forwarded for Eric. Jim ____________________Forward Header_____________________ Subject: RE: Conduit entry dimensions Author: "Eric Monk" <[email protected]> List-Post: [email protected] Date: 10/08/99 12:24 AM
Hi Richard and group. ELECTRICAL CONDUIT SYSTEMS IN THE UK. Electrical conduit systems in the UK were converted during metrication to their nearest metric equivalent. Sizes refer to outside diameters. The more common sizes are 20 mm (3/4"), 25 mm (1") and 32 mm (1 ½"). Larger than this there is a tendency to opt for metal trunking. 16 mm must be based on the old 5/8" conduit which I cannot confirm is still available in the UK, until I receive an updated catalogue. Knockout dimensions are simply a clearance hole for the applicable metric diameter of the conduit size recommended for the application. The preferred method of termination at an enclosure is to cut and thread the conduit a distance from the box, equal to the diameter of the conduit. Fit an 'internally' screwed coupling (like an oversize sleeve) to the end of the conduit and secure it to the enclosure with an 'externally' screwed brass bush inserted from inside of the enclosure. (bush is the same diameter as conduit thread) The brass bush has an hexagonal flange larger than the thread to tighten onto the enclosure firmly gripping the edge of the knockout hole between the brass bush and the coupling and providing earth continuity. The inside edges of the brass bush are chamfered and smooth to prevent damage to cable insulation when cables are pulled through the conduit into the enclosure. Variations are to terminate into a threaded elbow or T-piece if this is dictated by space constraints. (ie. bush thro k/o into elbow - conduit into elbow) An alternative is to bring the threaded end of the conduit through the knockout and secure it in the enclosure with a locknut on the outside and an 'internally' screwed bush on the inside - but this is not considered good practice. However the termination is accomplished in practice, the knockout dimensions are the same - Close tolerance clearance hole for the diameter of conduit specified for the application. Regards Eric Monk. Technical Director - E M Consulting Ltd. INTERTest Systems is the trading name of the test laboratory of E M Consulting Ltd. ***** Your best support in "TESTING" situations ***** ***** INTERTest Systems UK ***** ***** International Product Certification ***** ***** ONE-STOP-SHOP for ALL testing ***** *** PO Box 321 - Bucks HP9 1XJ - England - ++44 (0)1494 673438 *** ***** INTERTest Systems UK is the trading name of ***** ***** the test laboratory of E M Consulting Ltd. ***** --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
