ks6788 Posted January 3 Share Posted January 3 (edited) Electric shower keeps tripping the RCBO intermittently. Seems to be doing this when you’re in the shower for longer time, over 10 minutes plus? It’s ok with shorter time spent in the shower, having a quick shower? Is this a fault with the shower itself or the RCBO? Any idea or advice ? Do I call a plumber or electrician to have a look at it? Edited January 3 by ks6788 Link to comment Share on other sites More sharing options...
Jenki Posted January 3 Share Posted January 3 (edited) Electrician. Test the RCBO on tripping current and ramp test 0 and 180deg. Check cable for insulation resistance,measure current draw etc. plumber will check there's water then he's stumped 😂. Q What's the shower rating, cable size and RCBO rating out of curiosity ? It does sound like a thermal overload. So the answers to my question might point to the issues. Edited January 3 by Jenki more info 1 Link to comment Share on other sites More sharing options...
ks6788 Posted January 3 Author Share Posted January 3 The shower unit is 8.5kw, cable size 6mm, 30amp RCBO The shower unit was originally wired to 30amp cartridge fuse, never tripped, very reliable, replaced to RCBO years ago. Thermal overload, is this the thermal cut out switch, what is the fix for this? Link to comment Share on other sites More sharing options...
ProDave Posted January 3 Share Posted January 3 8.5kW at 230V is 37 amps. It will be the over current function that is tripping, not the RCD function. Replace it with a 40A rcbo. 3 Link to comment Share on other sites More sharing options...
ks6788 Posted January 3 Author Share Posted January 3 Don’t think it’s recommended to replace it with a 40A RCBO as the cable size is 6mm? 40A RCBO requires 10mm cable? Link to comment Share on other sites More sharing options...
ProDave Posted January 3 Share Posted January 3 4 minutes ago, ks6788 said: Don’t think it’s recommended to replace it with a 40A RCBO as the cable size is 6mm? 40A RCBO requires 10mm cable? In a perfect world yes. Depends on the reference method, but if it has been working without issue for a number of years with a cartridge fuse, then the cable is probably not going to come to harm. I would start by measuring the actual current drawn in use. Link to comment Share on other sites More sharing options...
Ferdinand Posted January 3 Share Posted January 3 If you have teenage children who like over-long showers, and a sufficiently Machiavellian mindset, is this an opportunity for lifetime indoctrination to short showers? Just asking .... 😇. 1 1 Link to comment Share on other sites More sharing options...
ks6788 Posted January 3 Author Share Posted January 3 It’s the wife, not the children! 🤫 1 Link to comment Share on other sites More sharing options...
Mr Punter Posted January 3 Share Posted January 3 3 hours ago, ks6788 said: Is this a fault with the shower itself or the RCBO? It is the Gods of electricity telling your Mrs to hurry up. Link to comment Share on other sites More sharing options...
ks6788 Posted January 3 Author Share Posted January 3 49 minutes ago, ProDave said: In a perfect world yes. Depends on the reference method, but if it has been working without issue for a number of years with a cartridge fuse, then the cable is probably not going to come to harm. I would start by measuring the actual current drawn in use. Never had any problems with the cartridge fuse, don’t remember it ever blowing so maybe just swap the RCBO back to the original cartridge fuse? Link to comment Share on other sites More sharing options...
Jenki Posted January 3 Share Posted January 3 11 minutes ago, ks6788 said: Never had any problems with the cartridge fuse, don’t remember it ever blowing so maybe just swap the RCBO back to the original cartridge fuse? Noooooooooo. The cartridge fuse is still pulling the same current, so the cable is / will be under the same conditions. Ideally upgrade cable, but in reality, change the RCBO to 40a and it's safer than using a cartridge fuse. (Short circuit protection) You'll more than likely have 240v+ so closer to 35 amps. Link to comment Share on other sites More sharing options...
ks6788 Posted January 4 Author Share Posted January 4 17 minutes ago, Jenki said: Noooooooooo. The cartridge fuse is still pulling the same current, so the cable is / will be under the same conditions. Ideally upgrade cable, but in reality, change the RCBO to 40a and it's safer than using a cartridge fuse. (Short circuit protection) You'll more than likely have 240v+ so closer to 35 amps. The 30A RCBO only started tripping intermittently recently, no problem beforehand? Would changing the RCBO to 40A solve the issue? Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4 Share Posted January 4 5 hours ago, ks6788 said: The 30A RCBO only started tripping intermittently recently, no problem beforehand So something seems to have changed. Scale in the shower maybe. Saying that it was not a problem in the past when the fuse wire was in place is not a reliable analysis of the problem. Link to comment Share on other sites More sharing options...
ks6788 Posted January 4 Author Share Posted January 4 (edited) 1 hour ago, SteamyTea said: So something seems to have changed. Scale in the shower maybe. Saying that it was not a problem in the past when the fuse wire was in place is not a reliable analysis of the problem. I’m thinking, if swap back to original cartridge fuse & if it blows, the issue is with the shower unit & replace it? If it doesn’t blow, the issue is with the RCBO so replace the RCBO? Shower unit is quite old but has been very reliable. Edited January 4 by ks6788 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4 Share Posted January 4 1 minute ago, ks6788 said: I’m thinking, if swap back to original cartridge fuse & if it blows, the issue is with the shower unit & replace it? Shower unit is quite old but has been very reliable. Fuses and RCBOs work differently. A fuse is purely an over current device and can take more current than its rating for a short period of time, sometimes for minutes A RCBO is also an over current device and also can handle overcurrent, but usually for a much short amount of time, usually milliseconds. It also senses any difference between the incoming current and the outgoing current, if it senses a different, it assumes that some of the current has gone elsewhere i.e. into your water, and disconnects the load. As your shower unit, and the possibly undersized wiring is quite old, there could be a breakdown of the electrical insulation anywhere. So probably best to sort it properly. Link to comment Share on other sites More sharing options...
ks6788 Posted January 4 Author Share Posted January 4 (edited) 15 minutes ago, SteamyTea said: Fuses and RCBOs work differently. A fuse is purely an over current device and can take more current than its rating for a short period of time, sometimes for minutes A RCBO is also an over current device and also can handle overcurrent, but usually for a much short amount of time, usually milliseconds. It also senses any difference between the incoming current and the outgoing current, if it senses a different, it assumes that some of the current has gone elsewhere i.e. into your water, and disconnects the load. As your shower unit, and the possibly undersized wiring is quite old, there could be a breakdown of the electrical insulation anywhere. So probably best to sort it properly. Changing the 30A to a 40A RCBO is the advice from other members based on the shower 8.5KW, 6mm cable size & 30A RCBO? 15 minutes ago, SteamyTea said: Edited January 4 by ks6788 Link to comment Share on other sites More sharing options...
Jenki Posted January 4 Share Posted January 4 Winter? Temperature of incoming cold, shower is drawing more current would be my guess. Back to my original post. Get it tested incl current draw, it is drawing 35/37amps as would be expected, then swap the RCBO if he is willing to with regard to the install method. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4 Share Posted January 4 1 minute ago, ks6788 said: Changing the 30A to a 40A RCBO is the advice from other members as well It won't fix an earth leakage fault, it will warm the wiring up a bit more. My car worked reliably for many years, now it has a fault. I don't drive it as fast as I used to as I don't want to make matters worse before I get to fixed. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4 Share Posted January 4 1 minute ago, Jenki said: Temperature of incoming cold, shower is drawing more current would be my guess. Very good point. Link to comment Share on other sites More sharing options...
Jenki Posted January 4 Share Posted January 4 Within the regs, 6mm t&e can carry 32A install method A and 47A clipped direct. Changing to a 40A RCBO IMHO will be fine the cable will handle way more than 47A for short periods of time. So check the current draw if it's under 40A, and insulation resistance is acceptable then get it changed and worry about something else. Link to comment Share on other sites More sharing options...
ProDave Posted January 4 Share Posted January 4 Incoming water temperature makes no difference. It is a fixed heater element that is always on, it does not adjust the power. If the incoming water is colder you will have to turn the temperature dial up, which will reduce the water flow rate to achieve the output temperature you want. Most people don't realise that in the majority of electric showers the temperature know bust adjusts the flow rate of the water through the shower. It could be the rcd function tripping it, that's the trouble with rcbo's, if it trips you don't know if it was over current or earth leakage. It was probably a 7kW shower installed originally. You could just change your 8.5kW shower for a 7kW but you would get even less hot water out of it. Link to comment Share on other sites More sharing options...
ks6788 Posted January 4 Author Share Posted January 4 (edited) Any idea if the shower is still safe/ok to use for the time being until I find an electrician to check it out? It trips the RCBO intermittently when you using the shower for aprox 15 to 30 minutes, you have weeks when nothing happens, everything seems ok? No tripping the RCBO with a quick shower! Edited January 4 by ks6788 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4 Share Posted January 4 54 minutes ago, ProDave said: It is a fixed heater element that is always on, it does not adjust the power. Is that true for all electric showers (near enough, there are always posh ones), I thought some did modulate, or is that what you mean by the 55 minutes ago, ProDave said: bust adjusts Just like my old electric hob used to. So full power, then no power, then full power... 48 minutes ago, ks6788 said: It trips the RCBO intermittently when you using the shower for aprox 15 to 30 minutes, you have weeks when nothing happens, everything seems ok It could be a small leak inside the shower unit, the RCBO should keep it safe. It is really hard to diagnose an electric problem remotely, there are too many variables, even on a simple installation. Link to comment Share on other sites More sharing options...
joth Posted January 4 Share Posted January 4 1 hour ago, SteamyTea said: Is that true for all electric showers (near enough, there are always posh ones), I thought some did modulate, or is that what you mean by the I thought they modulate by adjusting the flow rate? So if output is too hot, they increase flow rate and vice versa. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 4 Share Posted January 4 55 minutes ago, joth said: thought they modulate by adjusting the flow rate I think most do, which means they are usually pulling maximum power. Not as if people choose to have a shower at below maximum flow rate. I can't think of a time I have ever reduced the flow rate on a shower, even the one on a ferry that was run directly of the propeller I think. Best shower I have ever know. Link to comment Share on other sites More sharing options...
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