RCBO for Growatt SPH 3000

[monkeybadger]

Hi,
I've a Growatt SPH 3000 hybrid inverter and 3KW Growatt Battery. I'm getting my Consumer unit changed and my electrician is trying to understand what type of RCBO is required for this inverter - Type A, F or B. He and I, have contacted Growatt, but not had any replies. The documentation doesn't specify anything in particular.

Does anyone know what type would be required?

Thanks.

 

[binky]

Hi,
I've a Growatt SPH 3000 hybrid inverter and 3KW Growatt Battery. I'm getting my Consumer unit changed and my electrician is trying to understand what type of RCBO is required for this inverter - Type A, F or B. He and I, have contacted Growatt, but not had any replies. The documentation doesn't specify anything in particular.

Does anyone know what type would be required?

Thanks.

If the cabling allows you don't need a RCBO at all.

 

[monkeybadger]

The documentation does state there should be a breaker. At the minute it is going into a type A 32 A MCB which is part of a shared RCD.

 

[Geoff1946]

It should not share any RCD.

 

[monkeybadger]

Yep, which is one of the reasons that I'm getting the board updated and individual RCBOs installed, but not sure on the type of RCBO to use.

 

[Murdoch]

Tell the electrician to fit a mcb if the cable installation methods allows

A little surprised the OEM isn’t giving this or any advice

 

[wytco0]

If the cabling allows you don't need a RCBO at all.

I am in a similar position as the OP, also with a Growatt SPH inverter. I have been told that it can be installed with an MCB and no RCD/RCBO but I havnt seen anything that explains why this is the case, I am interested in what you meant my 'If the cabling allows you don't need a RCBO at all'

My inverter is very close to the CU and we are planning to install its MCB in a small sub board, is that permitted?

Thanks

 

[binky]

I am in a similar position as the OP, also with a Growatt SPH inverter. I have been told that it can be installed with an MCB and no RCD/RCBO but I havnt seen anything that explains why this is the case, I am interested in what you meant my 'If the cabling allows you don't need a RCBO at all'

My inverter is very close to the CU and we are planning to install its MCB in a small sub board, is that permitted?

Thanks

If for some strange reason you decided to plaster cables less than 50mm deep in a wall then RCD is compulsory unless mechanically protected.

 

[wytco0]

If for some strange reason you decided to plaster cables less than 50mm deep in a wall then RCD is compulsory unless mechanically protected.

OK Thanks so if the cable is in a surface mounted plastic trunk from the CU to the Inverter which is about a meter away, would that be OK for 'Mechanical Protection' I guess the sparky could use SWA but that seems excessive for a short run in the garage.

 

[binky]

OK Thanks so if the cable is in a surface mounted plastic trunk from the CU to the Inverter which is about a meter away, would that be OK for 'Mechanical Protection' I guess the sparky could use SWA but that seems excessive for a short run in the garage.

Mechanical protection within a plastered wall, such as steel conduit. You don't need RCD for surface cable run like you describe.

 

[Joules]

Hi,
I've a Growatt SPH 3000 hybrid inverter and 3KW Growatt Battery. I'm getting my Consumer unit changed and my electrician is trying to understand what type of RCBO is required for this inverter - Type A, F or B. He and I, have contacted Growatt, but not had any replies. The documentation doesn't specify anything in particular.

Does anyone know what type would be required?

Thanks.

The type of RCD can be found in the Growatt Installation & Operational Manual 6.2 Wiring AC Output. Type A 300mA 2 Pole can be used but a 500mA should be considered.

There is no galvanic isolation between AC and DC sides which can give rise to a continuous DC leakage current. The inbuilt RCD required by IEC regulation is Type B if Ginlong Solis inverters are anything to go by.

 

[wytco0]

The type of RCD can be found in the Growatt Installation & Operational Manual 6.2 Wiring AC Output. Type A 300mA 2 Pole can be used but a 500mA should be considered.

There is no galvanic isolation between AC and DC sides which can give rise to a continuous DC leakage current. The inbuilt RCD required by IEC regulation is Type B if Ginlong Solis inverters are anything to go by.

Yes I have seen that although its not in the printed version of my manual, this also makes me think that the inverter is galvanically isolated as Type A does not protect against smooth DC. Type A protection is against pulsed DC.

I just noticed that the document you linked to is for a different inverter but the wording is the similar for the SPH series.

 

[Joules]

Hi,
I've a Growatt SPH 3000 hybrid inverter and 3KW Growatt Battery. I'm getting my Consumer unit changed and my electrician is trying to understand what type of RCBO is required for this inverter - Type A, F or B. He and I, have contacted Growatt, but not had any replies. The documentation doesn't specify anything in particular.

Does anyone know what type would be required?

Thanks.

Let me put myself in your position only this time I’m going to install a Ginlong Solis inverter. Fortunately, Solis provide a Topology Declaration which says that an inbuilt RCD is present without saying what type it is and whilst directing the use of a 100mA Type A RCD on the incoming supply.

At this point I consult MCS ISBN 978-0-9574827-1-5 and section 2.3.2 RCD Protection on Page 44 which concludes by saying “Where any doubt exists about the capability of the inverter to prevent d.c. fault currents entering the a.c. side of the system then the manufacturer shall be consulted.”

I write to Solis and they come back to say it is Type B.

Although given the go ahead to fit a Type A in the consumer unit I instead choose to install a Type B as IEC 62423:2009 requires. This is because the customer may change the type of inverter and doubts might exist especially where the manufacturer has not provided an RCD Topology Declaration.

MCS ISBN 978-0-9574827-1-5 Page 46 provides an RCD Decision Tree however, the use of a Type A RCD should not infer electrical (galvanic) isolation between AC and DC sides of an inverter without evidence of the actual topology. When in doubt fit a Type B upstream of a Type A.

 

[wytco0]

Let me put myself in your position only this time I’m going to install a Ginlong Solis inverter. Fortunately, Solis provide a Topology Declaration which says that an inbuilt RCD is present without saying what type it is and whilst directing the use of a 100mA Type A RCD on the incoming supply.

At this point I consult MCS ISBN 978-0-9574827-1-5 and section 2.3.2 RCD Protection on Page 44 which concludes by saying “Where any doubt exists about the capability of the inverter to prevent d.c. fault currents entering the a.c. side of the system then the manufacturer shall be consulted.”

I write to Solis and they come back to say it is Type B.

Although given the go ahead to fit a Type A in the consumer unit I instead choose to install a Type B as IEC 62423:2009 requires. This is because the customer may change the type of inverter and doubts might exist especially where the manufacturer has not provided an RCD Topology Declaration.

MCS ISBN 978-0-9574827-1-5 Page 46 provides an RCD Decision Tree however, the use of a Type A RCD should not infer electrical (galvanic) isolation between AC and DC sides of an inverter without evidence of the actual topology. When in doubt fit a Type B upstream of a Type A.

Thanks Joules very interesting and the links are very handy.

One of the problems that my electrician made was that there are few if any Type B RDC/RCBOs available especially with the required mA rating. Do you have any links to suitable products.

 

[binky]

Let me put myself in your position only this time I’m going to install a Ginlong Solis inverter. Fortunately, Solis provide a Topology Declaration which says that an inbuilt RCD is present without saying what type it is and whilst directing the use of a 100mA Type A RCD on the incoming supply.

At this point I consult MCS ISBN 978-0-9574827-1-5 and section 2.3.2 RCD Protection on Page 44 which concludes by saying “Where any doubt exists about the capability of the inverter to prevent d.c. fault currents entering the a.c. side of the system then the manufacturer shall be consulted.”

I write to Solis and they come back to say it is Type B.

Although given the go ahead to fit a Type A in the consumer unit I instead choose to install a Type B as IEC 62423:2009 requires. This is because the customer may change the type of inverter and doubts might exist especially where the manufacturer has not provided an RCD Topology Declaration.

MCS ISBN 978-0-9574827-1-5 Page 46 provides an RCD Decision Tree however, the use of a Type A RCD should not infer electrical (galvanic) isolation between AC and DC sides of an inverter without evidence of the actual topology. When in doubt fit a Type B upstream of a Type A.

So lets assume some DC leakage, if not sharing an issue RCD with another cct what issues arise ?

 

[Joules]

Thanks Joules very interesting and the links are very handy.

One of the problems that my electrician made was that there are few if any Type B RDC/RCBOs available especially with the required mA rating. Do you have any links to suitable products.

Thank you. Choosing an inverter RCD is a blind spot, I know it was for me so I hope it helps readers. As to what you fit, well its down to cost, Type B 2 Pole RCD at 500 mA are very expensive compared with Type A, its really between you and your electrician to decide the best way forward on cost.

The reason why Chinese Inverters are so attractive on price is that invariably they lack high frequency transformers that provide isolation. Now had you fitted an SMA inverter galvanic isolation comes as standard as do Type A RCD the best of both worlds and better still they are 30mA.

Roland W an expat Austrian Electrical Engineer living in Thailand has a YouTube piece on the merits of fitting Type B RCD on the AC side of inverters. Technically, you don’t need to fit an RCD were there is isolation but you must perform a Zs loop impedance test to determine whether protection is adequate. By fitting an RCD this step can be avoided.

 

[binky]

Roland W an expat Austrian Electrical Engineer living in Thailand has a YouTube piece on the merits of fitting Type B RCD on the AC side of inverters. Technically, you don’t need to fit an RCD were there is isolation but you must perform a Zs loop impedance test to determine whether protection is adequate. By fitting an RCD this step can be avoided.

Zs is a compulsory test for all new circuits as part of ensuring compliance with BS7671

 

[wytco0]

Following a tip for another member here I found this Growatt RCD selection statement this seems to confirm inverter internal protection and that only a Type A RCD is needed, if required by local standards.

I will speak to my sparky but I am inclined to got for a MCB only as I believe this is allowed with surface cable for the short distance between the Inverter and its own small CU.

 

[binky]

Following a tip for another member here I found this Growatt RCD selection statement this seems to confirm inverter internal protection and that only a Type A RCD is needed, if required by local standards.

Local standards IE BS7671 says MCB.

The whole bit about leaking DC down the cct and confusing RCDs is linked to DC currents confusing shared RCDs. Most modern appliances have electronics protected by ' smoothing ccts' which leak a little leccy down the earthing. Lots of DC leakage from lots of appliances or IT equipment can confuse RCDs apparently. Your solar/ battery needs to be on it's own cct not sharing any form of RCD protection with any other cct, so the DC leakage is irrelevant, and if you did have serious fault within the inverter, it will probably do something very scary involving lots of conversion of leccy into smoke and blow internal and external fuses.

 

[Joules]

So lets assume some DC leakage, if not sharing an issue RCD with another cct what issues arise ?

Assuming the Growatt has an inbuilt Type B RCD it would sense continuous DC leakage and disconnect the inverter from the AC supply side so no interaction. Anyway, the rule is exclusively, only one RCD per inverter. Its AC side must not be shared with any other electrical device.

Following a tip for another member here I found this Growatt RCD selection statement this seems to confirm inverter internal protection and that only a Type A RCD is needed, if required by local standards.

I will speak to my sparky but I am inclined to got for a MCB only as I believe this is allowed with surface cable for the short distance between the Inverter and its own small CU.

Have a look at this affordable Austrian RCBO Combined MCB/RCD (RCBO) 1+N, AMPARO 10kA, B 16A,100mA, Typ A not seeing a Type B out there.