Test Button On Safe T Cut Fuse Box

[nattydread]

last year I paid to have installed in my g/f home a safe t cut electrical fuse box to replace the 30 year old death trap original set up

it has four of the six fuses connected.....main house..kitchen...wahing machine...electric shower

I was at the house today and looking at the box I decided to press the yellow test button expecting the switches to trip and nothing happened

i adjusted the RCBO setting switch to see if that was the problem but same result

am I doing something wrong ie. not testing the unit correctly or is there a problem with the RCBO?

I know that their tv aerial was hit by lightning a few months ago and the box tripped out if thats any help

if there is a fault with the RCBO unit how much to buy a replacement

thanks for any advice

[Crossy]

If it's not tripping when you press 'Test' (and it's not set to 'bypass') then it's busted and the RCD section needs to be replaced, the lightning strike may well be the cause. Before you bin it, try operating the main switch a few times, could just be stuck.

One is of course assuming the power is actually on and it's not still in the box.

As to cost, no idea for a Safe-T-Cut branded unit, best to start with the place that supplied it.

[electau]

If power is available and the RCBO does not operate when the test button is pressed the unit is defective and must be replaced.

[lopburi3]

You posted a photo of unit in shipping box. As said the left side breaker should trip if making such a test and it is actually wired up correctly (but if never done/tested it may not have even been wired into the circuit). Do you lose electric if you manually switch that left side breaker? If not suspect it was never wired in (could be broken but my money is on not installed if fails to remove power). Not sure of cost if new unit is actually required but just checked stand-alone at Home-Pro two days age and was about 4,500 baht (but not sure of size).

[doglover]

As suggested, there could be faulty wiring. It could be that the electrician only fed the live wire through the main breaker of the RCBO and ran the neutral wire directly to the neutral bar (for example). In which case the main breaker will still function but the RCD will not be doing anything. If you are comfortable with the risk in doing so, you could remove the cover of the consumer unit and post a photo of the existing wiring. Most likely the RCD section is defective as suggested, but there is the possibility of incorrect wiring.

[electau]

Make sure that the RCBO is connected correctly and you carry out an insulation test L to E and N to E on all protected circuits.

[nattydread]

persuaded safety cut to give us a new/recon RCB switch as it was still under gurantee

inserted this into the box and the RCB still doesnt work

so bearing in mind that 2 RCBs arent working could the problem be that the box hasnt been wired correctly

is there a way of wiring the box that bypasses the actual RCB module?....could the main isolater switch which is an integral part of the complete RCB module when purchased be at fault?

can anyone give me a wiring diagram on how the box should be wired up...its just a two wire home system

thanks

Edited October 22, 2012 by nattydread

[Crossy]

Should be something like this http://www.crossy.co...wiring/CU-2.jpg

Probably easiest to pop the lid and take a photo to post here.

Has the test button ever worked? it is possible to wire an RCD up so it won't work, but should be almost impossible with an integrated unit like you have.

[electau]

　

The RCBO must be correctly connected. The line ( L and N) from the main switch connect to the line side of the device, this should be marked. The load circuits all connect to the load side of the device.

To test power must be available. the selectivity switch must NOT be in the direct position.

You should first test the device before you connect the load circuits. If RCBO trips it is functioning normally. Then connect one circuit at a time and test. the RCBO should trip when the test button is operated.

You must make sure that you do have an earth on the load neutral(s) and you do not have interconnected circuits or crossed neutrals, these are a common defects in Thai electrical installations.

[electau]

　

RCBOs/RCDs are not repairable and must be replaced. A new RCD should be in a sealed package with installation instructions and warranty information from the manufacturer.

You should never accept an RCD unpackaged. It is possible that you may receive one that has been previously returned as is faulty.

An RCD is a safety device and if found to be faulty should be destroyed. If under warranty the supplier should return to the manufacturer or manufacturers agent.

[lopburi3]

Does the breaker at far left side control all power (turn it off and all power is off)? Does it turn off when test button touched? Or does it just have no apparent function? What is the setting of the rotating switch which controls sensitivity of the RCD? Do not believe the new units have a "direct" setting but older units did which may take the test button out of circuit.

[electau]

The test button on the RCBO when operated creates an imbalance between the L and N which trips the unit. this is known as a functional test. It tests the operation of the RCBO.

It does not test the continuity of the protective earthing conductor on the circuit. To do this requires a plug in RCD test device to a socket outlet.

The test button should be operated at least once every 3 months in a residential electrical installation.

[lopburi3]

He should not even require a ground to have the RCBO circuit activate using the test switch and understand that but he has not asked about ground system or a means to check that - he just says the test switch is not tripping electric but does not even specify if main breaker he is talking about or the sub breaker panel or what the selection switch setting is pointed at. We need to start somewhere.

[electau]

Many consumers may think that the test button operation also checks the earth, it does not, the test button causes an imbalance between the Line on the load side and the N on the line side of the RCBO. this is carried out internally within the device, no earth is required.

To test the earth continuity with an RCBO connected on the circuit the test is L to E at 30mA or 10mA , the RCD must trip. It must NOT trip on 50% of rated current in mA.

The RCBO should be tested with the test button with power applied and NO circuits connected , this will prove that the RCBO does trip. If it does not trip it is faulty and must be replaced.

[nattydread]

The RCBO should be tested with main breaker on and NO circuits connected , this will prove that the RCBO does trip. If it does not trip it is faulty and must be replaced.

so if I switch off all the breakers and test the RCBO with just the main breaker on this should prove that the replacement is also faulty?

for information the main breaker switch does cut all power to the house when off

will try the above next week if i am there

i have found a shop in CM that sells the safe t cut main breaker with the RCBO as a package for 1750 baht but dont wish to spend that money if its proved that the wiring is at fault

[Crossy]

PLEASE Take some internal photos so we can look at the wiring.

Which part did you replace?

[electau]

The RCBO should be tested with main breaker on and NO circuits connected , this will prove that the RCBO does trip. If it does not trip it is faulty and must be replaced.

so if I switch off all the breakers and test the RCBO with just the main breaker on this should prove that the replacement is also faulty?

for information the main breaker switch does cut all power to the house when off

will try the above next week if i am there

i have found a shop in CM that sells the safe t cut main breaker with the RCBO as a package for 1750 baht but dont wish to spend that money if its proved that the wiring is at fault

Disconnect ALL circuits physically (both the L and N) from the LOAD side of the RCBO. You will have supply connected to the LINE side of the RCBO, L and N.

Make sure the MCB of the RCBO is in the ON position. Make sure that you have power at L and N on the LINE side of the RCBO.

Press the test button, the RCBO should now trip.

If it does not trip then the RCBO is faulty.

Edited October 23, 2012 by electau