water heater switch on socket ring final circuit

[olsonn]

Went to look at a job today in a one bedroom purpose built flat which consists of two lighting circuits, a single ring final circuit for the sockets, a shower circuit and a cooker circuit with a single socket outlet. The customer wanted to upgrade the old fuse box to a CU in what on the surface appeared to be a straightforward job.However when looking in the kitchen I spotted an illuminated switch marked up Water Heater. I asked the customer what this was for and they said that there is a water heater in the loft, but that was all she knew. There was no reference to a water heater in the fuse box, but when I pulled the ring final circuit fuse I discovered that the switch was wired into this circuit. I havent been in the loft yet to see what sort of heater it is, but shouldn't a water heater be on its own circuit ?. Typically the flat has all recently been decorated and when I said about the water heater, the customer said it had been like this for years and never caused any problems. Not too sure what to do now, any advice greatly appreciated.

 

[Guest123]

Firstly, we don't know what type of heater the 'water heater' is.

The only nod in BS 7671 regarding this is in appendix 15 which 'recommends' that appliances over 2KW should not be connected to a standard A1 RFC.

You need to find out what this 'water heater' is, immersion etc, and make a decision based on what you find.

 

[Knobhead]

There was electricity before the 17th, immersion heaters were frequently wired off a ring.
As Lenny said above 2KW isn’t recommended but you’ve got to weigh up the pros and cons. Suggest wrecking Mrs. Browns decorating and the chances are you’ll be back in your van pronto!

 

[Guest112]

i agree with tony you cant really knock it if it doesnt comply with 17th if it wasnt installed to the 17th. Your only doing a cu change, make a comment if you wish on the report and suggest that it would be better on its own circuit to the customer to cover yourself the balls in her court then

 

[Dunc]

Risk assessment and comment on the EIC if it is over 2kW. Was standard practice in the late 60s to 70s judging by the CU changes i've done. If it's an easy fix without destroying the customers house then you could recommend installing a separate circuit for the water heater.

 

[platty1005]

I would leave it
I don't think there is a specific reg to prohibit this but don't have my copy to hand to confirm this.
It is not best practice and goes against App15 recommendation but it isn't dangerous if the circuit tests out OK
I would put a comment on the EIC in comments on existing installation box

The reason it is not recommended is that the RFC will be pre loaded to about 13A if it is a 3Kw immersion.
If the RFC is then loaded with other appliances it may give rise to nuisance tripping.

 

[Guest123]

If the RFC is then loaded with other appliances it may give rise to nuisance tripping.

I wouldn't agree with nuisance tripping being the main reason for App 15 not reccommending it.

It's more to do with ensuring equal load sharing all the way round a RFC and trying to eliminate the scenario of overloading one leg of the RFC which is, as we know, a cable with an (Iz) less than (In) which in turn flies in the face of cable calcs as we know them.

Cable will start to overheat before nuisance tripping occured if an RFC is not evenly loaded hence the reccomendation in App15.

As you suggest, there is no specific regulation prohibiting doing this, only App15.

 

[malcolmsanford]

What always amazed me with that appendix is that it advised that a cooker, ovens and hobs exceeding 2Kw should be on their own dedicated radial, but water heaters regardless of Kw, and most are 3Kw, just not connected via a ring final, wonder why these were not granted the dedicated radial status

 

[MarkieSparkie]

OSG, 8.5; EGBR 4.5 and GN1, C4 advise "Water heaters fitted to storage vessels >15 litres ... should be supplied by their own separate circuit."
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