Domestic SPD's help please

[LWB Electrical]

Hi,

Apologies if this has been posted before which I expect it has but did a search and couldn't find it. Wabt a bit of information on SPD's in domestic premises when carrying out a consumer unit change. Do we have to recommend they are installed now and if not carry out a risk assessment or are we ok not to carry out a risk assessment as its a single dwelling? Also am I right in thinking its a type. 1 that mounts in a din rail enclosure and if so does anyone have a decent wiring diagram. Did a bit of research but still unclear.

Many thanks

 

[Pete999]

Hi,

Apologies if this has been posted before which I expect it has but did a search and couldn't find it. Wabt a bit of information on SPD's in domestic premises when carrying out a consumer unit change. Do we have to recommend they are installed now and if not carry out a risk assessment or are we ok not to carry out a risk assessment as its a single dwelling? Also am I right in thinking its a type. 1 that mounts in a din rail enclosure and if so does anyone have a decent wiring diagram. Did a bit of research but still unclear.

Many thanks

What was the results of your research? Regulation 534.1 Appendix 16 table 534.4.10 and table OSG 3.7.3 refers.

 

[LWB Electrical]

That I believe its type 1 that is used and that single dwelling didn't require it but was all a bite unclear

 

[Ian1981]

It would be a type 2 SPD.
Type 1 SPD’s are used in installations with lightning protection.
It’s a conversation to be had with your customer as they are not mandatory for domestic single dwellings where the losses of equipment are tolerable Where SPD’s are not installed.
Offer it to your customer and if they decline then so be it.
Note it on the EIC

 

[LWB Electrical]

But does it require a risk assessment if not and does anyone have a wiring diagram?

 

[Ian1981]

No risk assessment for domestic, you fit one or you do not ,based on the equipment it protects.
Wiring diagrams are given in appendix 16 of bs7671 and you can get manufacturers instructions/ diagrams

 

[LWB Electrical]

Thanks. Am I right in thinking you feed it from a breaker or do you input it before main switch?

 

[telectrix]

Thanks. Am I right in thinking you feed it from a breaker or do you input it before main switch?

it must go after the main switch.

 

[LWB Electrical]

So fed from a breaker then from within the consumer unit. What size breaker? Sorry its just easier to ask on here and get direct responses, appreciate the advice from you all

 

[Ian1981]

So fed from a breaker then from within the consumer unit. What size breaker? Sorry its just easier to ask on here and get direct responses, appreciate the advice from you all

A type 2 cpc connection must be 6mm2 minimum.
Connections should ideally not exceed 0.5m but must not exceed 1 meter in length ie the live and cpc conductors in total combined.
The ocpd need only provide fault protection.
If on the load side of an rcd the rcd should be an S type with an immunity to surges of 3ka

 

[Ian1981]

Check out BEMAS guide to SPD’s

 

[J.C.E]

main switch >> 32a MCB
6mm out the load of the 32a MCB and a 6mm out the N bus bar

domestic will be a type 2 SPD at the DB

my interpretations is becuase the total value of the installation will in most if not all cases exceed the cost of what it would cost to install a SPD (an additional £60+ odd quid in materials when installing a new DB)

therfore 443.4 is not a get out of free card in my eyes

i see it the only way to get out of not installing a SPD when installing a new DB is doing the risk assessment- but good luck doing that accurately and with confidence

 

[Ian1981]

main switch >> 32a MCB (need a high integrity board if it dual rcd)
6mm out the load of the 32a MCB and a 6mm out the N bus bar

domestic will be a type 2 SPD at the DB

my interpretations is becuase the total value of the installation will in most if not all cases exceed the cost of what it would cost to install a SPD (an additional £60+ odd quid in materials when installing a new DB)

therfore 443.4 is not a get out of free card in my eyes

i see it the only way to get out of not installing a SPD when installing a new DB is doing the risk assessment- but good luck doing that accurately and with confidence

The CRL risk assessment is not applicable to domestic single dwelling units
Fitting one is as you say , is based on an assessment of what it’s protecting and cost.

 

[Ian1981]

 

[LWB Electrical]

Many thanks. To me id interpret that as no risk assessment needed. Guess it's only a matter of time till an amendment makes them compulsory everywhere and all boards have in built ones

 

[Ian1981]

Many thanks. To me id interpret that as no risk assessment needed. Guess it's only a matter of time till an amendment makes them compulsory everywhere and all boards have in built ones

Well we work for some of the known house builders and with new sites tenderd to the 18th edition we are to fit Hager dual rcd boards with 2x 100amp 30mA rccb’s type A.
Also 2 x high integrity ways for SPD’s and electrical vehicle charging points as in a recent tech talk I was informed that the government, when they are finished with brexit are implementing a scheme that all new builds to have a provision provided for electric vehicle charging, so a circuit from the DB left unterminated to an outside enclosure for future proofing.

 

[Ian1981]

Duplicate post

 

[Nebu1a]

OSG 3.7.2 Implies SPD protection is not required for domestic single dwelling units but the impulse withstand voltage must meet Table 443.2.
Is this printed on the appliance or must we dig out the instructions to every appliance in the property?

Beama guide suggests a written assessment of the value of the installation. If this value is 5 times greater than the cost of fitting an SPD then an SPD should be fitted. (pg 63 beama guide)

I guess it depends on the size of the job. For a couple of extra sockets can I justify it to the client then probably not. Id give them the option though.
For a rewire then yes.