adam2

If y proposed 8 gang sockets were supplied by a single 2.5mm cable then the cable should be protected by a suitably rated MCB, probably 20 amp, possibly 25 amp. Just like any other 2.5mm radial circuit with multiple 13 amp sockets.

If supplied by TWO cables each 2.5mm as part of a ring circuit then the usually used 30 amp fuse or 32 amp MCB would be suitable. Just like any other ring final circuit with multiple 13 amp sockets.

If supplied by a single 4mm cable then a 32 amp MCB would be used as for 4 number twin sockets on a radial circuit.

If the 8 gang socket was designed for a total loading of 40 amps, then a 40 amp MCB and cable to suit could be used. Such an arrangement could be very useful in a small catering kitchen, for perhaps

Kettle, toaster, microwave, dishwasher, coffee machine,  infra red grill, portable fan, radio, cellphone charger.

On 10/7/2022 at 9:09 PM, Paul TC said:

Th IET magazine published an article that suggested "black start" of the UK supply from total failure would take several days and longer if it failed first time.

There has never been a UK wide black start, so we do not know how long it would take, but several days is plausible.

There HAS been a regional black start in London and the south east immediately after the great storm of 1987, that took only a few hours. 

Coal burning power plants can take up to 24 hours to black start from "cold and dark", but much quicker if they were running before the emergency and then tripped to "house load only".

These days we have little coal burning capacity, and black start facilities are provided by gas turbine power stations and by hydroelectric stations. International interconnectors are of no direct use for black starting as they are DC and the inverters used wont feed into a dead system. Once limited grid supplies are available then interconnectors could help.

The pumped storage schemes at Dinorwick in Wales and at Cruachan in Scotland are important black start facilities.

The national grid have particular requirements for black start power stations, including the ability to make at least three attempts at black starting in case the grid trips during the first attempts, and sufficient fuel (usually light oil) stored on site for 72 hours operation. And the ability to handle sudden changes in load.

During a black start emergency the grid frequency may vary between 52 cycles and 47.5 cycles, and down to 47 cycles briefly, a much larger range than allowed under normal conditions.

The present concerns over the price and availability of natural gas are most unlikely to lead to a complete blackout, Rota power cuts certainly, but a complete outage no way !

2 hours ago, themadhippy said:

An unfused 8 gang  would require a rewrite of the wiring regs making them  a bit pricey even if you never fitted one

In what way is it different to 4 twin sockets ? except in neatness and ease of wiring.

5 minutes ago, Andrew C said:

MK used to do green indicators for the Grid Switch range.  They may still do so...

AFAIK they are still available, but bulky and expensive if compared to a standard design of fused connection unit but with a green light instead of red/orange.

Several electrical accessories, for general use not just entertainment venues.

13 amp plugs designed to neatly and safely accept 2.5mm 3 core flex to reduce voltage drop in extension leads.

A range of fused connection units and 20 amp DP switches with GREEN indicators, more suitable than red or orange for loads intended to be left on. Including mains supply into fire or intruder alarms.

An EIGHT gang 13 amp socket for fixed installation use, not a trailing socket for extension leads. Useful when large numbers of sockets are needed. Two versions, one with a 13 amp fuse when it is desired to limit the total load, and one without any such fuse and rated at 32 or 40 amps in total.

On 9/12/2023 at 4:40 PM, alistermorton said:

Alternatively, a 650W or 1kW profile running 24/7 (or even 8 hrs a day) would soon get expensive to run. May actually be better to look at LED shop fittings specifically  designed for projecting logos, in the long run.

A 1kw lantern operated 24/7 will use 8,760 units of electricity. At present electricity prices of about 40 pence a unit that is about £3,500 a year just for electricity. If the 1kw lamps cost £20 each and last for 500 hours, that is about another £340 for lamps.

15 hours ago, Tomo said:

Usual causes of this kind of failure are bad crimping, undersized/low quality connector and undersized wire.
Undersized wire is a leading cause of bad crimping, of course.

If the issue really is that the wire is undersized for the load & conditions, then it'll eventually burn out further up or at the other end.

I'd recommend replacing the whole run, don't just patch in across the failed bit.

Also, the greenish tint likely indicates moisture, so have a look for signs of corrosion elsewhere before closing everything up.

The observed greenish tint could be due to chlorine or chlorine containing compounds, released due to overheating of PVC insulation.

On 8/5/2023 at 11:29 AM, J Pearce said:

To go further down the rabbit hole - is a fitting setup with a plug-in ceiling rose hardwired or on a plug?

I think that that the common types are called "luminaire supporting couplers" and not plugs and sockets, therefore not subject to pat testing.

It might be simpler to obtain mains voltage incandescent lights that consist of 20 small 12 volt lamps wired in series and connected directly to the mains. No transformer or controller.

Inherently dimmable, less popular these days but can still be found on line and in some stores. Usually about 20 watts total loading, you may need to add a load lamp on the same dimmer channel to ensure proper operation. 

"A tree of piggy back plugs" is a bit concerning. Use of these plugs permits of multiple plugs being powered from one wall socket. This is unwise in the case of appliances with substantial running currents such as incandescent theatre lanterns, or other appliances with high inrush currents such as HID or LED lanterns.

7 minutes ago, kerry davies said:

Why should anyone want rusty 240V AC lights that you can't get lamps for? Now if anyone has a pile of polished bronze shields as used in the amphiteatre....????

 

Why would anyone want old  oil lamps when they have electricity ? (I have several) There is a market for old or retro style lighting for d0m3stic use, the lack of the originally used lamps is of little importance, retrofit them to accept mains voltage GLS lamps or low energy equivalents. For a brighter and better focused output fit a modern vehicle headlight bulb and transformer.

Try offering it for sale cheaply, or even as a give away on this forum. As has been said demand is limited. 

A 13 amp fuse would be the norm for even a small electric drill due to starting or inrush currents. 1.5mm flex is arguably larger than is needed, and almost certainly larger than that originally fitted, but not dangerous.

PAT monkeys tested AND PASSED a Tilley lamp at one of my workplaces.

The natural gas price has moderated somewhat, but before any undue optimism breaks out, note the following.

The present price is about 100 pence a therm, between two and three times the historical norm of about 40 pence a therm.

Prices are expected to increase in Autumn and Winter.

An industrial dispute appears likely in an Australian LNG plant. Any such dispute will tend to restrict supplies and increase prices.

I again urge that urgent consideration be given to ensuring that gas and electricity are used wisely and that waste is avoided.

Energy efficiency should be carefully considered when purchasing replacement or additional equipment.

My personal view, and what I actually did when in charge of electrical safety for a group of small businesses, was formal PAT testing at the following intervals.

High risk equipment, every 3 months. Included anything involving water and electricity, washing machine, electric kettle, dishwasher, ice maker, sump pump, etc. Also anything normally carried or held in use, power tools, cleaning equipment, hairdryers, beauty appliances. Extension leads if regularly moved, e.g. for cleaning equipment. Theater follow spot.

Low risk equipment, every five years .Most office and entertainment equipment, if seldom moved. Extension leads in semi-permanent use for such loads.

Standard risk, most other appliances. Once a year.

Theater lanterns, annually if regularly moved or handled. If largely fixed in place, then after de-rigging and before re-use, or after five years, whichever occurs first.

News report here https://www.bbc.co.uk/news/world-us-canada-65145104

One person dead and several more injured at the venue, and a number of other lives lost to the tornado.

It might be worth trying it set for 240 volt mains, not 230.  The change from 240 volts to 230 volts was largely a theoretical change. The actual measured supplied is still 240 volts most of the time in most places. And can be 250 volts if close to the transformer.

Later reports state that death toll is 146.

Many crushed to death in scenes variously described as a panic, stampede, or rush. It is feared that the death toll may increase.

https://www.bbc.co.uk/news/world-asia-63440849

Very sad, and perhaps a reminder of the need for proper planning when large crowds are expected.

Agree, EL drivers should be permanently connected to a suitable length of EL wire. All switching and control should be either on the ELV input to the drivers, on the mains voltage supply into the PSUs that operate the EL wire drivers.

Use only one driver per length of wire, the output is high frequency AC and there is no simple way to make multiple drivers run synchronised.

On 10/4/2022 at 2:55 AM, Jivemaster said:

Sadly unless you have and maintain a satphone you will be accessing a cell tower and network before you get to satellite networks and still rely on ground networks to handle the connection to and emergency call handler who may or not be in your country.

 

Disagree, as far as I can tell, the whole point of this new service is that the text signal travels DIRECTLY from the cellular handset to the satellite, without any use of the cellular network.

The main market is for emergency connectivity in remote places without any cellular telephone infrastructure.

Once the satellite communication company have your text message they will pass this on to the emergency services, in the right country, they already know your location. The link from the satellite ground station to the emergency services is presumably via landline, but these are duplicated and equipped with backup power supplies. 

On 10/6/2022 at 8:52 PM, bruce said:

I recently took part in a contingency planning exercise, with people from power companies, water and utilities, fire/police/ambulance, local and central government etc. 

One of the exercises was discussion on recovering from a complete widescale unplanned power outage - a "black start". The sort of thing that happened on US west coast a few years ago, where cascading trips took out tens of millions of consumers.

The "TL;DR" is that it takes much, much longer than you might think to put power back on, and there are lots of implications that may not be foreseen.

• If power is off, water pumping stations do not work. How long before your water stops? If you're on the top floor of a tower block, it might stop immediately.  How long before sewage starts spilling onto streets?
• How long will gas last for?
• What about comms - wired and mobile phones. After a few hours, none of it will work.
• Generators may be the answer in some cases, but will they be able to get diesel supplies? Who has priority - emergency services, or telcos, or hospitals?
• You can't buy fuel, cos petrol pumps don't work. In fact, you can't buy anything cos card payments fail.
• Electric vehicles cannot be charged. That's one reason that the electricity companies don't use EVs for their maintenance vehicles! Every Scottish Power Energy Networks main depot has a bowser with several thousand litres of diesel, and a hand pump.
• ... and the list goes on

 

Water supply------Varies, some places have gravity supply from elevated reservoirs and should be OK for days. Others are reliant on pumps at the waterworks, these should have backup power, but reliability is unknown. In tower blocks yes it would go off very quickly.

Sewage-------Probably OK in MOST places as it flows by gravity to the sewage works, if power is not available for treatment there is generally an emergency overflow to a watercourse or into the sea. Not ideal but better than flooding the streets .In some very low lying districts gravity flow is not possible, the waste then flows into a pit or cavern under the road, from whence it is pumped electrically to the sewage works. The pit or cavern will take many hours to fill up, so no problem for a three hour rota cut, but if it was off longer term, yes flood of sewage. 

Comms------Traditional copper wire telephone lines should be fine as the exchanges have large batteries for exactly this eventuality. However as discussed elsewhere there is growing reliance on fibre optic and internet based telephone service this is very vulnerable. Cellphones are vulnerable to loss of power to the masts, MIGHT be ok in an urban area by connecting to a mast that still has power.

Generators-------------Could be most valuable, but run time is limited to the fuel STORED ON SITE do not count on any resupply in a prolonged outage. In the case of rota power cuts, then re-supply should be simple between the cuts. If possible for say a theatre, store enough fuel for 10 hours operation. 3 power cuts each of 3 hours, plus a margin. That should last a week, remembering that some cuts will be when you are not open. Rule of thumb is to allow one litre of diesel for every 3 kwh. So to run a 100 kw generator for 10 hours that is 1,000 kwh or about 333 litres of diesel fuel. You might well get 4 kwh per litre, but do not count on this. 

Vehicle fuel wont be available without power at the filling stations. No problem for 3 hour rota power cuts, simply fill up before or after the 3 hour power cut, or in an area that has power. Could be serious in a prolonged outage. Keep your vehicle tank at least half full, store spare fuel if you can safely.

Electric vehicles should also be fine in 3 hour rota cuts, They should charge just fine between the cuts. A serious problem though in the event of a long term failure.

Natural gas supplies----------Should be fine. Natural gas pumping stations are either "protected loads" not liable to rota power cuts, OR use gas turbine pumps.  

On 10/6/2022 at 9:16 AM, sleah said:

Seriously? They'll cut off hospitals 😮 I know they should have backup power but surely only for dire emergency?

Presume they are not of national importance. Apart of course for any where someone important is having treatment I bet!

Yes, hospitals will be cut off, if supplied by the local distribution system as most are. It must be repeatedly stressed that a planned or rota cut will affect EVERY consumer in the area cut off. There is simply no way to leave selected customers on.

Hospitals have standby generators some of which will work when called upon. Very few hospitals have 100% backup power. A common approach is about 25% of the lighting and about 25% of the socket outlets, with 1005 backup only for ICUs and operating theatres.

It is an NHS policy that pre planned major surgical operations must not be started unless TWO electrical supplies are available such as mains and a backup generator. Therefore if the mains supply is already off no planned surgery may be started. Unless duplicated generators are available.

Minor surgery may be performed with an assistant holding a torch.

The geographical area covered by one load group varies a great deal so as to ensure that each load group contains about the same amount of load. In an urban area, an area still on will often be within walking distance. In a rural area the distances are much greater.

Street lights are in the same load group as other loads in the area.

It is unlikely that trains will run. The traction current for electric railways SHOULD STAY ON as it should have a dedicated high voltage grid connection and is a "protected load" not liable to rota power cuts. The lack of station lighting will prevent use during the hours of darkness. Lack of power for signals may close many lines. A limited service can be operated on some lines without any signalling.

Buses should still run, but beware creeping elfansafety that deems unlit streets to be too dangerous for buses. 

I recall the last lot of rota power cuts ! electric trains still operated then, with stations lit by oil lamps, but these days I doubt that the railway HAVE any oil lamps. 

Rota powercuts for three hours at a time will be most inconvenient but hardly a national disaster.

A national power failure, recovery from which requires a black start is far more serious. Most power stations require an external source of electricity to start up. A minority can "black start" generally from diesel engines that start from batteries or air bottles. 

There has never been a national black start in the UK. There WAS a regional black start after the great storm of 1987.

A generator is certainly worth considering if it enables a performance to go ahead rather than being cancelled.

Great care is needed to ensure EVERYTHING safety critical is connected to the generator. In particular make certain that the "mains" input to the emergency lighting is connected to the generator, this is often neglected, fire alarm ditto.