UK Old 8.5K shower wired to 30 amp fuse with no RCD. Is it still safe & ok to use?

[koko88]

8.5K shower unit is wired to plastic box consumer unit to 30 amp cartridge fuse with no RCD

It’s the original shower installed when the house was built around 1995

The shower is still fully working after all these years, never blowing the cartridge fuse before

Am I right to presume RCD wasn’t required during installation in 1995?

Is it still safe to use with no RCD or am I breaking electrical regulation law?

Do I need the shower circuit updated with RCD fitted to comply with electrical regulation law or just leave it?

All the kitchen sink, bathroom & toilet basin pipes have Earth bonding around the house so is this supplementary bonding?

 

[Vortigern]

Regulations are not law. Items that were installed that long ago are subject to the rules/regs extant when they were installed. As to modern standards it would no doubt raise eyebrows. Breaking it down a bit; 8.5 kw equates to 37 A so you are potentially running over the fuse capacity. However cartridge fuses are pretty hardy and can run over their rating up to four hours at 1.5 times their load. Certainly that was the thinking way back then. Is there any evidence of melting cables? The likliehood is that there is not and everything is fine. I have seen 7.5kw showers run on 4mm cable surprisingly nothing happened. The fuse is there to protect the cable and the rating of 6mm cable is adequately protected by a 30 A fuse. So in summary there does not appear to be a problem.
Having said that, there is every reason to consider upgrading the box and protective device to enhance the safety of the installation. A quick IR test will ensure the cable is ok and a new box and RCBO would be about £60, plus the labour (2 hours?) So for about sub £200 you could upgrade your safety. IRL you probably have a supply where the voltage is tapped at 240v, and often it is above that. Therefore the overcurrent would be around 4-5A not a lot really for the situation. If it aint broke don't fix it, but don't let that stop you from increasing the safety of having a shower!

 

[koko88]

Thanks for the reply as you get a lot of conflicting information online!

Basically, I don’t have to do a thing as when the shower unit was installed at the time by the builders, it complied with the regulations

The 6mm cable wired to the shower unit looks fine, no melting, the copper conductors have no discolouration so I presume it still safe to use without RCD protective device?

RCD protection or RCBO is just an good option and not compulsory?

I’m thinking of replacing the original shower with a newer up to date unit in the near future so probably makes sense to get the RCD or RCBO installed at the same time.

 

[MJPD29]

If it is upgraded it will be the electricians responsibility to ensure their work is complaint so will need to have rcd protection at that stage anyway

 

[brianmoooore]

Your 8.5kW shower will have that rating at 240V. The declared voltage in the UK is now 230V, so the calculated current for your shower is done using this voltage, whatever it actually might be, and works out to be just under 34A, so still overloading a 30A fuse, but not by as much as said earlier (even though, in reality, it still might be).
If your voltage was too drop to 203V while using the shower, it wouldn't be overloading the fuse at all.

 

[davesparks]

Your 8.5kW shower will have that rating at 240V. The declared voltage in the UK is now 230V, so the calculated current for your shower is done using this voltage, whatever it actually might be, and works out to be just under 34A, so still overloading a 30A fuse, but not by as much as said earlier (even though, in reality, it still might be).
If your voltage was too drop to 203V while using the shower, it wouldn't be overloading the fuse at all.

The current should be calculated at the rated voltage of the appliance.

230V is not the declared voltage, it is the nominal voltage!

 

[brianmoooore]

OK, the nominal voltage, but I disagree about calculating at the voltage shown on the appliance. They still show the headline power rating at 240V to this day, but the 230V rating is usually shown as well, in much smaller and lighter type.

 

[davesparks]

OK, the nominal voltage, but I disagree about calculating at the voltage shown on the appliance. They still show the headline power rating at 240V to this day, but the 230V rating is usually shown as well, in much smaller and lighter type.

My point is that you should calculate current for a given power rating at the given voltage.

IF you have a 240V power rating you calculate current at 240V, if you have a 230V power rating then calculate current at 230V.
It is wrong to take a 240V power rating and use that to calculate current at 230V, it will give na incorrect answer and result in the wrong size cable being used.

 

[brianmoooore]

The original box may well have had power ratings for 240V and 220V, if it is a model that was sold in the UK and in Europe.
This shower was sold when the nominal voltage was 240, but now it's 230, so, in my opinion its power should be recalculated.

 

[davesparks]

The original box may well have had power ratings for 240V and 220V, if it is a model that was sold in the UK and in Europe.
This shower was sold when the nominal voltage was 240, but now it's 230, so, in my opinion its power should be recalculated.

 

[littlespark]

Agree with above. It was deemed safe at the time of installation, and only needs upgrading if and when work is done to that circuit.

Maybe save your pennies and get a full board change so all circuits are protected by rcd/RCBO

 

[Vortigern]

As to safe to use, well I have never accepted the idea of water and electricity being used together. Never mind voluntarily standing underneath it, never really sits right with me. Personally I would want an RCD on my shower for safety reasons. If you are upgrading the shower you may find that there is 9.5kw which will mean a new circuit. You can get 7.5Kw still. In fact I am mildly surprised such an old shower is not 7.5Kw as that seemed to be all there was back then.

 

[Intoelectrics]

The 6mm cable wired to the shower unit looks fine, no melting, the copper conductors have no discolouration so I presume it still safe to use without RCD protective device?

RCD protection or RCBO is just an good option and not compulsory?

I’m thinking of replacing the original shower with a newer up to date unit in the near future so probably makes sense to get the RCD or RCBO installed at the same time

Ok, look at it this way. The purpose of the RCD/RCBO is to add additional protection in the event of a fault occurring. The basic idea being that if a fault occurred during use that could potentially kill you this additional device will operate so that you are least likely to receive an electric shock that would result in your death.

Not scare mongering, but my question is; would it be value for money in your own mind to have an additional safety device installed that would give you the piece of mind that you have done your best to prevent a potentially fatal accident in the unlikely, but real possibility of a fault occurring?

It is now, and has been for a long while, mandatory in the regulations that these type of devices are fitted for this type of installation. This is for a very good reason, as you can now appreciate.

 

[brianmoooore]

I wouldn't be at all happy with having an electric shower in my house that wasn't supplied via a 30mA RCD.

First electric shower I installed (before RCDs existed in this country) was rated at 6kW and had a bare, coiled element wire in direct contact with the water passing through it.
The people using it all survived, and one of them became my wife.

 

[Dino44]

Can a new 3 amp Mira XS manual Shower operate with a 30amp unit, from old electric shower.

 

[davesparks]

Can a new 3 amp Mira XS manual Shower operate with a 30amp unit, from old electric shower.

A 30A supply could be altered to make it suitable by an electrician yes.

 

[timhoward]

A 30A supply could be altered to make it suitable by an electrician yes.

Agreed.
What I was wondering is whether changing types of shower and modifying the circuit to include appropriate overload protection still considered a like-for-like replacement?
Personally I'd prefer to be dragging things up to date and complying with the requirement that all circuits supplying a bathroom have RCD protection. I think that's in his best interests really.
I'd also be checking supplementary bonding is up to scratch if leaving it on a rewireable fuse board.

 

[7029 dave]

I would give the CU upgrade priority ASAP

 

[Dino44]

I would give the CU upgrade priority ASAP

Thanku very much indeed for your wise and good info. I have been quoted £140 to fit a new RCD ( 5 Amp) unit, and disable the 30 amp old HRC electric shower unit.Unless anyone disagrees with this please advise.

 

[JBW175]

Thanku very much indeed for your wise and good info. I have been quoted £140 to fit a new RCD ( 5 Amp) unit, and disable the 30 amp old HRC electric shower unit.Unless anyone disagrees with this please advise.

It’s hard to advise without seeing what you’ve already got installed. Even then, nothing beats a site visit where a proper appreciation of the installation can take place.

I’d say you need an electrician to come round and take a look. £140 seems way too cheap in my eyes.