adam2

To return to the O/P, to measure the current in a circuit used from a 13 amp socket, make up an adaptor as earlier described. I have been known to use a coil of ten turns around which the clamp meter is used. Many clamp meters are not very accurate at low currents, and this helps by passing the same current through the clamp meter ten times. Divide the meter reading by ten. Strictly speaking, as has already been said, this should be double insulated wire, though I will admit to use of a piece of single core 2.5mm single insulated conduit cable. I did put this measuring coil in the neutral to reduce the consequences of any damage. If prolonged use rather than a brief test is expected then I would use 2.5mm rather than 1.5mm as ten conductors are in effect bunched together. A 13 amp plug fuse should carry 13 amps continually. they often carry 20 amps for some minutes, but don't count on this. No great accuracy can be expected when calculating the amps used by theatre lanterns or other incandescent lamps. The actual design voltage of the lamps is probably unknown and might be 220 volts, 230 volts, or 240 volts. The actual supply voltage is also probably unknown, and even if measured it may later vary. It could be as low as 200 volts or as high as 254 volts. The actual current used by a lamp may also vary a bit due to manufacturing tolerances, 2% is common, and variances of 5% occur. The running current of a filament lamp also slightly reduces as the lamp ages.

Yes. Though even in the UK there are still some non-standard legacy systems that go back to DC days.. The present day supply is of course AC, but non standard in various ways so as to utilise mains networks intended for 3 wire DC. The street mains contain only 3 wires, one of which is half size or less. The substation contains either a special transformer called a "diametric transformer" or a pair of transformers one of which has reversed polarity. Each existing main is supplied with single phase, 3 wire AC at 240 volts from either pole to the neutral, and 480 volts between poles. Note 480 volts, not 415 as with three phase. The half sized neutral carries only the out of balance current, and the system works fine. Any customer wanting three phase has to either pay for a new main from the substation, or use converting plant, or resort to a generator.

4 wire, 3 phase delta is rather an odd system and more or less confined to the USA, virtually unknown elsewhere. 3 single phase transformers are used, each with a 240 volt secondary, delta connected. One of these transformers has an earthed center tap (the bottom transformer as conventionally drawn) This provides a 3 wire supply at 120/240 volts. By ignoring the neutral and utilising the 3 phases, a standard 3 phase motor may be used. With this system, great care must be taken to connect lighting and small appliances ONLY between the neutral and either of the two bottom phases (as usually drawn) any connection between the neutral and the top phase will supply 208 volts. The top phase is often known as the "high leg" or the wild phase, and in most states must be coloured orange. Accepted colour codes for three phase, 4 wire delta. Bottom left phase-------------------Black Bottom right phase----------------red top phase----------------------------Orange, or less commonly blue. Neutral--------------------------------White. Voltages, black/white--120 volts red/white--120 volts orange/white----208 volts any combination of black, red, and orange---240 volts. Typical usage, larger homes with central air conditioning that need three phase services. Farms that need three phase service for machinery and large pumps, but still need 120/240 service for farmhouse.

110 volt 3 phase as used on a UK building site is 3 phase, 4 wire with 110 volts between phases and 67 volts between any phase and the earthed neutral. 67 volt loads are not intended to be used and the neutral is not distributed beyond the transformer. 4 core cables and 4 pin plugs and sockets are therefore used for the 3 phases and a protective earth. USA d0m3stic 3 phase supplies are 3 phase, 4 wire with 208 volts between phases and 120 volts between any phase and the earthed neutral. Lighting and small appliances are connected between any phase and the neutral at 120 volts. Larger and usually non portable appliances are either 208 volt single phase, connected between any two phases, or are 208 volt 3 phase connected to all 3 phases. Depending on design, these appliances may, or may not need the neutral as well. Other systems exist including single phase, 3 wire at 120/240 volts. and 3 phase 4 wire delta at 120/240 volts.

As has been said, there is no law that specifically prohibits the throwing of a lit match on stage. However, so doing MAY be de-facto prohibited by the building owners or their insurers. Many prohibit ANY use of "real fire or flame" on stage. Even in the absence of any such prohibition, the idea makes me uneasy, though it is doable with suitable precautions. The obvious precautions include making certain that the surroundings are fire retardant and the provision of buckets of water and sand, fire extinguishers, and persons to use same. Two less obvious but still important considerations include, firstly a good standard of cleaning in the area to avoid any build up of potentially flammable dirt, dust, or refuse, and secondly a careful examination of the stage surface to ensure that it has no small holes, gaps, or crevices down which a lit match could fall and perhaps start a fire. Many "proper" stages consist of wooden boards with storage below, a lit match going down a crevice between the boards could have most serious results. Many temporary stages consist of moveable sections, perhaps with slight gaps between them, down which a dropped match could fall and perhaps ignite dust or litter. Finally remember that the spent match is PROBABLY safe, but should be broken in half and put in a metal tin as an extra precaution.

I do not believe that voltage sag during startup is relevant. As has already been said, the mains into the unit is rectified and then smoothed with a large capacitor. A mains voltage of say 250 volts will cause a greater inrush current than a mains voltage of say 200 volts. A supply voltage of 110/120 volts would further reduce the inrush current as the energy needed to "fill" the capacitor is much less. A lower supply voltage will increase the RUNNING current, but NOT the inrush current. As has already been said, the best solution is to spread the lights over more circuits. Or to devise some way of starting them in sequence rather than all together. Other options include fitting an inrush current limiter to the circuit, this however means (minor) alteration to the fixed wiring installation which will probably be looked upon with disfavour by the building owner. Such a device may also give misleading results when the wiring is next tested. Or fit an inrush current limiter to each light, this will void the warranty but might be worth considering if the warranty has expired. Yet another option is to make inrush limiters with a plug and socket to go between the supply and the lantern. Rather expensive/time consuming in view of the numbers needed. Inrush current limiters generally consist of an NTC (negative temperature coefficient) device in series with the supply. They get warm in use, and can fail explosively at end of life or if an external fault occurs. They should therefore be enclosed in earthed metal and connected via porcelain terminal blocks. Sounds simply to use multiple circuits.

I agree that sensible kids should be allowed up a tower. One approach that worked in a local school was to re brand a tower as a "mezzanine floor" with approach via stairs rather than a ladder. Children are of course allowed to use stairs to reach the upstairs of a school. The structure was built by a local firm and is very sturdy. It consists of a welded steel frame and a floor of heavy duty beech plywood. Can be dismantled for storage. Used for follow spots and also very useful for refering sporting events, and invigilating examinations.

Can you justify the purchase of a large amount of 3 core, 1.5mm TRS or similar cable as used for stage lighting. If so, consider use of such cable with all 3 cores paralleled so as to give in effect 4.5mm cable. A second similar cable being used for the other pole of the circuit. After the event the cable can be re purposed for stage lighting.

Compressed air from a foot pump or an electric air compressor can indeed be used to dispense keg beer instead of carbon dioxide. It only works well if the keg is sold promptly once started. If the started keg is not sold within a couple of days, then the air causes the beer to oxidise and spoil.

I am a larger drinker, about 120 kilos I fear. But I normally drink ale and not lager. More seriously it is possible to dispense lager and keg ale without carbon dioxide if this be in short supply.

For those not already aware, there is currently a serious shortage of carbon dioxide caused by a combination of factors including seasonal shutdowns and increased demand. For venues that use carbon dioxide in cylinders for special effects, it would be well to obtain extra stocks whilst you still can. If your venue has a bar, remember that carbon dioxide is also used for dispensing keg beer and carbonated soft drinks. A shortage of canned and bottled beer and of carbonated soft drinks is possible, and it might be worth increasing stocks of these products. Dry ice may also be in short supply, though not much can be done about that since it does not keep. It might be worth looking at alternatives to dry ice. Drifting slightly O/T, if you expect much consumption of beer and fizzy soft drinks at home, it might be worth buying now rather than the day before the party/football match/barbecue. Historically, most of the carbon dioxide sold in the UK was produced by Distillers PLC, a company noted for the production of distilled spirits. Recently however it has been found more economic to capture, process and sell the carbon dioxide that is a by product of fertiliser production. Fertiliser demand is limited at this time of year resulting in many fertiliser plants shutting for maintenance. The present high price of natural gas has made fertiliser production in the UK less profitable, and some factories are extending the maintenance shutdown until either natural gas gets cheaper, or fertiliser prices increase.

Might I take this opportunity to suggest that all public venues should review their preparations for incidents and disasters in general. Ensure that first aid kits fully meet the legal requirements, and preferably go a bit beyond the legal minimum. Remember that an attack could result in many injuries, and that the emergency services will attend first to the more serious cases, perhaps leaving the walking wounded in the care of venue staff. Ensure that firefighting equipment is in good working order, and perhaps provided in excess of the minimum requirements. Explosions can start multiple fires, and remember that fire brigade attendance could be delayed by congestion. Provide plenty of battery operated lanterns and torches and chemical lightsticks. Do not put your faith in fixed emergency lighting installations that may be damaged by an explosion or concealed by dust and smoke. Perhaps keep a supply of blankets to provide warmth and decency to the injured whose clothing may have been ripped off by an explosion or for medical attention. Or of course for covering the deceased. Recent events are very sad, but rather than ONLY saying "how terrible" please take a few minutes to consider how well your venue would cope with a major incident, not just a suicide bomb but also a mass shooting, the release of toxic materials, impact by an HGV, or a hostage or siege situation.

To add to the points already made, I consider it likely that some of the poorly written or incomplete job applications may be from people who don't really want the job, or know that they are unlikely to be suitable. Those claiming jobseekers allowance are often expected to apply for a certain number of jobs each week, even if there are no or very few suitable positions available. Being able to state that "I have sent my CV to 10 potential employers this week" ticks the box and allows continued benefit payment.

Yes, emergency procedures and precautions for theatres are primarily against fire breaking out, and ensuring speedy escape if fire does occur. In this unfortunate accident, it seems that the ceiling fell almost instantly, no evacuation procedure will allow persons to outrun a falling ceiling. Emergency lighting is most important in theatres or other large public buildings, but probably not relevant in this particular case. I would presume that the normal mains powered lighting was available, pictures posted on line seem to show this.

Pictures posted on line show that some fairly substantial pieces of timber have fallen, suggesting structural failure rather than just plaster falling. Looking at the size and weight of some pieces, it is most fortunate that no lives have been lost. I am sure that we all wish the injured a speedy recovery.

[moderation] Topics merged hence some duplicate comments. [/moderation Bit surprised that no one else has posted regarding this. A large area of the ceiling collapsed, an area about 10 meters by 10 meters according to some reports. During yesterdays evenings performance. About 80 persons injured, some seriously, the police requisitioned a bus, some reports state more than one bus, to take the less seriously injured for treatment. Although reports refer to the failure of a CEILING, the pictures show some substantial timbers have fallen, not just plaster, suggesting structural failure not just falling plaster. It is most fortunate that no lives were lost in this sad accident. I am sure that we all wish the injured a speedy recovery. No point in me posting a link as this is widely reported on line and in the morning papers. EDIT TO ADD I was in the general area and noted that the weather was very wet and windy, though not truly exceptional.

Are you certain that the laser cutter can not cut even thin metal ? Many laser cutters that are intended for other materials will cut very thin stainless steel, I would give it a try. Unlike trying to cut unsuitable material with a physical cutting tool, trying unsuitable material in a laser cutter should not break anything.