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The fan relay draws 6.0A. That is a safe current for 16 gauge wire. The safety fuse is tripped at 15A which is too much 16 gauge wire.

References: The below pdf link shows the Installation Instructions for my thermostat. http://www.kele.com/Catalog/22%20Thermostats_Controllers/PDFs/SuitePro%20Installation%20Instructions.pdf. On page 2 in the specification section shows Safety Fuse Amps at 15A. Fan Relay Amps is shown as 6.0A for 120 Vac which is what I have.

Background: My super installed three of these thermostats to control our Fan Coils in various rooms. So far we have had no issues. Recently, a Fan Coil tech came in to replace the motor and told me that the wires that is being used are too small in diameter and therefore dangerous. The length of these wires are about 2-3 feet. The work was done 4-5 years ago.

My Question: I understand if there is no power surge, there won't be any issues. If there is a power surge, would the 16 gauge wire burn before the fuse is tripped? Even if fuses are supposed to trip at 70% of their capacity, the surge may still first burn the 16 gauge wire before the fuse is tripped, wouldn't it? So far so good. But, I keep wondering if one day it would set my home on fire.

Thank you for your time and feedback.

Y. Eman
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    This is likely a better fit for [diy.se]. This site is for the analytical design and engineering of electronic systems, while that site has subject experts on practical use of electrical systems in the home, including their safety and building codes. – nanofarad Dec 05 '20 at 02:23
  • 16 AWG copper will easily carry 16A (your not going to hit the melting point of copper any time soon), its just going to be hotter than thicker wire. If the insulation is rated to a high enough temperature then it might be OK. What is the temperature rating on the insulation? – user4574 Dec 05 '20 at 02:56
  • your title question is not answerable ... it is same as `will I die if I fall out of a 4th story window?` ... see? not answerable – jsotola Dec 05 '20 at 03:17
  • https://media.distributordatasolutions.com/ThomasAndBetts/v2/part2/files/File_7437_emAlbumalbumsOcal20(USA)oc_1_g_nec31016pdfClickHerea.pdf NEC would consider 15 Amps safe for 16 awg. And that's really the safe limit not the actual limit. – Passerby Dec 05 '20 at 03:19
  • Passerby, thank you very much. You put my worries to rest. – Y. Eman Dec 05 '20 at 03:36
  • user4574, thank you for feedback. How could I look up the temperature rating of the insulation? Thank you. – Y. Eman Dec 05 '20 at 03:38
  • The insulation should have markings on it, maybe. From manufacturer part number or the actual temperature rating in F or C. – Passerby Dec 05 '20 at 03:47
  • Thank you @Passerby, that is good feedback. I looked up how long it takes for copper wire to heat up. I found this page: https://electronics.stackexchange.com/questions/22334/how-do-i-calculate-the-temperature-rise-in-a-copper-conductor which shows it'd take 18 minutes! The scenario I'd envisioned was an instantaneous power surge which doesn't leave enough time for a temp rise. I have a hard time imagining a realistic situation where a power surge hovers around 6-15 A for minutes. – Y. Eman Dec 07 '20 at 03:39
  • @nanofarad, thank you for enlightening me as I didn't know. leveraging guidance, I'll be posting future topics properly. – Y. Eman Dec 07 '20 at 17:56

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