Type B or C RCBO

[La Poste]

Greetings.

Friend of mine has a fridge freezer and a standing freezer that need RCBO protection.

Both these appliances run off the same socket which is a separate radial so easy to protect as it will only be these two items on this one particular circuit.

I am not sure of the starting current of these appliances and so was wondering whether to fit a type B or type C 16 Amp RCBO.

What do you think?

Thanks a lot.

 

[telectrix]

firstly, measure the Zs of the circuit. if it's above the max. for the 16A type C, ( 1.44 ohms ) . fit a type B.

 

[Deleted member 9648]

Never had a problem with a type B in these circumstances...as it is unlikely that both appliances will start at exactly the same moment there are not likely to be any issues.....I would fit whatever I happen to have,a Type B or C...as it is RCD protected Zs is not likely to be an issue either....1667 ohms applies..

 

[Engineer54]

Never had a problem with a type B in these circumstances...as it is unlikely that both appliances will start at exactly the same moment there are not likely to be any issues.....I would fit whatever I happen to have,a Type B or C...as it is RCD protected Zs is not likely to be an issue either....1667 ohms applies..

I think it does, or at least could!! RCD protection is classed as ''Additional'' in other words ''Don't Rely on it!! RCDs can and often DO fail!! Then your Zs becomes very important, very fast!! lol!!

 

[Octopus]

Greetings.

Friend of mine has a fridge freezer and a standing freezer that need RCBO protection.

Both these appliances run off the same socket which is a separate radial so easy to protect as it will only be these two items on this one particular circuit.

I am not sure of the starting current of these appliances and so was wondering whether to fit a type B or type C 16 Amp RCBO.

What do you think?

Thanks a lot.

Why do you think you need RCD protection?

 

[GLENNSPARK]

surface run it......mark the outlet for fridge/freezer only.....get round the earth leakage issues that these appliances are known to suffer from..........

 

[Amp David]

Never had any issues using Type B RCBOs for radials supplying fridgefreezers/fridges.

How large are starting currents on fridge freezers usually?

 

[GLENNSPARK]

just little compressors on em....cant see the load being that high.........

 

[Deleted member 9648]

I think it does, or at least could!! RCD protection is classed as ''Additional'' in other words ''Don't Rely on it!! RCDs can and often DO fail!! Then your Zs becomes very important, very fast!! lol!!

An RCD may be classed as either additional protection or to satisfy disconnection times....411.4.9.

If in the case of the OP if it was found that starting surges were a problem with a type B...and the Zs exceeded the maximum allowable for a type C OCPD would you rewire the circuit in a larger cable to bring it within the allowances for a type C..??,(or some other expensive fix?), when the regulations permit the RCD element of the device already installed to meet the requirements for disconnection times?
If you prefer the first option I'm glad I'm not one of your cutomers.

 

[nickblake]

I'd be inclined to go with glen sparks point and run in a radial but i would run it in a 4 or 6mm only reason is the cpc is larger in these so there fore the Zs readings should be lower i am a big fan of keeping the Zs as low as possible ,and for reasons eng54 has stated RCD's do fail , for certain circumstances you can install sockets without RCD protection

 

[telectrix]

not only fail, but trip when you are away for a few days and leave you with a soggy, expensive mess of what used to be frozen food. bang it on it's own radial, no RCD and bury the drop in a length of 20mm galv. conduit ( earthed, ofd course) sssimples.

 

[La Poste]

It's in a garage with a damp floor.
The lead sheathed TN-S cable runs right under the garage so for safety reasons I was thinking of an RCBO.

Personally I would prefer no RCD at all, the wiring is in surface clipped PVC conduit and the socket is already on its own radial but seeing as how everybody is health and safety mad these days I think it best to RCBO it.

The fuse board has a spare way which will have a 16 Amp non RCD protected MCB ready just in case the fridge freezer does trip out.

I'm really in two minds about this, maybe I will just give them a socket next to the fuse board for when they go away, they can plug their freezers into this socket whilst on holiday.

ZS is below 1 Ohm.

 

[spark 68]

Personally I would prefer no RCD at all, the wiring is in surface clipped PVC conduit and the socket is already on its own radial but seeing as how everybody is health and safety mad these days I think it best to RCBO it

Although just labelling said sockets is allowed within the regs, if you are that bothered (sockets may be used outdoors blah blah), you could put special plugs on the appliances and change the socket outlet to match, eg. you can get plugs (and sockets) where one pin is turned through 90 degrees, so nothing else will be able to be plugged in.

And put that outlet on a non RCD side of the board.

 

[SPARTYKUS]

Or cut plug off and wire it into a fused spur <WAITS for warranty expires if-you-do-that post....>

 

[Marvo]

Or cut plug off and wire it into a fused spur <WAITS for warranty expires if-you-do-that post....>

I heard a rumour that cutting moulded plugs off invalidates your car insurance and stunts the growth of any veggies your growing in your garden. :biggrin:

 

[telectrix]

I heard a rumour that cutting moulded plugs off invalidates your car insurance and stunts the growth of any veggies your growing in your garden. :biggrin:

what's car insurance? and we don't have plumbers or kitchen fitters growing in our garden.

 

[Octopus]

So its a new circuit, and thus its notifiable.

 

[La Poste]

No it's a spur off a radial.
An RCD'd spur off a radial.

 

[GLENNSPARK]

An RCD may be classed as either additional protection or to satisfy disconnection times....411.4.9.

If in the case of the OP if it was found that starting surges were a problem with a type B...and the Zs exceeded the maximum allowable for a type C OCPD would you rewire the circuit in a larger cable to bring it within the allowances for a type C..??,(or some other expensive fix?), when the regulations permit the RCD element of the device already installed to meet the requirements for disconnection times?
If you prefer the first option I'm glad I'm not one of your cutomers.

might only need an additional cpc ....parralleled up with the existing one in the cable..........

 

[GLENNSPARK]

I'd be inclined to go with glen sparks point and run in a radial but i would run it in a 4 or 6mm only reason is the cpc is larger in these so there fore the Zs readings should be lower i am a big fan of keeping the Zs as low as possible ,and for reasons eng54 has stated RCD's do fail , for certain circumstances you can install sockets without RCD protection

4mm??...bad cable to use nick mate as dont forget....still only a 1.5mm cpc..........

 

[La Poste]

Zs is 0.6 Ohms.

TN-S system, quite close to the transformer.

Surprisingly the voltage this afternoon at about 15:30 was 245 Volts.

 

[Octopus]

No it's a spur off a radial.
An RCD'd spur off a radial.

You've lost me now

 

[La Poste]

You can get RCD'd FCU, if you attached one to the end of a radial would it then be notifiable?

 

[GLENNSPARK]

if its an addition or an alteration to an existing circuit then its a minor works ......if in a garage (remote or attached as in this case) then it isn`t notifyable....

 

[La Poste]

if its an addition or an alteration to an existing circuit then its a minor works ......if in a garage (remote or attached as in this case) then it isn`t notifyable....

That's how I see it.

It's an extension of a radial which is fused at 32 Amps in the house.

 

[Engineer54]

An RCD may be classed as either additional protection or to satisfy disconnection times....411.4.9.

If in the case of the OP if it was found that starting surges were a problem with a type B...and the Zs exceeded the maximum allowable for a type C OCPD would you rewire the circuit in a larger cable to bring it within the allowances for a type C..??,(or some other expensive fix?), when the regulations permit the RCD element of the device already installed to meet the requirements for disconnection times?
If you prefer the first option I'm glad I'm not one of your cutomers.

That's all well and good wirepuller, until that RCD your now relying on for your disconnection times, decides to give-up the ghost!!

That's the point these day's, your all relying on this ''cure all'' 1667 ohms that an RCD provides instead of getting a decent Zs on your installation circuits.. You can look at it anyway you wish, on a TN supplies an RCD should always be looked on as ''Additional'' Protection NOT your only means of protection!! That type of protection should be limited to a UK TT system, and even that, doesn't sit too well with me, but i can live with it ...to a point....lol!!!

 

[Octopus]

You can get RCD'd FCU, if you attached one to the end of a radial would it then be notifiable?

I was wondering how we got from a question about which RCBO's to use, to using an existing circuit and adding a RCD FCU!!

 

[La Poste]

Well why is it that we can add a FCU to an existing radial and it is classed as a non notifiable extension.

And yet when we add a small DB to the end of a radial it then in your opinion becomes notifiable.

So its a new circuit, and thus its notifiable.

Please explain this to me.

 

[Octopus]

That's how I see it.

It's an extension of a radial which is fused at 32 Amps in the house.

Out of interest what is on the main board? Is it RCD'ed

 

[La Poste]

This particular radial is not, it's fused at 32 Amps, but the rest of the house board is.

 

[Octopus]

This particular radial is not, it's fused at 32 Amps, but the rest of the house board is.

Hum, now things are a bit clearer. If you're adding socket(s) in a garage on a SDB they do need to be RCD'ed IMHO.

That said I do think the RCD for all new sockets is a completely daft idea. I recently lost some work because I quoted by the book an another sparky didn't and he fitted new sockets without RCD protection

Is this the garage/outbuilding you've been working on recently?

 

[La Poste]

Yes, this is for my assessment.

It's a 6mm SWA from the house non RCD protected fused at 32 Amps.
Sub board in the garage with lights and sockets all RCD protected.

One socket for fridge freezer that may or may not be RCD protected (the owner will be told to not use this socket for anything else)

 

[GLENNSPARK]

just telling em wont be enough mate....it wont stop em using it for something else "just this once"........and sods law will dictate it will be THEN that a fault occurs.....need to label it up clearly and make a note of it on your paperwork......but as has been suggested here already...you can surface run this cable..or.. you can run it in an earthed metalic conduit....thats if buried at a depth of less than 50mm...would still need labeling up though......and as its a garage it wont require notification (assuming its an alteration or addition to an EXISTING circuit)...if its a new circuit (back to the board)....then its notifyable and a minor works wont cut it either then...........

 

[Octopus]

Not sure I'd be using a circuit/socket without RCD protection for my assessment!

Isn't this a rebuilt garage and haven't you fitted a new SBD in the garage?

 

[La Poste]

It's a rebuilt garage with a new SDB yes.

The cable was left from the old existing garage.

Why would the assessor not like a non RCD protected socket if it is clearly labelled?

 

[GLENNSPARK]

Not sure I'd be using a circuit/socket without RCD protection for my assessment!

Isn't this a rebuilt garage and haven't you fitted a new SBD in the garage?

but if its in the regs that it can be done (under certain conditions) Murdoch then wouldn`t an examiner see this as an UNDERSTANDING of the regs?.......

 

[Octopus]

It's a rebuilt garage with a new SDB yes.

The cable was left from the old existing garage.

Hum, don't you love these cans of worms.

IMHO, not notifiable, EIC required, including a formal test on the "supply" radial, all sockets in garage RCD protected.

 

[Octopus]

but if its in the regs that it can be done (under certain conditions) Murdoch then wouldn`t an examiner see this as an UNDERSTANDING of the regs?.......

reg number?

 

[La Poste]

Supply radial has been tested very well.

EIC good, this may impress the assessor, non RCD protected socket I can see where you are coming from, I may just leave it and not fit it.

 

[GLENNSPARK]

reg number?

411.3.3 brb

 

[La Poste]

411.3.3 brb

I agree, I also like the idea of putting special plugs on the equipment and a special socket that will only work with these plugs.

But for overall safety I think I will opt for the circuit with its own RCBO feeding just this socket and leave it at that.

 

[SPARTYKUS]

Or cut plug off and fit a fused spur!!

 

[La Poste]

Yes that is the best idea, make it fixed equipment and have no socket at all.

It still leaves the problem of the damp though, best to RCBO it IMHO.