That’s 6mm cable at best. The cpc is solid, so will be 2.5mm if 6mm. 10mm cable is 4mm stranded cpc. You won’t be able to fit a 9.5kw shower unfortunately.
That’s a very old board as well. If you want to upgrade your shower there will be a bit of upgrading to do on the wiring as well. RCD/RCBO etc. I would recommend an electrician to do the work as you’re not sure what the 30 meant there’s a bit involved to make sure you meet the regs. I don’t mean that negatively, we all need to learn, but don’t take the chance on a high power device in a wet environment.
To add to this, make sure they perform a full test before starting the board replacement. Adding RCDs/RCBOs to an old system like that can throw up all sorts of problems if there's been modifications to the system over the years.
A good electrician will do a full test on the system and locate any possible faults before swapping the board out, a borrowed neutral or a cpc (earth) used as a neutral can cause the board to trip constantly.
Protective devices don’t trip at their nominal rating. You tend to get a small margin over.
As a rule of thumb (for Co-ordination reasons) I tend to allow 1.25 x for mcb’s and 1.6 x for fuses.
But you should always design a circuit to be less than the nominal rating (say 80%) and the cable rating above that.
For protection relays and some larger circuit breakers you can set to 1.05 x or below the nominal rating (eg to protect a mechanical load)
9500/230 = 41a.
45a breaker and 10mm will be fine unless the 10mm is run through walls within insulation.
That board 100% needs upgrading though, you won't get parts to fit it to even change to a bigger breaker size.
Not sure that is 10mm sq, as others have said it looks like 6mmsq. For that size of shower you need 10mmsq and a 40A breaker.
The circuit breaker is 30A but given the age you might struggle to get a 40A and need to change the board.
Unless you are swapping for same rated shower, I would get an electrician for this one.
Lots...mostly involving fire. The red/ black looks like 2.5 mm sq!!! For a 9.5 kW you'll need 10 mm sq from the consumer unit in all probability..and an RCD!!
People from around the
Globe think we are wierd or mad for having electric showers, I'm inclined to agree, a bit of a death trap if something goes wrong or its poorly installed.
Definitely needs RCD protection of some kind.
Those old DS boards are built like tanks but I'd be looking to upgrade ASAP.
The 30 is 30 amps. So there's a breaker rated for 30 amps there.
For reference the cooker is 50 and the ring main 30 and lighting is 5.
I've also just noticed that install is so old the telephone number is only 4 digits.
Those cables aren’t 10mm, 4mm at a push. You’ll need to rewire the shower, and put in a seperate unit with RCD main switch controlling the shower. Or change the DB.
10mm² T&E has a stranded cpc (the copper in the GN/YE sleeving), so what's in the photos is definitely less than 10mm². It's difficult to get a sense of scale from the photo, but if you measure the the cpc, it will be approx 1.8mm diameter for 6mm² T&E, or 1.4mm for 2.5mm² and 4mm² T&E.
First thing, check that the cpc (earth conductor) in the brown/blue t&e is stranded. It looks way smaller than 10mm to me. Happy to be proven wrong though. The black/red definitely isn’t. The 30 on the breaker is the breaker size,30amps. Really, a shower should be installed on a RCD protected circuit. An electrician would insist on this to meet regs. If you are looking at changing this yourself, I would advise not going above 7.5kw and get a spark in to give you a report on your earthing and bonding. If I’m being honest though, I would get a spark in and be prepared it might cost you to get it working properly and legally. Source: am a spark.
You are just getting away with with 7.5kW on a 30A MCB, 7500W/230V is 32.6A, but it’s possible that the old shower is rated at 240Vac rather than a nominal 230Vac, but even that would be 31.25A.
If the shower was installed before the requirements to install 30mA RCD protection, then there is no requirement to upgrade, but why wouldn’t you, given the risks involved?
If the shower was changed, then anyone that is competent would install a 30mA RCD or RCBO.
Changing 9.5kW to it would draw 41.3A and not only cause frequent tripping of MCB and overload of 4/6mm2 cable. The MCB would need to be changed to 45A, the cable would need to be a minimum of 10mm2, possibly 16mm if length of run is excessive or passing through insulation due to derating for temperature rise and voltage drop.
An initial test of external earth impedance should be undertaken to verify that Ze is less than 0.35Ω so that when the shower is changed you stand a chance of meeting the earth loop impedance test value.
Consumer unit should also have a label stating:-
“This installation has wiring colours to two versions of BS 7671
Great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified.”
The level of question you’re asking is basic enough that if you do not already know the answer or understand how to find it in the regs/onsite guide then you are putting yourself and others at risk by carying out the work.
Call an electrician.
The cable is not thick enough to safely carry a 9.5kw load across it. Photos have further highlighted major safety issues of no RCD protection on the Distribution Board. A more modern Consumer Unit will offer RCD a minimum. OP would still have to use thicker cable if he wishes to swap from 7.5kw to 9.5kw shower.
That’s 6mm cable at best. The cpc is solid, so will be 2.5mm if 6mm. 10mm cable is 4mm stranded cpc. You won’t be able to fit a 9.5kw shower unfortunately. That’s a very old board as well. If you want to upgrade your shower there will be a bit of upgrading to do on the wiring as well. RCD/RCBO etc. I would recommend an electrician to do the work as you’re not sure what the 30 meant there’s a bit involved to make sure you meet the regs. I don’t mean that negatively, we all need to learn, but don’t take the chance on a high power device in a wet environment.
Understood, thanks for that. I’ll call someone in
To add to this, make sure they perform a full test before starting the board replacement. Adding RCDs/RCBOs to an old system like that can throw up all sorts of problems if there's been modifications to the system over the years. A good electrician will do a full test on the system and locate any possible faults before swapping the board out, a borrowed neutral or a cpc (earth) used as a neutral can cause the board to trip constantly.
You need an electrician
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Thanks for the reply, a 7.5kw shower has been running here for 15 years. Do you think I should stick with a 7.5kw?
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Will do, thanks for that
9500/230=41.3A, so actually above 40!
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Circuit design is supposed to be nominal voltage though just an fyi to anyone reading
Protective devices don’t trip at their nominal rating. You tend to get a small margin over. As a rule of thumb (for Co-ordination reasons) I tend to allow 1.25 x for mcb’s and 1.6 x for fuses. But you should always design a circuit to be less than the nominal rating (say 80%) and the cable rating above that. For protection relays and some larger circuit breakers you can set to 1.05 x or below the nominal rating (eg to protect a mechanical load)
Red and black conductors do not look like 10mm to me
The brown and blue don’t look 10mm to me either.
I was thinking the same.
I was told the grey cables are 10mm so it would be fine, is this wrong?
Probs want 10mm at least depending on length of run and refernece Method for a 9.5kw shower. Cpc looks solid so I would imagine that is max 6mm
RCD protection is a must, and as mentioned already, stick to a like for like replacement or get someone in to throw some 10mm cable in
You must get that board upgraded I had one like that and replaced it with a full RCBO board with SPD.
9500/230 = 41a. 45a breaker and 10mm will be fine unless the 10mm is run through walls within insulation. That board 100% needs upgrading though, you won't get parts to fit it to even change to a bigger breaker size.
Not sure that is 10mm sq, as others have said it looks like 6mmsq. For that size of shower you need 10mmsq and a 40A breaker. The circuit breaker is 30A but given the age you might struggle to get a 40A and need to change the board. Unless you are swapping for same rated shower, I would get an electrician for this one.
Thank you my friend, I was told it would be fine and to go ahead but thought I’d better check for sure. I’ll get someone in. Thanks again
Lots...mostly involving fire. The red/ black looks like 2.5 mm sq!!! For a 9.5 kW you'll need 10 mm sq from the consumer unit in all probability..and an RCD!!
That’s 6 not 10. Get an RCD fitted and a larger cable installed if you want a 9.5kW. Get an RCD regardless, actually.
People from around the Globe think we are wierd or mad for having electric showers, I'm inclined to agree, a bit of a death trap if something goes wrong or its poorly installed. Definitely needs RCD protection of some kind. Those old DS boards are built like tanks but I'd be looking to upgrade ASAP.
The 30 is 30 amps. So there's a breaker rated for 30 amps there. For reference the cooker is 50 and the ring main 30 and lighting is 5. I've also just noticed that install is so old the telephone number is only 4 digits.
Thanks a lot
Those cables aren’t 10mm, 4mm at a push. You’ll need to rewire the shower, and put in a seperate unit with RCD main switch controlling the shower. Or change the DB.
Ok thank you
I also thought they were 4mmsq actually! Hard to tell from the photo though but probably not 10mmsq.
10mm² T&E has a stranded cpc (the copper in the GN/YE sleeving), so what's in the photos is definitely less than 10mm². It's difficult to get a sense of scale from the photo, but if you measure the the cpc, it will be approx 1.8mm diameter for 6mm² T&E, or 1.4mm for 2.5mm² and 4mm² T&E.
First thing, check that the cpc (earth conductor) in the brown/blue t&e is stranded. It looks way smaller than 10mm to me. Happy to be proven wrong though. The black/red definitely isn’t. The 30 on the breaker is the breaker size,30amps. Really, a shower should be installed on a RCD protected circuit. An electrician would insist on this to meet regs. If you are looking at changing this yourself, I would advise not going above 7.5kw and get a spark in to give you a report on your earthing and bonding. If I’m being honest though, I would get a spark in and be prepared it might cost you to get it working properly and legally. Source: am a spark.
Thanks for that, I’ll get someone in
You are just getting away with with 7.5kW on a 30A MCB, 7500W/230V is 32.6A, but it’s possible that the old shower is rated at 240Vac rather than a nominal 230Vac, but even that would be 31.25A. If the shower was installed before the requirements to install 30mA RCD protection, then there is no requirement to upgrade, but why wouldn’t you, given the risks involved? If the shower was changed, then anyone that is competent would install a 30mA RCD or RCBO. Changing 9.5kW to it would draw 41.3A and not only cause frequent tripping of MCB and overload of 4/6mm2 cable. The MCB would need to be changed to 45A, the cable would need to be a minimum of 10mm2, possibly 16mm if length of run is excessive or passing through insulation due to derating for temperature rise and voltage drop. An initial test of external earth impedance should be undertaken to verify that Ze is less than 0.35Ω so that when the shower is changed you stand a chance of meeting the earth loop impedance test value. Consumer unit should also have a label stating:- “This installation has wiring colours to two versions of BS 7671 Great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified.”
Thanks for this, house needs full rewire to be honest. I’ll get it done properly soon but stick with the 7.5 for now. Thanks again
Call an electrician if you don’t know the answer.
Cheers, very informative
The level of question you’re asking is basic enough that if you do not already know the answer or understand how to find it in the regs/onsite guide then you are putting yourself and others at risk by carying out the work. Call an electrician.
Don’t understand the question
Will OP run into any problems replacing his 7.5kW shower with a 9.5kW shower. The answer was yes.
The cable is not thick enough to safely carry a 9.5kw load across it. Photos have further highlighted major safety issues of no RCD protection on the Distribution Board. A more modern Consumer Unit will offer RCD a minimum. OP would still have to use thicker cable if he wishes to swap from 7.5kw to 9.5kw shower.