Hi, need some help with a MK Sentry Consumer Unit problem.

[pollensa1946]

Hi...great forum, looking for some help...

I have a MK Sentry Consumer Unit box, fitted in my home, normal residential load, around 1984, containing a 4-module LN 5780 ELCB 80A 30ma. This is regularly tripping when a new load is applied, for example switching a random light or power load on, suggesting it needs to be replaced. I understand the design of MK Sentry modules was subject to a design change, meaning newer RCD units are no longer compatible with my box. So I figure the most cost effective solution is to completely disconnect the ELCB and replace it with a new MK external 4-module enclosure containing a 100A isolation switch and latest model MK 80A 30ma RCD. Run the existing meter tails into the new enclosure and new meter tails into the old enclosure.
Does this make sense?

With regard to the old ELCB I would like to do this right and completely remove it but I'm not sure I can get suitable blanks to fill the 4 module spaces. Any suitable blanks I can get hold of? Alternatively I could leave it in place and simply put a sticky label over it with the words..."Faulty, completely disconnected from the load" ...or similar. Would that pass an inspection?
Thanks.

 

[pollensa1946]

Can a Surge Protect Device cause RCD problems?

This problem has become so annoying that I have spent a rainy w/e carefully investigating, collating and comparing my findings with past experience, and I am now doubting my initial analysis.

Problem only ever occurs when my computer rig is powered up and in-circuit. This consists of a variety of devices all supplied through a master switch which is in turn connected to power through a SPD All devices are left with their individual power switch on, so hitting the master switch powers everything up simultaneously.
Switching the computer rig on may cause a power trip, but not always. Most times it happens after powering the computer rig on and then shortly after powering some other load on. At that point (when the power trips) it can only be restored when the computer rig is removed from power entirely.
In the past the power trip happened when I switched the computer master switch off. At that time I renewed the SPD and the problem disappeared for about 1 year, only to return with the onset of autumn and the house fully loaded in the evening.
So my question at the top?

 

[ImpededLoop]

So long as the old ELCB is labeled as no longer being connected I can't see a problem. However, for all the messing about, I would consider changing the 30 year old consumer unit for a new split load consumer unit which has 2 RCD's so that you only lose some of the circuits if one of the RCD's operate.

 

[Richard Burns]

The fact that you have an RCD that trips is not usually indicative of a faulty RCD but is indicative of a fault on one of the circuits it protects.
Even though it is old it is probably still doing its job and protecting you from potential electric shock.
It would be best to check the circuits for faults first before you spend lots of money changing something that may be working.

 

[pollensa1946]

Thanks, good advice. I just spent a rainy w/e investigating this in depth...

Can a Surge Protect Device (4-way extension lead) cause RCD tripping.

After collating lots of RCD trips I established that it only happens when my computer rig is powered up. Sometimes powering up the computer trips the power, in the past powering it down would trip it but that no longer happens. Typically I power up the computer, and then sometime after power up another load and the power trips. Tried isolating individual devices in the computer rig but trips continue. The only common factor is the SPD, the power light of which is continually flickering. So I'm off the B&Q.

 

[ImpededLoop]

The fact that you have an RCD that trips is not usually indicative of a faulty RCD but is indicative of a fault on one of the circuits it protects.
Even though it is old it is probably still doing its job and protecting you from potential electric shock.
It would be best to check the circuits for faults first before you spend lots of money changing something that may be working.

Yes, very good point.

You may need to get help with the testing if you don't have access to an insulation resistance tester and experience of how to conduct the tests.

 

[davesparks]

Hi...great forum, looking for some help...

I have a MK Sentry Consumer Unit box, fitted in my home, normal residential load, around 1984, containing a 4-module LN 5780 ELCB 80A 30ma. This is regularly tripping when a new load is applied, for example switching a random light or power load on, suggesting it needs to be replaced. I understand the design of MK Sentry modules was subject to a design change, meaning newer RCD units are no longer compatible with my box. So I figure the most cost effective solution is to completely disconnect the ELCB and replace it with a new MK external 4-module enclosure containing a 100A isolation switch and latest model MK 80A 30ma RCD. Run the existing meter tails into the new enclosure and new meter tails into the old enclosure.
Does this make sense?

With regard to the old ELCB I would like to do this right and completely remove it but I'm not sure I can get suitable blanks to fill the 4 module spaces. Any suitable blanks I can get hold of? Alternatively I could leave it in place and simply put a sticky label over it with the words..."Faulty, completely disconnected from the load" ...or similar. Would that pass an inspection?
Thanks.

What testing have you carried out to confirm that the existing RCD is faulty?

The symptoms you describe sound more like those of a neutral to earth fault than a faulty RCD.

 

[pollensa1946]

I appear (so far) to have solved this. There were 2 x SPD 4-way strips in the power supply circuit for the computer rig. The kind that have a green light indicating the SPD function is operational and a red light indicating the power is on. On one of them the green was very dim and red constantly flickering. Took both out and rewired the complete circuit with non-SPD strips and a single good quality SPD plug from Screwfix, mounted right next to the master switch so it can be easily removed from the circuit for testing. I also found an external floodlight which was badly deteriorated due to the weather, and may have contributed to the problem since switching that circuit on regularly caused the trip (as long as the computer rig was powered up, cumulative residual currents?). Now replaced with a LED flood. So far no more trips.
Thanks for the advice. Good for my wallet also since MK (the complete DB is MK) responded to my enquiry advising that I replace the entire DB.