RCD for professional sunbed circuit installation (edited.)

[JohnD]

This kebab grill is 7.2kw, so yours should cook a human in less than two hours.

the inside may still be underdone.

 

[JohnW2]

Have decided it is not going to be within the house cicuit ( Blue phase) , am taking a feed from one of the phases ( Yellow phase ) in another part of the farm building, and putting it in a room within the farm building, where we have set up has a training/weight lifting etc room , the 3 phase feed to the farm is a TT system, there is several earth rods around the buildings .

Fair enough.

Where the supply comes from (and which phase) doesn't really make any difference to anything, but the fact that you're talking about a TT system moves the goalposts a lot. That means that MCBs/RCBOs cannot provide the required fault protection (hence what I said about maximum loop impedance in my last post doesn't apply), so you would have to rely on the residual current device (RCD or RCBO) to provide the fault protection - and a 100 mA one would be fine for that.

Whether or not it would be wise to get onto/into a sunbed which did not have 30mA residual current protection is perhaps a debatable question (and I'm still wondering where all that power is going!).

Kind Regards, John

 

[ericmark]

I agree with AC capacitive and inductive linking can cause a leakage to earth even when with DC there would be no leakage, in the main we use 1/3 of the RCD rating as the maximum leakage allowed, so with a 30 mA 9 mA is considered as the maximum. BS 7671 does go into high earth leakage.

Equipment having a protective conductor current exceeding 10 mA shall be connected to the supply by one of the following methods:
(i) Permanently connected to the wiring of the installation, with the protective conductor selected in accordance with Regulation 543.7.1.3. The permanent connection to the wiring may be by means of a flexible cable
(ii) A flexible cable with a plug and socket-outlet complying with BS EN 60309-2, provided that either:
(a) the protective conductor of the associated flexible cable is of a cross-sectional area not less than 2.5mm² for plugs rated at 16A and not less than 4 mm² for plugs rated above 16A, or
(b) the protective conductor of the associated flexible cable is of a cross-sectional area not less than that of the line conductor
(iii) A protective conductor complying with Section 543 with an earth monitoring system to BS 4444 installed which, in the event of a continuity fault occurring in the protective conductor, automatically disconnects the supply to the equipment.

I would guess BS 7671:2018 has some thing similar, but you would need to check, it is clearly a special case, and not some thing one could use in a private house, I have used it with a batching plant, seem to remember a problem complying with British regulations as Batching plant came from Germany designed for export and did not even comply with German regulations. It caused the end of my working life.

I would say you need to employ the services of a safety officer, who can advise what the council planning will allow etc. This is clearly not a DIY job.

 

[bernardgreen]

You definitely need to get a competent electrician involved.

 

[spike47]

Therefore use a higher rated 100mA RCD, 63A or 80A perhaps, with a 40A MCB after it.
The ampere rating of an RCD refers to the rating of the contact current, not any form of tripping capability.

Yes sorry, meant the RCD has to have a 100mA trip , not the 45A MCB, I did say that it my first post !

 

[spike47]

I agree with AC capacitive and inductive linking can cause a leakage to earth even when with DC there would be no leakage, in the main we use 1/3 of the RCD rating as the maximum leakage allowed, so with a 30 mA 9 mA is considered as the maximum. BS 7671 does go into high earth leakage.

I would guess BS 7671:2018 has some thing similar, but you would need to check, it is clearly a special case, and not some thing one could use in a private house, I have used it with a batching plant, seem to remember a problem complying with British regulations as Batching plant came from Germany designed for export and did not even comply with German regulations. It caused the end of my working life.

I would say you need to employ the services of a safety officer, who can advise what the council planning will allow etc. This is clearly not a DIY job.

Not going into a House , will be in a room within the Farm buildings !

 

[bernardgreen]

will be in a room withing the Farm buildings !

in which case you may need to apply to the local council for planning permission for change of use before making any significant investment

 

[flameport]

(and I'm still wondering where all that power is going!).

It ends up as heat, which is why sunbeds require substantial ventilation systems in the building they are used in.

 

[spike47]

It ends up as heat, which is why sunbeds require substantial ventilation systems in the building they are used in.

Yes there is large fan above it, why is this post now getting so complicated, there is not much difference in wiring this up as there is in wiring up a 8KW shower !.

Spike

 

[spike47]

This is what I am thinking of putting in .

 

[bernardgreen]

there is not much difference in wiring this up as there is in wiring up a 8KW shower !.

There is a lot of difference

An electric shower would not create more than a few mA (milli-Amps) of Earth leakage current, far less than the 30 mA that would trip the 30mA RCD that an electric shower has to have to reduce the risk of death by electrocution when the shower becomes faulty.

The sunbed when operating normally appears to produce more than 30mA of earth leakage current hence the manufacturer/seller saying a 100mA RCD is needed.

If there is a fault that allows current to flow to ground through a person then the RCD needs to operate at less than 30mA to reduce the risk of that person dying from electrocution.

 

[spike47]

There is a lot of difference

An electric shower would not create more than a few mA (milli-Amps) of Earth leakage current, far less than the 30 mA that would trip the 30mA RCD that an electric shower has to have to reduce the risk of death by electrocution when the shower becomes faulty.

The sunbed when operating normally appears to produce more than 30mA of earth leakage current hence the manufacturer/seller saying a 100mA RCD is needed.

If there is a fault that allows current to flow to ground through a person then the RCD needs to operate at less than 30mA to reduce the risk of that person dying from electrocution.

Yes understand that, will get a 100mA if I can find one, can't see it been a risk using a 30mA , other than it will keep tripping if the leakage is as they say, read on this same forum posts fro 2018, where Electrcians are saying they put in 30mA RCD's and they have never had a problem with them tripping will feel better if 30mA will run ok , if not then will have to buy another RCD 100mA, prepared to do that .

Spike

 

[Taylortwocities]

will get a 100mA if I can find one,

https://www.tlc-direct.co.uk/tcl/search?query=100mA&Submit=Search

 

[ericmark]

There is a difference between domestic and commercial, from hiding cables, to planning permission, and clearly this is a commercial venture. So your looking at health and safety at work act, offices shops and railway premises act not Part P.

So a new circuit, with no hidden cables i.e. doing all that is required not to require RCD protection.

I see the idea, clearly you have visitors to the farm and this is going to be one of the attractions, I know where hot tubs have been installed with the same idea, and where a shepherds hut has been sited, in the main to get around council tax and other problems when a permanent building is involved.

 

[spike47]

There is a difference between domestic and commercial, from hiding cables, to planning permission, and clearly this is a commercial venture. So your looking at health and safety at work act, offices shops and railway premises act not Part P.

So a new circuit, with no hidden cables i.e. doing all that is required not to require RCD protection.

I see the idea, clearly you have visitors to the farm and this is going to be one of the attractions, I know where hot tubs have been installed with the same idea, and where a shepherds hut has been sited, in the main to get around council tax and other problems when a permanent building is involved.

No it is not a commercial venture, we have purchased this second hand for our own use