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edexlab

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I've been to a job this week just for a few odds and ends and there seems to be some power usage issues there which came up in conversation, the customer has worked in this building for several years and therefore has copies of the monthly electricity bill going back 3 years (I've only seen one) and they tell me that the bill has almost doubled recently compared to previous years , even though there are now fewer staff and less equipment being used.
I said could it be down to heating/lighting due to the cold/darker weather, and he said no they've turned most of the storage heaters off when they noticed the bill increase but they didn't really use them anyway (2 had faulty DP switches and couldn't be turned on) and the worst months bill was December when the office wasn't used for 2 weeks There are also fanheaters which I'm told aren't used very often.

So I started looking about, 3 phase supply recently tested and given a clean bill of health although I haven't been able to get a look at the certs,
as its an office all lighting is recessed fluorescent (600 x 600mm 4 x 18 watt) 2 ccts split over 2 phases, upto 9 pc's although usage varies, one is used as a server, on 24/7 , individual pc's and 3 which are used to run specific programs total of 9. as they are Surveyors they are on site a lot so its usually only half the Pc's being used at any time on 2 separate rings on separate phases and a few printers, chargers etc.

I thought it was possible that there could be circuits in the unit next door fed from the DB as I've seen that a few times, one firm was getting free electric for 6 years before anyone realised so this was checked.

Had a good look around found nothing suspicious but I haven't tested any of the final circuits, its a very tidy install throughout, got the fluke clampmeter out and checked the line currents these varied from 4.6A L1 3.46A L2 0.86A L3 Neutral had 4.5A on it (not too surprised at that) and there was 0.4 A on the main earth presumably from the PC's etc I'm going to borrow a earth leakage clampmeter to confirm the actual current here but I have notified the customer.

So obviously there's an inbalance which probably wouldn't occur if the circuits were utilised more but due to the way this office is used its inevitable that there will be some inbalance.
The next thing I'm looking at is getting the meter and supply checked/ monitored or analysed and I know an Energy consultant who's going to check the tarriff arrangement and capacity charges to rule out any issues there, I don't think this will be the cause as the standing charges haven't increased just the consumption but I'm thinking along the lines of a low power factor possibly being the real problem.

This is something I have no experience with other than the calculations I did at college where I was told it would only affect larger installations, so I've been doing a bit of reading and obviously fluorescent lighting and switched mode power supplies and fan heaters have an effect on power factor, can anyone with experience of power factor issues tell me if I'm heading in the right direction and does the size of an install or connected loads matter ie smaller loads can be still be adversely affected.
Another question my mate who's recently qualified said he was told at college that to find the PF of an install there is a formula along the lines of Ze - the resistance of the circuit in question, I'd not heard of this and I've looked in textbooks my old college notes etc and cannot find any mention of this I asked him to find it ,but I'm sceptical that its that simple, especially when you look at the price of test equipment capable of determining PF ,but I would be interested to hear of any methods which can be used without the use of the specialist testers.
 
http://www.allaboutcircuits.com/vol_2/chpt_11/3.html

Enjoy your read. And to answer, the complication of the mathematics of it is subject to your ability.
 
Seeing as the cost of Electricity has risen substantially over the past few years i can well understand his bills almost doubling, the same as everyone else's has... lol!!
 
I would expect a small office to be billed for KW/h used.

Have you tried simply adding up all the loads in use, lighting is easy as its constant , ditto PCs and IT equipment. Then work out what their bill should be in KW/h and times by about 11ppKW/h and compare, will tell you at least if power is being syphoned off or the meter is poorly.
 
http://www.allaboutcircuits.com/vol_2/chpt_11/3.html

Enjoy your read. And to answer, the complication of the mathematics of it is subject to your ability.

Thanks for the link it looks like a useful site
It wasn't really the calcs I was after, I have already been brushing up about PF not having done it since college
What I would like is to hear from anyone who has come across similar issues in a similar small installation and if they found a solution
As for the bill/ tarriff rising this doesn't seem to be the problem as the energy consultant has confirmed the tarriff is suitable for the size and usage of this company and there are no under capacity charges, the bill for October and November were less than half of Decembers.
 
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That could be down to estimated readings, as far as i hear, it's common now to have 50/50 over a 12 month period, actual read and estimated bills.... lol!! It's very rare for meters to go bad, not unheard of mind, but very rare!!
 
Customer said its not an estimated reading and yes I agree you very rarely hear of a dodgy meter they do seem to be reliable

Also in reply to plugs and sparks I have done this and it did seem to be close to what the meter was displaying over a 4 hr period which again leads me to think its not the meter, customer has also been keeping a log. ( my measurements excluding the storage heater loads as its on the night tarriff which looks about right)

Its frustrating as the load here is low unless the fan heaters were to go on or the storage heaters are used which is fair enough, you use it you have to pay but in this case the bill does seem disproportionate.
I'm advising them to have a company who specialises in power analysing take a look if the DNO doesn't come up with any possible causes.
 
I cant see PF making an impact on a installation that small with relatively low amount of usage. Plus surely a poor PF would mean pulling in KVAr which i believe import meters cannot even read?
 

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