In my recent Vaillant install I had some lengthy discussions with my installer as to why I needed another consumer unit and this special RCCB from Hager.  I gave in at the end.  Added over £600 to my install costs.

What was the reason given.  You don't even need an RCD for external fixed plant, an MCB will suffice (although an RCD is certainly to be preferred).

Posted by: @jamespa

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What was the reason given.  You don't even need an RCD for external fixed plant, an MCB will suffice (although an RCD is certainly to be preferred).

Manufacturers requirement.

@jamespa 

Vaillant have specific requirements in term of RCD type and MCB curve. Contactum sell these types of RCBOs in 16A for £25 (in boxes of 5). 

I am yet to see information from Vaillant requiring a specific brand of CU, but the supposed requirement is one of those that some sparkies do not forget. Also some add an SPD for good measure. 😀 Why not, anyone getting a heat pump must have cash to spare? 😉 

Posted by: @batpred

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Vaillant have specific requirements in term of RCD type and MCB curve. Contactum sell these types of RCBOs in 16A for £25 (in boxes of 5). 

@trebor12345 @batpred 

My version of the Vaillant installation manual, from about 2 years ago, has specific requirements for RCD type if an RCD is specified for the installation (which is fair enough).  However it does not require that an RCD is specified for the installation and neither does the IET regs (which is also fair enough).  I looked online last about 6 months ago and the wording had not changed.  Maybe it has subsequently changed.

@jamespa 

I fear the average installer will not question it. The way it was explained to me is that it is required by Vaillant for the warranty. But then the detail was that there is an inverter inside the Arotherm and if faulty, it can push out DC currents. 

I would expect that, in that casem the protection would be for the rest of the installation to not get DC from a faulty heatpump. So how could this have an impact on the Vaillant warranty I cannot understand.. 

Posted by: @batpred

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@jamespa 

I would expect that, in that casem the protection would be for the rest of the installation to not get DC from a faulty heatpump. So how could this have an impact on the Vaillant warranty I cannot understand.. 

The first question to ask is, does it?  What does the latest Vaillant Installation manual actually say?  Bear in mind that some tradesmen speak out of the wrong part of their anatomy!

Posted by: @jamespa

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Posted by: @batpred

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Vaillant have specific requirements in term of RCD type and MCB curve. Contactum sell these types of RCBOs in 16A for £25 (in boxes of 5). 

@trebor12345 @batpred 

My version of the Vaillant installation manual, from about 2 years ago, has specific requirements for RCD type if an RCD is specified for the installation (which is fair enough).  However it does not require that an RCD is specified for the installation and neither does the IET regs (which is also fair enough).  I looked online last about 6 months ago and the wording had not changed.  Maybe it has subsequently changed.

The requirement for me came from the following document.

Although we can't see the part number on that photo above, I assume that the Hager RCD in the upper consumer unit is this one.
See the short-form technical guide which can be downloaded here.

As it's only an earth leakage trip, presumably there must also be an MCB in the main consumer unit which provides over-current protection.

Vaillant are specifying a Type-B earth-leakage trip in order for it to function when there is a DC-component being imposed onto the mains waveform.

And the additional 'HP' specification allows it to also trip-out when there are harmonics present above 1kHz.

That suggests to me that the Vaillant power supply is 'sub-optimal' in that it's imposing distortions onto the grid which shouldn't be there.

Harmonics (multiples of 50Hz) create losses on the grid, which is of concern to DNOs.

The symbol on the front of the Hager Type B RCD do not indicate the presence of a filter. Both the DC component and the higher frequency harmonics will pass straight through.

That raises the potential problem of those improper frequencies adversely affecting earth-leakage trips which feed other circuits from the same Consumer Unit.

I don't understand why the electrician working for @trebor12345 chose this particular Hager unit.

For about the same price, he could have bought a 1-module-wide RCBO designed and manufactured in the UK by Proteus.
That would seem to do the same job, and could've been installed within the existing Consumer Unit.

Posted by: @trebor12345

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The requirement for me came from the following document.

 

@trebor12345 

Noted.  As I say the Valiant installation manual I have does not require an RCD, but does specify the type if one is fitted.

I would say that the document above could be read either way however if you read it as RCD mandatory then a fuse is also mandatory and hardly anyone is going to fit one of those.  Thus I would personally refer to the installation manual for clarification.

Posted by: @transparent

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I don't understand why the electrician working for @trebor12345 chose this particular Hager unit.

For about the same price, he could have bought a 1-module-wide RCBO designed and manufactured in the UK by Proteus.
That would seem to do the same job, and could've been installed within the existing Consumer Unit

At a guess because he is one of those electricians that will only put a component from manufacturer x in a box from manufacturer x and will refuse to mix manufacturers.  There are plenty of those around it seems.  Or because he prefers not to touch the existing CU which seems to be a frequent position in the renewables industry.  Either way STC (you can work it out!)

The current Vaiilant manual says the same as mine, IE it specifies the type of RCD if an RCD is fitted, but does not specify that an RCD must be fitted.  That latter decision is, by implication, left to the installer/local regs.

7.3 Requirements for electrical components
Flexible hose lines that are suitable for routing outdoors must
be used for the power supply. The specification must com-
ply with the standard 60245 IEC 57 with the abbreviation
H05RN-F as a minimum.
The electrical partitions must have a contact gap of at least
3 mm.
For the electrical fuse protection, slow-blow fuses with C
characteristics must be used. With a three-phase power sup-
ply, the fuses must be three-pole switching.
To protect people, type B universal-current-sensitive resid-
ual-current circuit breakers must be used if these are stipu-
lated for the installation site.
For the eBUS line, no lines with twisted wire pairs must be
used.
7.4

Posted by: @transparent

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As it's only an earth leakage trip, presumably there must also be an MCB in the main consumer unit which provides over-current protection.

There is NO MCB in the main consumer unit for the heat pump.  The electrician took the feed for the heat pump straight into the new Hager Unit in the new consumer unit.  Are you saying that the new Hager unit still needs to be protected by a MCB?