is surge protection needed ?

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D

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Many years ago, I was having my house improved with new heating, additional lights etc. I had the electrician install two unswitched pairs of sockets behind the Hifi from a dedicated spur. It always sounded great and I had no unwanted clicks from heating thermostats and fridges, which were the main culprits back then (c. 1988). Of course, I couldn’t compare it with anything.

Two years later I was relocated for work, and bought a brand new house. There I always used the supplied sockets. Psychologically, I liked the idea of a dedicated supply, but I couldn’t objectively say it was better.

Nowadays we have far more garbage to contend with, thanks to mobile phones, umpteen chargers and wall warts, wireless internet, etc. In yet another property now, I’m thankfully free of symptoms, though I use a noise sniffer and carefully route my cables.

For another take, this pdf download is a good guide to wiring options, but a costly one to install. I’d prefer to buy better kit, but if you have the cash and inclination then it’s possible.
thanks for this. its an interesting guide, however, its via russ andrews which is like swearing on this (or any !) forum !

the woven ring main cable though often runs into problems with electricians however as they refuse to fit it for safety reasons (?).
 

Gray

Well-known member
When I was a boy my Mum plugged the Hoover into the same double socket as the TV. As the Hoover powered up, the back e.m.f. (voltage) from it's motor killed the TV (blew a diode).
Point is, same Hoover, never a problem elsewhere on the ring main - where that same surge was still connected to the TV - but usually being sufficiently dissipated by the ring wire.

Taught me a bit about close-proximity surges.
To this day, even with surge protection, in my house vac or equipment connect to mains, never both.
 
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shadders

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I did read up on it. how would it be nonsense in your view
Hi,
The purpose of a metal oxide varister (MOV) is to conduct at its specific threshold voltage, shunting the current. The two links below describe surge suppression operation.


As per the second link, the over voltage protection is expected to be for a few 10's of microseconds, and the MOV will be undamaged. Of course, if the over voltage lasts too long, then the device will fail.

Regards,
Shadders.
 

TrevC

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TrevC I'm assuming you know more about MOVs than I do, having done a little research online. Would I be right to think, that when the MOVs start to conduct, the power is then dumped to earth, thus tripping the earth leakage circuit breaker and safely cutting the power supply?
Yes, that is correct. Some surge protectors have three, one between live and neutral, one live and earth and one neutral and earth. The more the merrier!
 
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D

Deleted member 188516

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When I was a boy my Mum plugged the Hoover into the same double socket as the TV. As the Hoover powered up, the back e.m.f. (voltage) from it's motor killed the TV (blew a diode).
Point is, same Hoover, never a problem elsewhere on the ring main - where that same surge was still connected to the TV - but usually being sufficiently dissipated by the ring wire.

Taught me a bit about close-proximity surges.
To this day, even with surge protection, in my house vac or equipment connect to mains, never both.
apologies if its a stupid question but many claim digital sources (a cd player) put "noise" back onto the mains (correct ?). therefore, when i plugged my cd player into the same double socket (next to) as my amplifier, could this of affected (possibly) the operation of the amplifier ?
 

Simon 13th note

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Hi,
The purpose of a metal oxide varister (MOV) is to conduct at its specific threshold voltage, shunting the current. The two links below describe surge suppression operation.


As per the second link, the over voltage protection is expected to be for a few 10's of microseconds, and the MOV will be undamaged. Of course, if the over voltage lasts too long, then the device will fail.

Regards,
Shadders.
I understand that - thanks for quoting. but my point is if they are in series then surely there is current delivery effects?
 

Simon 13th note

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apologies if its a stupid question but many claim digital sources (a cd player) put "noise" back onto the mains (correct ?). therefore, when i plugged my cd player into the same double socket (next to) as my amplifier, could this of affected (possibly) the operation of the amplifier ?
definetly think it can because that's the reason of having a power bar that has individually screened sockets.
 

Gray

Well-known member
apologies if its a stupid question but many claim digital sources (a cd player) put "noise" back onto the mains (correct ?). therefore, when i plugged my cd player into the same double socket (next to) as my amplifier, could this of affected (possibly) the operation of the amplifier ?
If it's got a 'CE' mark it's supposedly been proven to neither cause (nor be susceptible to) interference to/ from other devices.
 

Simon 13th note

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Hi,
The varister is not in series, but across the live and neutral, as an example, so it is in parallel.

Regards,
Shadders.
I know that is very often the case (the two pronged MOVs must be connected that way) but ive been reading people online say that they can be connected in series with the 'drain' to neutral and hence the three pronged ones I think. They say they use them in higher power applications, but no idea why. If the MOV is in series then clearly its easy to understand resisting current effect for great hifi. I suppose take off the back of your strip and see how it's connected!
 

shadders

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I know that is very often the case (the two pronged MOVs must be connected that way) but ive been reading people online say that they can be connected in series with the 'drain' to neutral and hence the three pronged ones I think. They say they use them in higher power applications, but no idea why. If the MOV is in series then clearly its easy to understand resisting current effect for great hifi. I suppose take off the back of your strip and see how it's connected!
Hi,
In series makes no sense. The varister is high resistance until a specific voltage is reached.

Do you have the web link where it states the varister is in series ?

Regards,
Shadders.
 
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Simon 13th note

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Hi,
In series makes no sense. The varister is high resistance until a specific voltage is reached.

Do you have the web link where it states the varister is in series ?

Regards,
Shadders.
I just google it and searched for 'metal oxide varistor connected in series'. first thing that comes up is ...metal oxide varistors can also be connected in series.
 

shadders

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I just google it and searched for 'metal oxide varistor connected in series'. first thing that comes up is ...metal oxide varistors can also be connected in series.
Hi,
The search phrase you provided, presents the phrase in the top search result :

"Metal oxide varistors can also be connected in series to increase the clamping voltage rating."

So, this is self explanatory, you either use the varister at the voltage rating required, or create the equivalent using two varisters in series.

Regards,
Shadders.
 

Friesiansam

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A quote from https://www.electroschematics.com/metal-oxide-varistor/

"They can be connected in parallel for increased energy-handling capabilities.
MOVs can also be connected in series to provide higher voltage ratings or to provide voltage rating between the standard increments.
A Metal Oxide Varistor remains non-conductive as a shunt mode device during normal operation when voltage remains well below its “clamping voltage”. If a transient pulse (often measured in joules) is too high, the device may melt, burn, vaporize, or otherwise be damaged or destroyed.
The varistors must on all accounts be connected parallel to the electronic circuits to be protected."


Note the sentence I have underlined.
 
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Simon 13th note

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not if the varistor has three prongs surely (playing devils advocate)? One must be to ground and the other two for series connection? If you are using varistors in series then that goes back to the point I made about current, so I can understand my electrical engineer friend saying what he does about using surge protection with MOVs being a bad idea,

I dont bother and can understand why most of the bog standard audiophile power bars dont use surge protection eg my titan audio styx, which is just star wired - no busbars for dissipating current which often means the socket down the end has less current.
 

shadders

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not if the varistor has three prongs surely (playing devils advocate)? One must be to ground and the other two for series connection? If you are using varistors in series then that goes back to the point I made about current, so I can understand my electrical engineer friend saying what he does about using surge protection with MOVs being a bad idea,
Hi,
You are now changing the discussion to a 3 pin varister. Can you provide a link as to which specific 3 pin varister you are referring to.

The series aspect makes no sense. A varister is high resistance until the voltage reaches the specified threshold (in general), so what application are you referring to where a varister is used in series ?

(obviously you will not be referring to series connection to increase the threshold voltage, but you are referring to another application).

Regards,
Shadders.
 

shadders

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I was only putting it up for discussion tbh, hopefully in a friendly debate. No right or wrong obviously. often like lots of hifi.
Hi,
The three terminal MOV has the third pin as an indicator/monitor that the MOV has clamped the voltage, or not depending on the implementation.

There is NO serial connection except for the implementation to increase the threshold voltage.

EDIT :
Have to add, that electrical and electronic engineering is NOT anything like hifi where people just throw bits together. There is wrong and right with electrical engineering, where wrong can kill people.

Regards,
Shadders.
 
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D

Deleted member 188516

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Apology accepted!
thanks but do you therefore think that a cd player, plugged in next to an integrated amplifier, can cause interference with the amplifier ?
(i'm guessing your answer is no but i would appreciate a more "technical" explanation as to why ?).
 

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