ECN Forum Forums General Topics of the Trade General Discussion Area Will a 240v window air conditioner run OK on 208V?

Any thoughts or experience with this?

My bet is no but the answer will be on the label.

If the nameplate say 240 .... no, it won't run properly.

If the nameplate REALLY says 230, you can run it at exactly 208. Any voltage drop at all and you're SOL.

If it says 220, you're good to go.

In theory, a boost transformer would solve the problem, by raising the 208V to 240V. Something like this place (no affiliation, others may have better product) http://www.transformeronline.com/buckboost.htm

Being code may be an issue.

I'm unaware of ANY recent HVAC equipment whose motors couldn't tolerate 200-230 nominal, delivered voltages.

More current will be drawn at the reduced voltage.

The big issue for many HVAC systems is not the motor -- but the control power transformer.

Many are multi-tap -- in which case re-tapping would be most wise.

Unlike the motor, the control logic is pretty finely dialed in.

230 rated single phase motors will run at 208 volts, but will probably not last long (more than a few weeks or months) before they burn up.

I'd also question whether a 'window' unit will have any control transformer multi-tap ability, it might though, it seems some of the newer units are dual rated.

Just my opinion, but...why not just get a window unit that is rated for nominal 208 volts?

Yes, you can install a buck-boost transformer onto the AC circuit back by the panel, but IMHO the labor and materials will probably be $$$ more than another AC; unless we are talking about a really 'big' window unit.

230 rated single phase motors will run at 208 volts, but will probably not last long (more than a few weeks or months) before they burn up.

Virtually all small motors made in the last thirty years will ENTIRELY tolerate 200-230 VAC nominal -- its even on their name-plate.

You have to get into larger ( industrial ) sizes before it's an issue.

And, yes, I've installed 240VAC 1 phase HVAC units where only 208VAC power was available. Six years later the units were still running strong.

The HVAC industry has standards -- one of which is to make it possible to run their equipment at both voltages.

There are NO END of apartments out their receiving two legs of 208Y120 power. Ditto for small businesses.

It is in the nature of small hermetic A/C systems for them to operate entirely surrounded by refrigerant -- and to actively reject their heat to the outside.

Their motors can take it, and take it, and take it.

I just looked a couple up on the internet (LG and Frigidaire) they say 230/208v.

The real answer is going to be on the nameplate of the one in question but it looks like Tesla is right on.

I'm with Tesla on this - but I wouldn't even look for taps on a window AC, if they have a transformer. The motor has overload protection and undervoltage probably won't hurt the controls.