Auto resetting RCD? help please...

[telectrix]

the power fail alarm is a good option. no wiring, no regs. to worry about. it's just a plug, program and play device.

 

[j.mawer]

Having said all that just looked up some aquarium kit and it does all say it should be used with an RCD and if that's what the manual says ...

 

[oldtimer]

Having said all that just looked up some aquarium kit and it does all say it should be used with an RCD and if that's what the manual says ...

If you take your fish tank seriously and I think you do then go for my earlier posting and we can get all sleep at night and as for protect it without an RCD dont even go their the whole industry is going down that road so dont buck the trend. This is not a lecture but you need to see the big picture if you decide to move then you will leave the next resident comprimised with regards to safety I for one do not want to see a rouge socket in a house without protection.

 

[Deleted member 26818]

What if it was beige?

 

[mogga]

Ross (Neweys)and even the big orange shed do a nice line in "decoratice trunking" seperate circuit along with individual RCBO seems liek the way to go

 

[BlueToBits]

Rather than trying to remedy the symtom, address the cause of the fault that is tripping the RCD. RCD's should be quite reliable and a 200W heater should not be a problem for it.
If the problem is caused by spikes from timeswitch then change it for a soft start triac one.
Another alternative solution could be to fit a safety isolating transformer between the tank wiring and the wall socket. This would remove any earth connection that may cause the RCD to trip.

 

[papalazarou]

Rather than trying to remedy the symtom, address the cause of the fault that is tripping the RCD. RCD's should be quite reliable and a 200W heater should not be a problem for it.
If the problem is caused by spikes from timeswitch then change it for a soft start triac one.
Another alternative solution could be to fit a safety isolating transformer between the tank wiring and the wall socket. This would remove any earth connection that may cause the RCD to trip.

Thanks, I'll look into the safety transformer when I get home in a few weeks. For the record all the other electric components in the house were switched off as I am currently abroad. This is the only thing that led me to believe it may be the tank light timers. It is the first time anything like this has happened in the 8 months the tank has been running!

 

[papalazarou]

Gentlemen, thank you all so much for all the replies and info, it has been very helpful.

At the moment and in the short term I am getting one of the power failure alarm modules. It will give myself and my tank sitters peace of mind that any problem like this can be dealt with before any real damage is done. When I return home after my trip away I will get all the tank components tested to make sure there are no faults.

Keeping a marine fish tank is by nature quite frustrating in that you tend to always want more than you have. It is for this reason that later in the year I am thinking of upgrading to a bigger tank. (Fortunately my losses were limited in that it is only a small tank) If this is indeed the way I go then along with the setting up will be room for a little work on the electrics. I will be talking to an electrician mate when I get home to find out more about old timers idea of putting the new tank on a separate protected circuit. I will also have a second aquarium heater and pump running off the main rcd too so there is at least a back up if either circuit trips. This, along with the power fail alert system should be enough to put my mind at rest!

Once again guys, thank you, its been a pleasure and I know where to come for good advice!

 

[eskimo39]

Sorry if this has been covered already but it is getting late and I am too tired to read through all the posts. Is it an RCD or the MCB tripping?? If it is the MCB, you could get a local electrician to come and test the Zs of the circuit to see if it would be possible to install a Type C or D MCB which has better characteristics which may suit your set up.

If it was the RCD, what do you have running on the circuit? Could it be possible that a faulty appliance (eg refrigerator) could be causing the problem?

As far as I know a UPS would not be large enough to actually run equipment for any length of time, they are usually made to give you 10-15 minutes to save documents etc in the event of a computer supply failure.

The only other thing that may be possible would be to have a supply brought down from the upstairs ring (if it is on a different circuit) and with the use of a relay/contactor have 2 feeds present from the 2 different circuits. The downstairs (original) feed would keep the contactor open and therefore power the equipment, in the event of a power failure the contactor would switch across and make the link from the second (upstairs) supply the primary feed. This way you may only need to make a small chase on one wall. However (I don't have any regs to hand) I believe you would need to put a notice on the new supply and perhaps the DB to warn that an upstairs feed is present in a downstairs location. Not sure if this would work as it is late and I have just got back from training but hopefully a member on here might know what I am trying to say.

 

[malcolmsanford]

It is becoming quite a concern with the lack of understanding associated with RCD protected systems. Ever since I came into the industry we have used Residiual Current protection devices in one form or another. It was originally a voltage operated ELCB and then a current operated one for TT systems, to what we have now, installing RCDs in a much wider range of systems.

The overiding principles of our testing procedures though have not changed with the advent of RCD protection becoming more widly spread, this I feel is due to the practice in the UK of not using the RCD in many commercial/industrial enviroments. I believe that within the next few BS 7671 editions this will also change, to incorporate the use of the RCD in these enviroments. So though our testing must reflect the use of MCB/Fuses for fault protection and therefore Zs valuse, we are not trained to distinguished between these and RCD protection.

In Europe where RCD protection as been in use for many many years, they find our testing procedures to be totally archaic, and as I beleive in the future things like Zs testing will be a thing of the past.

When we have in most domestic situations today, the use of RCD for fault protection the normal Zs value becomes totally irelevant. Be it either RCD/MCB or a straight RCBO protection the MCB side of the protection for fault conditions is superceded by the Residiual Current side of the operation.

So when I see posts where this type of protection is providing advising if the Zs allows then it's pointless, Zs is not even considered as in tables 41.3 but is in fact taken from table 41.5 and is a value of 1667.

The use of a type C MCB/RCBO will have no effect on it's fault protection capabilities, it will though give you an added advantage in very few domestic situations.

 

[Deleted member 26818]

Unfortunately at present, RCDs are considered to be additional protection.
As such we are required to ensure that circuit parameters are such that ADS is provided without reliance on the RCD.
Then of course, there is to be considered that RCDs often fail to operate.

 

[malcolmsanford]

Additional protection or not, if you use a RCD for fault protection on final circuits not exceeding 32amp and I believe in the new amendment they are considering this for circuits exceeding 32amps now, then your EFLI or Zs should be 1667. Any other reference to MCB Zs is nulled by this.

In a certain report regarding RCD failure there were quite a few anomolies, ie RCDs bypassed and the majority of the failures were also due to the fact that the quarterly test procedure was not done. It amazes me that if a gas plumber advised a homeowner that to make sure their boiler worked safely they had to press a button every 3 months, they would do it without hesitation, we tell them and it's forgotten before we walk out of the door.

 

[ezzzekiel]

without reading through all the posts is the rcd common to a few circuits if so then maybe an rcbo or standalone rcd for the tank may eliminate the problem.

 

[Engineer54]

Malcolm,

The total reliance on the various RCD devices as a means of protection against earth faults is a little foolish to be honest. Yes RCD devices are a very welcome addition to safety, in the home and throughout the industry, but there really is no alternative or substitute to having a good earthing system present at any type of earthed electrical system.

Don't dismiss the fact that present day RCD devices are inherently unreliable compared with say the HRC fuse and MCBs. On my last project, the contractor was literary sending a full box or two of failed RCD devices for replacement Every Month!!!! and they were from a ''Top of the Range'' manufacturer....

Contrary to what you state about the Europeans view on our testing procedures, they have virtually the same requirements as the UK, in fact in practice, you could use the standard test equipment used in say Germany/France in the UK, and visa versa.... In fact, some earthing requirements are More stringent than in UK!!

Maybe in the future we will be able to rely totally on an RCD device for earth fault protection, ...but i doubt if it will be in our working life times. As i say, i've seen too many failures of these devices, (some with dire consequences) to have any confidence of ongoing total reliability, ....not yet anyway!!!

One more thing, the test button facility on RCD devices are, for want of a better word ''crude''!! It does not and cannot prove it will trip in an appropriate times, or trip within it's tripping current range.
Don't get me wrong, i will always use an RCD device in whatever situation that merits it's inclusion, whether by need or regulation, but i'd also be making dammed sure, that i have a Good earthing system in place too, for those times that the RCD Fails to operate.... Zs is going to be here with us, for a good time to come, ...and you may be thankful one day that it IS!! ...lol!!!

 

[malcolmsanford]

I'm sorry old mate but I can't agree with you about RCDs. Recently as last year in the UK there was a major recall of Wylex MCB's due to them being faulty so it is not just the RCD that as inherent problems. If an RCD is tested at the installation stage and it complies there is no evidence that it will fail during it's life service, or certainly not more than a MCB will also fail in service.

France, Spain, and most other countries rely totally on RCD protection for earth faults. We have in fact now brought ourselves in line with them, and they are so confident in them that they have no heistation in fitting socket outlets in bathrooms as they have total faith in them. I have worked here in saudi with Merin Gerin and their "wigi" system and have yet to find a problem with them.

The push button test though is for the mechanical operation side of the RCD. So really it is not designed to give you it's operating characteristics or times, it is purely to make sure that it as not seized.

We can batter this around as much as we wish, the bottom line is that RCD protection is the safest form of fault protection on the market today. The regs clearly state that for a 30mA RCD to operate within 40mS the EFLI rating is 1667 and therefore any other Zs value is nulled.

Where RCD protection is not used then you are totally correct that a good earthing system is vital to obtain the correct disconnection times.