How can we check if\u00a0a radiator (or anything)\u00a0is an extraneous-conductive part?<\/strong><\/p>\nA radiator may be insulated from earth due to the building\/construction materials used. To check the effectiveness of this insulation the following formula can be used…<\/p>\n
Rcp > (Uo\/Ib) – Zt<\/p>\n
Where…<\/p>\n
Rcp = Resistance \u03a9 of the radiator to the Main Earth Terminal (MET)
\nUo = Nominal Voltage to Earth (230V)
\nIb = Max value of current through human body, 30mA (lower values of 0.5mA and 10mA can be used)
\nZt = Impedance of human body usually 1000\u03a9<\/p>\n
So the minimum resistance between the radiator and the MET of the building is<\/p>\n
(230\/0.03) – 1000 = 6666\u03a9 or 6.67k\u03a9<\/p>\n
Anything less than this and the radiator can be considered to be an extraneous-conductive part and as such if it also doesn’t comply with 701.415.4.5 (iv), (v) and (vi)\u00a0then supplementary bonding will be required.<\/p>\n
How to check if existing supplementary\u00a0bonding is effective<\/strong><\/p>\nTo check the\u00a0effectiveness of the connection of extraneous-conductive parts to earth in a bathroom have a look in Part 7 at the NOTE at the bottom of regulation 701.415.2<\/p>\n
This sends you to regulation 415.2.2<\/p>\n
R \u2264 50\/Ia<\/p>\n
If there are RCDs protecting the bathroom then Ia would be 0.03 (30mA) so R \u2264 50\/0.03 = 1667 ohms<\/p>\n
If it’s an older bathroom and there are no RCDs then R \u2264 50 divided by the current needed to disconnect the protective device (fuse or circuit breaker) within 5 seconds. See the current \/ time disconnection graphs in Appendix 3.<\/p>\n
So if its a bathroom with two circuits protected by Type B, BSEN 60898 circuit breakers, Lights 6A and Shower 40A then the amount of current needed to disconnect\u00a0 the devices is 5 x their rating (see page 525) so Ia would = 30A or 200A ‘you always use the highest’. So in this case R \u2264 50\/200 = 0.25 ohms.<\/p>\n
Thank you to BS7671 and Guidance Note 8 and hours of fun.<\/p>\n
<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
This may not be an issue in\u00a0newer bathrooms that comply with current editions of BS7671 as supplementary bonding in bathrooms may be omitted when regulations\u00a0701.415.4.5 (iv), (v) and (vi) are met. However, supplementary bonding the radiator\u00a0has always been a grey area especially in older bathrooms because\u00a0the radiator may or may not be an extraneous-conductive part….<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1,14,7],"tags":[],"class_list":["post-347","post","type-post","status-publish","format-standard","hentry","category-general","category-part-5-selection-and-erection-of-equipment","category-part7-special-installations","th-blog blog-single has-post-thumbnail"],"yoast_head":"\n
Supplementary Bonding Bathroom Radiators? - the-Regs : BS7671 18th Edition Online Training<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/the-regs.co.uk\/blog\/?p=347\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Supplementary Bonding Bathroom Radiators? - the-Regs : BS7671 18th Edition Online Training\" \/>\n<meta property=\"og:description\" content=\"This may not be an issue in\u00a0newer bathrooms that comply with current editions of BS7671 as supplementary bonding in bathrooms may be omitted when regulations\u00a0701.415.4.5 (iv), (v) and (vi) are met. 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