Surge Protection 5 - Wiring Lengths, Connection Options
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- čas přidán 21. 02. 2020
- Wiring connections and wire lengths to consider when installing surge protection devices.
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Your tear down and explanation is very lucid , very helpful info to all electrical installers designers !
I have been having troubles with spd in terms of understanding but you have brought relief to me with your series of videos
Thank you Mr Ward, attention to detail, as usual ☘️🇮🇪☘️
Great series. Learn something new everyday. Thank you for the clear explanations.
Thanks John, an excellent video, as always !
Excellent description and basically to retrofit using an external enclosure treat it like adding an isolation switch before the consumer unit so unit needs 100A Main switch like the Wylex one shown (tails come in and out to CU, including the earth)
Brilliant explanation. Thanks John.
Hiya John, at 3.20 you mention that the left hand module connects between line and earth. In actual fact if you bell these connections/terminals out you’ll discover that the left hand module connects between line and neutral. The right hand module connects between neutral and earth. I am unsure if this is an industry standard across all other brands, but certainly wylex and probably Crabtree (electrum) are configured in this way, great videos John keep then coming👍
thank you-sir very informational-and greatful- florida
Thank you very much for this comprehensive surge protection series.
I only have one comment about voltage drop due to wire lengths and your explanation. In this particular case I do not think that voltages are going to be added one to another, but due to the high current, voltage drops on wires would be high and theoretically voltage drop on SPD during operation is around 0, which means that if big voltage drops on the wires, SPD would go out of the operation because of not having sufficient voltage level and over-voltage would be transmitted further once big voltage drops have SUBTRACTED from 10kV in your example... Please note that is only my opinion following your introduction.
Thank you again
Regards
I also think the same, it will be subtracted from what is applied on SPD, hence SPD will not reduce the resistance.
Just a minor point. Actually twisting the leads together doesn't reduce the inductance, it might even make it a bit worse bearing in mind the thick insulation on these wires. The important thing is to keep the two wires as close as possible to each other. This is why the regs use the term binding rather than twisting.
Just to clarify, twisting wires does provide other advantages. Twisting the signal and return wires in a communications cable reduces the crosstalk between adjacent pairs, reduces interference from noise sources and it is also used to control the impedance of the cable.
This is correct. The intent is to reduce the area enclosed between the two conductors as much as possible as this reduces the inductance. Laying the two conductors side-by-side achieves this area reduction as effectively as twisting the conductors without the additional wire length introduced by twisting.
Wonder how you’d attach one to a triple pole distribution board. Would have thought this would be extremely hard to comply with. Excellent videos thanks.
thanks so much, i spend all day to watch your video, such a valuable time
Oh giver of knowledge! 👍👍👍👍👍
Very interesting topic particularly with a combined Master Switch and SPD fitted at the DNO intake point
Also interesting (?) is a what if I've been thinking about. What if you have one of these, so you no longer need a main switch in your CU, and let's say it's an all RCBO one so it has no RCCB either. With no incomer, how do you connect L to the busbar?
@@anonnona8099 Switch off the Isolator in the DNO meter cupboard
@@Mike_5 1) There might not be one.
2) It's irrelevant - that's an answer relating to isolation and safe working. My question is there you are, with tails entering your CU. How do you connect the L to the busbar?
@@anonnona8099 Bellend. Do your homework properly ...
@@Mike_5 Thank you for replying to me with the same level of courtesy as I have shown to you. You are a credit to the human race.
Thank you for the explanation of the cable lengths, not sure how the plastic enclosure sits with the Amd 3 change though, I seem to remember a manufacturer being admonished as they issued an illustration of a TT installation with an external Type S RCD in a plastic enclosure at the time of Amd 3 of the 17th being introduced. What are your thoughts on this?
Thanks John, I thoroughly enjoyed your video series on SPDs, very well explained so that even a quantity surveyor could understand it. :-)
I live in Thailand and our electricity supply is all over the place and I'm forever losing my LED downlight luminaires. Would that be due to voltage surges? Would a reduced voltage also adversely affect the luminaires?
Do voltage surges affect luminaires when they are turned off or only when they are switched on?
Is there such a thing as a stand alone SPD that can be fixed in front of the luminaire so that each downlight has its own SPD protection - that would avoid me having to mess with the CU?
Thanks sir.
Brilliant video as always
I am trying to work out the best way to implement SPDs in temporary events, We are often fed buy a 125A 3p C-form or 400A power lock outlets from the permanent electrical system in the venue, The supply cable from said outlet is normally 20-40m long then this goes to a PDU containing all the protective devices and then cables feeding the loads from this point are often 50-100m long. Would an SPD inside the PDU or inline on the supply cable still provide protection despite the long cable lengths (the cable lengths from the conductors to the SPD would be short although)?
Many thanks Marcus
Thank you for explaining how ‘shorter is better, I will use this argument with the good lady 👍👍👍
Thanks John, great video as mentioned in previous comments ,I'm trying to get the installation of SPD's correct i have looked at installing the Wylex REC2SPD unit at the origin of supply TN-S and also a type 2 at the consumer unit which is located over 10 mtr away from the switch fuse would this arrangement be suitable? Any advice would be much appreciated 👍
Found this very interesting/helpful.
Im installing Hager SPD in a 3 phase board, from what I understand it needs to be supplied via 32a mcb (3pole). This would be the first configuration you described but from the SPD to the mcb will be a greater distance than 25cm per conductor?
Hello John ,with SPD connected as regs Fig 534.9 or V type . I have read somewhere the supply in and supply out of the SPD have to be run completely apart ? Cannot find any thing about it in the regs.
Love the way JW shuts the regs book when showing the wire length diagram 😂😂😂 Actions say a thousand words 👍
Hi, something confusing me about the max length of wire. I have an ev charger that is fed from a two pole rcbo in an enclosure connected in parallel with the tails. If I fitted an spd in the ev enclosure to protect the charger, is my max wire lenghts between the rcbo and spd within the enclosure, or does it include the length of the tails back to the connector block?
Why does the Wylex unit not require over current protection for the spd ?
I was always a little confused as to what you define as "length" especially of the earthing conductor. On a TT earthing system is it the distance to the earthing rod? That is definitely way over 1 meter. Is it the distance to the PE bar on the DB? But that's where all the earthing lines from the house power outlets meet. So if the SPD, channels the high voltage surge from a possible lightning to the earthing rod THROUGH the PE bar, then all the connected devices will receive it as well (fridges, TVs, washers etc).
Length between the SPD and the main earth terminal of the installation.
That might be the earth bar in a consumer unit or distribution board, or it could be a separate bar/block located somewhere else.
I have 3 phase main head, then isolator, then Ryfield which supply 2 x3phase DB. where should i instal my external enclosure with 3x63A breakers and 3 phase SPD type 1? behind isolator and before Ryfield?
Good video, thanks for sharing....quick question wouldn’t this come under switchgear and assembly and therefore require to be in a metal clad enclosure?
I would say that it's impossible not to class one of these as a "similar switchgear assembly", and therefore yes, 421.1.201 calls for a non-combustible enclosure.
What way do I include an overcurrent protective device in that stand alone wylex example. Are they built in?
Some have a fuse built in, others require a separate MCB. If built in, it's wired as in this video. For the others, L goes to a suitable MCB first, then from the MCB to the surge protection device. N*E are always directly connected. Type and rating of the MCB will be specified by the manufacturer.
Thanks John for the video. I'm fitting a Wylex board with same type of SPD as the isolator you show already fitted in the board. In the installation instructions it shows a connection to PE from the terminal of the top right unit and a separate connection to earth from the top left terminal of the other unit. Do I need to install an earth rod for this or link to the in the board MET? I'm on a PME system. Thanks for your time.
In a consumer unit, it's just a link from the earth bar in the consumer unit to one of the earth terminals on the SPD.
@@jwflame Thanks John
Is that switch next to the SPD an MCB or is it just an isolator? It cant be read with the switch in the off position.
Also... Is there an update to this video? Has this technology improved as yet? Do I still need both Type1 and Type2 SPDs in my home?
Hi John, Excellent video as always. According to the manufacturers instructions for that Wilex Spd, the earth goes in a different place if it is a TT system? It looks like the R/H terminal goes to the MET; whereas, for a TN-s the L/H terminal goes to the MET? No mention of PME! Can you help?
Both E terminals are connected together, it makes no difference which one is used.
The differences for SPDs are between TT and TN systems, some can be used for both, others TN only. If it's suitable for TN-S, it will also be suitable for TN-C-S.
@@jwflame thanks for the help John.
If even short cables have significant inductance where spikes are involved what effect will the circuit breaker protective the SPD have.
Very little, if installed properly the MCB will only add a few centimeters of length to the wiring,. Although MCBs have a magnetic coil inside, for the ratings typically used with SPDs it's only a few turns of very thick wire.
Can you explain how the surge protection device actually works and what it actually does in depth please
Hi John - very interesting video - thanks for posting. I just have one question. If the inductance of the short lengths of wire to the SPD can create such a significant voltage drop as to reduce the effectiveness of the SPD, why is it that theinductance of the umpteen metres of cable in the installation don't reduce the incoming voltage spike to a trivial level without the need for an SPD? I live in the countryside and my property is fed by overhead lines and as far as I know I have never had anything damaged by voltage spikes in the last 35 years.
The volt drop due to inductance occurs when the SPD is conducting, the current through the SPD and the connecting wires is very high.
With no SPD, the voltage will be high but the current low, so any volt drop will be insignificant, with most of the voltage across devices within the installation which will cause damage.
Mr Ward, how would you install this SPD Isolator in a domestic situation without pulling the Main Cut-out Fuse in order to replace the existing Isolator? It would be silly to install it after the isolator (giving you two isolators) and indeed there wouldn't be any room in the meter cupboard! Thanks.
That Wylex item is designed to replace any existing isolator.
Alternatively the SPD could be installed in the consumer unit.
@@jwflame Wow! Thank you for replying :-) I have been intently watching a lot of your videos as someone whom I trust... If I were to split the tails after the isolator (in "Henley Blocks") to feed two consumer units, would this be sufficient to cover both CUs or would you recommend installing one in each CU? Thanks.
Would these minimize the effect of certain heavy loads causing lights to dim when they kick on and activate in-rush current? For example, when a large air conditioner kicks on, the lights will dim for a moment because of the huge momentary draw (surge). Do these SPDs minimize this sort of internal switching impact (smooth out the fluctuations) or do they only apply when there are huge fluctuations from the outside ?
No, these only work for overvoltages. They won't do anything for voltage sag/dip.
However they do reduce the overvoltage spikes created when heavy loads are switched off.
@@jwflame thanks for the clarification
@@jwflame are there any products available that would address voltage sag/dip caused by internal switching events? I’ve heard of things like “voltage conditioners” and “voltage stabilizers” not sure if that’s what they do.
Do you use an spd per circuit? Or just one on the complete house breaker box supply lines?
One for the whole house for normal sized houses.
Large buildings will require more than one.
Hey John,what will happen if I interchange phase and neutral connection?And should I do it or not
Did you find out, because I have a similar need to interchange one phase and neutral in a 4 pole SPD?
what should be the earth resistance ? in case of surge the electricity will flow towards earthground. what should be its value. does SPD require separate ground?
Doesn't matter what the earth resistance is for the SPD.
The SPD connects to the existing circuit, not to a separate ground.
@@jwflame If an equipment is grounded and someone touches will be get electrocated?
2.why we do system grounding ?
3.the earth is not a perfect conductor does current return back to it's source?
Hi John,
I have bought same as yours Wylex SPD but mine has only one earth terminal instead of two. Yours have two earth terminals.
What should I do or how Will connect mine please.
Many thanks and best wishes,
Ahmed
Leicester ENGLAND
Both earth terminals are connected together in the device, it doesn't matter if there is one or two, only that earth is connected to it.
What is a decent external surge protected, at a reasonable price, also while you at it rcbo, which let's face it is pricey, but, I need to sell em to the customers, which price is a factor,
I don't understand why only the lengths of wires to nearest connection affect the inductance, the surge may have traveled a mile down the grid but an extra few cm's in the db is critical? Dosn't make sense. Thinking about it, in electronics when current is switched off to an inductor the magnetic field collapsing causes a voltage spike, but I still can't see how the wiring to the spd makes enough of a difference to write a reg about it.
This has been bothering me as well. The HF transient does not originate 50 cm away from the SPD.
When the SPD operates, current will flow from the source of the transient to the MOV. This could be a lightning strike 500 m away.
Could it be inductance and capacitance in the long cables causing resonance to occur?
Have you come across an explanation yet?
I'm curious, why are plastic enclosures allowed for items like this when we have to have metal C U's, surely they can catch fire too ⁉️☘️
That's what I was thinking too.
exactly. The metal consumer unit thing is just rubbish
Because when everyone has largely got metal they can change their minds again and have some fire retardant plastic with glass fibre reinforcement as a rule - just because.
Best me to it! One rule and logic for one then the opposite for another.
Because it doesn't have any load in it during normal operation. It's a voltage driven device installed in parallel. It fails to open circuit and will quench any transient in nano-seconds so no time for any thermal rise. The correct SPD installed in the right place in the right way poses no fire risk. That's why they can be in plastic enclosures.
Which book you are using in this video?
BS7671, list of suppliers here: electrical.theiet.org/bs-7671/fake-awareness/
Hello john...thank you for such an informative video. I have one questions if you might want to answer.
In BS 7671 fig 534.8 - Connection of SPD, why OCPD is shown connected to SPD? What is the function of OCPD there? As per my understanding that will defeat the whole purpose of SPD. Please explain.
It very much depends on the SPD manufacturer and the size of your incoming supply, in almost all domestic applications you do not need any OCPD for an SPD, in larger industrial /commercial sites you probably will need OCPD. It's worth remembering that SPD's are designed to deal with transients, very high frequency short events so the reason for the OCPD is to protect the SPD from potential long term over voltage or high current events.
⚠️ no twisting
Considering resistance depends on not only length but also thickness of the wires why don’t the regulation mention about the thickness of the wire connected between the supply and the SPD
The main factor when the SPD deals with a surge (transient) is the inductance of the wires. Length of those wires will change the inductance significantly, wire size has a very small effect.
Thanks. Never thought inductance was such a key player.
Are these cheap devices allowed in the country. Is there not approval required for safety. Just wondering. I have no idea
Brilliant as always John. Someone should explain inductance to BG, since the SPD-PE link on their "18th-edition" CUs with SPD must easily be 50 cm on its own. see: cdn.aws.toolstation.com/images/141020-UK/800/87798-3.jpg
Actually, I've just realised that the N-E combined wiring length for the SPD on these split-load boards must be the best part of 1 metre (assuming the 16 mm² main PE coming in to the CU is connected to the main earthing bar at the closest position to PE supplied for the SPD). See 1drv.ms/u/s!AqBvF7glEgubgshh8kcqCXblGSINYg where I've tried to scale the image to the dimensions of the CU and then measured some lines.
But it's plastic enclosure
I wonder if this stuff is being pushed by the authorities to harden UK electricy networks against new EM pulse weapon technology.
No. It's being pushed by manufacturers to sell more over-priced widgets.
Tim Boler It’s being made explicitly allowed because everything now has electronics in.
We used to have incandescent bulbs for lighting, AC synchronous motors running clockwork in our appliances (oven clock, central heating timer, etc), and bimetallic strips regulating temperature (thermostats in your heating, oven, fridge, freezer), etc; none of which were that bothered by a momentary power surges.
Now we have LED lights with electronic drivers, and electronic powers supplies and controls in our appliances.
Electronics don’t like these kinds of voltages, the insulator layers within an integrated circuit are very thin (more than thick enough for the normal conditions), a component might not totally fail the first time it is hit by a surge, but it creates a weak spot, where subsequent surges will cause further damage. It’s usually an accumulation which causes the final failure, not an obvious event like a near by lightening strike.
SPDs are designed to reduce those surges to a level where the electronics can tolerate the remaining energy without being damaged.
I'd bet more on insurance companies etc. wanting more protection for sensitive electronics. Always follow the money.
@@Bin216 Maybe a problem if you live in a rural area where the incoming supply is fed via an overhead line susceptible to lightning strikes, but for most houses fed by underground cable, I'm not sure.
@@benbaselet2026 My line is IT, especially data centre management. We put significant amounts of time, effort and money into securing our power supplies because a single incident could potentially cost many millions.
However this is just guarding against an expensive but very remote possibility. Most European data centres are on urban (so usually underground) and notably stable supplies. In 25 years I've not seen such an incident, not even one caught on monitoring systems that did not reach critical equipment.
So I would be genuinely very surprised if this figured very high in insurance companies' calculations.
For the moment I remain sceptical - even cynical - about the merits of domestic surge protection. They seem to be even less value than the arc fault protection devices that are also being heavily promoted by the manufacturers. If you're following the money I'd say it's there that the trail leads.
Do you own a cat? My hand looks like that sometimes 11:35 :)
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