Type B rcd availability

No, but I am wondering:

1 why 1 x 100 A rather than 3 x 32 A RCBOs?

2 why type B - is that what the VSD manufacturers require?

3 if it's to go in a DB, are you not confined to whatever the manufacturer has to offer?

Depending on the depth of pockets

Schrack 100mA 4 Pole B type RCD looks like it might do the right sort of thing  also available in ‘bigger’ current and price tag . I've not used one - things a bit like it but not that.

Why does the submain need 100mA protection - is the supply TT and it is armoured ? If soft cable I'd have expected 30mA or nothing.

Do beware of   ‘B type’  RCBOs - the ‘B’ refers to the thermal MCB like part , the RCD is usually like an A or AC, so might be ‘blinded’ by DC.

I assume you have checked with the makers that the B type is really what is needed given the eye-watering costs, you do not want to over specify.

Mike.

Try CHINT - I got a type B (as in RCD characteristic) for around a hundred quid.

Have a look at their NL210 range.

Are you certain you need an RCD at all? What exactly are you attempting to protect against? Unless you can directly answer this question with a credible difficulty, you do not need an RCD of any type, particularly a type B. You need to understand that a motor winding fault does not produce a DC fault of any kind, this requires a short from an internal point in the circuit to Earth. The drive senses all kinds of output faults and shuts off the power to the load, so you are looking at a very unlikely fault indeed to need a type B, and at 100mA  it cannot be for shock protection. Figure A53.1 shows a number of possible faults, but none of these are in any way connected to the load. Please provide full information as above. 

I think it's the mantra of blindly following ‘Manufacturer instructions' (As required also by BS7671) which are generally a one-size-fits-all ***-covering exercise on the part of the manufacturer. Sometimes it is just easier to meet their requirements than to take time to think it through.

This is on a farm and as such rcd protection is required on all circuits. the db that the inverters are going to be supplied from has other existing circuits connected which also require rcd protection. The sub main requires rcd protection as its a farm installation. In regards to ‘does it really need a type b rcd’, I can confirm that it does. I installed an identical inverter a while back and it tripped both an ‘a’ and an ‘ac’ rcd. Fortunately the mcb provided adequate fault protection in this instance so was able to remove the existing rcd

You need to understand that a motor winding fault does not produce a DC fault of any kind, this requires a short from an internal point in the circuit to Earth. The drive senses all kinds of output faults and shuts off the power to the load, so you are looking at a very unlikely fault indeed to need a type B, and at 100mA  it cannot be for shock protection. Figure A53.1 shows a number of possible faults, but none of these are in any way connected to the load. 

What about earth faults within the inverter itself? Granted I'd sort of expect ‘disconnection by exploding electronic component' if the fault was downstream of any kind of rectifier but perhaps that's not quite by the book.

   - Andy. 

Baldyhugh: 
I installed an identical inverter a while back and it tripped both an ‘a’ and an ‘ac’ rcd. 

Baldyhugh, thank you for the clarifications. It looks like Mike's eye-wateringly expensive device is what is required.

I am not surprised by either the tripping on types a and ac, or the price.

Hang on, this “tripping of type A or AC” is NOT why you fit a type B! A type B should trip just as a type A or AC does, it is only that it is not STOPPED from NOT tripping by DC faults. You have a problem here that is probably inrush rather than DC faults. It is possible that type Bs are more resistant to this unspecified parameter, but there is no reason not to use a type AC or A with a time delay (S type). A type B should see a single half-cycle surge as a DC fault, but from your comments does not, perhaps the inrush lasts several cycles, although I don't quite see why it should unless there is some internal series resistance. 

Andy, whilst it is theoretically possible that there could be an internal DC short to Earth, surely reducing or eliminating this possibility would be a DESIGN requirement? Are we simply making the wiring regulations correct improper designs (again - EVs)? I have an invertor where this is not possible by any reasonable mechanism except poking a bare wire into the equipment. Have we got completely to the “idiot-proof” point for everything? Surely if I poke wires into things I should expect some kind of risk? Note that such a short would pop the CPD due to excess current, or perhaps the short would be in the range where the CPC is raised to a dangerous voltage but not quite blow the CPD? You may like to calculate that range for a 32A supply and a 2kW inverter. Is it credible?