there is a DB board fed from a centre tapped transformer only on single pole breakers. The board feeds instrumentation. Is there any issue changing it to 110v and tie the neutral to earth there is no socket outlets fed on this so can’t see it as an issue?
It says 5s disconnection times for the 55v centre tapped would it still be the same for 110v if I doubles the ZS values say a type b 10 amp is 1.05 ohms so 2.10 ohms I for a 110v to earth?
Sounds about right to me.
As a sanity check using the same method for 230V would give 1.05Ω / 55V * 230V which gives 4.39Ω which seems to about match Table 41.3's 4.37Ω for a B10 for 5s disconnection time at 230V (allowing for some rounding in the printed numbers). In all cases you just need to ensure the MCB sees enough current to trip within the required time - and that current is the same regardless of voltage - so you just need to adjust the resistances so you get the same current for differing voltages (Ohm's Law).
It says 5s disconnection times for the 55v centre tapped would it still be the same for 110v if I doubles the ZS values say a type b 10 amp is 1.05 ohms so 2.10 ohms I for a 110v to earth?
Sounds about right to me.
As a sanity check using the same method for 230V would give 1.05Ω / 55V * 230V which gives 4.39Ω which seems to about match Table 41.3's 4.37Ω for a B10 for 5s disconnection time at 230V (allowing for some rounding in the printed numbers). In all cases you just need to ensure the MCB sees enough current to trip within the required time - and that current is the same regardless of voltage - so you just need to adjust the resistances so you get the same current for differing voltages (Ohm's Law).
