Ask an Electrician anything...
Discussion
Paynewright said:
Why do stainless cooker hoods not need an earth? (Just purchased a new SMEG appliance and only has brown & blue wires).
I remember a fatality at work where one of the gas engineers put his hand on a metal hood in a customers house and it was live!
if the cooker hood is Class II its said to be double insulated so will not require an earth. I remember a fatality at work where one of the gas engineers put his hand on a metal hood in a customers house and it was live!
CLASS II EQUIPMENT
Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as supplementary insulation are provided, there being no provision for the connection of exposed metalwork of the equipment to a protective conductor and no reliance upon precautions to be taken in the fixed wiring of the installation.
williamp said:
Serious: what is the difference between single and 3 phase?
Oh, and what is electricity?
difference in number of wires and the voltages will be different. With three phase the voltages all have the same frequency but are separated by a time difference of a third. Oh, and what is electricity?
single phase has 240v ac to neutral same as three phase to neutral. but across the phase you have 415v just the way that its generated, the physical difference between the phase windings on the rotor. etc.
Electricity - its a flow of molecular matter. dc it flows around a circuit. ac it vibrates in a circuit.
dundarach said:
If I have 12v's DC from a Scalextric transformer, how can I step this down inside a model to 5v's DC in a simple component say 1cm without much heat.
So that I can use 5v motors rather than 12v motors, across the power band from the standard Scalextric controllers.
Hugs kisses and thanks
So that I can use 5v motors rather than 12v motors, across the power band from the standard Scalextric controllers.
Hugs kisses and thanks
this arrangement would do it - it would step down 12v dc to 5v dc to power your motor and it would be regulated. Would need to have a heat sink on it... but it should do
eltawater said:
What's the worst thing you've seen which has prompted you to declare "No f**king way am I touching that" ?
A chiller panel that had been bastardised by a previous incumbert. needed rework to make is safe again. too many cables not dressed properly and a chance of a short that could have been accross 415v 400A incommer tailsLostM135idriver said:
Baldchap said:
ruggedscotty said:
Electricity - its a flow of molecular matter. dc it flows around a circuit. ac it vibrates in a circuit.
Isn't it the flow of electrons, i.e. subatomic particles?steve-V8s said:
A Sparky question rather than one about your van.
Can I, within the regs somehow mix PME and an earth stake ? The previous house had a nice big earth stake where the current one is PME. I have some equipment which is sensitive to supply noise and some which generates RF earth currents. The PME earth, where probably electrically safe has a far higher impedance at high frequencies and is less than ideal. With an earth stake system it was possible to whack in an additional stake local to the equipment and all was well.
Plainly with PME that would be unwise as my stake could end up being the earth for a fault in the neighbour's house and if I separate the two earths the chassis of my equipment could be at a different potential to other things nearby.
Why PME is now preferred is a mystery to me, I can perhaps see it for a block of flats but not for individual dwellings, presumably it is cheaper to install but I can't see any way it is actually better. There are now so many cheap plug in power supplies in use, all adding noise to the supply which you can't filter out without a good low impedance local earth.
mains earths are a black art. and as you rightly point out your seeing some issues with current loops. The mass of the earth you have to take as zero - now if you have an earth spike and that connects to your equipment you will get a current flow to earth if there is any current flowing to earth in your equipment. its about watching the equipment and ensuring that you cut down on those current loops and that should address the problem.Can I, within the regs somehow mix PME and an earth stake ? The previous house had a nice big earth stake where the current one is PME. I have some equipment which is sensitive to supply noise and some which generates RF earth currents. The PME earth, where probably electrically safe has a far higher impedance at high frequencies and is less than ideal. With an earth stake system it was possible to whack in an additional stake local to the equipment and all was well.
Plainly with PME that would be unwise as my stake could end up being the earth for a fault in the neighbour's house and if I separate the two earths the chassis of my equipment could be at a different potential to other things nearby.
Why PME is now preferred is a mystery to me, I can perhaps see it for a block of flats but not for individual dwellings, presumably it is cheaper to install but I can't see any way it is actually better. There are now so many cheap plug in power supplies in use, all adding noise to the supply which you can't filter out without a good low impedance local earth.
PME is prefered as it ensures that there are multiple points on the neutral that are grounded instead of one. this means that on a longer run the neutral is kept close to earth at as many different points. does that help ? if not i can try and find some more info for you.
MK1RS Bruce said:
How do you connect the cable between the consumer unit and the meter, there doesn't seem to be anyway to isolate the top of the meter to make such connections in mine.
The meter has a fused cutout at the service hear. This is board property and is usually sealed. The tails from the meter to the consumer unit are now being fitted with an isolator switch to allow isolation of the installation. I see this in more and more places. Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff