Strange voltage on immersion controller

[richardspooner]

The meter shown earlier is an aldi one,I have one as well and they work ok for basic measurements but i will point out that all my meters give false readings when the battery is low.



andy

Yep. Aldi special.

I replaced the battery tonight just to be sure.

 

[Spark123]

The live will go to the MCB
The neutral will go to a neutral rail in the CU - as it is on it's own main switch then there will more than likely be on it's own.

 

[richardspooner]

The live will go to the MCB
The neutral will go to a neutral rail in the CU - as it is on it's own main switch then there will more than likely be on it's own.

MCB = Circuit Breaker?

CU = Consumer Unit?

Whats the difference? I thought the MCB was in the CU?

 

[Spark123]

Yes, sorry about the abbreviations.
An MCB is what I took you to mean a few posts up when you said "fuse thingy"
CU is what the MCB sit in.
The neutral doesn't connect to the MCB, it connects to a metal rail in the CU.

 

[philiprreeves]

First thing first;
1) Identify the immersion heater circuit at the mains board. I notice that there is a normal peak board and an off-peak board. The imm should be wired to the normal peak board via a 16A circuit breaker. This is the board which feed the house lighting and sockets.
2) Now the live (red wire) to the imm switch will be connected into THE TOP of this 16A circuit breaker INSIDE THE CU UNIT( CONSUMER UNIT WHERE ALL THE FUSES AREA). The neutral (black) wire will be connected to the neutral bar WITHIN THE CU UNIT NORMALLY JUST ABOVE THE FUSE AT THE TOP OFTHE CU UNIT. Please I.D these two wires along with the EARTH wire inside the CU (consumer unit). Please remove all 3 wire (make note of where they were connected)
(YOU SHOULD BE ABLE TO TRACE THE RED WIRE BACK TO IT’S GREY SHEATH WITHIN THE CU UNIT AND THERE YOU WILL FIND THE BLACK AND GREAN/YEALLOW WIRES WHICH NEED DISCONNECTING)
3) The three wires (Red, Black and earth) will go to the imm heater switch which your 1st pic shows. I see that you have marked the top two cables as supply. Please ALSO disconnect the earth at the switch as well. The yellow/green wire which is connected to the metal plate that i can see. Now with the wires ALL disconnected from the mains (CU)short out the live wire with the neutral at the IMM switch ONLY!!!.
4) Using a bell tester or continuity tester test the wires AT THE CU UNIT, NOT AT THE SWITCH. Always better if you have a friend who can tap the live and neutral wire together on and off a number of times ( AT THE SWITCH) to prove the wires are the right ones GOING BACK TO the mains board. You can repeat this test with a live and earth then neutral earth proving continuity of all three wires with no breaks.
5) Now separate all wires and test between with a insulation resistance tester, failing that u will just have to use your multimeter although it won’t prove this type of test put will show a short circuit if there is one.
6) Now test between live and neutral. Should be open circuit.
7) test between live and earth and then neutral earth. All should read open circuit not closed(short circuit).

If this is the case (open circuit) we have proved that the wiring up to this point is sound. If you were to reconnect it up (leaving the switch disconnected) you should have between 220-240v (depending on time of day) between Live and earth, between live and neutral and 0V between earth and neutral.
8) Now disconnect the imm heater. These are always going down and showing faults due to corrosion.
9) Once disconnected repeat steps 4 to 7 just with the output wire from your imm sw to the imm heater remembering to disconnect the heater.

Thanks, Phil