Type B rcd availability

Hang on, this “tripping of type A or AC” is NOT why you fit a type B! 

Well said Dave.

I had a customer, a friend. New build extension, Granny flat type thingy if you will. From Cut out to switchfuse  then to it`s own DB , couple of rings, couple of lighting circuits , a couple of radials, pretty bog standard. RCD protection of course. Removed RCD because it kept tripping. I discovered that on a ring final (B32) he put a car lift that was 3 phase on his single phase circuit - it had a single phase converter to run it. (surge anyone?) he ran it from output of granny flat main switch in the DB therefore the only OPD in line was the switchfuse near the cut out.

could you consider  

a slow trip (s-type) first to ride the inrush, if that is what it is causing the trips. 

Or filters if it is an HF / spikes issue. 

Or filters wired a kind of ‘open delta’ if earth “leakage ” from RFI filters is the issue. (so we put filter caps L-L-L and L-N,  but not large ones L-E. We then have a larger one NE)  Can sometimes be done after the fact by ‘neutralling’  the earth terminal of a traditional potted filter, putting it in a plastic box and taking the CPC around it.

Mike.

Another point, my lathe VSD (single-phase in 3 phase out, 4kW) does not trip a type AC ever, neither does the 3kW SP motor on my compressor on 99% of the switch on's. It does on the odd occasion which is a B nuisance, but I am not particularly inconvenienced so not worth a soft starter.

Note that the inverter is wired to start with no load, and then the motor is started with a normal control signal to the inverter which slowly accelerates the motor. It should not be used any other way, although it can act in a soft start manner on power up with some other settings.

it is only that it is not STOPPED from NOT tripping by DC faults.

Is it me or is there one too many NOTs in that?

B-types should trip on faults with a d.c. component that A- and AC-types might be blind to. 

   - Andy.

It is probably correct Andy although not very clear. I don't like the term “blinded” because that is not what happens in many cases, although the trip sensitivity may change. Type B is supposed to remain unchanged by a DC current imbalance or DC from one conductor to Earth, which causes the imbalance between the two live conductors. I have a lot of test results from this, every make is different! I have not tested a type B because they cost a lot and are a bit like hens' teeth even to borrow.

davezawadi (David Stone): 
Another point, my lathe VSD (single-phase in 3 phase out, 4kW) does not trip a type AC ever …

By contrast, mine (which is only 1.5 kW) trips an SRCD (= AC) every time, but not a type A BS 61009 RCBO. (So it stays on an ordinary socket.)