It sounds like a very old installation that should be surveyed by an electrician at this stage.
RCDs were optional in Ireland on installations before about 1980, but unlike many countries, rules around earthing were very robust and wet areas had very limited electrical devices.
They were initially mandated on socket circuits only, and considerably earlier than the UK, but older installations may not have them.
When the UK mandated them, they leap frogged ahead for a while, requiring them on all circuits, Irish regs did similar in a slightly later revision to regs.
You can sometimes find RCDs on older installations installed as an optional or retrofitted thing too.
If there is an RCD on the board is would be very obviously there. You’ll see a device labelled RCD (or sometimes the older ELCB terminology was used as a generic term on the handwritten labels).
It should be a wider module, with a test button and mention RCD or residual / differential and have 30mA printed on it somewhere. Usually they’ve a little circuit diagram on the module.
If it’s a very large device marked ELCB next to the meter, you’re likely looking at an extremely old TT installation which should be reviewed.
Diazed (ceramic bottle shaped screw in) fuses remained in common use in Ireland into the 1980s and some rather conservative electricians seemed to prefer them and took a long time to trust MCBs. So you can often find modern DIN rail boards with an RCD yet have Diazed fuse modules on the final circuits.
Irish installations also always have an extra main fuse on the consumer side, usually rated at 63 amps.
That’s often a Diazed fuse or a Minized fuse switch module on the distribution board.
This is in addition to the sealed service fuse, owned by ESB networks, which may look similar to the British type, or can be a Diazed module in a see though box with a seal in some installations.
I’m not quite sure of the date that RCDs were mandated in Ireland, but it was much earlier than the UK. They started to appear in the 1970s and were mandated on socket circuits by the early 80s. The logic for excluding lighting circuits was shared neutrals and a notion that you could be “plunged into darkness” as installations tended to just have one RCD across a whole row.
The current regs extend that to pretty much all circuits and installers now make a lot more use of individual RCBOs.
The bathroom regulations also tightened a lot regarding RCD coverage for lighting. The old regs, much like in the UK, relied a lot on excluding electrical devices and wall switches from bathrooms entirely and very thorough Earth bonding. That still applies, but they’ve harmonised to a fairly conservative interpretation of IEC and CENELEC norms, adding mandatory RCDs.
The most recent regs also add recommendations for AFCIs (Arc fault circuit breakers) for sleeping areas and so on.
In general though it sounds like you’re looking at an older installation which may need to be modernised.
The biggest concern would be pre-PVC wiring which can deteriorate, but also just old DIY work and inadequate circuits for modern needs.
Definitely get a survey carried out of it’s that old.
The current regs are IS 10101 : 2020 a 700 page epic classic, which replaced the ET 101 (4th edition) - if you fancy a long read!!
Also bear in mind that other than like for like replacements and simple extensions of existing circuits, all other works and all bathroom works in Ireland must be carried out by a licensed electrician. You can run into serious issues with insurance and even legal consequences these days for DIY work.
Basically the consumer unit / distribution board and any complicated wiring is out of bounds.
