I have a 900VA/480Watt UPS/surge unit, and it doesn’t quite reach the wall where I need to plug it in. I'm using it to power an iMac. The unit has a 3x16 AWG cord. Is there any harm or difference, in using a heavy gauge extension cord that matches or exceeds the original cord on the unit itself? Say a 10,12,or 14 AWG cord to connect it to the wall? Or even a 16 AWG cord (like the actual gauge with the unit)?

  • Does the unit itself have any indication as to whether an extension cord can be used? Many high amperage devices forbid such connections. If so, it could be a violation to do so.
    – bib
    Aug 18 '17 at 17:11
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    Most such restrictions on a device pertain to warranty claims and not to the rules of the local electrical inspector. They are usually intended as a general warning for those who have no clue that extension cords come in different ampacities, including some that are more than sufficient.
    – Upnorth
    Aug 18 '17 at 17:17
  • @Upnorth Understood, but doesn't UL require that a device be used as intended, and anything else voids its (and maybe code's) approval?
    – bib
    Aug 18 '17 at 17:19
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    Of course it is OK to use an extension cord--16 ga or heavier. There can be no reasonable objection to this. Aug 18 '17 at 17:49
  • @bib In theory, violation of the installation and operation instructions of a device (including warning labels) can be deemed a "violation". NEC 110.3(B). This may be discovered by someone investigating AFTER an incident, but doesn't necessary CAUSE a hazard, making it moot.
    – Upnorth
    Aug 18 '17 at 19:51

It's a heavy load like an air conditioner, so use an air conditioner extension cord.

Manufacturers can be greedy/cheap about sizing extension cords, using the absolute minimum UL requires for safety. Bumping to the next size could cost them 25 cents a unit wholesale, which on 100,000 units, is real money.

Using a same-gauge extension cord is not a good idea, then you would be substituting 6 feet of 16AWG for 12 feet of 16AWG, and that is worse.

  • Nothing heavy load like that. Running an iMac with a total pull of less than 350 watts under full load.
    – v15
    Aug 18 '17 at 18:03
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    Regardless, the wall-UPS connection must accommodate the full rating of the UPS, because the UPS itself can draw that. The 900VA number is of particular concern. Aug 18 '17 at 18:08
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    @hwp08 - The UPS will use extra current while it's charging the batteries so actual current draw will be greater than just your Mac after a power outage (how much more depends on the capacity of the battery charger in the UPS). Just use a heavy duty 12 gauge appliance cord and be done with it, it's unlikely that the wires in your wall are larger than that for a 15a or 20a outlet.
    – Johnny
    Aug 18 '17 at 18:08
  • @Harper Johnny, great thoughts here guys. Is there any reason why using an extension cord from the iMac TO the UPS would be a problem? Thinking if i can't extend the reach of the UPS, I could extend the reach TO the UPS. Again one rated slightly higher than the original cord, probably 14 gauge.
    – v15
    Aug 18 '17 at 18:12
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    Apple power supplies are very good, so a 350W Mac won't be over 400VA. That's 3.33 amps at 120V so a 16 AWG extension cord should be fine. Aug 18 '17 at 19:06

900vs is only 7.5 amps a standard 16 gauge cord would be plenty. Unless you want to go +50' . cords have different ampacities than house wiring. Per table 400.5.a.1 , 16 gauge 13 amps.

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