Use of cpc as functional earth in appliances

[LastManOnline]

some time back a customer rang up saying a tenent was getting shocks from a shower .Investigation revealed the problem lay with a broken cpc (caused by new insulation installers) resulting in a voltage of approx 27 v on the metallic parts of the shower .However the finger of blame was initially been directed at the electrician We recently got written confirmation from the shower manufacturer who confirmed the issue lay with their use of the cpc as functional earth.

My question is twofold..

1) Would it not make sense for all appliance manufacturers to state in their instruction manuels that they are using their cpc as a functional earth and avoid the kind of confusion described above?

2) Bearing in mind the requirement on electricians to ensure circuits are designed and protected properly for their intended use ,is,nt it now necessary that we know the value and type of "functional earth leakage current"?

 

[radiohead]

I dont really see what difference it makes, in the case of a standard shower effective earthing is required for protective measures and if not in place a hazard exists. The manufacturers instructions will clearly state there is a requirement for earthing, regardless, if the cpc performs a functional purpose as well as protective it is clearly required to be connected to a means of earthing.

 

[moose]

The problem with manufacturers is they do things on par with regs. Meaning its all written or those sneaky pictures showing the Earth type

They will I am sure have used the picture of maybe Functional Earth. They are sneaky as most electricians don't read manuals very well unless you are the employer.

It is a male problem we never read instructions. The only thing that does seem odd is you mostly always get a CPC point to accept cable. Was it an import?

Good luck

 

[Lucien Nunes]

One could argue that any appliance with Y-caps in their suppressors (i.e from L & N to E) uses the CPC as a functional earth, so that will include most class I equipment with any electronics or motors. As mentioned above, when considering a single class I appliance, this is not generally of any concern as the requirement for a protective earth is invariable. I would only expect attention to be drawn to a functional earth if it is required for correct operation on a device that does not require a protective conductor to be safe, such as a device with class II protection.

Regarding the normal leakage current delivered into the conductor, yes it would be handy if that was given in the product specs. It would be of interest in certain situations e.g. when multiple units are to be powered from a single circuit or plug where it is necessary to verify at design stage that the total leakage does not exceed the threshold where a higher integrity of CPC is required. I sometimes have to think about this when integrating large numbers of electronic units into portable systems, although I have a good idea of what leakage to expect from each device (and I keep a record for all models of equipment that I have fitted) and can fairly accurately predict the total for each rack.

 

[LastManOnline]

The problem with manufacturers is they do things on par with regs. Meaning its all written or those sneaky pictures showing the Earth type

They will I am sure have used the picture of maybe Functional Earth. They are sneaky as most electricians don't read manuals very well unless you are the employer.

It is a male problem we never read instructions. The only thing that does seem odd is you mostly always get a CPC point to accept cable. Was it an import?

Good luck

I went through the instructions several times and there is not a mention of functional earthing.Your point about a symbol is a valid one though and will look into that.Obviousely the manufacturers are entirely within their rights in what they are doing.Thats not an issue.Its just that traditionally almost no appliances used this facility whereas now its commonplace and this is a developement that sparks will appreciate knowing.The shower was one of the established brands

 

[LastManOnline]

One could argue that any appliance with Y-caps in their suppressors (i.e from L & N to E) uses the CPC as a functional earth, so that will include most class I equipment with any electronics or motors. As mentioned above, when considering a single class I appliance, this is not generally of any concern as the requirement for a protective earth is invariable. I would only expect attention to be drawn to a functional earth if it is required for correct operation on a device that does not require a protective conductor to be safe, such as a device with class II protection.

Regarding the normal leakage current delivered into the conductor, yes it would be handy if that was given in the product specs. It would be of interest in certain situations e.g. when multiple units are to be powered from a single circuit or plug where it is necessary to verify at design stage that the total leakage does not exceed the threshold where a higher integrity of CPC is required. I sometimes have to think about this when integrating large numbers of electronic units into portable systems, although I have a good idea of what leakage to expect from each device (and I keep a record for all models of equipment that I have fitted) and can fairly accurately predict the total for each rack.

Yes I can appreciate that in your line of work leakage current plays a much bigger role than for a general electrician like myself.And of course with the progressive change to CU,s becoming all rcbo,s then it becomes less likely that we will ever find ourselves having to get the calculator out to calculate cumalitive leakage currents.But as you mentioned it would be good to know these values anyway and also to know the manufacturers recommended type of rcd for safety purposes

 

[telectrix]

reading the OP, surley the "fault" was caused by the insulation apes damaging cable with thier size 10's .clodhopping steel toecaps. in which case they should take the stick and foot the costs incurred.

 

[pc1966]

Personally I don't see this as a "functional earth", it is a safety earth due to it being Class 1 appliance and must be connected.

The filter leakage is actually fortunate - they found out about the open CPC before any fault that would have needed it to protect them from a potentially fatal shock!

But I agree that all equipment should state the max leakage current for any calculations of total loading on RCDs, etc.

 

[Strima]

As we are to take into account earth leakage when designing and installing manufacturers really need to start stating what currents they expect their equipment to have.

This would also include AC and DC so we can select the correct type of RCD.

 

[LastManOnline]

Personally I don't see this as a "functional earth", it is a safety earth due to it being Class 1 appliance and must be connected.

The filter leakage is actually fortunate - they found out about the open CPC before any fault that would have needed it to protect them from a potentially fatal shock!

But I agree that all equipment should state the max leakage current for any calculations of total loading on RCDs, etc.

As I was compelled to write up a report on the incident I asked the shower manufacturer if they could respond in writing regarding my suspicion that the cpc was been used as a functional earth. Their reply was..

"You are correct in assuming the cpc is being used as a functional earth.."

 

[LastManOnline]

I dont really see what difference it makes, in the case of a standard shower effective earthing is required for protective measures and if not in place a hazard exists. The manufacturers instructions will clearly state there is a requirement for earthing, regardless, if the cpc performs a functional purpose as well as protective it is clearly required to be connected to a means of earthing.

That's a good answer. Pity it does, nt relate to the question asked

 

[LastManOnline]

PC1966
"the filter leakage is actually fortunate-they found out about the open CPC before any fault that would have... a potentially fatal shock"

That's an interesting take on the issue. I think however if you felt 27 volts standing in a shower tray which was on a concrete floor in an old cottage with water swirling around your feet you would think again about that proposal. I felt the 27 volts while wearing my shoes and socks. Not pleasant.
In fact the shower model has since being taken off the market. It was, nt their first time experiencing this issue and no one (manufacturer or end user) would appear to have seen any advantages to it.

 

[pc1966]

That's an interesting take on the issue. I think however if you felt 27 volts standing in a shower tray which was on a concrete floor in an old cottage with water swirling around your feet you would think again about that proposal. I felt the 27 volts while wearing my shoes and socks. Not pleasant.

No, not pleasant, but only a milliamp or two.

Nothing compared to being in a shower and finding 230V with a half amp or so flowing for tens of milliseconds until the (we hope!) RCD cuts it off!

 

[LastManOnline]

No, not pleasant, but only a milliamp or two.

Nothing compared to being in a shower and finding 230V with a half amp or so flowing for tens of milliseconds until the (we hope!) RCD cuts it off!

Agreed.no comparison between 27 and 230 volt.But rather than viewing getting a shock of 27 volt as a " helpful" arrangement which informs the end user ( in a very unpleasant way ) that he needs to call an electrician , why not have an arrangement where the shower manufacturer ( if he chooses to use the cpc as a functional earth) builds protection into his appliance (via a relay) that prevents said shower from being operated?