Instant Water Heater Behind Partition (Tool), Isolator Location?

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jason1958

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Consider a service partition for a shower/basin ensuite, accessible via use of a tool.

Services such as digital instant water heater (digital remote control), whale pump, yadda.

Seems obvious to stick the 45A isolator outside the service partition, on the wall outside Zone 2 - but walls soon get cluttered and grid ain't doing 45A. Pullcord is not to clients taste (this is a 20m2 ensuite, clear frameless).

So... why not stick an isolator within the service partition - as for an immersion within its cupboard?

The problem I have with this is reg 132.15.1.

The isolation point should be SUITABLY positioned and provided to PREVENT or REMOVE danger.

Suitable for who?

End-user wanting accessible 45A isolator - for what, heater also supplies the basin 24/7?

Maintenance fine with 45A isolator inside service partition? Indeed I think an IPx4 isolator in there is safer?

Best clutter job I've seen is SFCU & double socket above every unit in a packed all on one side of a long corridor kitchen. Better to have a few grid every so often, keeping within the 2m isolation rule.

 
An isolator facilitates isolation of a fixed appliance during maintenance.
 
However, isolation may be provided via the main switch (eg, as kitchen appliances), unless the MI say otherwise.
 
To counter that, instant water heaters present a particular failure mode: unrelated plumbing works may introduce air into their CW supply, turning the HW tap on causes the heater detects flow, powers up the bare wire element on an air bubble, so destroying itself (99% the price of the heater!!).
 
OK so the isolator is for mechanical maintenance.

Why in that case does it need to be outside the enclosure?

The enclosure would be opened up for mechanical maintenance, thus the isolator easily accessible, and under control of the person undertaking the maintenance, thus actually negating the need for LOTO perhaps.

So, would the isolator being outside the enclosure protect the water heater from that failure mode when being used by an unskilled and unsuspecting person?

 
An isolator outside the enclosure (partition containing water heater) provides little value - it just seems traditional as with conventional electric showers :)

Skilled:

- Isolation can be handled by a main switch or CPD (w/lockoff).

- Mechanical maintenance could use the CPD (w/lockoff), but frankly a local isolator makes sense here re "lights still on" servicing etc.

Emergency:

- Emergency is handled by the RCBO re EF OC SC faults.

End User:er

- Functional switching is handled by the device itself.

- MI simply say 3mm gap re main switch (no specification of a local isolator)

End User is left to interact with a wireless/SELV digital device.

It seems only a cooker actually requires specific local isolation by regulations (historically very logical re fires), rest comes down to MI.

 
I think then from your last post you have convinced yourself that inside the enclosure is fine?

Cooker, accessible yes, as you say fire.

Shower, outside the enclosure, yes, ip rating, though, really you could fit a ceiling mounted pull switch over a shower enclosure, if, it was appropriately ip rated for the location, and, if you think about it, that would be convenient for the user.

So as long as the MI don't specify that the isolator must be in s particular location, that insists you put it outside the enclosure, then?...

 
Pull cord might suit a shower, but this is a 24/7 instant heater...

- basin for hand washing

- shower for body washing

Functional switching is via flow sensing...

- shower stop valve (on/off) with fixed shower head

- hot tap valve (on/off)

Emergency switching can be said to be handled by a) local functional valve & b) digital output temperature regulation which operates irrespective of pressure/flow changes, and other safety cutouts. It got picked by the NHS for high risk areas.

MI simply specify permanent connection (so no 13A plug!), contact separation of at least 3mm on all poles (so no wiring to meter tails!), circuit breaker of suitable rating (ditto! :). MI do not specify a local isolator. Regs do not mandate a local isolator.

If it were a remote immersion heater offering similar functionality...

- Digital TMV + Secondary cutouts

- Remote switch - for occupier convenience (eg, downstairs)

- Local isolator - for maintenance convenience (eg, trivial cost over a junction box to join FTE to HR flex)

Ok...

- All items in the enclosure (partition) have IPx4+ rating.

- Both pump & TX have integral IPx4+ switch for maintenance.

So for convenience, if not regs, a local IPx4+ isolator does ease maintenance of the instant-heater.

 
Apologies, forgot to thank you for your replies & discussion - much appreciated.

 
Fine, no worries, BTW, I was not suggesting a pull cord for your heater, I realised what type it was.

I was just discussing in general the merits of local isolation and the different types, for different applications and locations etc.

Now you seem to have made your mind up, I'll give you my take on it.

Personally, I would put it in the enclosure! ;)

 
Thanks, trying out a clipsal aquaseal isolator.

Never used that particular model, but more compact in height than a rotary.

40A. IP66. 2 pole, lockable, M25 (backbox does rotate), will be interesting to see what wiring space is like.

Pratley #2 flat gland on FTE, roll of SIHF 6mm left over so a few inches are ok (never any H07RNF 6mm left due to welder in the family!).

 
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