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I live in an old apartment building, and there is only a single outlet anywhere near the only window in my living room. My Air Conditioner works great with it, but now I can't use the desk lamp and digital piano that were plugged into that outlet (with a splitter) while the A/C is running without running an extension cord across the floor.

I realize that you're never supposed to use power strips or extension cords with air conditioners, but there are ones that are apparently meant for this. However, I can't find any that are splitters (i.e. they all are just one male to one female).

I don't need an extension cord per se - just a splitter, like this. This is rated for 15 amps, and the A/C says it's only 6.3 amps, so I'm assuming it's ok (not sure what the piano is, but it uses a thin cord without a ground so I assume it's not much).

Would that be ok?

Side question - even the cheapest power strips I can find are rated for 15 amps - and from what I can tell, the household outlets are usually 15 amps. So why can't I just use any power strip or extension cord, if the A/C only pulls 6.3 amps?

  • Have you talked to your landlord about your outlet shortage? If it's allowed, surface raceway wiring is likely a better solution than faffing with extension cords... – ThreePhaseEel Jun 20 '15 at 17:04
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Your AC only draws 6.3amps when its running. But when it turns on, for a moment as the motors start, it draws significantly more. Many window air conditioners say in the manual that they need a dedicated circuit because of this.

These startup surges may melt cheap powerbars and splitters, eventually causing enough damage to be a fire hazard.

Additionally, those surges cause the voltage to drop which can wreak havoc on delicate electronics like an electric piano. Usually not destructive, but enough to make it malfunction.

Assuming you cant get permission to have more outlets installed, run an extension cord, preferably for the other electronics near the window. Make sure that extension runs to an outlet on another circuit, and that no other large loads or sensitive electronics are on that circuit.

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    By this logic, wouldn't the A/C unit also melt the receptacle? – Tester101 Jun 18 '15 at 23:16
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    If you run an extension cord for the other items, wouldn't you want to make sure the receptacle you're extending from is on a different circuit? – Tester101 Jun 18 '15 at 23:18
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    @johnny A well built outlet splitter may work fine. The difficulty is finding a well built one - even expensive ones from reputable companies are often crap. I have seen too many melt or have burn marks on them to use them for high power devices anymore. – Grant Jun 19 '15 at 2:50
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    I'm curious about @Tester101's question too - "By this logic, wouldn't the A/C unit also melt the receptacle?". I think I've read that the outlets are only rated for 15 amps (and sometimes 20) as well. Is that correct? If so, why doesn't the same warning apply to the outlet as the power strip/splitter? – Jer Jun 19 '15 at 20:36
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    Extension cords are a temporary wiring device. Suggesting using one in a more permanent manner, is just as bad as plugging the A/C into the power strip. – Tester101 Jun 20 '15 at 2:33
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I'm in Australia so I'm not sure if my answer would be completely applicable in your circumstance. We have 240V here so 10A max... Anyway I'll let you be the judge of whether what I say will be relevant to you or not...

Personally I would buy a good quality powerboard (you guys seem to call them a powerstrip) and test it out myself. Here in Australia the good quality ones have built in surge protection and load protection. Like Grant said your AC will draw more than the 6.3A when it kicks in, but with a decent quality powerboard the load protection will switch it off if it draws too much power. It won't do your wiring any damage and you'll know that it won't work!

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Power strips, formally called Relocatable Power Taps (RPT), are universally discouraged by fire protection authorities for long term use. Where they are tolerated, daisy chaining them is "bad" as explained here and by IFC 605.4.2 (2009) :

Relocatable power taps shall be directly connected to permanently installed receptacles.

Even when using an extension cord or power strip without protective components, the fact of adding more connections (plug + socket) provides greater voltage loss and heating, with potential for a runaway thermal meltdown: as a connection heats up, its resistance increases causing it to heat up more.

Your air conditioner nominally uses 6.3 amps, which is a cakewalk for a 15 amp circuit. However, it is normal for the a/c to use more power during startup when first turned on and each time the thermostat makes a fresh call for cooling. Elevated current also occurs at exceptional events like restarting after a power interruption while the high pressure side is still fully pressurized. During these times the current can easily reach 15 amps for a second or two and may maintain 12+ amps for almost a minute.


Instead of messing around with the air conditioner, I would plug it in directly at the window. Then install a long extension cord to snake around the room to provide power for the electrically tame lamp and piano from another outlet.

  • Ok, this makes sense - but then I'll ask the same question that a commenter on another asked: If the power strip is rated for 15 amps and the A/C and draw more than that during startup, thus damaging the power strip and potentially causing a fire, then why wouldn't the same thing happen to the receptacle which is also only rated for 15 amps? – Jer Jun 19 '15 at 20:35
  • @Jer: Using the power strip means there is one extra thing that can go wrong. Also since the outlet is secured inside the wall, the only (routine) way it can fail is through repeated plug insertion/extraction and electrical heating. A power strip is subject to mechanical stress from being kicked around, contamination from spilled/sprayed/blown debris, thermal stress from room heating/cooling/sunlight/etc., and (arguably) observational opportunity: seeing four spare outlets is more likely to attract devices than one spare outlet. – wallyk Jun 19 '15 at 23:11
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    Extension cords are a temporary wiring device. Suggesting using one in a more permanent manner, is just as bad as plugging the A/C into the power strip. – Tester101 Jun 20 '15 at 2:33

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