Amd2 SPD on smoke alarms

[Pretty Mouth]

Its getting crazy, as now all rentals need smoke detectors and to fit the new detectors (New circuit or alteration of lighting circuit) we need to install SPD, that's going to add £100 + to the job just on materials. the clients/landlord are going to think we are taking the ----. as we know most landlords are tighter than a ducks .......,

Crazy indeed, but AFAIK landlords can still install battery alarms, which is what they'll do if it's the cheaper option by a long way:

Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022: guidance for landlords and tenants

www.gov.uk

I feel this regulation needs rethinking, as it seems to be counter productive.

 

[bro8284]

Crazy indeed, but AFAIK landlords can still install battery alarms, which is what they'll do if it's the cheaper option by a long way:

Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022: guidance for landlords and tenants

www.gov.uk

I feel this regulation needs rethinking, as it seems to be counter productive.

That's good to know, but In Wales they got to be mains powered and interlinked.

 

[pc1966]

EDIT Mind you at £122 + vat that's 2/3 of the cost of changing the board to a Fusebox SPD board with RCBO's anyway.

Probably a lot less work to fit the switch/SPD though than changing 5-10 circuits to get more board space (if no other pressing reason to change).

 

[sparky1000]

Interesting - was he saying that there were no circumstances in which their products could be used then, since they didn't until very recently make their own enclosures/MCBs?

Might be worth contacting Kirsty, their technical person, who is the one who told me that at an Elex a few years back. She is on some of the Regs committees I think, and might be able to provide something in writing to wave at any assessor in future....

I believe she was the one who always took the view that the main fuse was not an acceptable overcurrent protection and may have been partly responsible for companies like Hager changing their boards to include an MCB for SPD protection.

Although interestingly, in their guide they state that smoke alarms in a domestic property must be SPD protected, so I'd take that as fairly clear guidance from an industry source.

With this being said about an spd must be fitted, after reading more and more into the set up and location of spds, an spd should be located less than 10meters from what ever it is protecting, with a type 2 spd located in a board and with a stand alone smoke alarm circuit leaving the DB the cable run is exceeding 10meters to multiple smoke alarms, does this mean type 3 spds will need to be installed at each smoke alarm to comply? Vert curious about this no more than 10meters rule as most electronic equipment will always be further than 10meters via a conductor from the fuseboard? Thoughts please

 

[littlespark]

What is this 10m rule?

As you say, whatever device the SPD is protecting is surely more than 10m away.

Does it actually mean that, if fitting an SPD, it must be as close as possible to the circuit source OCPD? So inside the same CU, or in another enclosure very close to it.


I’m just wondering when the Scottish govt will come up with “ oh… you know all those smoke detectors we made you fit last year? We should have said, they need an SPD now. You’ll have to go back.”


At least they let us use the 10yr battery ones

 

[sparky1000]

What is this 10m rule?

As you say, whatever device the SPD is protecting is surely more than 10m away.

Does it actually mean that, if fitting an SPD, it must be as close as possible to the circuit source OCPD? So inside the same CU, or in another enclosure very close to it.


I’m just wondering when the Scottish govt will come up with “ oh… you know all those smoke detectors we made you fit last year? We should have said, they need an SPD now. You’ll have to go back.”


At least they let us use the 10yr battery ones

see picture I have attached, its abit unclear to me, when it says 10meteres from the electronic equipment I can only assume it is via actual cable length as this would be the path of the over voltage would take, like you say it would be garunteed all smoke alarm devices would exceed 10meters so this would warrant a type 3 spd to fitted at each smoke alarm device, this Is how I am interpreting this, some one correct me if I am wrong please

 

[littlespark]

This is from an SPD manufacturer... not straight out of BS7671

They might have their own interpretation of how many are required for any given scenario.

 

[sparky1000]

This is from an SPD manufacturer... not straight out of BS7671

They might have their own interpretation of how many are required for any given scenario.

Agreed but I believe this will be the way the regulations will go, time will tell, but either way its only going to get more expensive for customers and more overkill, will be the same with afdds they will be required for every circuit in the future.

 

[UNG]

This is from an SPD manufacturer... not straight out of BS7671

They might have their own interpretation of how many are required for any given scenario.

But how effective is an SPD under all potential surge conditions and does a circuit need to be designed to mitigate the effects of any surge

It is all very well mandating their use but IMO there needs to be more information put out regarding their use just because the regs say we must install them do we just go with what the manufacturer fits into it's CU's as the default device needed on a one type / size fits all or should we be giving more consideration to what devices we are fitting

 

[Electro-tech]

BEAMA Guide to Surge Protection Devices (SPDs) – Selection, Application and Theory - https://www.beama.org.uk/resourceLibrary/beama-surge-protection-guide-.html for download.
Although not out of BS7671 we still need to install it according to the manufacturer's specifications.
I think we should be looking more into what devices we need to fit, as UNG has suggested.

Schneider reference:-
SPD Type - used to describe the intended application location of the SPD, either upstream or downstream of the main overcurrent protective device of the facility. SPD Types include:

• Type 1- A permanently connected SPD intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and Molded Case SPDs intended to be installed without an external overcurrent protective device.
• Type 2- A permanently connected SPD intended for installation on the load side of the service equipment overcurrent device, including SPDs located at the branch panel and Molded Case SPDs.
• Type 3- Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example, cord connected, direct plug-in, receptacle type SPDs installed at the utilization equipment being protected. The distance (10 meters) is exclusive of the conductors provided with or used to attach SPDs.
• Type 4- Component Assemblies -, a Component assembly consisting of one or more Type 5 components together with a disconnect (internal or external) or a means of complying with the limited current tests.
• Type 1, 2, 3 Component Assemblies - Consists of a Type 4 component assembly with internal or external short circuit protection.
• Type 5 - Discrete component surge suppressors, such as MOVs that may be mounted on a PWB, connected by its leads or provided within an enclosure with mounting means and wiring terminations.

 

[Electro-tech]

I think it was mentioned somewhere on another thread that Aico alarms have surge protection built in.

 

[pc1966]

I think it was mentioned somewhere on another thread that Aico alarms have surge protection built in.

All competent mains powered electronics has some degree of surge protection simply to meet the minimum EMC regulations for immunity. However, it is usually only for small surges (typically 1.5kV is specified) and from not-very-low impedance sources (ie. the CAT-III sort of location at end of final circuit).

Having a SPD at the DB should keep any surges down-stream to under that sort of value, and so they can then deal with the short over-voltage OK.

As for the "10m distance" aspect it is more complicated. If you are trying to coordinate SPD (say Type 1 at input, Type 2 and DB further away) then you want the first SPD (high power, higher flash-over voltage) to conduct first, and only what gets past is then clamped by the second lower-power / lower-voltage SPD. To achieve that selectivity you need some impedance, and for that read inductance, so usually a minimum of 10m of cable, or a dedicated air-cored coil (rare). Inductors often have ferrite or iron cores to increase inductance for a given size, but under big surge conditions those cores saturate and the inductance plunges to the air-cored equivalent, so you might as well go for air-cored to begin with!

It is also highly dependent on what you are trying to protect, and where the lighting might hit. In most cases it is a far away strike coming in via power cables and the first SPD it finds does the job. If very near than all sorts of cables within the installation and/or to extraneous parts can pick up the induced current and cause grief. Usually I would only see the point in a SPD at a sub-board if very far away or other reasons to expect high local current (LPS present, big motors likely to dump switch off spikes, etc, etc).

 

[pc1966]

Just to say I have used the Kingsmill stuff and they are good, if not cheap. But you also have to balance the realistic needs for protection in a given type of installation against what they are trying to sell!

 

[Lister1987]

Just to say I have used the Kingsmill stuff and they are good, if not cheap.

Surely they're (bread) crumby?