Water heater problem

[Tony Hillyard]

Afternoon everyone,
May I pick your brains? I have a water heater only a couple of years old, she keeps tripping the fuse. I have fitted a new 1200w heater element, new thermostat, new 25amp fuse unit and new wiring. Yet she still keeps blowing the fuse when the overnight low rate power comes on. Any ideas please?

 

[Pete999]

Afternoon everyone,
May I pick your brains? I have a water heater only a couple of years old, she keeps tripping the fuse. I have fitted a new 1200w heater element, new thermostat, new 25amp fuse unit and new wiring. Yet she still keeps blowing the fuse when the overnight low rate power comes on. Any ideas please?

 

[Pete999]

Have, or did you do any testing, apart from switching it on?

 

[DT1991]

What is tripping?

MCB?
RCD?
Fuse?

 

[Pete999]

What is tripping?

MCB?
RCD?
Fuse?

Check book and Pen!! lol

 

[Tony Hillyard]

I originally tested the element and it was suspect so I decided to change that and the thermostat while I was at it. It still tripped the MCB. I have had problems with mice chewing stuff before so I ran a pair of test wires from the MCB direct to the element. thereby creating a new clean circuit. Still it trips the MCB so I'm a bit baffled.

 

[Pete999]

I originally tested the element and it was suspect so I decided to change that and the thermostat while I was at it. It still tripped the MCB. I have had problems with mice chewing stuff before so I ran a pair of test wires from the MCB direct to the element. thereby creating a new clean circuit. Still it trips the MCB so I'm a bit baffled.

What were the results of the testing you did? sounds like you have, either a faulty element or you have connected it incorrectly.

 

[GBDamo]

I originally tested the element and it was suspect so I decided to change that and the thermostat while I was at it. It still tripped the MCB. I have had problems with mice chewing stuff before so I ran a pair of test wires from the MCB direct to the element. thereby creating a new clean circuit. Still it trips the MCB so I'm a bit baffled.

Does the tank have two elements?

The duel rate water heates ive seen have two elements, an off peak lower element and a boost element towards the top of the tank.

A picture of the controller and tank would help.

 

[GBDamo]

Could be MCB faile due to repeated tripping.

 

[Deleted member 9648]

You need to adopt a logical approach. Carry out IR tests on both the element and wiring back to the MCB. If all is OK carry out continuity tests on the wiring from the MCB to element terminations. If all OK check the voltage at the supply and load ends, and use a clamp to check the current drawn is compatible with the calculated expected current. If no problems are identified then it is likely the MCB device is either faulty.... or poorly terminated resulting in heat under load at the MCB connections. Also check for temperature rise in adjacent MCB's which may affect the heater MCB.
These sort of faults can always be identified by logical testing, as you have discovered randomly replacing parts is an expensive waste of time, the fault remains and you are no further forward.

 

[Deleted member 9648]

BTW....just a thought....you stated 1200w.....are you sure it's that and not 12000w? That would explain why a 25a mcb is not holding!!

 

[Tony Hillyard]

Pete999, my test was basic, just a resistance test. the element fitted was brand new. I double checked the connections with the correct wiring diagram, all appears OK.
GBDamo, this heater only has one element. Here in France it is a very common unit. 100 litres with just the one element. The MCB was replaced and has only tripped twice, so I would have thought that should be OK.
Wirepuller, I will do the checks you suggest and get back to you all. absolutely certain it is a 1200w element. But a good thought. The off peak power comes on at 10pm, that is when it trips each time.
As you all suggest, it is something basic, but I'm blowed if I can see it!

 

[GBDamo]

Off peak time clock faulty?

 

[mkuligowski]

Try 5500 watt or 6000 for tank like this one 1200 is a mistake

 

[mkuligowski]

My tank is 60 gal and I got 2 5500w elements in my opinion this element working all the time to hold temp and you probably changing this element often