- Reaction score
- 386
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.
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.