What's inside an SPD?

[aptsys]

Not much at all. Came across this video - I would imagine there's scope for a fairly rapid decline in cost once they become more commonplace given the minimal number of parts inside.

 

[JohnW2]

Not much at all. Came across this video - I would imagine there's scope for a fairly rapid decline in cost once they become more commonplace given the minimal number of parts inside.

Thanks. I haven't really done much looking uinto this yet, but do these devices actually address a problem that needs to be addressed?

Kind Regards, John

 

[aptsys]

Not really. Almost every electronic device that would be sensitive to transients would normally have suppression built in.

 

[JohnW2]

Not really. Almost every electronic device that would be sensitive to transients would normally have suppression built in.

Thanks. That's what I suspected.

Kind Regards, John

 

[FrodoOne]

If you in the UK have electricity supplied by underground cables you may not have a need for "Over Voltage" protection.
However, if the supply is via aerial wires and there is a possibility of lightning strikes affecting the supply, "Over Voltage Arrestors" (such as Hager SPN 040D and SPN 208S) may be a good investment.

 

[JohnW2]

If you in the UK have electricity supplied by underground cables you may not have a need for "Over Voltage" protection. However, if the supply is via aerial wires and there is a possibility of lightning strikes affecting the supply, "Over Voltage Arrestors" (such as Hager SPN 040D and SPN 208S) may be a good investment.

My UK supply (and the supplies of many like me) is 'overhead' (for many miles) - and, of course, the highest voltage distribution (I would think in most/all countries) is all 'overhead'.

Lighting certainly does 'affect my supply', in that lighting anywhere within miles of me will often result in one of the distributor's devices tripping, resulting in loss of power for 5-30 seconds until the device resets. However, I have never personally experienced anything electronic failing due to transients/'surges' at the time of nearby lightning - and, of course, no local devices would appreciably protect my installation from the results of a direct strike on one of my supply cables.

Some manufacturers have made a fortune out of selling 'surge suppressing' extension leads and adaptors etc., and I'm not convinced that anyone/anything other than the bank balances of the manufacturers has benefited from use of such things.

Kind Regards, John

 

[dannyboi2003]

I've got some snake oil if anyone's interested?

 

[JohnW2]

I've got some snake oil if anyone's interested?

Many of us have! However, we're talking here about a type of snake oil which regulations might well one day 'require' us all to have!

Kind Regards, John

 

[dannyboi2003]

@JohnW2 Indeed we probably will have to fit them eventually, my personal opinion is they are a waste of money but i will indeed comply when the time comes.

 

[flameport]

but i will indeed comply when the time comes.

That time has already arrived - BS7671 18th edition has Chapter 44 and Annex A443 which cover about 20 pages, and a further 10 pages in Section 534.

 

[JohnW2]

That time has already arrived - BS7671 18th edition has Chapter 44 and Annex A443 which cover about 20 pages, and a further 10 pages in Section 534.

Indeed - and, quite frankly, I haven't yet bothered to pay it much attention. However, am I right in saying that such devices are not yet routinely 'required', at least in normal domestic circumstances?

Kind Regards, John

 

[aptsys]

There are criteria for when such a device is required however as with everything in the regs, many don't understand the nuances, therefore they're likely to get fitted to every board.

 

[FrodoOne]

My UK supply (and the supplies of many like me) is 'overhead' (for many miles) - and, of course, the highest voltage distribution (I would think in most/all countries) is all 'overhead'.

Lighting certainly does 'affect my supply', in that lighting anywhere within miles of me will often result in one of the distributor's devices tripping, resulting in loss of power for 5-30 seconds until the device resets. However, I have never personally experienced anything electronic failing due to transients/'surges' at the time of nearby lightning - and, of course, no local devices would appreciably protect my installation from the results of a direct strike on one of my supply cables.

Some manufacturers have made a fortune out of selling 'surge suppressing' extension leads and adaptors etc., and I'm not convinced that anyone/anything other than the bank balances of the manufacturers has benefited from use of such things.

Kind Regards, John

Thank you for your considered response.

I agree with you concerning the matter of "'surge suppressing' extension leads and adaptors etc.", which is why I do consider the "Whole House" protection afforded by the items such as those which I mentioned to be a better option, although the devices which I mentioned are not cheap.

Those "Over Voltage Arrestors" were fitted to that CU after the following "event" :-
12 V "LED Garden Lights" powered via an iron core transformer were installed at the house concerned.
These were activated by a commercially designed control device, which turned ON when light levels were low (at dusk) but stayed on for only a chosen number of hours - so that the Garden Lights would turn OFF at around midnight.
One evening after the lights had turned on, I happened to be walking through the garden to my car parked in the driveway as a storm was approaching.
While doing so, there was a brilliant flash of lightning, followed almost immediately by the clap of thunder (within one second) and, at the same instant, the Garden Lights went out.
When checked the next day, the control device mentioned above was found to be "non operative", although the transformer could still power the lights directly.

Fortunately, no other equipment (Radio,TV etc.) within the house was affected - and the computer, although connected to the socket outlet, was not turned ON by the switch on that outlet at that time.

Following this "event", these devices were fitted by my son, who is a licenced electrical contractor. He does recommend these to his customers, if asked, and they were earlier fitted at my house also.

You should note that (unlike those in the initial post) these devices each include an "indicator", which shows that they have not been stressed beyond their limits and are still able to absorb an over voltage "spike", up to their design limits.

Of course, you are quite correct when you wrote "no local devices would appreciably protect my installation from the results of a direct strike on one of my supply cables."

 

[LearningSpark]

Indeed - and, quite frankly, I haven't yet bothered to pay it much attention. However, am I right in saying that such devices are not yet routinely 'required', at least in normal domestic circumstances?

Kind Regards, John

As far as I understand the 18th edition unless you can provide a risk assessment which says the value of goods within the property likely to be damaged by an over voltage is less than the cost of an SPD then one must be fitted in domestic.

 

[bernardgreen]

When checked the next day, the control device mentioned above was found to be "non operative", although the transformer could still power the lights directly.

The damage would ( almost certainly ) have been caused by a "surge" from the cables to the lamps with the energy of that surge going back into the controller. If the lightning was a ground strike then the voltage gradient through the ground can be several hundred volts per metre fo a few milliseconds. Any buried cables in the area will have large potentials induced onto them.