Surge protection devices

[Roberts7286]

Hi Guys

Hoping for a straight forward answer. Please can someone tell me if SPD's are mandatory in domestic dwellings at the moment (Amd1) and are they going to be mandatory with AMD2.

Thanks

 

[pc1966]

The answers are (1) mostly and (2) almost always.

Currently (AM1) you have 4 cases where it is mandatory (risk to life, culture/public services, business activity, many folks impacted) and for other also required unless you perform the impractical risk assessment that says otherwise. Which is likely to say needed for most places outside of city with very limited cable exposure and low lightning incidence! There is a case for "single dwelling units" where the value of electronics does not justify the cost of the SPD, but really that is very unlikely (e.g. cost of LED lights alone, add in always-on fridge, cooker, etc, with electronic controls).

Under AM2 the risk-assessment has been dropped, and so it is more or less mandatory, but there is a get-out if the owner is willing to sign off on the risk having understood it...BUT...if any safety systems are involved they must be fitted. So even if owner not interested, if they have hard-wired smoke alarms, emergency lighting, or any medical/disability support it is back to mandatory.

TL;DR - just fit them (also really should be Type 1 if rural overhead lines, or if lightning protection system involved)

 

[Roberts7286]

The answers are (1) mostly and (2) almost always.

Currently (AM1) you have 4 cases where it is mandatory (risk to life, culture/public services, business activity, many folks impacted) and for other also required unless you perform the impractical risk assessment that says otherwise. Which is likely to say needed for most places outside of city with very limited cable exposure and low lightning incidence! There is a case for "single dwelling units" where the value of electronics does not justify the cost of the SPD, but really that is very unlikely (e.g. cost of LED lights alone, add in always-on fridge, cooker, etc, with electronic controls).

Under AM2 the risk-assessment has been dropped, and so it is more or less mandatory, but there is a get-out if the owner is willing to sign off on the risk having understood it...BUT...if any safety systems are involved they must be fitted. So even if owner not interested, if they have hard-wired smoke alarms, emergency lighting, or any medical/disability support it is back to mandatory.

TL;DR - just fit them (also really should be Type 1 if rural overhead lines, or if lightning protection system involved)

Thank you. In a nutshell just fit them

 

[Pretty Mouth]

if any safety systems are involved they must be fitted. So even if owner not interested, if they have hard-wired smoke alarms, emergency lighting, or any medical/disability support it is back to mandatory.

I had been wondering about whether smokes etc meant SPDs were mandatory, so I emailed AICO who replied that their alarms have surge protection built in. Apparently the standard that they are built to calls for it:

Good morning Pretty Mouth,

Yes our alarms do have surge protection in accordance to relevant manufacturing standards.

Our alarms are tested to the smoke alarm standard EN14604, which in turn specifies EN50130-4:1995 for EMC performance. This standard specifies units are to be tested with fast transient bursts of +/-2kV, and slow high energy surges of +/-0.5kV and 1kV.

Many Thanks,
AICO

I'm not an expert on surge protection, but perhaps smokes don't automatically mean that SPDs must be fitted?

 

[pc1966]

Our alarms are tested to the smoke alarm standard EN14604, which in turn specifies EN50130-4:1995 for EMC performance. This standard specifies units are to be tested with fast transient bursts of +/-2kV, and slow high energy surges of +/-0.5kV and 1kV.

All mains-powered devices have EMC requirements, including lightning and fast-transients. But it is not as much as you can see on the supply. For example, CAT-II which is test equipment for final circuits:

Measurement category - Wikipedia

en.wikipedia.org

Has 2.5kV impulse rating, and closer to the DB (CAT-III) it is 4kV and 2 ohms (i.e. 2kA as well).

Now that should be rare, and many home have gone for years without needing SPD, but probably we have all seen odd failures correlated to lightning and/or industrial situations with big motors.

I'm not an expert on surge protection, but perhaps smokes don't automatically mean that SPDs must be fitted?

I don't have a copy of AM2 yet, but the extract I have seen has SPD required if the consequences "Result in failure of a safety service, as defined in part 2" with a safety service defined as "An electrical system for electrical equipment provided to protect or warn persons in the event of a hazard, or essential to their evacuation from a location". So even if smoke alarms have some built-in protection, the AM2 regulations are saying you ought to fit protection at an installation level anyway.

 

[Pretty Mouth]

All mains-powered devices have EMC requirements, including lightning and fast-transients. But it is not as much as you can see on the supply. For example, CAT-II which is test equipment for final circuits:

Measurement category - Wikipedia

en.wikipedia.org

Has 2.5kV impulse rating, and closer to the DB (CAT-III) it is 4kV and 2 ohms (i.e. 2kA as well).

Now that should be rare, and many home have gone for years without needing SPD, but probably we have all seen odd failures correlated to lightning and/or industrial situations with big motors.



I don't have a copy of AM2 yet, but the extract I have seen has SPD required if the consequences "Result in failure of a safety service, as defined in part 2" with a safety service defined as "An electrical system for electrical equipment provided to protect or warn persons in the event of a hazard, or essential to their evacuation from a location". So even if smoke alarms have some built-in protection, the AM2 regulations are saying you ought to fit protection at an installation level anyway.

How does the protection quoted by AICO compare to that of a board mounted SPD? I tried to compare it to a couple of different manufacturer's offerings, but couldn't really understand the data.

 

[pc1966]

How does the protection quoted by AICO compare to that of a board mounted SPD? I tried to compare it to a couple of different manufacturer's offerings, but couldn't really understand the data.

It varies a bit, but looking at this example data sheet:

https://www.surgedevices.co.uk/wp-content/uploads/2020/06/SY1C40X-1.pdf

It limits the voltage to 1kV for 5kA surges, and 1.25kV for the maximum nominal rated 20kA (for induced 8/20us waveform, Type 1 has similar currents but much more energy due to the longer 10/350us waveform). So they are less typically than the AICO limit for practically any survivable surge.

 

[Pretty Mouth]

It varies a bit, but looking at this example data sheet:

https://www.surgedevices.co.uk/wp-content/uploads/2020/06/SY1C40X-1.pdf

It limits the voltage to 1kV for 5kA surges, and 1.25kV for the maximum nominal rated 20kA (for induced 8/20us waveform, Type 1 has similar currents but much more energy due to the longer 10/350us waveform). So they are less typically than the AICO limit for practically any survivable surge.

So, does this mean the inbuilt surge protection of the alarms is actually better than that offered by SPDs? (sorry if this seems a stupid question, when I said I'm no expert, I actually meant I know squat).

 

[pc1966]

So, does this mean the inbuilt surge protection of the alarms is actually better than that offered by SPDs? (sorry if this seems a stupid question, when I said I'm no expert, I actually meant I know squat).

No, it means the alarm is protected to 1-2kV depending on the waveform, so if the supply is kept below that it should survive.

The SPD specification says it will keep the supply voltage during a surge below 1kV for surges to 5kA current. That sort of peak current could well be associated with a surge that is 8kV or more open circuit voltage, though typically you will never see more than that sort of voltage on a LV system as accessories, terminals, etc, are likely to flash over above that.

So basically the SPD will, for all but a direct hit on the building or its supply cables, keep the peak voltage low enough that correctly designed mains products will survive.

The main difference between the alarm built-in protection and the CU SPD is really about energy handling. The small MOV seen built in to good quality consumer electronics typically can absorb a couple of Joules, maybe peak currents of 250A or so for the small surface mount types, up to maybe 10J / 500A for the larger through-hole leaded sort. Whereas the sort used in SPD products typically can absorb something like 500J and up to 40kA absolute max as well as having thermal protection in case of sustained over current (e.g. open PEN worst case, etc)

 

[Pretty Mouth]

No, it means the alarm is protected to 1-2kV depending on the waveform, so if the supply is kept below that it should survive.

The SPD specification says it will keep the supply voltage during a surge below 1kV for surges to 5kA current. That sort of peak current could well be associated with a surge that is 8kV or more open circuit voltage, though typically you will never see more than that sort of voltage on a LV system as accessories, terminals, etc, are likely to flash over above that.

So basically the SPD will, for all but a direct hit on the building or its supply cables, keep the peak voltage low enough that correctly designed mains products will survive.

The main difference between the alarm built-in protection and the CU SPD is really about energy handling. The small MOV seen built in to good quality consumer electronics typically can absorb a couple of Joules, maybe peak currents of 250A or so for the small surface mount types, up to maybe 10J / 500A for the larger through-hole leaded sort. Whereas the sort used in SPD products typically can absorb something like 500J and up to 40kA absolute max as well as having thermal protection in case of sustained over current (e.g. open PEN worst case, etc)

Thanks for the explanation @pc1966