Street CCTV

[BQW]

Fitted some Street CCTV Cameras with plastic cases, on coulomb's, they are powered from a 24 volt Power supply which is is double insulated class 2. the out put feed from this is then taken to the Camera in shoot gun cable with the video.
Customer claims Highway Street Furniture ECS regulations (never herd of it ) requires even 24volt SELV equipment to be earthed. Cant find any ref to ECS. Any help appreciated

 

[OwainDIYer]

ECS is the electrotechnical equivalent of CSCS safety assessment
https://www.ecscard.org.uk/ECS-Health-and-Safety-Assessment

Street furniture is in the Wiring Regulations, as are the requirements for FELV and SELV supplies.

 

[BQW]

Therefore as its is 24v SELV, my interpretation of the Wiring Regs is, no earth connection is required. In any case there is no facility for a earth connection, the 24v is connected via a small jack plug.

 

[bernardgreen]

Provided the double insulation of the 24 volt SELV supply is ensured not to fail under under circumstances then SELV is likely to be safe without an earth.

BUT there are circumstances where the double insulation can fail and the 24 volt supply can become connected to conductors that are at mains voltages.

A risk assesment is needed as to whether the SELV power unit can withstand all situations that might affect / degrade it's double insulation.

 

[JohnW2]

Provided the double insulation of the 24 volt SELV supply is ensured not to fail under under circumstances then SELV is likely to be safe without an earth.

Indeed. In fact, as I understand the definitions, it is actually impossible to have SELV which does have an earth - since, if it has an earth, it becomes PELV. Is that not the case?

Kind Regards, John

 

[bernardgreen]

This is a matter than really bugs me. Unless the SELV supply unit is from batteries or other ELV source there is always a risk that the SELV will drift or be pulled up to a voltage that is no longer safe. Still 24 volt between the Pos and Neg therefore what ever equipment it is supplying operates apparently without problems but either the Pos or the Neg is at a dangerous high potential above ground.

If the SELV supply unit is not in clear view and any damage or adverse environmental condition affecting the SELV supply cannot be seen then I personally would be extremely wary when dealing with equipment supplied by that SELV.

A door bell transformer affected by damp in a cellar led to the door bell push giving severe finger jarring shocks to callers. When one side of it was earthed the RCD for the mains tripped. With the dubious quality of some double insulated SELV supplies ( such as phone chargers ) then SELV supplies may not be as safe as one thinks they are.

 

[OwainDIYer]

With the dubious quality of some double insulated SELV supplies ( such as phone chargers ) then SELV supplies may not be as safe as one thinks they are.

I doubt any phone chargers are designed or sold as safety extra-low-voltage. Very few extra-low-voltage supplies are actually SELV

 

[JohnW2]

This is a matter than really bugs me. Unless the SELV supply unit is from batteries or other ELV source there is always a risk that the SELV will drift or be pulled up to a voltage that is no longer safe. Still 24 volt between the Pos and Neg therefore what ever equipment it is supplying operates apparently without problems but either the Pos or the Neg is at a dangerous high potential above ground.

A genuine concern, but I'm not sure necessarily satisfactorily addressed by changing from SELV to PELV, per se. I suspect that you are suggesting that one goes one stage further than that, and actually connects one side of the output to earth, but that could raise other issues.

Kind Regards, John

 

[JohnW2]

I doubt any phone chargers are designed or sold as safety extra-low-voltage. Very few extra-low-voltage supplies are actually SELV

I'm not sure I understand your point. The 'S' of 'SELV' stands for 'Separated'.

Kind Regards, John

 

[ban-all-sheds]

Fitted some Street CCTV Cameras with plastic cases, on coulomb's, they are powered from a 24 volt Power supply which is is double insulated class 2. the out put feed from this is then taken to the Camera in shoot gun cable with the video.
Customer claims Highway Street Furniture ECS regulations (never herd of it ) requires even 24volt SELV equipment to be earthed. Cant find any ref to ECS. Any help appreciated

Who/what are you?

Who is the customer?

Where are these cameras?

How come you're taking money for installing them when you don't know what's involved?

 

[OwainDIYer]

I doubt any phone chargers are designed or sold as safety extra-low-voltage. Very few extra-low-voltage supplies are actually SELV

I'm not sure I understand your point. The 'S' of 'SELV' stands for 'Separated'.

"SELV" stands for "separated extra-low voltage" in installation standards (e.g., BS 7671) and for "safety extra-low voltage" in appliance standards (e.g., BS EN 60335). Wikipedia

safety extra-low voltages (SELV), protective extra-low voltages (PELV) and functional extra-low voltages (FELV) circuits. London South Bank University

UK and European Safety Extra Low Voltage (SELV) and product requirements Vent-Axia

The use of SELV (Safety Extra-Low Voltage): Safety by extra low voltage SELV is used in situations where the operation of electrical equipment presents a serious hazard (swimming pools, amusement parks, etc.). Schneider Electric

Separated or Safety Extra Low Voltage (SELV) Ideal Power

regardless of nomenclature, a CCTV extra-low-voltage power supply is not certain to comply with a SELV requirement unless it it particularly stated to be compliant.

 

[JohnW2]

I doubt any phone chargers are designed or sold as safety extra-low-voltage. Very few extra-low-voltage supplies are actually SELV

I'm not sure I understand your point. The 'S' of 'SELV' stands for 'Separated'.

"SELV" stands for "separated extra-low voltage" in installation standards (e.g., BS 7671) and for "safety extra-low voltage" in appliance standards (e.g., BS EN 60335). Wikipedia

Fair enough. I didn't realise that but I'm not sure it alters my point. I don't have access to 60335, but if your linked Wikipedia article is to be believed, the requirements for SELV (either "Separated..." or "Safety...") include "the lack of a return path through earth (ground) that electric current could take in case of contact with a human body.". So it still seems that, even when "S" stands for "Safety", an earthed circuit does not qualify as "SELV" - or have I (or the Wikipedia) got that wrong too?

Kind Regards, John

 

[Spark123]

A SELV source has no connection with earth, the current using equipment should not be earthed either. PELV has a connection with earth at source.

 

[stillp]

Never trust Wikipedia! I thought the "S" stood for "separated", but it seems I was wrong: http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=826-12-31

 

[JohnW2]

A SELV source has no connection with earth, the current using equipment should not be earthed either. PELV has a connection with earth at source.

That's what I've been saying all along!!

Kind Regards, John