Instyle LED Lighting Specialists UK
This official sponsor may provide discounts for members

Discuss Maximum Disconnection Times in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

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?
 
Wetroom Store - Network Wetroom Suppliers
This official sponsor may provide discounts for members

davesparks

-
Mentor
Arms
Esteemed
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?
We don't use 150V supplies, but we do have 110 and 230 so in reality whether you set the limit at 120 or 150 the real world effect will be the same.

What is your logic behind saying its better at 150V rather than 120V?
 
  • Thread Starter Thread Starter
  • #3
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).
 

Attachments

Last edited:

Megawatt

-
Arms
Advent Win
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).
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.
 
  • Thread Starter Thread Starter
  • #5
Asking for the codes reasoning mainly. And if changing it will violate the IEC's body graph.
 
  • Thread Starter Thread Starter
  • #7
Well, the NEC does frequently talk about 150 volts to ground over or under. Would be nice to harmonize the IEC with the NEC.
 

davesparks

-
Mentor
Arms
Esteemed
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).
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.
Post automatically merged:

Well, the NEC does frequently talk about 150 volts to ground over or under. Would be nice to harmonize the IEC with the NEC.
That will be pretty difficult with the big differences between electrical installations in different countries.
 
  • Thread Starter Thread Starter
  • #9
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.
Post automatically merged:

Yup

That will be pretty difficult with the big differences between electrical installations in different countries.

Usually, but in places like the Philippines, Saudi Arabia and parts of Latin America one is often left working with both codes. An NEC system with IEC standards applied to them.

See page 8:



120/240 and 138/240Y is found in older installations that have been changed from 120 to 230 volt distribution equipment. Makes for some interesting stuff.
 
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?
Think of it as Time and "energy Received" , cooking a resistor .
..Where the resistance is a human wishing to survive an electric shock...
Simplify things thinking the first 50V is wasted getting through your skin !
Post automatically merged:

Think of it as Time and "energy Received" , cooking a resistor .
The reality is we are saving equipment from fire risk , limiting total amount of energy received - is how we stay safe !
 
Last edited:
  • Thread Starter Thread Starter
  • #16
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.
 

DPG

-
Arms
Esteemed
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.
Err OK then.
 
  • Thread Starter Thread Starter
  • #18
Its ok. :) Just this forum is to quick to assume things.
 
Last edited by a moderator:

Megawatt

-
Arms
Advent Win
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 US
 
  • Thread Starter Thread Starter
  • #22
130 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.
 
Also got a post deleted in another thread for saying the stuff on Amazon made by China is often not safe to install.
Tricky tight rope - Negative opinions ..
( I'm older and just love moaning )
You get what you pay for, (and some local wholesalers risk a big hit , when they have to honour their returns policy)
Need to educate customers to spend more!
 
  • Thread Starter Thread Starter
  • #24
Education is key. Which is why I spoke up. But shady manufacturers/sellers know people buy solely based on cost.
 

Megawatt

-
Arms
Advent Win
130 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.
On paper is one thing, in the real world it’s a totally different world. Why the emphasis on exactly 138vac
 
  • Thread Starter Thread Starter
  • #32
710? I had 41.1 in mind. I'm curious how those voltage cutoff values were derived.
 

Megawatt

-
Arms
Advent Win
710? 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
Post automatically merged:

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
I’m trying to learn the UK ways of doing electrical work
 
  • Thread Starter Thread Starter
  • #34
Right, but for AC we have 120 volts and under at 0.8, 0.4 for 120 volts and over. Is any real harm granted in having 0.8 cover up to 150 volts?
 
  • Thread Starter Thread Starter
  • #35
UK wiring requires that general socket and lighting circuits trip a breaker in a required amount of time based on the line to earth voltage.
 

Megawatt

-
Arms
Advent Win
UK wiring requires that general socket and lighting circuits trip a breaker in a required amount of time based on the line to earth voltage.
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 US
Post automatically merged:

Asking about the code's reasoning. And Megawatt- I fully get you!
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 opinions
 
Last edited:

Dan

Admin
Staff 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. :)
 

Reply to Maximum Disconnection Times in the Electrical Forum area at ElectriciansForums.net

Aico 3000 Range
This official sponsor may provide discounts for members

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
Top Bottom