Splitting circuits accross RCDs

[Manator]

I really dont get the minimize inconvenience bit of the regulation. A dual RCD board i dont really consider to minimize inconvenience , all RCBOs would but only if the installation was divided up enough in the first place. I realise the regs cant be specific but this hardly points us in the correct direction, dual RCD board become available around the time of the 17th edition and become known as 17th edition boards so everyone fits them. Am i the only one that thinks like this?

16th edition boards were non compliant but a compromise against costs, I am afraid it is just the same with dual split RCD boards, its a compromise in the regulations against costs.

 

[Chr!s]

Hi sidewinder

OK,Both sides of this "argument" have points.

The nominal voltages are there for the designs to be based upon.

I agree

The VPhase device does not hold a constant voltage.

That im not sure of

Thus it modifies the nominal voltage values that are delivered to the install.

Thus by rights you "SHOULD" recalculate the required impedances.

I dont see why you would need to modify, B7671 does not require this, its within the nominal range.

Will this make a difference?

Not in my opinion

That is the designers shout.

IF you are using these then you should get confirmation in writing from the manufacturer.

Wouldnt disagree there

Especially of you have borderline impedance values.

Oh, & I don't personally consider an RCD a suitable cop out for poor EFLI design.

Though perhaps the scams & the brb disagree, but I never got on that commitee!

 

[NozSpark]

Noz are you asking because you don't know the answer?

:red card

I'm sorry if this caused offence,,,

What I was trying to get across in my preceding post was that the supply voltage could quite legitimately be 220v and that in those circumstances we wouldn't be recalculating the max allowed Zs for the OCPD

 

[Sidewinder]

Plumber,

If you look at the readings that are posed earlier then you will see that the Vphase device does not hold a constant voltage, it seems to cap the voltage.

Thus it is conceivable for the voltage to fall below the nominal values with tolerances applied from 7671.

However, you are starting with a different NOMINAL voltage anyway...

 

[Chr!s]

Plumber,If you look at the readings that are posed earlier then you will see that the Vphase device does not hold a constant voltage, it seems to cap the voltage.

Thus it is conceivable for the voltage to fall below the nominal values with tolerances applied from 7671.

However, you are starting with a different NOMINAL voltage anyway...

Well providing the voltage doesn't fall outside the nominal i see no issue.

 

[Sidewinder]

True, Plumber, though the only ones who can guarantee this are the manuf', so perhaps the Q needs asking officially?...

With an input voltage of 230-6% what would be the o.p. V?

Not to the forum, but the Manuf' I mean!

The device may not be linear.

 

[steptoe]

16th edition boards were non compliant but a compromise against costs, I am afraid it is just the same with dual split RCD boards, its a compromise in the regulations against costs.

non compliant with regards to what Manator?

if they meet with the relevant BS then they are compliant, its all to do with the way they are utilised as to whether something is compliant with a certain reg then or not. IMO.

 

[Sidewinder]

Would the IEE have sufficient data on the device?

However, if that is the manuf info then that is what you have to go with and they are the ones that will be standing in the dock as long as you have the info in writing to keep you safe.

I know that it was slated on the IEE forum.

By some clever guys too.

 

[ADS]

Plumber and Noz are right - if the 'actual' voltage is within the +/_ range, then your 'nominal' voltage is 230V.

My 'Megger' does it's PFC measurements based on this as well - i.e. actual voltage 242V, voltage used in measurement calculation 230V..........actual voltage 223V, voltage used in measurement calculation 230V.

If it didn't do this then you'd get different readings every time you took a measurement on the same circuit, just because of a change in the incomming supply voltage.

Nominal voltage doesn't get adjusted - it's (as it's name implies) a named voltage for measurement/calculation purposes, which covers a set range of 'actual' voltage.

With these 'v PHASE' things, I'd be more concerned about volt drop.

If you're starting off with 220V, then you're already -10V off the nominal before you leave the CU