06 PM
User is offline View Users Profile Print this message



leckie

Posts: 4146
Joined: 21 November 2008

Originally posted by: Zoomup

Perhaps the airing cupboard is a location presenting a fire risk above and beyond other locations because of the following reasons.



a, It is a confined space where heat build-up is possible above normal room temperatures.



b, It contains combustible items such as nylon sheets, synthetic materials such as duvet covers and possibly other items of domestic clothing etc.



c, It may have combustible wooden shelving comprising wooden slats.



d, It may contain an immersion heater timer in a plastic case. These may have been non professionally added by a D.I.Y. house holder. There have been recalls of faulty immersion heater timers that can catch fire.



e, It may contain a 13 Amp switch fused connection unit that runs very hot at the fuse position.



f, There are many cited cases of airing cupboard fires reported on-line and in the press suggesting an immersion heater as the source of fire. This description includes the supply to and control equipment of the immersion heater. There may be many other cases of airing cupboard fires that are not reported in the press or on-line.



g, The immersion heater is often covered with clothing.



h, The supply flex is often covered over with clothing.



i, There may still be many immersion heater thermostats that are of the older type with no safety cut-out, just operational contacts that may weld together and cause a permanently ON situation. This happen top me about a year ago.



j. The immersion heater flex is often snagged and pulled about when people use the airing cupboard to fill it with clothes or remove them. It can be damaged or crushed.



k. Airing cupboard electrics are not often professionally inspected for safety.



l. Some airing cupboards have electric convector airing cupboard heaters on which clothes etc. can fall and cover them, as well as an immersion heater.



m. How non-combustible is copper cylinder spray-on tank thermal insulation? I have not been able to find out.



Z.


Well the problem with that list Z is that fitting overload protection probably would have no statistically measurable effect. What needs to happen is that the issues such as older thermostats, snagged flex, etc., need addressing. If you do consider the cupboard to be a location presenting a fire risk, it should not contain, time clock, switch fused Spurs, etc. But I personally don't think it is, I'm with AJ and David Z on the broad interpretation of the risk.

Let's as Geoff to look in his copy of GN4

I'm off now to swat RnR with my handbag
 10 August 2017 05:30 PM
User is offline View Users Profile Print this message



leckie

Posts: 4146
Joined: 21 November 2008

 10 August 2017 05:44 PM
User is offline View Users Profile Print this message



weirdbeard

Posts: 3078
Joined: 26 September 2011

Originally posted by: Zoomup

This airing cupboard fire seems to have started at the top entry immersion heater and burnt down via the tank thermal insulation. http://www.huntspost.co.uk/pol...e_630/image.jpg





The article says the tank was empty, no suggestion of any electrical faults, The flex looks in good condition!

http://www.huntspost.co.uk/new...n-house-fire-1-3917777

-------------------------
:beer)
 10 August 2017 08:14 PM
User is offline View Users Profile Print this message



geoffsd

Posts: 1601
Joined: 15 June 2010

Originally posted by: leckie

Let's ask Geoff to look in his copy of GN4


 10 August 2017 09:26 PM
User is offline View Users Profile Print this message



alancapon

Posts: 6838
Joined: 27 December 2005

Originally posted by: Zoomup
This airing cupboard fire seems to have started at the top entry immersion heater and burnt down via the tank thermal insulation. ">http://www.huntspost.c...pol......jpg



Another non-example. According to the article the photo is from, the tank was empty and not in use. The immersion heater has been switched on with just air in the tank, and the tank overheated, burning off the insulation. There is no apparent damage to any of the cabling. Even the plastic cap of the heater is in fair condition given the scenario.

Regards,

Alan.
 10 August 2017 09:32 PM
User is offline View Users Profile Print this message



davezawadi

Posts: 3806
Joined: 26 June 2002

Z lets give this up. It appears that I diagnosed each of your pictures in 30 seconds flat, and wrote up the genuine causes.. If you didn't do the same you need some retraining on fire forensics. Anyone else who needs assistance please ask. No problem, but if it goes to court it will cost ££££!

-------------------------
David
BSc CEng MIET
david@ZawadiSoundAndLighting.co.uk
 11 August 2017 06:48 AM
User is offline View Users Profile Print this message



Zoomup

Posts: 3169
Joined: 20 February 2014

Good morning all on this bright and sunny morning,
thanks for the observations and comments. They have been very enlightening for me. Much appreciated.

Now I was wondering if diverted neutral currents could cause an airing cupboard fire? If the house supply cable developed a high resistance or open neutral, then diverted current of some magnitude could be carried by the immersion heater c.p.c., which may only be 1.5mm2 in size. With a TN-C-S supply and a good metal water pipe supplying the house any neutral currents would pass along the immersion heater's flex C.P.C. to the water pipes and then to "true" earth. This may cause over heating of the flex and poses a fire risk, as the C.P.C. could be carrying several tens of Amps for quite a long time. Could this happen?

Z.
 11 August 2017 08:02 AM
User is offline View Users Profile Print this message



dustydazzler

Posts: 1177
Joined: 19 January 2016

I wonder if bob the plumber makes all these considerations when he replaces an immersion tank and connects his new bit of wiring flex to the existing swi fuse in the cupboard
 11 August 2017 09:03 AM
User is offline View Users Profile Print this message



leckie

Posts: 4146
Joined: 21 November 2008

Well if you had an open/floating neutral on the supply side you could have a higher than expected voltage across the supply side. I saw this recently and posted on the subject. It resulted in one house completely burnt down and others damaged. The one I looked at had an immersion supplied via a 13A switched fuse spur and a E7 timer that switched between two elements. The spur was burnt out and ditto the timer. But you can't account for this when you are wiring an installation.

Adequate protective bonding conductors for TNCS are to accommodate diverted neutral currents. Remember when they were increased from 6mm min to 10mm some time ago.
 11 August 2017 09:04 AM
User is offline View Users Profile Print this message



Zoomup

Posts: 3169
Joined: 20 February 2014

Repetition for emphasis. Just what could have caused this airing cupboard fire? http://www.kentlive.news/a-ton...625-detail/story.html

Z.
 11 August 2017 09:13 AM
User is offline View Users Profile Print this message



Zoomup

Posts: 3169
Joined: 20 February 2014

Airing cupboard fire. Smoke alarm batteries removed. http://www.london-fire.gov.uk/...015_20_suttonfire.asp

Z.
 11 August 2017 11:46 AM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 15632
Joined: 13 August 2003

Now I was wondering if diverted neutral currents could cause an airing cupboard fire? If the house supply cable developed a high resistance or open neutral, then diverted current of some magnitude could be carried by the immersion heater c.p.c., which may only be 1.5mm2 in size. With a TN-C-S supply and a good metal water pipe supplying the house any neutral currents would pass along the immersion heater's flex C.P.C. to the water pipes and then to "true" earth. This may cause over heating of the flex and poses a fire risk, as the C.P.C. could be carrying several tens of Amps for quite a long time. Could this happen?

Only if the main bonding was missing - if present it should shunt the majority of the N current away from the c.p.c.s If the bonding was missing, probably a bigger worry is the 0.75mm2 c.p.c. to the gas boiler.

- Andy.
 11 August 2017 01:27 PM
User is offline View Users Profile Print this message



geoffsd

Posts: 1601
Joined: 15 June 2010

Originally posted by: Zoomup

Repetition for emphasis. Just what could have caused this airing cupboard fire?


It is obviously impossible to say from reading the article, however, it is likely that the installations were as you would like them to be.
That is with all the devices and cables rated as you and everyone else would have fitted them yet the fire and all the others still happened.

I presume you think it confirms your belief that airing cupboards are a fire risk in the meaning of the regulation so it would seem to be a good idea to have them constructed of non-combustible material and forbid clothing and bedding material from being placed in an airing cupboard.

Where would you stop? Open fires are obviously a fire risk.
 11 August 2017 03:08 PM
User is offline View Users Profile Print this message



weirdbeard

Posts: 3078
Joined: 26 September 2011

Hi zoomup, it's any help I don't think you did anything wrong by fitting your 16A MCB in the airing cupboard, it's not like it's cost the customer loads and I'm sure you did a fine job, but as mentioned in post 2 of this topic and by others, a 20A switch would be fine.

I'd always put money on any airing cupboard fire being caused by a faulty plastic timer. It might reduce fires those timers were only used as a switching device for a nice clunky contactor?

-------------------------
:beer)
 13 August 2017 06:27 AM
User is offline View Users Profile Print this message



leckie

Posts: 4146
Joined: 21 November 2008

Originally posted by: AJJewsbury

Now I was wondering if diverted neutral currents could cause an airing cupboard fire? If the house supply cable developed a high resistance or open neutral, then diverted current of some magnitude could be carried by the immersion heater c.p.c., which may only be 1.5mm2 in size. With a TN-C-S supply and a good metal water pipe supplying the house any neutral currents would pass along the immersion heater's flex C.P.C. to the water pipes and then to "true" earth. This may cause over heating of the flex and poses a fire risk, as the C.P.C. could be carrying several tens of Amps for quite a long time. Could this happen?


Only if the main bonding was missing - if present it should shunt the majority of the N current away from the c.p.c.s If the bonding was missing, probably a bigger worry is the 0.75mm2 c.p.c. to the gas boiler.



- Andy.


Do you mean that a 0.75mm supply to a boiler from a 3A fused connection unit is not permitted?
 13 August 2017 08:32 AM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 15632
Joined: 13 August 2003

Originally posted by: leckie

Originally posted by: AJJewsbury



Now I was wondering if diverted neutral currents could cause an airing cupboard fire? If the house supply cable developed a high resistance or open neutral, then diverted current of some magnitude could be carried by the immersion heater c.p.c., which may only be 1.5mm2 in size. With a TN-C-S supply and a good metal water pipe supplying the house any neutral currents would pass along the immersion heater's flex C.P.C. to the water pipes and then to "true" earth. This may cause over heating of the flex and poses a fire risk, as the C.P.C. could be carrying several tens of Amps for quite a long time. Could this happen?




Only if the main bonding was missing - if present it should shunt the majority of the N current away from the c.p.c.s If the bonding was missing, probably a bigger worry is the 0.75mm2 c.p.c. to the gas boiler.







- Andy.




Do you mean that a 0.75mm supply to a boiler from a 3A fused connection unit is not permitted?


Not at all, it's the omission of main bonding that's not permitted.

- Andy.
 13 August 2017 12:49 PM
User is offline View Users Profile Print this message



leckie

Posts: 4146
Joined: 21 November 2008

Oh good. I know in the past you have been of the opinion that the output of a fused connection unit was a circuit. I thought for a minute you were going down the line of the fused spur constituting a circuit and therefore as its heating not lighting, the minimum size cable was 1.5mm!

Edited: 13 August 2017 at 01:19 PM by leckie
IET » Wiring and the regulations » Immersion Heater Supply Question.

<< 6 7 8 9 10 Previous Next Last unread
Topic Tools Topic Tools
Statistics

New here?


See Also:



FuseTalk Standard Edition v3.2 - © 1999-2017 FuseTalk Inc. All rights reserved.

..