switching neutral in single phase motors?
switching neutral in single phase motors?
(OP)
Hi all
are they any BS standards that state that it is recommended or must switch the neutral (so the neutral is taken thru a set of n/o on the motor contactor) as well as the phase to a single phase motor 240v motor?
thanks
Dave
are they any BS standards that state that it is recommended or must switch the neutral (so the neutral is taken thru a set of n/o on the motor contactor) as well as the phase to a single phase motor 240v motor?
thanks
Dave





RE: switching neutral in single phase motors?
Is this relating to a specific application?
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I don't suffer from insanity. I enjoy it...
RE: switching neutral in single phase motors?
respectfully
RE: switching neutral in single phase motors?
Goodmorning
You are questioning whether or not to break the neutral conductor, yet later you refer to the voltage as 240 volt. It is a very rare motor that requires a neutral at 240 volt. Are you sure of the voltage?
One other point is that when you install a motor that requires a neutral in a hazardous location, the disconnect must open the "hot(s)" and the neutral.
Bigbillnky,C.E.F.....(Chief Electrical Flunky)
RE: switching neutral in single phase motors?
Gunnar Englund
www.gke.org
RE: switching neutral in single phase motors?
I didnt think there was a BS standard.
UK generation is 240V.
EU requirement for single phase harmonisation is 230V.
UK still generates 240V. And is unlikely to change due to huge implications on generation network.
Dave
RE: switching neutral in single phase motors?
That way you get double pole isolation and the overload works as it should
RE: switching neutral in single phase motors?
See BS EN60079-14
RE: switching neutral in single phase motors?
You ARE 230 V AC, like it or not - and even if your voltmeter says 240 V. That's why the continent changed from 220 to 230 V and you changed from 240 to 230 V. The adaption period is over.
Gunnar Englund
www.gke.org
RE: switching neutral in single phase motors?
I always thought switching of neutral has to be different from phase. For safety reasons, the neutral needs to precede the phase while closing whereas open after the phase while opening.
RE: switching neutral in single phase motors?
Gunnar Englund
www.gke.org
RE: switching neutral in single phase motors?
Chuck
Getting older is inevitable
Acting your age is optional
RE: switching neutral in single phase motors?
----------------------------------
I don't suffer from insanity. I enjoy it...
RE: switching neutral in single phase motors?
RE: switching neutral in single phase motors?
The ground, earth or terre is not usually switched. If it is disconnected with a plug connection, the ground pin or stab is longer than the others to effect a late break, early make on the protective earthing terminal.
respectfully
RE: switching neutral in single phase motors?
And, Bill. You dig up (or know) facts in an impressive manner. I did not know about that Canadian requirement. That's why I thought it was the PE Chuck was thinking of.
Gunnar Englund
www.gke.org
RE: switching neutral in single phase motors?
Thank you ScottyUK and David I have seen reference to PE on our German equipment it was always combined with a ground symbol and connected to a green/yellow wire, I just assumed it was an abbreviation of German language for ground never giving much thought otherwise.
Chuck
Getting older is inevitable
Acting your age is optional
RE: switching neutral in single phase motors?
I am a long way from my copy of the NEC. I have the Canadian code, and it is reasonably close to the NEC. Anyone who is motivated may search the index of the NEC for a similar rule.
In North America, the neutral is virtually always the grounded circuit conductor.
Rule 14-016 states that:
Devices (Switches, breakers, fuses) shall not be connected in any grounded conductor EXCEPT WHERE;
(a) the devices simultaneously or previously disconnect all ungrounded conductors;
(b) an overcurrent device is in a two wire circuit having one wire grounded and there is a possibility that the grounded conductor may assume a voltage difference between itself and ground due to unreliable grounding conditions of sufficient magnitude to create a dangerous condition: or
(c) overcurrent devices are located in that part of a circuit that is connected by a two pole polarized or unpolarized attachment plug provided that the circuit is rated at 15A, 125 V or less.
Personally, I don't switch neutrals under any circumstances on three wire single phase circuits or the shared neutrals of three phase circuits.
I have seen too many problems and too much expensive and needless damage caused by failures or improper action of switches in neutrals.
I have never seen damage or encountered any problems caused be a solid (unswitched) neutral.
Another interesting point re the close similarity between the Canadian and American codes is in regards to voltage drop.
The NEC RECOMENDS that the voltage drop between the consumers service and the point of utilization not exceed 5%.
The Canadian code REQUIRES that the voltage drop between the consumers service and the point of utilization not exceed 5%.
respectfully