I see that I can buy different types of lamps: industrial and domestic.
Thinking back to the dim past of college, I recall that they have a power factor such that your meter doesn't measure the full consumption. I assume that one has some form of correction built in.
Which sort do I need? (Which will be cheapest to run)
I assume Scottish Power can't measure the power factor at my house.
Martin L
Power factors are generally low for ballast-ignited and run lights, but on an average domestic load it has other stuff (ordinary lamps, cooker rings/lights) that is resistive to even things up. The average pf of 0.8 is calculated from 'average' loads, but these days 'everything' has a switch-mode front end and they now have to have pf correction to get through the approvals.
Resistive loads have a unity power factor (1) transformers have a low pf of about 0.6, inverters with pf correction are quite high up, I have seen claims for over 0.9 which is pretty good.
The board can't determine your pf at home unless they put a pf meter in which involves metering the current and voltage, the electronics works out leading and lagging power factors and displays it on screen. I have one somewhere in the workshop.
Peter
-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:
I would assume that the domestic type have a PF correction capacitor fitted, whilst the industrial type does not. This allows an industrial user to use a PFC unit further up the power distribution chain. The type with PFC will be cheaper to run.
Domestic properties, AFAIK, do not have their power factor measured. Large industrial consumers do, and are charged a premium for having a power factor outside a certain range.
HTH
Anthony Remove eight from email to reply Website:-
Thanks for the replies.
I suppose I had better have a look in the loft for my old text books. I assumed if I can get the current and voltage out of phase that the meter would read less. You imply it would read more.
I don't suppose a 6' tube is going to cost much to run in comparison to the heater anyway :-)
I wish I had had the sense to run a hot water spur off the house central heating before we laid the patio :-(
Martin L
Power factor is only measured on 3 phase systems. In a 3 phase supply, kW consumed is (VOLTS x AMPS x 1.73 x Power Factor) / 1000. The Electricity Company supply you VOLTS x AMPS and they have to supply extra to make up for the loss caused by poor Power Factor. When the power factor falls below a set figure, the electricity supply companies charge a premium on the kW being consumed, or, charge for the whole supply as kVA.
You will get no cost reduction from fitting power factor capacitors to single phase domestic units. Although fitting capacitors to fluorescent units seems to halve the current it does not effect your domestic meter. Have a word with Scottish power they will explain it.. I live in the south west and run a Coral Farm. This involves a lot of fluorescent lights. I have spoken to my local electricity board and that was their comments. I could have 3 phase fitted to my house but the cost would never be recovered.
GrimReaper
Not sure what that first sentence implied :-))
It is measured on both single and three-phase systems, perhaps you meant that the supply boards only measured it on three-phase?
We have a single-phase pf meter as already posted, and they are freely available from various suppliers.
Typically we were originally interested for the purposes of rating generating sets that ran HMI/CSI discharge lighting which were a ballast type of discharge light.
Kind regards,
Peter
Peter Forbes Prepair Ltd Luton, UK email: snipped-for-privacy@easynet.co.uk home: snipped-for-privacy@easynet.co.uk
Sorry Peter I am a marine biologist and know very little about this subject. I commented because I got the info from my Electricity board
Yes My electricity boards does not measure domestic power factor. I asked if they would but told me there was no point. It will only save me money if I have a three phase supply, which they were happy to look at. just not worth it. If I expand I will rent an industrial unit which come with three phase installed.
The original post asked "Which sort do I need? (Which will be cheapest to run)" Basically I was trying to say that it would not save him any money to have power factor capacitors fitted on a single phase domestic supply. I hope I have not mislead him
Regards GrimReaper
Absolutely no apology required, I was just trying to make sure we didn't confuse the issue :-))
I don't think there is any problem, between the various posts I think we covered everything. It's always worth looking at other comments, I find, as there is always something new to learn, especially from people like yourself with different jobs and interests.
It's only because we are supposed to have pf correction on our chargers, and we can't do it economically on the big stuff that I have had an involvement, plus the job I had in the film & TV days when we ran single phase gennies with the halide lights. The crews tried to get 50kW out of a 50kW genny, but they couldn't unless they were straight filament lamps. It caused no end of rows with the crews so we ended up putting a pf meter on the generator panel, to show exactly what they were doing and why the output available with ballasted lights was only about 36kW.
Regarding three-phase supplies, it is only really a problem with factories that have large amounts of motors and flourescents and peak loads that tend to be hit by the boards. We have 100A per phase here and at home, but rarely use that amount. The nearest was last summer when we had 80A per phase on a big 60kW charger.
Kind regards,
Peter
Peter Forbes Prepair Ltd Luton, UK email: snipped-for-privacy@easynet.co.uk home: snipped-for-privacy@easynet.co.uk
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