I don't have any particular problem with noisy mains, but it occurs to me that I should protect my amp's power supplies from unusual surges due to (for example) lightening affecting the power lines.
I see that some people use MOVs (of around 275-300v for UK nominal 230v supplies), and these are only about 40p each. But I'm nervous that any DIY MOV setup I made would be over-simplistic and/or untried compared to a commercial surge protection device. Would just adding a few MOVs be a poorer solution than a decently rated surge protector from (say) APC or Belkin?
Secondly, the cost implications may depend on how I plug in the components: my pre amp and active speaker amps will be in different places and could be plugged into convenient but separate wall-sockets - requiring three plug-in protectors if i chose them rather than MOVs. BUT, should I be trailing all the power leads back to the same multi-way power-block anyway (in a sort of external star pattern for the ground), to help avoid ground loops in the mains wiring and interconnect shields? It would mean a single protected multi-way would be more cost effective, and I'm half tempted to do that in any case as it would probably make remotely powering on/off the active speaker amps simpler.
Cheers
Kev
I see that some people use MOVs (of around 275-300v for UK nominal 230v supplies), and these are only about 40p each. But I'm nervous that any DIY MOV setup I made would be over-simplistic and/or untried compared to a commercial surge protection device. Would just adding a few MOVs be a poorer solution than a decently rated surge protector from (say) APC or Belkin?
Secondly, the cost implications may depend on how I plug in the components: my pre amp and active speaker amps will be in different places and could be plugged into convenient but separate wall-sockets - requiring three plug-in protectors if i chose them rather than MOVs. BUT, should I be trailing all the power leads back to the same multi-way power-block anyway (in a sort of external star pattern for the ground), to help avoid ground loops in the mains wiring and interconnect shields? It would mean a single protected multi-way would be more cost effective, and I'm half tempted to do that in any case as it would probably make remotely powering on/off the active speaker amps simpler.
Cheers
Kev
Why not buy plenty of ( P1.5KE280 suppressors) for that purpose? Anyway, what you gonna buy from internet eventually would be containing these elements.
because the UK supply can rise to 253/254Vac do not use 250Vac MOV. You must use 270Vac or higher.
I usually fit 4 MOV inside the multi-way power block. I usually fit a single inside the equipment.
In case the MOV go short circuit when they fail, be sure you have a sensible fuse upstream. The UK plug tops have a fuse receptacle for <=13A. Don't fit 13A here, when a 1A, or 2A, or 3A is sufficient for the equipment.
I usually fit 4 MOV inside the multi-way power block. I usually fit a single inside the equipment.
In case the MOV go short circuit when they fail, be sure you have a sensible fuse upstream. The UK plug tops have a fuse receptacle for <=13A. Don't fit 13A here, when a 1A, or 2A, or 3A is sufficient for the equipment.
Thanks, that (roughly) confirms the voltage rating I was suggesting, which is helpful. I'd just realised I'd been assuming without any verification that the MOV rating was RMS rather than peak voltage and was going to check, but if 270V is sufficient then presumably it must be RMS as I'd imagined.
Its an interesting idea to put them in the multi-way; I'd not thought of that at all. I guess if it were dedicated only to this use then I could fit a smaller fuse without any issue. I can see why it would be a good idea, if the MOV fails short-circuit under a spike condition.
Cheers
Kev
Its an interesting idea to put them in the multi-way; I'd not thought of that at all. I guess if it were dedicated only to this use then I could fit a smaller fuse without any issue. I can see why it would be a good idea, if the MOV fails short-circuit under a spike condition.
Cheers
Kev
Yeah, I've been looking at some specs; from what i can work out it may be a balance between choosing the best protection by going for a voltage rating only just above the max it is to be used on, vs longevity by going for a higher rating less stressed by routine conditions. At 40p its probably no biggie if they do wear out in time, so personally I'm tempted to lean towards protection rather than longevity.
As I understand it though, lifetime isn't easy to judge as its dependent on both the frequency and magnitude of whatever spikes the MOV experiences. It could even be one or two big spikes that i don't realise happened. I believe they don't necessarily fail short-circuit when they do finally go, so I'd probably want some way of knowing if my MOVs have been taken out or not.
Cheers
kev
As I understand it though, lifetime isn't easy to judge as its dependent on both the frequency and magnitude of whatever spikes the MOV experiences. It could even be one or two big spikes that i don't realise happened. I believe they don't necessarily fail short-circuit when they do finally go, so I'd probably want some way of knowing if my MOVs have been taken out or not.
Cheers
kev
In the commercial power strips the MOV is in series with a neon, so you know when it's still alive. Commercial ones are made to a (low) price so it's feasible you can "make" a better one quite easily and cheaply.
With regard to earth loops, running all your equipment off one power strip is the way to minimise them. Using balanced inputs and outputs avoids this constraint though.
With regard to earth loops, running all your equipment off one power strip is the way to minimise them. Using balanced inputs and outputs avoids this constraint though.
The only good surge suppressor is the whole home unit at the service entrance to the building. But if you insist, note that MOV's are rated at 3 000 000 surges.
Also note that at point of use surge protectors. The MOV's should only be connected Hot to Hot or Hot to Neutral, never Hot to Protective Earth.
Also note that at point of use surge protectors. The MOV's should only be connected Hot to Hot or Hot to Neutral, never Hot to Protective Earth.
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Geez, what a poor assessment about thinking of putting movs in, and also removing them. MOV's are used in a huge amount of equipment, and usually by people who know what they are doing, and how to implement them.
Maybe it's a good idea for the OP not to put a new part in the primary side of mains powered equipment - that's not a place for inexperienced people to work in.
Maybe it's a good idea for the OP not to put a new part in the primary side of mains powered equipment - that's not a place for inexperienced people to work in.
Thanks for all the replies! Very helpful.
I'd not considered the possibility of a main/house protector, I'll have to look into that. I can see the benefit, but it may be too costly if (as i suspect) its one of those things that I'm required to get professionally fitted. We are allowed to do stuff like primary and secondary earth bonding here (unless thats changed very recently) but most other things to do with the main consumer unit (or before) are banned these days.
I suppose the failure mode of the MOV should be considered if i use them; i can see that as it is a destructive failure there may be situations in which it doesn't fail ideally, but then the consequence of not using them is that something else less predictable may fail instead. Perhaps the best approach would be to use them but design for a possible meltdown or ignition to occur safely, without affecting anything else.
I'll definately have a look around at failure-detection circuits too; the neon sounds simple, but I read somewhere the MOV can fail open circuit so perhaps that would only work sometimes.
Cheers
kev
I'd not considered the possibility of a main/house protector, I'll have to look into that. I can see the benefit, but it may be too costly if (as i suspect) its one of those things that I'm required to get professionally fitted. We are allowed to do stuff like primary and secondary earth bonding here (unless thats changed very recently) but most other things to do with the main consumer unit (or before) are banned these days.
I suppose the failure mode of the MOV should be considered if i use them; i can see that as it is a destructive failure there may be situations in which it doesn't fail ideally, but then the consequence of not using them is that something else less predictable may fail instead. Perhaps the best approach would be to use them but design for a possible meltdown or ignition to occur safely, without affecting anything else.
I'll definately have a look around at failure-detection circuits too; the neon sounds simple, but I read somewhere the MOV can fail open circuit so perhaps that would only work sometimes.
Cheers
kev
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A group of MOVs inside the metal case of the distribution board seems ideal.
The Mains fuse is the electricity suppliers fuse.
The metal case prevents explosive bits flying around the house.
Virtually no risk of fire if the MOVs do explode on failure.
Safer than inside the plastic case of a 4way lying on the carpet !
None of my protected 4ways have failed destructively. I don't know if they have simply stopped working.
It is in the distribution board that Curl suggests for the Hot to Neutral 10uF capacitor to attenuate the HF.
The Mains fuse is the electricity suppliers fuse.
The metal case prevents explosive bits flying around the house.
Virtually no risk of fire if the MOVs do explode on failure.
Safer than inside the plastic case of a 4way lying on the carpet !
None of my protected 4ways have failed destructively. I don't know if they have simply stopped working.
It is in the distribution board that Curl suggests for the Hot to Neutral 10uF capacitor to attenuate the HF.
On my designs, I put the MOV after comon mode filter coil. The inductance of coil will limit/reduce the slewrate of current in case of MOV trigering and in some cases will help MOV to not be destroyet by high voltage spikes. Any case in front of MOV MUST be a calibrated fuse.
Regarding signaling of destroyed MOV, there are some type of MOV with 3 pins and one pin it is used for signaling in case a bad MOV.
Regarding signaling of destroyed MOV, there are some type of MOV with 3 pins and one pin it is used for signaling in case a bad MOV.
Ah interesting, I'd not seen the 3-pin MOVs before -sounds ideal, thanks! I was already thinking of using a filtered IEC inlet socket on my amps; not sure if the coils in those would be robust enough to make much difference, but I guess they may help.
Andrew, I've been checking out the legalities down here wrt the main switch/distribution-board areas of the house wiring, and its not good news unfortunately. It seems that I'm not permitted to alter almost anything there any more, and I may also be invalidating my home insurance if I tried it. In fact, I can't quite believe this but it 'seems' like I may not even be permitted to change a standard MCB these days... I don't know if its the same in Scotland but it appears that England may have gone too far!
So all in all I think I'll keep things simple and legal and just add some movs somewhere after the wall-socket outlet. I could perhaps employ a dedicated metal box screwed to the plaster wall to house the MOVs; which could probably be part way along a fire resistant flex leading to a multi-way trailing socket. Not perfect, considering some of the great ideas in this thread, but hopefully a decent compromise between protection and expense.
Cheers
Kev
Andrew, I've been checking out the legalities down here wrt the main switch/distribution-board areas of the house wiring, and its not good news unfortunately. It seems that I'm not permitted to alter almost anything there any more, and I may also be invalidating my home insurance if I tried it. In fact, I can't quite believe this but it 'seems' like I may not even be permitted to change a standard MCB these days... I don't know if its the same in Scotland but it appears that England may have gone too far!
So all in all I think I'll keep things simple and legal and just add some movs somewhere after the wall-socket outlet. I could perhaps employ a dedicated metal box screwed to the plaster wall to house the MOVs; which could probably be part way along a fire resistant flex leading to a multi-way trailing socket. Not perfect, considering some of the great ideas in this thread, but hopefully a decent compromise between protection and expense.
Cheers
Kev
You may be able to get an electrician to insert a GPO in the distribution board, and ask the sparky to use large gauge short links. You may not need a new mcb, as it could go on an existing power circuit.
But of course any protective device you attach to that point may be the easiest path for any transient in your street. Whether or not that is an advantage or disadvantage, or moot, is not easy to appreciate.
But of course any protective device you attach to that point may be the easiest path for any transient in your street. Whether or not that is an advantage or disadvantage, or moot, is not easy to appreciate.
Kev,
although our house building regs are different in Scotland, we have a similar situation.
All electrical work must be approved by Building Control, or carried out by an approved and currently accredited Electrician.
If the work went beyond minor, like changing an MCB, or light bulb, then I suspect we need Building Control approval before work can start.
I wonder how the light bulb is legislated?
There are obviously some exceptions to cover very minor works. The wording may give an escape for DIY in a very few "deemed to be safe" works.
I have just swapped the three 100W halogen PSUs in the ceiling space, to one 30W LED PSUs, without asking Building Control ! Quite a bit less light in my dining room, but it was a bit too bright anyway. Reduced from 300W of lighting, to 30W of lighting.
I can download the current Scottish Regs from our Scottish Government website. I have not done so since I started building my house in 2002, before the new "electrician regs" came into force. Looks like I need a new copy.
Can you download the England/Wales version?
although our house building regs are different in Scotland, we have a similar situation.
All electrical work must be approved by Building Control, or carried out by an approved and currently accredited Electrician.
If the work went beyond minor, like changing an MCB, or light bulb, then I suspect we need Building Control approval before work can start.
I wonder how the light bulb is legislated?
There are obviously some exceptions to cover very minor works. The wording may give an escape for DIY in a very few "deemed to be safe" works.
I have just swapped the three 100W halogen PSUs in the ceiling space, to one 30W LED PSUs, without asking Building Control ! Quite a bit less light in my dining room, but it was a bit too bright anyway. Reduced from 300W of lighting, to 30W of lighting.
I can download the current Scottish Regs from our Scottish Government website. I have not done so since I started building my house in 2002, before the new "electrician regs" came into force. Looks like I need a new copy.
Can you download the England/Wales version?
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Thanks chaps, helpful once again.
Andrew, yes I downloaded documentation for 'Part P' here. Its not the easiest read in the world but from what i can gather I'm permitted to do simple things like replacing sockets, adding a spur and so on, 'provided' its not in a sensitive area like a kitchen, bathroom or outside. However anything to do with the consumer unit or there abouts requires testing and certification by competant persons or the local authority. A competant person is a legal definition requiring certification though, not just a case of being competant or not.
I dare say that it would be hard to tell when things were done, so possibly one could get away with it in some cases. But I notice cable and so on tends to be dated (not to mention being 'harmonised' colours) these days so i'd possibly have to look for old/used components. My feeling is that just for this, when there is the option of using MOVs on the equipment end of things, its probably not worth me fiddling with stuff I shouldn't. As i understand it, nothing (that i'd want to pay for) would deal with a direct lightening strike anyway, and the equipment-level movs would cover most of the general surges/spikes likely, so thats probably a reasonable compromise.
Trobbins, thats a very interesting point about potentially creating a preferential path to my house, and i agree its hard to work out the pros/cons of that. I think you're right that getting an electrician in would still be a good answer though, but I've been given redundancy notice recently so I'm trying not to spend too much on this. The sparky would be obliged not just to come out and do it, but also to test and certify everything as well, so even though its a relatively small job in itself it would end up costing significant money.
Cheers
Kev
Andrew, yes I downloaded documentation for 'Part P' here. Its not the easiest read in the world but from what i can gather I'm permitted to do simple things like replacing sockets, adding a spur and so on, 'provided' its not in a sensitive area like a kitchen, bathroom or outside. However anything to do with the consumer unit or there abouts requires testing and certification by competant persons or the local authority. A competant person is a legal definition requiring certification though, not just a case of being competant or not.
I dare say that it would be hard to tell when things were done, so possibly one could get away with it in some cases. But I notice cable and so on tends to be dated (not to mention being 'harmonised' colours) these days so i'd possibly have to look for old/used components. My feeling is that just for this, when there is the option of using MOVs on the equipment end of things, its probably not worth me fiddling with stuff I shouldn't. As i understand it, nothing (that i'd want to pay for) would deal with a direct lightening strike anyway, and the equipment-level movs would cover most of the general surges/spikes likely, so thats probably a reasonable compromise.
Trobbins, thats a very interesting point about potentially creating a preferential path to my house, and i agree its hard to work out the pros/cons of that. I think you're right that getting an electrician in would still be a good answer though, but I've been given redundancy notice recently so I'm trying not to spend too much on this. The sparky would be obliged not just to come out and do it, but also to test and certify everything as well, so even though its a relatively small job in itself it would end up costing significant money.
Cheers
Kev
The sparky would probably have to give you a document stating the work done. The length of time for that work - if there was no mucking around to be done in the switchboard - would be their minimum call out cost. Where I come from, you can sometimes be lucky and find a sport or social 'mate' who is a 'sparky' and the cost is a 'slab'. You can then work out what you want to plug in to the GPO, although you may also find limitations on the type of any accessory equipment that is placed inside any enclosure where the main distribution board is located.
You may also be lucky enough to have a GPO that is 'very close' to the main distribution board.
You may also be lucky enough to have a GPO that is 'very close' to the main distribution board.
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