Forums
New posts
Search forums
What's new
New posts
New media
New media comments
Latest activity
Media
New media
New comments
Search media
Members
Current visitors
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Main Forums
Electrician Talk Forum
The realities of trying to test in occupied domestic properties
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support Talk Electrician Forum:
This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Message
<blockquote data-quote="SPECIAL LOCATION" data-source="post: 508461" data-attributes="member: 250"><p>If you have measured R2 on a lighting circuit...</p><p></p><p>Using the resistance tables from the OSG, it is actually possible to calculate an approx length based on an assumption that the cable may be 1.0mm or 1.5mm..</p><p></p><p>So.. from this length you could also estimate what a potential worst case R1 would have been, had you been able to measure it..</p><p></p><p>e.g. cables may be..</p><p></p><p>1.0mm / 1.0mm T&amp;E or singles</p><p></p><p>1.5mm / 1.0mm T&amp;E</p><p></p><p>1.5mm / 1.5mm singles</p><p></p><p>Using any combinations of these values, added to your Ze,</p><p></p><p>you could get a rough idea if a potential Zs, was anywhere near the max permissible values..</p><p></p><p>(Its not hard to knock up a spread sheet where you enter your R2 reading and it will return possible R1+R2's for each of three the above cable options) </p><p></p><p>If worst case assumptions are well clear of max permissible.. then Don't worry... Move on...</p><p></p><p>But.. If estimated calc's are getting a bit to close for comfort..</p><p></p><p>Then go and dismantle the fitting and do a proper accurate measurement..</p><p></p><p>Any decorative metal metal fittings you will need to confirm earth continuity anyway..</p><p></p><p>unless you know for a fact that they are Class 2 fittings..</p><p></p><p>So measure R2 from CU to external metalwork of fitting while verifying earth continuity to the fitting..</p><p></p><p>Note:-</p><p></p><p>Assuming you did a site visit prior to work commencing..</p><p></p><p>these type of potential problems would have been identified and costed into the job anyway!</p><p></p><p> Guinness </p></blockquote><p></p>
[QUOTE="SPECIAL LOCATION, post: 508461, member: 250"] If you have measured R2 on a lighting circuit... Using the resistance tables from the OSG, it is actually possible to calculate an approx length based on an assumption that the cable may be 1.0mm or 1.5mm.. So.. from this length you could also estimate what a potential worst case R1 would have been, had you been able to measure it.. e.g. cables may be.. 1.0mm / 1.0mm T&E or singles 1.5mm / 1.0mm T&E 1.5mm / 1.5mm singles Using any combinations of these values, added to your Ze, you could get a rough idea if a potential Zs, was anywhere near the max permissible values.. (Its not hard to knock up a spread sheet where you enter your R2 reading and it will return possible R1+R2's for each of three the above cable options) If worst case assumptions are well clear of max permissible.. then Don't worry... Move on... But.. If estimated calc's are getting a bit to close for comfort.. Then go and dismantle the fitting and do a proper accurate measurement.. Any decorative metal metal fittings you will need to confirm earth continuity anyway.. unless you know for a fact that they are Class 2 fittings.. So measure R2 from CU to external metalwork of fitting while verifying earth continuity to the fitting.. Note:- Assuming you did a site visit prior to work commencing.. these type of potential problems would have been identified and costed into the job anyway! Guinness [/QUOTE]
Insert quotes…
Verification
Post reply
Main Forums
Electrician Talk Forum
The realities of trying to test in occupied domestic properties
Top