I hope someone can help me with my three year old 8.5kw Triton Jade electric shower which has suddenly developed a fault. Here's the problem:
-on lower temperature setting and cold setting, shower works fine.
-on higher temperature setting, shower immediately trips the main "master" rcd at the consumer box (but not it's own individual rcd)
If the button on the shower unit is in the on position and the temperature is on the lower setting or cold setting, then when I switch on by pulling the pull cord the shower works fine. However, If I then pull the pull cord to switch off the shower, it trips the consumer unit. (On the higher temperature setting, I cannot use the pull cord to switch on or off without tripping.)
My first thought was that the shower is faulty and needs replacing, but the fact that I can get trips in cold setting makes me wonder if there's something wrong with my pull cord switch or consumer unit.
I tested the heater can elements in the shower, of which there are two, and they have 12.3 ohms so they seem to be fine.
You most likely have an earth fault on second element. You have not given sizes of RCD's if both 30ma I would expect the consumer unit one to trip first. There should be a difference between the two either 100ma and 30ma or 30ma and 10ma but it is common on up grades to leave the shower one in even though it is never likely to trip does no harm so why remove it.
Many thanks for your prompt response, it is really appreciated and I think it clears up why the whole consumer unit is tripping. When you say I have an earth fault on the second element, are you referring to the shower unit itself or something else.
Yes I do mean inside the shower its self.
Every circuit will have a slight amount of earth leakage and the one in the consumer unit sees all this leakage but one on shower only sees leakage from shower. Under the new regulations that come in on 1st July 2008 it addresses this problem and makes it clear that when we split into final circuits this includes the RCD and the days of single RCD controlling whole board are over.
Thanks, that's really helpful. One last piece of advice if I may. If the shower unit is the cause of the fault, do you think replacing the heater can assembly will resolve the problem, (it looks like its not beyond me, simply screwed in with spade connectors to the elements). Otherwise, should I buy a new shower, and have the hassle of different entry points.
Since you say 12.3 ohms you must have a meter. Measure on highest range between either terminal and the casing you need a reading of 1000000 ohms or more i.e. 1meg ohm if lower you are assured that it is faulty because your meter will measure at low volts it may not pick-up the fault ours use 500 volt to measure with but if it does they your 100% sure thats the fault assuming you have disconnected it before measuring. Then you can order your part but I think you may have problems getting it worth a try
If you can get a replacement heater can assembly for much cheapness then go for it, however as its the most important part of the shower, chances are it will be easier/cheaper to replace the whole unit.