At the home town house , the electrical water heater doesn't heat up as hot as usual since the heating knob at the middle would be enough but it's still warm or luke warm.
Since , call back home town , elderly doesn't know much about water heater safety neither do i since I am not in electrical field.
Also old 30 years housing doesn't have any dedicated RCCB or RCBO.Just the main DB MCB some kind of SMC brand.

1.The water heater is like over 10 years old with ELCB
2.Not hot even on middle
3.I ask them to take a picture of the MCB but the heater is quite high so i ask for the model and details
4.Possible to repair ? or change a new one ?

Thank you sharing knowledge.

May I know:
1) why ST allows 100mA main RCD (or even 300mA as I saw in some houses) when >50mA leakage is fatal?

2) when RCD ages, as in spring weakens, will it be easier to fail safe (trip off) or it doesn't trip easily? I'm thinking that if it's the former, it's safer albeit mote troublesome.

Not missing but busy.

I apologize for not replying.The updates

1.Sunday no technician.So I suggest to increase the heater to 75% hotter ( basic 50% before it get less hot ) and spray into the water tub.I confirm that the water is not hot and I forgot to mention , the water flow is also slow.
2.Monday call 3 technician , all 3 said no need to put extra RCCB outside since all new or old water heater have Elcb build in.All 3 technician said something stuck cause it to get water not hot.
3.Tuesday , Call again to main joven and panasonic technician for repair but need to book the time next week and the cs said go to electrical shop and choose a model
4.Yesterday plan to go out and have a look for the model , heavy rain , didn't go out.
5.Today , see whether still rain or not at the evening. as what Momo33 said , buy water heater first , then only find a good technician.
All technician also didn't recommend to have an extra RCCB , i really don't know why as they said all buid in, no need anything extra.

As some technician told us better change but some said can fix.Most of them doesn't have cert or just normal electrical technician.
I also don't know which decision to choose where the water heater is less hot and water flow very slow.If water flow slowly should be much hotter.
Anyone know what is the reason of part failure when water heater not getting hot ?

Now finding a good water heater but budget not over rm400.
Any suggestion for DH-3MS1 and DH-3N series ?

Thanks , will reply to you all but I don't really understand much on those DB and model and brand.I need to research more into it.SOrry for not updating in time and thank you again

No, ST is not recommending specifically = 100mA whole house as the only RCD.

Like that, all the 13A SSO is illegal.

Yes I know can install 100mA whole house and another 30mA for 13A SSO.

But when MS1979 COP already mentioned maximum allowed tolerance = a 30mA settle all for whole house and fully compliant

Q: Why waste money with 100mA RCD whole house when it is largely redundant in 2022 scope of work - no more fluorescent lamps; waste DB box space
Or it is a ploy by RCD maker to sell more RCD?

Hi ceo. I've got a question on point 3 of yours. How do you add the 10ma RCD under the 30ma/100ma RCD? my electrician told me if I do a hierarchy level that will cause side effects. eg. they trip each other off. so he told me to install flat level instead. eg. the rcds are totally isolated.