Hi,
Sorry for the long post however I have a problem with a new RC installation that I could really do with some help with.
Basically I recently moved into a rented house which had no shower so I decided to install one (yes, I am aware of part p of the building regualtions and will be getting the installation checked once it is actually working)
The CU that is installed in the house is an old fuse type Wylex one which had no spare fuses, as such I installed a new, secondary consumer unit in the follwing manner:
HB = Henley block
Initially everything seemed fine, the light on the front of the shower illuminates, however the problem is that the moment the button which actually starts the shower is pressed, the RCD trips.
In an attempt to identify the cause of the problem I have done the following:
1) Disconnected the wiring at the consumer unit which goes to the isolator switch. Then using a multimeter I have tested the resistance between all three wires, in all possible combinations. The results were that resistance was infinite, therefore leading to the conclusion that there was no damage to any of the wiring insulation.
I have also visually inspected all of the wiring and connections for any problems; none are present that I can see.
2) I considered that the shower unit itself may be faulty. To remove
this possibility I removed the plug end of an extension lead and connected it to the wiring which goes into the shower. Then I plugged a hoover (the appliance with the highest load I had to hand - 2kw) into the extension lead. The same result occured, the RCD tripped as soon as the hoover was switched on, so I assume it is unlikely to be a fault with the shower unit.
3) I tried connecting the extension lead directly into the secondary CU and to the RCD. Again, using the hoover to apply load to the circuit, the same thing happened - the RCD tripped, which again leads to the conclusion that there is no fault with the wiring between the secondary consumer unit and no fault with the shower unit.
4) With the previous tests in mind I decided that perhaps, even although it is new, there may be a fault with the RCD itself but after replacing it with another new one the fault still persists.
At this point I decided to measure the resistance between neutral and earth on the busbars inside the secondary consumer unit. Much to my surprise the multimeter started to beep, indicating a complete circuit.
The earthing connection for the secondary consumer unit is fed directly from the busbar inside the original consumer unit via a cable so I disconnected it and again tested for resistance between the earth busbar and the neutral basbar in the secondary consumer unit, this time resistance was infinite again confirming no faults between neutral and earth with the new wiring leading to the shower.
The final test that I did was to check for resistance between the neutral cable and the earth cable which feed in from the main fuse and meter which is located in a sunken box outside the house. Again the multimeter beeped indicating a complete circuit.
I appreciate some of these tests are quite crude but my test equipment is limited to pretty much just a multimeter.
My question is: Is the lack of resistance between neutral and earth that I have previously mentioned on the incoming cables causing the
RCD to trip all the time? If so, what is the best solution to correct the problem? If not, has anyone got any ideas to what is causing it to trip all the time?
The RCD which is currently installed as a 30ma one which is the rating recommended by the shower manufacturer.
Any help would be gratefuly appreciated as this is causing me a serious headache and taking up way too much time for what should have been quite a simple job.
Many thanks.
Sorry for the long post however I have a problem with a new RC installation that I could really do with some help with.
Basically I recently moved into a rented house which had no shower so I decided to install one (yes, I am aware of part p of the building regualtions and will be getting the installation checked once it is actually working)
The CU that is installed in the house is an old fuse type Wylex one which had no spare fuses, as such I installed a new, secondary consumer unit in the follwing manner:
![14367_Layout_122_213lo.jpg](http://img17.imagevenue.com/aAfkjfp01fo1i-20558/loc213/14367_Layout_122_213lo.jpg)
HB = Henley block
Initially everything seemed fine, the light on the front of the shower illuminates, however the problem is that the moment the button which actually starts the shower is pressed, the RCD trips.
In an attempt to identify the cause of the problem I have done the following:
1) Disconnected the wiring at the consumer unit which goes to the isolator switch. Then using a multimeter I have tested the resistance between all three wires, in all possible combinations. The results were that resistance was infinite, therefore leading to the conclusion that there was no damage to any of the wiring insulation.
I have also visually inspected all of the wiring and connections for any problems; none are present that I can see.
2) I considered that the shower unit itself may be faulty. To remove
this possibility I removed the plug end of an extension lead and connected it to the wiring which goes into the shower. Then I plugged a hoover (the appliance with the highest load I had to hand - 2kw) into the extension lead. The same result occured, the RCD tripped as soon as the hoover was switched on, so I assume it is unlikely to be a fault with the shower unit.
3) I tried connecting the extension lead directly into the secondary CU and to the RCD. Again, using the hoover to apply load to the circuit, the same thing happened - the RCD tripped, which again leads to the conclusion that there is no fault with the wiring between the secondary consumer unit and no fault with the shower unit.
4) With the previous tests in mind I decided that perhaps, even although it is new, there may be a fault with the RCD itself but after replacing it with another new one the fault still persists.
At this point I decided to measure the resistance between neutral and earth on the busbars inside the secondary consumer unit. Much to my surprise the multimeter started to beep, indicating a complete circuit.
The earthing connection for the secondary consumer unit is fed directly from the busbar inside the original consumer unit via a cable so I disconnected it and again tested for resistance between the earth busbar and the neutral basbar in the secondary consumer unit, this time resistance was infinite again confirming no faults between neutral and earth with the new wiring leading to the shower.
The final test that I did was to check for resistance between the neutral cable and the earth cable which feed in from the main fuse and meter which is located in a sunken box outside the house. Again the multimeter beeped indicating a complete circuit.
I appreciate some of these tests are quite crude but my test equipment is limited to pretty much just a multimeter.
My question is: Is the lack of resistance between neutral and earth that I have previously mentioned on the incoming cables causing the
RCD to trip all the time? If so, what is the best solution to correct the problem? If not, has anyone got any ideas to what is causing it to trip all the time?
The RCD which is currently installed as a 30ma one which is the rating recommended by the shower manufacturer.
Any help would be gratefuly appreciated as this is causing me a serious headache and taking up way too much time for what should have been quite a simple job.
Many thanks.