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Domestic PIR & maximum permitted Zs on a TT system
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<blockquote data-quote="Revved Up Sparky" data-source="post: 213086" data-attributes="member: 5050"><p>I have recently completed a certificate for a PIR on a TT system.</p><p></p><p>Another spark challenged me today for putting 200 ohms in the column where you enter the maximum permissible Zs. He said I should be entering the values as stated on the table which is on the inside page of the NICEIC book of certificates I use, eg 1.15 ohms for a 60898 B 32A MCB, 6.13 ohms for a 60898 6A MCB etc.</p><p></p><p>Well I responded by suggesting that he was incorrect and that those values on that table on the inside of that page are for TN systems only.</p><p></p><p>What is the point of putting 1.15 ohms down as the max permitted Zs when you know it's TT and the reading will be something like 147 ohms ?. Surely I would then have to enter a note that the circuit has failed the Zs test ?</p><p></p><p>Are the values on that table on the inside of the test certificate for TN systems only ?..... who is right ?..... please say me .... <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> -- otherwise I wil have to tell a joke.</p></blockquote><p></p>
[QUOTE="Revved Up Sparky, post: 213086, member: 5050"] I have recently completed a certificate for a PIR on a TT system. Another spark challenged me today for putting 200 ohms in the column where you enter the maximum permissible Zs. He said I should be entering the values as stated on the table which is on the inside page of the NICEIC book of certificates I use, eg 1.15 ohms for a 60898 B 32A MCB, 6.13 ohms for a 60898 6A MCB etc. Well I responded by suggesting that he was incorrect and that those values on that table on the inside of that page are for TN systems only. What is the point of putting 1.15 ohms down as the max permitted Zs when you know it's TT and the reading will be something like 147 ohms ?. Surely I would then have to enter a note that the circuit has failed the Zs test ? Are the values on that table on the inside of the test certificate for TN systems only ?..... who is right ?..... please say me .... :) -- otherwise I wil have to tell a joke. [/QUOTE]
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