immersion heater and a shower pump

[Deleted member 9648]

QUOTE what about bonding?

Where do you find a bare resistance wire in water?

Where then are the regs for the connection of domestic immersion heaters?QUOTE


Bonding is at the point of entry...a metallic pipe does not have to be continuous beyond the point of bonding.

I've never come across bare resistance wire in water,but then I've never come across bare electrodes in water and yet there are a set of regulations for those.

There are no specific regulations for the connection of domestic immersion heaters because general regulations apply. There are specific regulations for electrode and uninsulated elements because of the additional hazards associated with them which are not present with a normal insulated element.

Well thats my interpretation anyway!

 

[tonys]

Don't bare electrodes/elements do their job in insulated Tanks ?

Just answered the question myself I think lol

Bare element = class 2 insulated tank

Insulated element = class 1 metallic tank

 

[pushrod]

There are no specific regulations for the connection of domestic immersion heaters because general regulations apply. There are specific regulations for electrode and uninsulated elements because of the additional hazards associated with them which are not present with a normal insulated element.

Well thats my interpretation anyway!

Guidance Note 1 (Selection and Erection)
page 131 C5 WATER HEATING AND ELECTRIC SHOWER FINAL CIRCUITS
says that domestic immersion heaters should not be connected by a plug and socket outlet and the reg it refers to is 554.3.3!!!

OSG app 8 (standard circuit arrangements for household and similar installations) 8.5 WATER AND SPACE HEATING - immersion heaters should be connected by outlets complying with BS 1363-4

Where are these immersion heaters in domestic situations if not in our large copper hot water tanks

 

[Deleted member 26818]

Actually Tony, LV electrode heating can be in insulated tanks, or in non-insulated, conected to the neutral and earth tanks.

 

[MarkieSparkie]

In my previous post about the construction of an domestic immersion heater, I obviously didn't make myself clear, so hopefully the following will.

First an apology:
Sorry, I did not have my Regs book at hand (left it at work) and quoted the wrong Reg Number used elsewhere in our discussion thread so please ignore that and refer to my correction below.

The actual element of resistance wire is insulated from the earthed protective tube. If the insulator is air then the element will be wound on a former with regularly spaced supports, to prevent shorting to the tube. If on the other hand the insulating material is silica (refined sand in effect) the element can be a self supporting spiral of wire held under tension, the silica is then added under pressure to preventing shorting to the tube, the tube is then capped to prevent the loss of silica and then bent into a loop ready for fixing to the header.

A domestic immersion heater is an insulated element and therefore 554.3 does not apply.
The 554.3 group of regulations apply to instantaneous water heaters eg. showers and quick-boil heaters etc.

Correction:
Electrode boilers are covered by 554.1 group of regulations.

Once again sorry for any unintentional confusion caused.

 

[tonys]

Mark - So your of the same opinion that the heater element is of an insulated type ?

When the NICEIC get back to me by e-mail, if their response goes against what the retired engineer said/the Technical guy yesterday, it will be slightly embarrassing to say least, for them and me.

I've got work today so won't know any response until I get in later.

 

[Deleted member 9648]

Guidance Note 1 (Selection and Erection)
page 131 C5 WATER HEATING AND ELECTRIC SHOWER FINAL CIRCUITS
says that domestic immersion heaters should not be connected by a plug and socket outlet and the reg it refers to is 554.3.3!!!

OSG app 8 (standard circuit arrangements for household and similar installations) 8.5 WATER AND SPACE HEATING - immersion heaters should be connected by outlets complying with BS 1363-4

Where are these immersion heaters in domestic situations if not in our large copper hot water tanks

Pushrod you may well be correct and I'll put my hands up if you are...GN 1 is in the office and I will check out your reference later.
The sticking point for me is 554.3.2 I do not see how this can be applied to a normal domestic immersion heater,in fact it cant....it is that and that alone which makes me think that 554.3 does not refer to a type of heating element I am familiar with.

 

[Martin Bradley]

Exposed element.

 

[pushrod]

yeah you can see the coiled resistance wire encased in an insulator like magnesium oxide or something similar. It would be inconceivable to ever have a design where it was just flopping around inside the metal casing. It is the same with cooker elements.

 

[MarkieSparkie]

Stop Press: Immersion element construction update.
I've been in contact with half dozen leading manufacturers of domestic and industrial immersion elements this morning.
It appears air insulated elements are 'old school' and rarely manufactured today and silica insulated elements are reserved for the budget end of the domestic market.
In order to achieve higher wattage densities, thermal efficiency, maximum electrical insulation, hot spot reduction and long life the insulation material most manufacturers currently use is compacted refractory magnesium oxide (MgO) in both domestic and industrial immersion heaters.
Summary:
Electrical manufacturers confirm domestic immersion elements are of insulated construction and that the 554.3 group of regulations do not apply to their products. Heatrae Sadia and Santon going further, stating that the 554.3 applies specifically to shower and quick-boil instantaneous water heaters.

 

[tonys]

Mark

Thanks for your input.

Update from me

Still no e-mail from the NICEIC. But I got my QS yearly assessment dated 2007. Amongst it was a periodic which included a code for an immersion heater on plug top.

Now normally when you do something what does not comply with BS7671 the NICEIC Engineer notes the issue and put a cross in a box to show you never complied and offers an explanation as to why.

Now this sheet stated immersion heater on plug top does not warrant a code, now its looks like a number after the code, but can't fully make it out. But the regulation number quoted was in the 744 range. So it might of been the case where the immersion heater was in a airing cupboard which was in a bathroom.

But normally when the NICEIC Engineer believes a coding is warranted but you got the coding wrong they would offer a different coding, but in this instance he never.

Will update when I know more.

 

[Deleted member 9648]

Checked GN1 today and Pushrod is correct as it clearly states household immersion heaters should not be on a plug and socket and refers to reg 554.3.
However this gives the impression that regs 554.3 (immersed uninsulated elements) includes normal domestic elements.
This is at odds with the requirement of reg 554.3 which states that the elements referred to must comply with 554.3.2.
554.3.2 states that all metallic parts of the water heater except current carrying parts must be solidly connected to a metallic water supply pipe,and that water supply pipe must be earthed back to the MET by means independant of the circuit CPC.
A normal domestic imm heater is fed by a copper pipe from a plastic header tank,that pipe is not normally connected to the MET,does this mean that the majority of domestic water heaters dont comply?....no,I still believe 554.3 does not apply to domestic insulated elements and possibly GN1 is not referring to the correct regulation.

 

[tonys]

Wirepuller

When I used to quote guides etc to our Engineer, his answer was not interested in them, your working to BS7671 and that's what me and you refer to.

Guides are just that.

 

[pushrod]

554.3.2 states that all metallic parts of the water heater except current carrying parts must be solidly connected to a metallic water supply pipe,and that water supply pipe must be earthed back to the MET by means independant of the circuit CPC.
A normal domestic imm heater is fed by a copper pipe from a plastic header tank,that pipe is not normally connected to the MET,does this mean that the majority of domestic water heaters dont comply?....no,I still believe 554.3 does not apply to domestic insulated elements and possibly GN1 is not referring to the correct regulation.

I take your point that there seems to a discrepancy here. My own feeling is that it(reg 554.3.2) dates back to pre 17th where you would expect there to be supplementary bonding on the pipe work and that it has not been updated to go with the fact that installations to the 17th edition, with circuits under the control of RCDs, no longer require supplementary bonding to metallic boiler pipework. ??

If not i still ask where are the immersion heaters that these regs apply to?

Also, i think "uninsulated element" is not referring to the resistance wire not having insulation around it, but to the fact that there is no insulation around the outer metal case of the heating element.

It would be interesting to get a few more opinions, maybe someone like widdler or IQ.

 

[pushrod]

Wirepuller

When I used to quote guides etc to our Engineer, his answer was not interested in them, your working to BS7671 and that's what me and you refer to.

Guides are just that.

But the OSG and the Guidance Notes are all written by the same people - the IEE - to help explain BS7671, strikes me as a bit of an arrogant attitude by the engineer.