P272

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New Dexter
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P272

Post by New Dexter » Wed Aug 09, 2017 12:24 pm

Now I am not sure how many people will be aware of the changes to electricity metering that will affect business users. Someone persuaded the government that half-hourly metering would be a good idea. In that case, any meter with a "profile" of 5-8 would require to have this and it involves a business paying for the services of two companies to record and pass on the meter's readings.
I have had electricity supplied by one of the main companies and they have re-profiled my meter to half hourly metering and when the contract is up for renewal it's going to cost me far more than it does now. It's not the electricity that will cost so much more but the services I will need.
I have considered telling the company to remove their meter next year and I will use a generator. However, I need to know how to calculate the KVA requirement. Does anyone know how one does this?

John Hitchins
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Re: P272

Post by John Hitchins » Wed Aug 09, 2017 9:25 pm

If you are trying to calculate the load for your generator I would obtain a clip on ammeter and turn on all your equipment to measure the max load. That would give you some idea of requirements. I don't know how big your business is though.

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Sydsmith
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Re: P272

Post by Sydsmith » Wed Aug 09, 2017 9:45 pm

Simply speaking 100 amps is equivalent to 22 KVA at 240 volts 50 cycles.

Simply speaking 5 kilowatt at 240 volts is about 1.2 KVA.

Most equipment has a spec plate with one or other of these details.

The correct advice would be to make a note of and add up the current consumption of every item you have plus the lighting and heating requirements, and add 15% for safety, (current increases as voltage drops and except in the case of extremely well controlled units a 6-7% drop in generator voltage due to load is not uncommon)

If you can be absolutely sure not all equipment will be used at one time you can take a chance and reduce the ratings a bit.

Hope that helps. Syd

New Dexter
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Re: P272

Post by New Dexter » Thu Aug 10, 2017 10:19 am

Thank you for your comments and advice gentlemen. I had asked a local electrician if he could spare some time and he said he would call last week but he didn't.
There is a website where one can enter in various voltage and amperage requirements and using 415V, I have some three phase machines and 100 amps which is what is here at the moment it gave me 72KW which converted to 90KVA. On that basis I suppose I should be hunting for a 100KVA generator with 3 phase power but the website does recommend a certified electrician which is what is suggested by one of the power suppliers.

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Sydsmith
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Re: P272

Post by Sydsmith » Thu Aug 10, 2017 11:48 am

That's a hefty load and with three phase it is well worth getting professional advice, three phase is a potential killer if you get it wrong.

Make sure you find a man (or woman) who has three phase experience, the average domestic expert rarely sees three phase.

Some time back there were some really good 3 phase 50kva ex government trailer mounted generators sold off, a friend of mine ran a big saw mills on one, but they are hefty beasts with truck engines to drive the alternator, the big issue is of course noise.

It is perfectly legal to use tractor/red diesel in generators, there are strict rules about storage and marking of red diesel storage tanks not directly connected to a generator and also for generators on trailers.

My son was asked to find £12,000 to bring three phase to his woodwork shop, he bought a nice and very quite 50KVA ex mobile lighting generator set for £3,000 and tucked it away in a block built open fronted shed it is almost silent.

New Dexter
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Re: P272

Post by New Dexter » Fri Aug 11, 2017 10:26 am

When I had the power re-connected I was asked what sort of machines/equipment I would be using and I had to send a list of welders, lathe, saw etc. Now given that I am the only person likely to work in the place at any time and while I do try to involve myself in a little multi-tasking I cannot operate a welder and a lathe at the same time.
Somehow it was agreed that 100 amp fuses should be re-installed and I have a 100amp main switch. I have four items that are three phase and it is possible that the compressor could be running while I am using the lathe but all my three phase machinery has a 16 amp plug fitted. I think I have more capacity than I need but I do understand that welders can cause current spikes when the arc is struck, not while welding is taking place.
I have asked a local certified electrician if he could assess my electrical capacity requirement and he said he would "pop-in" last week but he hasn't so I have asked again. It's irritating because there was a Cheffins auction yesterday with several generators listed.

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Sydsmith
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Re: P272

Post by Sydsmith » Fri Aug 11, 2017 1:14 pm

Electric companies do belt and braces the calculation, they know you are unlikely to use all the kit at one time, but because it is there and you could, where do they draw the line safely.

That having been said when it comes to the decision about a generator, you could take a calculated gamble and chose a unit capable of what you calculate will be the maximum normal load, bearing in mind the damage an overload can cause. You could fit a cut out say 10% below your chosen generator output to protect it.

But the difference in cost between say a 20 or 25 KVA set is not that great, so better to have ample grunt than to be struggling.

You cannot have too big a generator, the drawback as I said earlier is that large generators tend to make a lot of noise, especially the older ones.

New Dexter
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Re: P272

Post by New Dexter » Sun Aug 13, 2017 10:42 am

I do have a space outside the part of the building which houses the electric switchgear which would be suitable for locating the generator should I have to go down that route. I can lay a decent, strong concrete base and then have someone wire it through the wall. I can have someone build a wall round it with some doors for access. Hopefully that would keep the noise down and there are some which are silenced already. I would really rather have mains electricity but with a standing charge of anything from 59p per day that starts to add up. Add the need to pay for someone to monitor my electricity usage and then a data collection company all because some crafty character/company convinced the government that we must have half-hourly metering so that we can monitor our usage. Each time I hear about that I am reminded of the Hans Christian Anderson story of the Emperor's New Clothes.
Who does? I had one fitted by my home electricity provider and never take any notice of it. I do what most careful people do which is to switch off anything I don't need.

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Sydsmith
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Re: P272

Post by Sydsmith » Mon Aug 14, 2017 10:11 am

One point I should have mentioned is that alternators do not like standing unused for long periods, if they do not work after a long time standing (12 months or so) they will need re-magnetising, which is a relatively simple but specialised job.

The best folk at this are usually agricultural electricians who will have met the problem before in milking parlour standby generators. It involves splashing 12 volts across the alternator coils.

Bear this in mind if you are contemplating buying a "barn find" or older set, either see it working or be prepared to find someone with the knowledge to sort it.

If you do go the generator direction it is a good idea to run it up and run some lighting or equipment for a short while every few months to avoid the problem.

The other consideration in your decision is the life expectancy of diesel fuel in storage, there are ways round the problem but modern diesel will be fine for 6 to 12 months depending on the conditions you store it in there are other issues in static tanks like microbes and water which need consideration.

New Dexter
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Re: P272

Post by New Dexter » Mon Aug 14, 2017 12:03 pm

Syd,
Thank you for that useful information, I confess I had not been aware or considered some of the subjects you mentioned. When renewing contracts one is allowed to "negotiate" up to 180 days before renewal and I am sure I will start to be pestered around November time.

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