Polarity .........

[Gees]

I have been following a thread on another forum regarding polarity of supply with respect to operation of connected appliences... Is there ANY AC applence that will not work correctly when connected either way across an AC supply ?

 

[ricicle]

Any Single phase AC appliance will function correctly.

 

[LoveRocket]

When people refer to the 'polarity' of a single phase AC supply, they are actually refering to the fact that the potential should be between phase and neutral, AND phase and earth. There should be no potential between neutral and earth. If a supply is 'reverse polarity', then you'll see 240v between neutral and earth, and 0v between phase and earth.

I hope that makes sense!

 

[nozspark]

I think some boilers won't work with reversed polarity?!?!

I think they might reference to earth on the PCB

 

[matt1e]

I think some boilers won't work with reversed polarity?!?!

I think they might reference to earth on the PCB

you think correctly nozspark
interlinked smoke alarms are another example as the correct polarity must be maintained after the first unit

 

[Click-Sure]

The big problem with reverse polaritry is that electrical systems to BS7671 generally rely on fusing of the phase/live side, in a reverse polarity situation where there is an overcurrecnt which cuts the protective device the device will stop functioning an appear dead whilst there is often 230v relative to earth kicking around in there.

 

[Gees]

I think some boilers won't work with reversed polarity?!?!

I think they might reference to earth on the PCB

you think correctly nozspark
interlinked smoke alarms are another example as the correct polarity must be maintained after the first unit

Yes but if they are all connected the same way with respect to each other. does it matter which way they are connected to the supply?

 

[matt1e]

I think some boilers won't work with reversed polarity?!?!

I think they might reference to earth on the PCB

you think correctly nozspark
interlinked smoke alarms are another example as the correct polarity must be maintained after the first unit

Yes but if they are all connected the same way with respect to each other. does it matter which way they are connected to the supply?

operation wise....no

 

[ericmark]

I had to do a load of Pat Testing and the tester first tests supply. I was surprised to find out how many socket outlets were wrong polarity. When doing a PIR normally only a percentage of sockets are tested and likely same ones every time.

In domestic yes PIR every 10 years or change of occupier so explain how there are so many people with questions about earths on lighting when rules changed in 1966? Even if not upgraded there should have been notice on CU.

 

[ColJack]

strictly speaking you can't reverse polarity in a single phase TN supply, live will always be measured with respect to earth, and neutral will always be at or close to earth potential..
you might have the wrong colours on the wires and be switching the neutral, but live is always live and neutral is always neutral.