Discuss Maximum Disconnection Times in the UK Electrical Forum area at ElectriciansForums.net
What is the reasoning behind having a 0.8 disconnection time for up to 120 volts Uo, but it then jumps to 0.4 seconds as soon as you go over it? Wouldn't it be better 0.8 seconds for 150 volts Uo and under, 0.4 seconds 150 volts and over Uo?
Cookie I got to be the one but are you asking a question or telling us. Nobody really knows how to respond to the 3 post you have made already.When using a single phase supply you get 120 volts line to earth, but on a 3 phase supply you get 138 volts to earth which increases the disconnection time requirements (ie faster trip mandated).
Ok sorry I can’t help you have a good dayAsking for the codes reasoning mainly. And if changing it will violate the IEC's body graph.
When using a single phase supply you get 120 volts line to earth, but on a 3 phase supply you get 138 volts to earth which increases the disconnection time requirements (ie faster trip mandated).
Well, the NEC does frequently talk about 150 volts to ground over or under. Would be nice to harmonize the IEC with the NEC.
No we don't, standard single phase and three phase supplies in the UK are 230V to earth.
The 120V would only usually be relevant to a reduced low voltage supply on construction sites.
[automerge]1574290644[/automerge]
That will be pretty difficult with the big differences between electrical installations in different countries.
Think of it as Time and "energy Received" , cooking a resistor .What is the reasoning behind having a 0.8 disconnection time for up to 120 volts Uo, but it then jumps to 0.4 seconds as soon as you go over it? Wouldn't it be better 0.8 seconds for 150 volts Uo and under, 0.4 seconds 150 volts and over Uo?
The reality is we are saving equipment from fire risk , limiting total amount of energy received - is how we stay safe !Think of it as Time and "energy Received" , cooking a resistor .
Why the disagrement on post #3?
How or why are they incorrect...?
Center tapped 240 is 120. Line to line 240 produces 138.
Republic of the Philippines uses this system.
Yes, BS7671 and IEC codes on how they would go about dealing with those two voltages.
I'm well aware line-line 240 is rare in Europe.
In a star connection phase to phase is 240 vac phase to earth 120vac the voltage you read can be as high as 130vac the same goes with 3 phase. It’s a plus or minus 5% on the voltage in the USCenter tapped 240 is 120. Line to line 240 produces 138.
Republic of the Philippines uses this system.
Yes, BS7671 and IEC codes on how they would go about dealing with those two voltages.
I'm well aware line-line 240 is rare in Europe.
That highest voltage I’ve seen is 130 to ground and where are you getting 138vac138-139 volts, at 252 volts (+5%) it is 145 volts.
Your drawings are irrelevant that’s not telling us nothingThat highest voltage I’ve seen is 130 to ground and where are you getting 138vac
Tricky tight rope - Negative opinions ..Also got a post deleted in another thread for saying the stuff on Amazon made by China is often not safe to install.
On paper is one thing, in the real world it’s a totally different world. Why the emphasis on exactly 138vac130 volts would be the highest in a 120/208 system, not a 240 volt wye system.
The drawings are correct for the system being depicted.
I’m from the US and we don’t have those kind arrangementsWhere's my post gone? I was sticking up for the forum!!!
I’m from the US and we don’t have those kind arrangements
DPG confusing is an understatement I don’t know if the OP is asking a question or trying to teach us. LOLI think there's some confusion between systems.
Cookie we can sit here all day and pull reference form the BS 7671 and posting table 710 which is in the medical locations. What’s that aboutAsking about the code's reasoning. And Megawatt- I fully get you!
Yes I missed table 41.1 maximum disconnection times on page 55 as far as how are the voltages are derived starts with AC and DC theory710? I had 41.1 in mind. I'm curious how those voltage cutoff values were derived.
Yes I missed table 41.1 maximum disconnection times on page 55 as far as how are the voltages are derived starts with AC and DC theory
We can test breakers or RCDs but we can’t fix them if there are 1/10th of a second to slow, as far as I go if they trip I’m happy. I read your profile and I applaud you for wanting to learn but don’t just post things you are reading and asking why. I’m here to help anyone that needs it if I can. I’m going to ask you a question are you from the UK or USUK wiring requires that general socket and lighting circuits trip a breaker in a required amount of time based on the line to earth voltage.
If you are looking for reasons why the code wants this or that is something every body wants. You have hundreds of people who make up rules and regulations in the BIS 7671 and they all have different opinionsAsking about the code's reasoning. And Megawatt- I fully get you!
So we got something in common good luckI'm from the US- but want to learn about both.
Sorry Dan and have a great dayStaff have cleared up some posts in this thread. Please keep threads on topic and don't respond to rubbish, just report it, it saves us time. Cheers.
Err OK then.
Center tapped 240 is 120. Line to line 240 produces 138.
Republic of the Philippines uses this system.
Yes, BS7671 and IEC codes on how they would go about dealing with those two voltages.
I'm well aware line-line 240 is rare in Europe.
BS7671 is primarily intended for use in the UK with our standard voltages.
Using BS7671 in the Philippines with USA standard supplies and voltages is never going to be fully compatible. Its a square peg and round hole situation.
BS7671 is primarily intended for use in the UK with our standard voltages.
Using BS7671 in the Philippines with USA standard supplies and voltages is never going to be fully compatible. Its a square peg and round hole situation.
I wonder if UK DNO. (Supplies) are over engineered !I'll ask this: how did loop impedance become a thing in the UK?
Reply to Maximum Disconnection Times in the UK Electrical Forum area at ElectriciansForums.net