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214 posts

Master Geek
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# 177173 24-Jul-2015 22:46
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Just bought a house which was built in 70s. Most of the things are fine, actually they were renovated recently. But the switch box is old fuse style There is no RCD on the main switch, the only RCD in the house is the one in bathroom's socket, which I think is required by the law. 

So I'm just concerned about the safety of the water heater. It was installed in early 2000's, installation quality looks good, earth connection seems good. 

The question is I would like to installed a RCD device beside the switch, is it legal to do it by myself? I'm quite confident on this small job but don't want to affect my house insurance. 

It looks like to upgrade the old fuse switch box to new MCB with RCD would cost thousands $$$, and as a DIYER one cannot modify anything on the fuse box except for replacing fuse. I'm fine with the old style fuse box as long as I can add some RCD protection to the water/elec appliance.  I understand one can upgrade the existing switch by DIY.

So I'm not gonna touch the switch box. There is a existing switch beside the water heater, Can I add a RCD next to it by myself? 




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576 posts

Ultimate Geek
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  # 1351394 24-Jul-2015 22:50
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You need a qualified electrician to instal it.



214 posts

Master Geek
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  # 1351395 24-Jul-2015 23:00
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k1w1k1d: You need a qualified electrician to instal it.






So, by law, I cannot install a RCD beside the switch by my self? :-(

 
 
 
 


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Uber Geek
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  # 1351411 24-Jul-2015 23:23
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You don't need an RCD on your HWC.

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  # 1351412 24-Jul-2015 23:27
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Fred99: You don't need an RCD on your HWC.


was thinking the same thing

why do you think you need one on it?

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Uber Geek
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  # 1351413 24-Jul-2015 23:35
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Hot water cylinders are not usually on RCDs.

You seem to have your ideas on safety backwards. You should at least get quotes to upgrade from fuses to circuit breakers and possibly RCD protect your power outlets. The RCD already fitted for the bathroom could possibly also protect other circuits.



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Master Geek
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  # 1351415 24-Jul-2015 23:41
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Jase2985:
Fred99: You don't need an RCD on your HWC.


was thinking the same thing

why do you think you need one on it?


I understand a good earth is important safety on HWC. But the additional RCD protection is bad thing? 

I have read people have HWC that will trigger RCD to break because the heat element starts to have minor leakage. I think it would be better to know if that happens. 



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Master Geek
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  # 1351417 24-Jul-2015 23:47
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Bung: Hot water cylinders are not usually on RCDs.

You seem to have your ideas on safety backwards. You should at least get quotes to upgrade from fuses to circuit breakers and possibly RCD protect your power outlets. The RCD already fitted for the bathroom could possibly also protect other circuits.


It seems MCD upgrade would cost an arm. But yes I would go for a quote anyway. 

If I don't need to have RCD on the main switch box, I think I can use the "fuse style" MCB to replace the fuse cover. Mitre10 sells ABB brand ones. They are expensive, but still way cheaper than actually upgrade the whole setup. And I will still got the slow/fast break function of the modern MCB. 

Yes the RCD socket in the bathroom protects the stainless steel towel heater as well, but maybe nothing else. 

It's good to know that "Hot water cylinders are not usually on RCDs."  Is earth protection good enough for water/elec combination? 


 
 
 
 




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Master Geek
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  # 1351418 24-Jul-2015 23:50
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...

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Uber Geek
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  # 1351449 25-Jul-2015 06:49
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1) no legal requirment for an RCD on a water heater
2) if you want one this will require installation by an electrician
3) the reason why rcd's aren't on water heater as heating elements tend to have leakage to earth, this would cause nuisance trips of the RCD and the only real way to figure out when it trips is when you run out of hot water

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Uber Geek
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  # 1351451 25-Jul-2015 07:53
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Greg has the answer.
And you would have a very hard time convincing an electrician to install an RCD on it. Leakage current is normal, and safe.

Modern regs require RCD's for most lights and sockets in homes, but that doesn't instantly make old stuff unsafe.

Old fuses aren't great to say the least, there are many things that make them unsafe, the main one though is the user.
Replacing them with plugin MCB's would be better than nothing, but you need to be careful about that too. Fuses/curcuit breakers need to be sized to the cable, and that's really not something the average user should try to do. If you get it wrong, they may not trip at all.




Location: Dunedin

 


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  # 1351465 25-Jul-2015 09:14
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In South Africa, where RCDs had been a requirement long before NZ, you don't put an RCD on a hot water cylinder as it is common to have some leakage as a result of the large surface area of the element (capacitive coupling).  Anyway, the whole thing is in an earthed cylinder (even when the earth wire is off, it is still mostly earthed through the water pipes or else through the water).  When things go wrong, you can't touch the phase )or neutral) wire so there is no need for an RCD (which is for protecting people, not appliances).  When you do have an internal breakdown, then the current will trip the circuit breaker/fuse.




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Uber Geek
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  # 1351664 25-Jul-2015 17:55
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I don't think that there is any requirement for an RCD on any permanently wired in electrical appliance such as a HW cylinder.

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