Generator switch wiring help

[Scott1978]

Hello all.

I have been asked by a customer to install a generator changeover switch so he is protected in the event on a power cut. He is proposing a 4kva generator. Just to offer enough power for his fishpond and the odd socket for a fridge etc.

I have seen lewden sell a 125amp switch which will do the job.

I wanted to ask if anyone has installed one and can offer helpful advice. Being honest. I have not installed this set up before. Though seems straight forward.

Thanks

S

 

[Andy-1960]

Installing an earth rod is essential when installing any type of generator on a TN-S supply. This is both for your safety and the poor DNO engineer that may be working on the cable feeding your property.

 

[Scott1978]

Installing an earth rod is essential when installing any type of generator on a TN-S supply. This is both for your safety and the poor DNO engineer that may be working on the cable feeding your property.

Thanks Andy 1960. Do you disagree with buzz lightyear comment earlier then on page 1 ? The frame work of a portable generator becomes the earthing. Is this framework does not exist then a ground rod should be used.

 

[Lucien Nunes]

The frame work of a portable generator becomes the earthing

Are you burying the generator in the ground?

Realistically though, there are four things that might or might not need to be connected together.
Installation earth (MET)
Planet earth
Generator frame
Generator neutral

I presume you don't yet know the output configuration of the generator as far as earthing the neutral is concerned?

 

[Scott1978]

Are you burying the generator in the ground?

Realistically though, there are four things that might or might not need to be connected together.
Installation earth (MET)
Planet earth
Generator frame
Generator neutral

I presume you don't yet know the output configuration of the generator as far as earthing the neutral is concerned?

The generator is not purchased as yet. I do know it will be a portable one and about 4kva maximum.

 

[davesparks]

Installing an earth rod is essential when installing any type of generator on a TN-S supply. This is both for your safety and the poor DNO engineer that may be working on the cable feeding your property.

This is not necessarily correct, not all generators have a N-E link and so an earth rod will achieve nothing in some cases.

 

[Lucien Nunes]

I do know it will be a portable one

On a typical portable generator, the frame earth terminal is just that, it connects to the frame. It doesn't connect to earth unless you bury the generator and it rarely connects to neutral. The output is IT - floating with respect to everything. That's OK for a single load where the likelihood of a double fault is small and little single-pole switching or protective equipment is in use. The advantage of IT in such a situation is that it is single-fault tolerant and does not require an effective earth connection. But the domestic installation will have been configured for TN with single-pole OCPD etc and will need a generator supply of this form.

At this point, many people get confused because they are used to dealing with consumers' installations, not supply ones. They talk of putting in a rod to make it 'TT' and other nonsense. If you need a TN supply, YOU have to make the N-E link and YOU have to reference the supply to true earth. Then you get a TN-S supply just like the real thing. Except for the PSCC...

 

[David Prosser]

Installing an earth rod is essential when installing any type of generator on a TN-S supply. This is both for your safety and the poor DNO engineer that may be working on the cable feeding your property.

This is not quite right you are within your rights to connect you generator to true earth through the D.N.O. provided earth (assuming they have provided one in the first place). What you can't do is use the gas or water pipes to connect the generator to true earth. You must supply a connection to true earth and one of the acceptable options is the local network earth as long as it meets the needs of your installation.

 

[davesparks]

This is not quite right you are within your rights to connect you generator to true earth through the D.N.O. provided earth (assuming they have provided one in the first place). What you can't do is use the gas or water pipes to connect the generator to true earth. You must supply a connection to true earth and one of the acceptable options is the local network earth as long as it meets the needs of your installation.

Water pipes can be used for an earth electrode, but as you say a pipe carrying flammable fluids cannot.

Using a DNO provided earth connection would require their consent, you don't have a right to use their distribution network in this way.

 

[David Prosser]

Where does it state that permission is needed? I've never found this information.
The HSE guidelines for installing a generator don't state that you need permission from the DNO but they do state you can use an existing earth terminal of a fixed installation.

You haven't been allowed to use water pipes as an earth since 1966, unless you have your own private pipes supply etc and can prove they are not connected to the water utility distribution network in anyway.

 

[davesparks]

Where does it state that permission is needed? I've never found this information.
The HSE guidelines for installing a generator don't state that you need permission from the DNO but they do state you can use an existing earth terminal of a fixed installation.

You haven't been allowed to use water pipes as an earth since 1966, unless you have your own private pipes supply etc and can prove they are not connected to the water utility distribution network in anyway.

I must confess I have never read HSE guidelines for installing a generator, but since they have nothing to do with the wiring regulations or ESQCR I doubt that will haveuch bearing in reality. Could you provide a link to this guidance document please.

The regulations do allow the use of water pipes or any other buried metal as an earth electrode, it does require permission from the owner and provision to ensure it is not compromised in the future.
Using a water supply pipe from a utility company is unikely to be possible.
Could you quote the specific rules that support your statement please?

 

[David Prosser]

I don't have my BYB with me but I think it's 542.2.6.

As it is the HSE who are likely to prosecute people I think there guidelines would have some bearing in reality. HSE OC 482.

 

[David Prosser]

BIg Blue Book even!