how do rcd's work?

[tom1]

not sure, i know these work but not the new thread. i just put one up about putting a socket spur straight into the ring mcb

 

[Lee321]

those 3 threads are showing as messages somehow

 

[Andy™]

you have no new threads, but you have visitor messages in your user profile....

where exactly are you going to make new threads?

 

[tom1]

thanks for help. not sure whats going on. will work it out, until then i will have to hijack, but i think that upsets some people

 

[tom1]

i click on my name and post mesage

 

[Lee321]

this is a crap thread so i don't mind tom ROTFWL

incidentially this thread does not show in new posts either! fk

 

[Andy™]

i click on my name and post mesage

no, thats how you leave a visitor message.

to make a thread:

go find the subforum you want form main page

click 'new thread' on the left, near the top of that subforum. then ask what you need and click submit new thread

 

[Andy™]

this is a crap thread so i don't mind tom ROTFWL incidentially this thread does not show in new posts either! fk

it shows in new posts to me. if it didnt, it wouldnt be getting a reply from me!

 

[Lee321]

here tom

..

 

[SPECIAL LOCATION]

this is a crap thread so i don't mind tom ROTFWL incidentially this thread does not show in new posts either! fk

It only shows in New posts when someone else had added to it since you last post...

e.g.

You can't have unknown New post that you have added yourself..

because you already know they exist..

you posted them!!!

Tis only other peoples posts that can be 'NEW'

 

[Lee321]

It only shows in New posts when someone else had added to it since you last post...e.g.

You can't have unknown New post that you have added yourself..

because you already know they exist..

you posted them!!!

Tis only other peoples posts that can be 'NEW'

thx for the obvious SL ROTFWL

still don't show for me.

waits for a plethora of threads from tom :^O

 

[tom1]

thank u all i think its worked, yes and now i am sure there will be many threds from my self. all i need to do now is type faster and learn how to spell (u will see a few of these)

:^O

 

[Apache]

i was told muscle contraction was more with dc, ac would grab then through u back

Allow me to explain.........

Nerves use small electrical signals to transmit messages along from the central nervous system (brain and spinal cord) to the muscles. To transmit a signal ions are pumped across membranes and the cell is said to depolarise and an action potential (AP)l results - this AP is the small electrical signal that passes down the nerve, to the muscle. The cells then have to re-polarise for this to happen again, they are capable of doing this 50 times per second.

The muscles responsible for gripping are stronger than the muscles that release the grip (for obvious reasons) - a bit like a alligator with powerful closing jaws but a child or a simple elastic band can hold them closed!

When alternating current is passed down through the body it results in the stimulation of all the nerves causing them to all send signals to the muscles. The muscles then all contract. The net effect (since grip is stronger than realease) is that you grip hold of whatever it is you are holding. Now since the AC is at 50 Hz (ie 50 cycles per second) the nerves are doing the maximum ammount of work they can and you can't send a signal down saying 'let go'. In effect the lines are engaged.

If we had our electricity at 30 Hz then there would be spare capacity for you to send a let go message. If the frequency was more than 50Hz then electrical signals would reach the nerves before they had re-polarised and would therefore have no effect, this may allow a brief period where you could let go. What I am saying is 50Hz is lethal, more or less would be far far safer.

The only electric shock I have ever had was from a damaged cable on a hedge trimmer and it brushed my hand - all the muscles in my arm and chest ached for a few days!

If anyone wants anything explaining or more detail I am pleased to answer!

 

[Lee321]

no that is quite enough of that :x

:^O

 

[SPECIAL LOCATION]

no that is quite enough of that :x :^O

Applaud SmileyApplaud Smiley:^O:^O:^O

Its like a bloody class room lesson tonight!!!! :^O

Guiness DrinkGuiness DrinkGuiness DrinkGuiness Drink

don't drink too much or you'll never understand any of it!!!

ROTFWLROTFWLROTFWL

 

[tom1]

so ac will grip and not knock u back?

 

[wozz]

pache's post begs the question, 'why do we use 50Hz if it is so lethal to the end user?'

 

[Apache]

so ac will grip and not knock u back?

It will cause muscle contraction. So if you grip hold of something live you will hold on. If you just touch it your muscles will contract and depending on your stance you will be thrown back.

 

[tom1]

dont know why my instructor told me diff. never mind, thats a good lot of info u got there. good job we got mcb and rcd

 

[Andy™]

pache's post begs the question, 'why do we use 50Hz if it is so lethal to the end user?'

easier to make it 50Hz than 300Hz