If I run a 240V portable AC unit off a long extension cord with a 10-12V drop, is this bad for these units? Maybe only the cheap brands?
Your air conditioner is probably going to be fine down to 208 volts or so, but I’m worried about your extension cord. 15 amps at a 12 volt drop means the cord has to dissipate 180 watts of heat. What gauge extension cord are you using and how long is it?
It’s a standard A/C unit with a 10A plug, you plug into house power point. My extension cord is 50Metres of 1.5mm2. volatge calc shows 11V drop irrc.
It’s not going to help it’s longevity. Anything it doesn’t get in voltage is made up in current and that’s what produces heat. Also your 220V may not be constant as it is. You are really pushing the limit of the cord, consider upgrading the cord to a thicker gauge as a quick fix.
Thanks, I do have a 2.5mm2 cord but it’s so hard big and hard to roll up.
Wait, my experience, such as it is, is only in American wire gauge (AWG), but when I look it up it looks like that converts to a 16 AWG. Are you really planning to run 50 meters of 16 AWG extension cord to a 2,200 watt air conditioner? Around my house 16 AWG is speaker wire. You better consult an real electrician, I feel like you’re starting to get into trouble.
Also consider that the inrush (startup current ) is typically 2 to 2.5 times the operating current.
A 50Metres of 1.5mm2 extension cord on offer fr Amazo UK has the following advice:
Remember that with 240 volts, we need less copper to get the power.
I know that the 240 volt requires less copper, but I worry about dissipating that much heat. It’s 5% of the total energy used by air conditioner going to heat the extension cord used to power it, plus, it all turns to heat increasing the load to the air conditioner itself. If it’s only 10 amps rather than the 15 I estimated it’s still 120 watts of heat. Think how much heat two sixty watt incandescent bulbs throw off. You couldn’t leave the wire coiled up, it just seems like a kludge. For a short term solution maybe, but you sure don’t want to think it’s a permanent thing.
Which means the steady-state current is probably less than 10 A.
You need to look at three things:
Knowing the steady-state current and gauge of the extension cord, how much heat (per unit length) is being generated by the extension cord during operation? Too much self-heating by the extension cord is dangerous. There are guidelines on this. Ambient temperature is also a factor; the max current the extension cord can handle decreases as the ambient temperature increases.
Knowing the steady-state current, and length & gauge of the extension cord, what’s the voltage drop of the extension cord? Too much voltage drop can burn up a motor.
As noted by am77494, there is also the issue of voltage drop due to inrush current. This is a function of the magnitude of the inrush current along with the length & gauge of the extension cord.
What is the manufacturer and model number for the unit?
Does the A/C have an actual voltage rating on the label? Sometimes min-max values are given.
FWIW, running the A/C when the voltage is “too low” will burn out the motor. Many things rated for 240V are actually rated for 220-5%. Make and model?