Socket inside an enclosure a not on a socket circuit

[markocosic]

Hello experts,


I'm putting together an energy monitoring system for a social housing application and need a mains socket inside an enclosure.


One enclosure sits next to the consumer unit for monitoring electricity use. I need to plug this specific transformer into it to power the system and obtain an AC voltage sample:

http://shop.openenergymonitor.com/ac-ac-power-supply-adapter-ac-voltage-sensor-uk-plug/

Another enclosure sits in the airing cupboard (electric immersion heating thermal store) and I'll be plugging a generic USB charger into it to power that system. Logistically it's easiest if the landlord installs the enclosures and sockets with their qualified trades, we bung our gear in the box, and hopefully nobody, including the tenants, touches it for the next 6 months.


Q1) Any rules against a socket inside an enclosure that requires a screwdriver for access?


Q2a) We don't want to add circuits. Can one add a socket (on a 1.5 mm^2 T&E running in conduit) to a lighting circuit at the consumer unit, provided that this socket is within that enclosure, labelled as to its specific use and the circuit it's fed from, and not accessible without a screwdriver. Maximum load <5W.

Q2b) Same question but in 2.5mm^2 T&E on the end of an immersion heater circuit in the airing cupboard, again inside a screwed shut enclosure.


I'd like a solution that a qualified electrician can wire in our absence with a clean conscience and we can arrive to plug our gear into later.


Thanks,


--
Marko

 

[plugwash]

I don't belive there are any regs prohibiting what you propose but some electrcians seem to be unhappy with sockets on anything other than socket circuits.

You also need to think about what will happen at end of life of the system, will there be a controlled removal or will someone take the lid off the enclosures, remove the monitoring equipment and leave the sockets accessible for general use......

It also wouldn't surprise me if you find some properties where the only circuit to the airing cupboard is a switched off-peak one.

I'd rather see the socket near the CU spurred off a socket circuit than off a lighting circuit.

Things will probablly go easier if you can persuade the landlords to let you use your own electrican for the work.

 

[JohnW2]

To re-iterate and agree with what plug wash has written:

Q1) Any rules against a socket inside an enclosure that requires a screwdriver for access?

Not of which I am aware.

Q2a) We don't want to add circuits. Can one add a socket (on a 1.5 mm^2 T&E running in conduit) to a lighting circuit at the consumer unit, provided that this socket is within that enclosure, labelled as to its specific use and the circuit it's fed from, and not accessible without a screwdriver. Maximum load <5W.

As plugwash has implied, you could just as easily run the socket as a 2.5mm² spur from one of the sockets circuit in the CU. There would then be no issues as regards what might get plugged into it (e.g. after your system was decommissioned) and, indeed, unless you wanted it to be, the socket would not even have to be in an enclosure.

Another enclosure sits in the airing cupboard (electric immersion heating thermal store) and I'll be plugging a generic USB charger into it to power that system ... Q2b) Same question but in 2.5mm^2 T&E on the end of an immersion heater circuit in the airing cupboard, again inside a screwed shut enclosure.

As plugwash has said, the immersion supply might not be permanently 'on'. However, if it is then why not install a dedicated USB power module (like those available from MK), rather than a socket? Again that would remove any questions about what might get plugged into a socket - and, again, would not need to be in an enclosure unless you wanted it to be.

Kind Regards, John

 

[markocosic]

Thanks chaps,


I'd assumed that a socket 'spurred' straight off the 32A socket breaker in the ring in 2.5 mm^w would be a no-no (A3 radials wanting a 20A MCB) hence feeding from a 6A lighting or 16A immersion MCB.

A 2.5mm^2 radial straight from a 32A MCB, if say <1 metre in length, is ok then? Could take both from the immersion circuit and relabel the MCB as 'immersion and heating controls' perhaps?


The socket does want to be inside the enclosure (w/tamper evident seals and tamper alarm if the lid is pulled or the comms go down) for operational reasons but this could affect where we put the whole enclosure: give them the option of an extra hall socket when the kit is removed.


Good shout on the USB power module. I'm a little wary of these because there's "2.1A" in China spec and then there's "2.1A" in the real world; there's phone-charing duty vs continuous duty cycle, and we have a hot airing cupboard environment. For plug in wall warts we have a 'known good' configuration for.

The MK one is fairly worthless because the outlets are only 1A each. (marginal for computing equipment that could draw near to that on occasion and doesn't ave internal batteries) but he LAP one has a nominal 2.1A available across both outlets. We'll see what it's like in reality...

http://www.tlc-direct.co.uk/Products/MKK5837W.html
http://www.screwfix.com/c/electrical-lighting/usb-module/cat6480004


Immersion supply is permanently live; E7 rate switching is a dual register digital meter and nothing is time switched other than locally at the point of use. Most immersions are on 24/7/365 to be honest.


The landlords contractors (social housing provider has in house 'odd jobs' team) are good; no problem with them accepting proposals if they're regs compliant: I just wanted to check what we were proposing before I present something silly in front of them.

(controls and plumbing side is our bag, not electrical/gas regs)

 

[JohnW2]

I'd assumed that a socket 'spurred' straight off the 32A socket breaker in the ring in 2.5 mm^w would be a no-no (A3 radials wanting a 20A MCB) hence feeding from a 6A lighting or 16A immersion MCB. ... A 2.5mm^2 radial straight from a 32A MCB, if say <1 metre in length, is ok then?

Yep, provided it's just one (single or double) socket. The MCB of a ring or radial circuit is no different from anywhere else on the circuit, so 'spurring' from the MCB is no different from spurring from a socket or JB in the (radial or ring) circuit.

Could take both from the immersion circuit and relabel the MCB as 'immersion and heating controls' perhaps?

With the possible distant future in mind (per plugwash comments), I'd be a bit less happy with that. Assuming it's probably a 16A circuit, the immersion will use most of that - thus leaving little left for whatever else someone might conceivably plug into the socket after you've 'abandoned' it!

The socket does want to be inside the enclosure (w/tamper evident seals and tamper alarm if the lid is pulled or the comms go down) for operational reasons but this could affect where we put the whole enclosure: give them the option of an extra hall socket when the kit is removed.

Fair enough. I was merely pointing out that, if spurred from a sockets circuit, the socket would not have to be in an enclosure unless you wanted/needed it to be (which you clearly do!)

Good shout on the USB power module. I'm a little wary of these because there's "2.1A" in China spec and then there's "2.1A" in the real world; there's phone-charing duty vs continuous duty cycle, and we have a hot airing cupboard environment. For plug in wall warts we have a 'known good' configuration for. The MK one is fairly worthless because the outlets are only 1A each. (marginal for computing equipment that could draw near to that on occasion and doesn't ave internal batteries) but he LAP one has a nominal 2.1A available across both outlets. We'll see what it's like in reality...

It was just a thought! I don't have detailed spec to hand, but the MK K5837 module claims to be "twin 2A", whatever that means.

Immersion supply is permanently live;

Fair enough - again, just checking!

The landlords contractors (social housing provider has in house 'odd jobs' team) are good; no problem with them accepting proposals if they're regs compliant: I just wanted to check what we were proposing before I present something silly in front of them.

As had been said, even what you proposing originally is probably reg-compliant, but as plugwash said, some electricians would not be happy connecting sockets to a lighting (or maybe even immersion) circuit.

Kind Regards, John

 

[JohnW2]

... The MK one is fairly worthless because the outlets are only 1A each....

It was just a thought! I don't have detailed spec to hand, but the MK K5837 module claims to be "twin 2A", whatever that means.

It seems that you were right - in some language, "twin 2A" appears to mean 2 x 1A

Kind Regards, John

 

[Lectrician]

I wouldn't be too worried what circuit it went on. It's in an enclosure and intended for a piece of kit on a temporary basis. The enclosure and socket is bound to be removed, as I'm sure you want your kit back.

What is it your actually doing? The kit in the airing cupboard, can this not go near the CU too?

 

[markocosic]

Me: www.coheat.co.uk

Airing cupboards in these flats have a thermal store in them. Immersion heats a vented cylinder and there's a pump + plate heat exchanger for producing mains pressure hot water on-demand. (a godawful Gledhill Pulsacoil III setup)

We're logging flowrate and inlet/outlet temperatures through/across the plate heat exchangers to work out how much hot water people use, when, and at what flow rate. "What's the REAL diversity on this (soon to be) communal heating system?" in electrical speak. Needs to sit in the pipework hence airing cupboard.

The CUs are by the front door. They monitor supply voltage and current on three circuits (total, storage heater, immersion heater) so that we can see how much heat is going into the building in total and how much of this is "controlled" heat from the storage heaters vs incidental gains from lighting/cooking and thermal store losses. We throw a temperature sensors at that too, so that we can spot when the door has been opened (door open, lights on, anybody home? etc) and whether they're heating an empty house or not.

A few temperature/humidity sensors complete the picture; duplicate across the entire development...


It's worse than "Twin 2A = 2x 1 A outlets" JohnW2. They're not even 1A continuous rated...


We'll retrieve the kit when we're done and include the socket in that. Keeps it stupid simple by the sounds of it. Thanks for the advice!

 

[JohnW2]

It's worse than "Twin 2A = 2x 1 A outlets" JohnW2. They're not even 1A continuous rated...

I see

We'll retrieve the kit when we're done and include the socket in that. Keeps it stupid simple by the sounds of it. Thanks for the advice!

I didn't really appreciate quite how temporary we were talking about, and that the sockets will be removed when you retrieve the rest of your kit. That being the case, I think your original proposal (or any of the other suggestions) would be perfectly OK.

Kind Regards, John

 

[OwainDIYer]

just watch the temperature for power supplies inside enclosures inside airing cupboards.

Apart from anything else, you don't want to find in x monmths' time that thermal failure has damaged your data collection placing the wider project at risk.

 

[markocosic]

Will do.

Site towards bottom of the airing cupboard and measure flowrate on the cold side.

Fortunately the landlord has already cut whacking great vents in the door to try stop the thermal store (Gledhill Pulsacoil III) burning through PCBs like sweets...