Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, concerning a single-phase circulation pump installation and contactor loop measurement values, is answered by Schneider Electric, which encompasses products previously known under the Telemecanique brand:
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| One of Schneider Electric\'s LC1D contactors. |
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Question: I have two small single-phase circulation pumps, which required having loop measurements taken. This was taken at the local rotary isolators and gave readings around 19 - 20ohms. I traced this down to the resistance through the
contactor on the live conductor, replacing the contactor with a like-for-like brand (Telemecanique). This has reduced the loop on the one pump to 7.35ohms, but this is still too high for the 6A
BS88 fuse, which requires a maximum
Zs of 6.9ohms. The loop for both pumps, with the contactor taken out of circuit, is 0.3ohms; at the control panel it is 0.15ohms.
How can I reduce this further so that it is in line with the regulations?
Answer: I've attached a few documents with information about Schneider Electric's range of contactors and MCBs. I don't know which contactor you are using, but our LC1D range has a very low impedance/pole, as you can see in the document. Of course, has you go higher in the range, the impedance will get lower and lower.
If you need to associate an MCB, there is also information about the loop Zs of our GV2 range. I hope you find this information useful.
You can also use the Schneider Electric website (www.schneider-electric.co.uk), where our entire main catalogues, technical publications and brochures are available to be used and can be downloaded free.
For any web queries, please use gb-customerservices@schneider-electric.co.uk or call 0870 608 8 608.
Please click on the link below to download the three PDF attachments (about 70kB file size in total).
To see many more Q & A in Voltimum UK's Experts Area, please click on the link:
www.voltimum.co.uk/consult.php?universe=consult.index.questions
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