Type of RCD required for HP

[sharpener]

Have just been informed I need to have an additional CU with a Type B RCD for my upcoming Vaillant HP (Arotherm + 12kW). Previously I had been led to believe they would just fit 2 extra mcbs in my existing CU for which there are sufficient spare ways, but they now want to fit a subsidiary board instead.

 

Has anyone else encountered this requirement? How important is it?

 

Is Type B even the correct spec for a single-phase inverter-driven HP, this site suggests that a Type F is adequate and Type B is only requried for 3-phase drives.

[The Bin Man]

The Panasonic 12kW I could be getting quotes a 30A breaker with 30mA 2P Type A RCD for the compressor and a 30A breaker 30mA 2P Type AC RCD for the backup heater.  

 

Both will be off sub boards.  I was told installers don't tend to like touching existing installed equipment and prefer to install sub-boards.  

 

Perhaps your spec is specific to the Arotherm+?  

Edited July 20 by The Bin Man

[JamesPa]

18 minutes ago, sharpener said:

Have just been informed I need to have an additional CU with a Type B RCD for my upcoming Vaillant HP (Arotherm + 12kW). Previously I had been led to believe they would just fit 2 extra mcbs in my existing CU for which there are sufficient spare ways, but they now want to fit a subsidiary board instead.

 

Has anyone else encountered this requirement? How important is it?

 

Is Type B even the correct spec for a single-phase inverter-driven HP, this site suggests that a Type F is adequate and Type B is only requried for 3-phase drives.

They just don't want to touch your existing cu imho.  Perhaps they can't get an RCBO or RCD to fit it, or they just don't touch existing CUs.  Nothing I am aware of says you can't run a single phase hp on an MCB with no RCD if you choose although obviously an RCD or RCBO is preferable.  And the second circuit is just control electronics = diddly squat power so can run off the ring main so long as you are happy it's sufficiently stable (IE you don't currently get too many trips).

 

Perhaps you can offer to provide the circuit for them and get a real electrician to fit it?

Edited July 20 by JamesPa

[JohnMo]

31 minutes ago, sharpener said:

Type B even the correct spec for a single-phase inverter-driven HP,

Mine (Maxa) says

"recommended to install a type

B differential switch, the installation of a different type switch could give rise to untimely trips."

 

Vaillant instructions states (section 7.3)

"To protect people, type B universal-current-sensitive residal-current circuit breakers must be used if these are stipulated for the installation site."

 

So pretty consistent.

[Mattg4321]

No idea whether or not it’s required to fit Type B RCD, but if it is (call Vaillant and ask?) then they are not available to fit into a standard consumer unit in general. You will have to fit a separate board/enclosure. 
 

Type AC RCD mentioned above. I wouldn’t fit these anymore and they have anyway been almost phased out. Type A is pretty much minimum standard installed and cost no more really. 

[sharpener]

55 minutes ago, JohnMo said:

Vaillant instructions states (section 7.3)

"To protect people, type B universal-current-sensitive residal-current circuit breakers must be used if these are stipulated for the installation site."

 

Thanks, found it. It's a bit tautologous as it says "if these are stipulated for the installation site". Who does the stipulating?

 

IMO this was drafted for the German market where the 3-phase model is more or less universal. In the UK on single phase I think a Type F would be adequate as per the link above. They are only 2/3 the price, though still over £100 e.g. this one (which is a standard 2 module DIN rail fixing so looks as though it could go in my existing CU, subject to my comparing the detailed dimensions).

[Mattg4321]

‘If’ Vaillant say Type B RCD must be fitted, then that’s what you will have to do. If you can get away with Type F, then great, but that will be stipulated by them. Why not call their technical support on Monday?

 

Either way, that type F RCD may not fit easily in your consumer unit, there are a few things to consider. Do you have a Hager consumer unit, because manufacturers equipment shouldn’t be mixed? Do you have enough space for the RCD and an MCB? How will you provide power to the RCD, will you need to buy flexible links to connect to the main switch - will they even fit in the terminal maintaining a suitable connection?

 

If I was the installer I’d likely rather fit a new consumer unit too I think. It saves opening a potential can of worms. Not to say it definitely couldn’t be fitted in your existing though, but more information is needed. 

[JamesPa]

28 minutes ago, sharpener said:

Thanks, found it. It's a bit tautologous as it says "if these are stipulated for the installation site". Who does the stipulating

The iet wiring regs presumably.  I read this as saying nothing more than you must fit the type of RCD locally required (basically it says nothing).  

 

10 minutes ago, Mattg4321 said:

Why not call their technical support on Monday?

That's what I would do too.

 

10 minutes ago, Mattg4321 said:

Either way, that type F RCD may not fit easily in your consumer unit, there are a few things to consider

Although din rails are standard it seems that the dimensions and positions of the apertures in CUs are not (maybe they have been standardised since my cu was fitted in 2010, I really don't know).

 

My personal experience of electricians is that they vary a lot in their interpretation of what is possible/legal!  As I mention above your installer may be happy for you to provide the circuit which may be an option if they won't do what you want but another electrician will (obviously always assuming it's safe).

[Marvin]

Our ASHP installation instructions stipulated a Type B and we were advised to ensure a healthy size of cable to avoid voltage loss as we were told that the ASHP was sensitive to voltage drop. Four year and no problems so far...  

 

M.

[JamesPa]

32 minutes ago, Marvin said:

Our ASHP installation instructions stipulated a Type B and we were advised to ensure a healthy size of cable to avoid voltage loss as we were told that the ASHP was sensitive to voltage drop. Four year and no problems so far...  

 

M.

How long was the cable?  Unless it was very long this seems implausible (provided the cable met the iet wiring regs), not least because they must cope with both UK and mainland Europe mains voltages and their tolerances.

 

For the avoidance of doubt I'm not questioning the requirement for a healthy size of cable, only the explanation for why its required. 

Edited July 20 by JamesPa

[sharpener]

29 minutes ago, JamesPa said:

your installer may be happy for you to provide the circuit

 

On a early site visit the head of the firm agreed they would fit extra mcbs to my CU and this was echoed on drawings I sent them 6 weeks ago. He didn't mention anything about a Type B RCD then or at any other time.

 

Better I suppose it comes to light now than when their electrician turns up the week after next with the wrong bits.

 

It is not straight forward because (as previously explained to them) the HP has to be fed from the 50A battery inverter output. It can't just be teed off the meter tails with Henley blocks which seems the usual approach. I have also got a DIN rail mounted meter which needs to go in the circuit somewhere. I went through all this with the previous people (who failed to install before Easter as they had promised) and they didn't mention anything about a Type B RCD either. Perhaps some regulatory body has recently issued new guidance/reminder.

 

48 minutes ago, JamesPa said:

Although din rails are standard it seems that the dimensions and positions of the apertures in CUs are not

 

 

The new meter goes on the rails and fits correctly through the aperture on the Crabtree Starbreaker CU, which was there in 2007 when we bought the house, maybe I have been lucky. Unfortunately they don't do a Type B which is odd because of their increasing use on EV charging point circuits.

 

5 minutes ago, JamesPa said:

Unless it was very long this seems implausible (provided the cable met the iet wiring regs).

 

Agreed. If to Euro standards it should work off anything 230V +/- 10%. UK supplies are for historical reasons 230 +10% -6% so at the upper end. And I see 250V at some point most days so very close to the highest permissible voltage. Fortunately it is a stiff supply so my PV doesn't push it up noticeably.

 

 

[Mattg4321]

8 hours ago, sharpener said:

 

On a early site visit the head of the firm agreed they would fit extra mcbs to my CU and this was echoed on drawings I sent them 6 weeks ago. He didn't mention anything about a Type B RCD then or at any other time.

 

Better I suppose it comes to light now than when their electrician turns up the week after next with the wrong bits.

 

It is not straight forward because (as previously explained to them) the HP has to be fed from the 50A battery inverter output. It can't just be teed off the meter tails with Henley blocks which seems the usual approach. I have also got a DIN rail mounted meter which needs to go in the circuit somewhere. I went through all this with the previous people (who failed to install before Easter as they had promised) and they didn't mention anything about a Type B RCD either. Perhaps some regulatory body has recently issued new guidance/reminder.

 

 

 

The new meter goes on the rails and fits correctly through the aperture on the Crabtree Starbreaker CU, which was there in 2007 when we bought the house, maybe I have been lucky. Unfortunately they don't do a Type B which is odd because of their increasing use on EV charging point circuits.

 

 

Agreed. If to Euro standards it should work off anything 230V +/- 10%. UK supplies are for historical reasons 230 +10% -6% so at the upper end. And I see 250V at some point most days so very close to the highest permissible voltage. Fortunately it is a stiff supply so my PV doesn't push it up noticeably.

 

 

If you have a Crabtree starbreaker board you are very limited in options. You won’t be able to put a Type B or Type F RCD in there. Or it is at least very unlikely. If you need a din mounted meter that may not fit either. They don’t have a totally standard din rail due to the pin busbar system. Great units though, I’d fit them all the time except for the price. 

[Marvin]

Hi @JamesPa

 

9 hours ago, JamesPa said:

How long was the cable?  Unless it was very long this seems implausible (provided the cable met the iet wiring regs), not least because they must cope with both UK and mainland Europe mains voltages and their tolerances.

 

For the avoidance of doubt I'm not questioning the requirement for a healthy size of cable, only the explanation for why its required. 

This comment was from the view point of my limited understanding.

The cable is only about 6 metres long. Technically a 1.5mm multicore could have been installed, but we were advised to use larger because of possible voltage drop during startup?  I notice on the most recent Coolenergy ASHP's there indicating a type C MCB, so things have moved on.

[JamesPa]

9 hours ago, sharpener said:

11 hours ago, JamesPa said:

your installer may be happy for you to provide the circuit

 

On a early site visit the head of the firm agreed they would fit extra mcbs to my CU and this was echoed on drawings I sent them 6 weeks ago. He didn't mention anything about a Type B RCD then or at any other time.

 

Better I suppose it comes to light now than when their electrician turns up the week after next with the wrong bits.

 

It is not straight forward because (as previously explained to them) the HP has to be fed from the 50A battery inverter output. It can't just be teed off the meter tails with Henley blocks which seems the usual approach. I have also got a DIN rail mounted meter which needs to go in the circuit somewhere. I went through all this with the previous people (who failed to install before Easter as they had promised) and they didn't mention anything about a Type B RCD either. Perhaps some regulatory body has recently issued new guidance/reminder.

 

11 hours ago, JamesPa said:

Although din rails are standard it seems that the dimensions and positions of the apertures in CUs are not

 

 

The new meter goes on the rails and fits correctly through the aperture on the Crabtree Starbreaker CU, which was there in 2007 when we bought the house, maybe I have been lucky. Unfortunately they don't do a Type B which is odd because of their increasing use on EV charging point circuits.

Hmm

 

All, I suspect, messy enough that the electrician has decided 'I cant be bothered with this'. 

 

I'm not an electrician myself, but can read, think and even do ohms law.  I have had variable success arguing technicalities with electricians who propose to do (or have already done) something apparently silly or, more usually, tell me that the bleeding obvious way to do something is not valid but without explaining why.*

 

If attempting to resolve it by amicable discussion doesn't work, my usual approach is to ask them which specific regulation they are referring to to justify their position.  Obviously this winds the less able ones up, who then resort to the usual trade bluster to cover up their ignorance and then dig their heels in.  The more able ones respond positively, and either rethink (yes it does happen) or point to the regulation in question.  The most able ones of course have already worked out what the customer would ideally want, have worked out whether there is a genuine reason to object or whether there is something even better they could propose, and if there is not come forward in the first instance with a sensible proposal.  However they appear to be pretty rare, at least in my part of the country.

 

As suggested above see what Vaillant say, but their electrician may have taken one look at the problem and decided that separation was the only way they were prepared to handle it.  

 

Houses seem rapidly to be approaching the point of having 'no user serviceable parts inside'; too few people want to touch the existing services for far of downstream claims.  In many ways I can understand it since people will all too frequently hold a tradesman responsible for anything even faintly associated with a job they have done, however implausible the connection is.  However in the end we all lose from this approach.

[JohnMo]

Just read this and then looked at my install, it has type B MCB and Type A RCDs. So I need to upgrade to type B RCD I believe.

 

https://professional-electrician.com/technical/18th-edition-rcd-requirements-for-heat-pump-installations-doepke/

[JohnMo]

Also found this in their technical guide. This requirement may be driving the additional CU so the heat pump can have a Type B RCD and the rest of the house etc a Type A.

 

[sharpener]

3 hours ago, Marvin said:

I notice on the most recent Coolenergy ASHP's there indicating a type C MCB, so things have moved on.

 

Much confusion has been caused by the authorities allowing the use of the word "type" for two entirely different concepts

 

For mcbs (miniature circuit breakers) and rcbos (residual current breakers with overload protection) the Type is the overload tripping characteristic, with the most widely stocked being Type B: immediate tripping on 3 to 5 times rated current (most domestic situations) and Type 😄 5 to 10 times (small motors and HPs).

 

OTOH for rcds (residual current devices) the Type is the level of protection against DC fault currents with AC being the least and then A, F and B as per the diagram here. As noted above type F appear to be adequate for single phase VFDs, but don't seem to be specified by HP mfrs, even for models which do not come in a three-phase version.

 

 

Edited July 21 by sharpener

[JamesPa]

3 hours ago, JohnMo said:

Also found this in their technical guide. This requirement may be driving the additional CU so the heat pump can have a Type B RCD and the rest of the house etc a Type A.

 

Makes sense.

 

Does this sentence from your previous post suggest its a matter for the HP manufacturer to specify?

 

"The characteristics of the HP inverter, and the location of the fault within the equipment, determine the characteristics of the residual current.

 

The selection of the Type of RCD must consider the fault current scenarios identified in the standards and by the HP manufacturer, in their design risk assessment documentation.

Electrical installers do not have access to the HP manufacturer’s inverter design characteristics and consequently cannot make the decision to use Type F in place of Type B, without the agreement of the HP manufacturer."

 

[sharpener]

4 hours ago, JamesPa said:

All, I suspect, messy enough that the electrician has decided 'I cant be bothered with this'. 

 

Yes, subject to them providing the functionality I need (and have discussed with his boss), which is to run the HP from the battery system not the incoming supply.

 

So my favoured approach to the current issue is to put a 32A Type C mcb in the existing board, and then take a 4 sq mm cable to a sub-board with their Type B RCD, the meter and a 6A mcb for the control circuitry inside it. Avoids the need for any heavy gauge meter tails too. Will phone them tomorrow with this proposition.

 

16 hours ago, JamesPa said:

Although din rails are standard it seems that the dimensions and positions of the apertures in CUs are not (maybe they have been standardised since my cu was fitted in 2010, I really don't know).

 

6 hours ago, Mattg4321 said:

If you have a Crabtree starbreaker board you are very limited in options. You won’t be able to put a Type B or Type F RCD in there. Or it is at least very unlikely. If you need a din mounted meter that may not fit either. They don’t have a totally standard din rail due to the pin busbar system. Great units though, I’d fit them all the time except for the price.

 

Yes, hence I have standardised on Starbreaker fittings, there are 3 sub-boards doing various things and it has allowed me to swap accessories as the system has evolved.

 

I already have their 4 module mini CUs housing an MK two-module SPD, a two-module Eastron meter and a different single module meter, the busbar doesn't get in the way. Just checked, it will also take the entire innards from a Proteus garage unit dating from 1995, so I have high hopes it would accomodate this Proteus Type B RCD though £200 is a hell of a price.

 

Personally I don't see the problem in assessing mechanical and electrical fit for myself, but the mfrs of course say they won't warrant this use, largely out of self-interest. Electricians are after all happy to use unbranded generic DIN enclosures, what is the difference?

 

[Mattg4321]

19 minutes ago, sharpener said:

 

Yes, subject to them providing the functionality I need (and have discussed with his boss), which is to run the HP from the battery system not the incoming supply.

 

So my favoured approach to the current issue is to put a 32A Type C mcb in the existing board, and then take a 4 sq mm cable to a sub-board with their Type B RCD, the meter and a 6A mcb for the control circuitry inside it. Avoids the need for any heavy gauge meter tails too. Will phone them tomorrow with this proposition.

 

 

 

Yes, hence I have standardised on Starbreaker fittings, there are 3 sub-boards doing various things and it has allowed me to swap accessories as the system has evolved.

 

I already have their 4 module mini CUs housing an MK two-module SPD, a two-module Eastron meter and a different single module meter, the busbar doesn't get in the way. Just checked, it will also take the entire innards from a Proteus garage unit dating from 1995, so I have high hopes it would accomodate this Proteus Type B RCD though £200 is a hell of a price.

 

Personally I don't see the problem in assessing mechanical and electrical fit for myself, but the mfrs of course say they won't warrant this use, largely out of self-interest. Electricians are after all happy to use unbranded generic DIN enclosures, what is the difference?

 

I wouldn’t do it personally and I suspect most electricians will say the same. Especially when you have another option as detailed above that should be fine subject to not overloading existing unit. (MCB from current unit, via RCD in separate enclosure).

There’s a good article here explaining things. 

https://electrical.theiet.org/wiring-matters/years/2021/87-september-2021/myth-busters-7-out-with-the-old-in-with-the-new/

 

This is probably the important bit. Why would any good electrician want to take that risk?

 

“In summary, can you mix devices in distribution boards (including consumer units)? Yes, you can. But you need to seek assurance from the manufacturer of the original assembly that the devices will be compatible, or conduct your own study to ensure the requirements are met. In the words of BEAMA, ‘The installer has responsibility to act “with due care”. If this is not done then there is a probability that, in the event of death, injury, fire or other damage, the installer would be accountable under Health and Safety legislation.’”

 

 

Edited July 21 by Mattg4321

[sharpener]

1 hour ago, Mattg4321 said:

“In summary, can you mix devices in distribution boards (including consumer units)? Yes, you can. But you need to seek assurance from the manufacturer of the original assembly that the devices will be compatible, or conduct your own study to ensure the requirements are met. In the words of BEAMA, ‘The installer has responsibility to act “with due care”. If this is not done then there is a probability that, in the event of death, injury, fire or other damage, the installer would be accountable under Health and Safety legislation.’”

 

And what if you want to add say a DIN rail meter to an existing board? AFAIK Eastron don't sell breakers or enclosures and Crabtree et al do not sell meters. Not readily available at trade counters anyway.

BEAMA are not a regulatory body, they are the trade association with the specific task of protecting their own members' interests (I had a lot of dealings with them when I was at the DTI).

 

So no-one is going to state that another's components are compatible even if that is manifestly the case. Crabtree probably wouldn't even tell you you can use their Loadstar accessories in a Starbreaker enclosure (but not the other way round). It's typical protectionist behaviour, though nowhere near as bad as battery drill manufacturers all having different incompatible batteries.

 

/rant

 

[Dave Jones]

12kw is massive. trying to heat buck house ?

[Dillsue]

1 hour ago, sharpener said:

So no-one is going to state that another's components are compatible even if that is manifestly the case. Crabtree probably wouldn't even tell you you can use their Loadstar accessories in a Starbreaker enclosure (but not the other way round). It's typical protectionist behaviour, though nowhere near as bad as battery drill manufacturers all having different incompatible batteries.

They have to CE/UKAS mark the products which will involve testing. They can't test their boards with every conceivable DIN rail mounted product from around the world so they can't advise to fit anything other than their own kit, which they have tested. They'd knowingly invalidate the CE/UKAS certification if they endorsed fitting any untested kit.

[Dillsue]

On the subject of RCDs, dont forget they are secondary protection to a properly designed and installed electrical system. Primary focus should be on a decent install.

[sharpener]

On 21/07/2024 at 07:51, Mattg4321 said:

If you have a Crabtree starbreaker board you are very limited in options.

 

Do you have a view on fitting a 32A Loadstar mcb into a Starbreaker board @Mattg4321? AFAICS they are 100% mechanically compatible and are of course made by the same manufacturer.

 

If I did that I could feed it via a jumper from the incoming (line) side of the Type A RCD rather than from the busbar, so then the HP current would not go through the Type A unit at all and then there would be no risk of it being blinded.

 

(Installer says he has been told Electrium will launch Wylex Type B RCDs later this year and so probably Crabtree ones in 2025, however that is not much help to me.)