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

I've installed them on three phase. Only problem is operator error

To clarify...

240VAC is the nominal DELIVERED voltage

230VAC is the nominal AVAILABLE voltage at the motor

208VAC is the nominal DELIVERED voltage ( 208Y120 )

200VAC is the nominal AVAILABLE voltage at the motor

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You will see a CONSTANT stream of cross confusion ...

240/208 is the same as 230/200

One is the nominal voltage supplied

The other is the nominal voltage available at the pecker head / motor tap.

I hope this helps the apprentices.

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A 230 VAC motor is ASSUMED to connect to 240 VAC supply....

A 200 VAC motor is ASSUMED to connect to 208 VAC supply.

ALL voltages are NOMINAL ... and change with loading.

A TOTALLY unloaded motor will climb up the voltage towards parity.

I.E. no load voltages = supplied voltages.

HUGELY stressing motors draw down the local voltage -- and pull in current like crazy.

Until their 'heaters' pop.

This is when the draw is so huge that the windings are in danger.

Heaters are ANALOGS to the dynamics of the motor.

They are specifically engineered to 'pop' BEFORE the windings are damaged.

I'd NEVER install a motor without such thermal protection.

MOST 'small' ( less than one horse-power ) motors have INTEGRAL thermal protection.

Note this when you're planning HVAC disconnects....

MANY small units need only a motor rated switch... !

The cost savings can be DRASTIC...

I was a foreman for a top 25 contractor.

They changed their disco procedure AFTER my re-analysis.

They cut their costs 60% at a stroke.

Such savings infuriated my boss.

So much for perfection.

Why was he infuriated?

Incompetent 'managers' ( out and out Gonnabbees ) fear and hate talent.

My first PM on the job ( eleven months long ) tried every nasty trick in the book to get me to quit. When he informed the Superintendent that he'd replace me with a 'Real' foreman -- my buddy freaked out -- and applied enough pressure to have my PM canned within 72 hours.

Months later, I was working solo, kicking out production at a higher tempo than my former five apprentices could perform. I simply told the Super, "I'm a one-man crew."

Once the 'shell' was complete the job transitioned to a custom build-out -- and a fresh contract. Again the big man made an attempt to move me out of the way -- blocked by the Super and his PM. By this time I'd won over even the office crowd -- whose HQ was just blocks away -- and this was their showpiece project. ( It got some industry award for tilt-ups -- their specialty. )

I was tasked with ANOTHER Gonnabbee PM -- after his foul-ups on this one job -- the Company's Number One Customer had him fired, too. This is the fellow who was infuriated.

His role was to be the customer's favorite -- instead of me. He didn't have a chance -- he couldn't pull a rabbit out a hat -- and become the Super's alter ego on the job site.

Typical example: he's on the roof -- and a visitor needs to meet/talk -- having found me -- I'd just speed dial the Super -- and hand over my phone. It was painless for me -- and quite the step saver for the Super.