My electric hot water tank has taken to tripping the mcb. This is a thought experiment as I won't be able to pull it all to bits until the weekend. There appear to be three possible places for the problem: the mcb, the timeclock, or the heater element.
The evidence, m'luds is as follows:
Element was replaced three years ago.
The timeclock (which is a fair age) is set to "on" from 6 to 7.30am. The other morning it had stopped at 3am. This morning it had stopped at 6am.
It is possible to turn the mcb back on and for water to heat up.
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Random thought process at work.
> The other morning it had stopped at 3am
Question, the MCB isolates what? just the tank? IS the timer switch single pole or does it isolate both poles to the element? (likely single pole)
Thought 1, its not the element, it wasn't powered up, could be anything in that MCB circuit up to the switch in the timer, including the synchronous motor.
Thought 2, 6:00am its far to much of a coincidence for it not to be the element. Or anything else in the chain.
In short, you need to investigate.
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Is it just protected by a mcb not a RCBO ? Fundamental difference in possible mechanism of failure.
Like Zero, the coincidence of 6.00am ? Not pure chance?
Last edited by: pmh on Wed 6 Jul 11 at 19:17
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There's nothing else on the circuit. Only the MCB (not an RCBO) (and the timer).
No idea whether timer is single or double pole. Why?
And what is a synchronous motor in this context?
Gut reaction is to replace the element... but it might just be the timeswitch.
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>> No idea whether timer is single or double pole. Why?
If the switch is single pole, its switching the live. Its possible for the problem to be in the neutral and kick off the MCB at any time. If the timeswitch is double pole then your 3:00am incidence was up stream of the switch.
>> And what is a synchronous motor in this context?
Drives the timer if its one of the mechanical ones - they can go (i had one on a 3 way valve that popped a MCB) and trip the MCB at any time.
Like you, I would hit the element first, its in a hostile environment and is a likely casualty.
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Me to. Elements thrown a wobbler, creates more resistance and trips the switch.
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Tripped at 6am again. Makes me wonder whether it's the timer.
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Can you - simply and safely - bypass the timer?
The last house I had with an immersion heater didn't have one.
It was used as a back-up and switched on or off when needed.
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>>Tripped at 6am again. Makes me wonder whether it's the timer.
>>Can you - simply and safely - bypass the timer?
I would strongly suspect the immersion heater.
As soon as the power is applied it trips the MCB.
As the heater is quite new it might just be the thermostat in the heater head.
If you are getting the heater replaced ensure you get the more expensive Incaloy version.
These have a different plating that reduces the rate at which they rot.
www.wickes.co.uk/heating/immersion-heaters/icat/hcimmheaters/
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>>I would strongly suspect the immersion heater. As soon as the power is applied it trips the MCB.
Apart from the fact that I can reset the MCB and it runs perfectly well, making hot water. It trips the moment the power is applied by the timer.
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Because at switch on the element has a current surge. Your finger overcomes the surge trip when you remake the MCB
Last edited by: Zero on Fri 8 Jul 11 at 13:38
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It was the element. Twisted and corroded beyond belief, the element split with the wires showing along more than half of the length of the element. Extraordinary that it was still working.
I also need a new timeclock - which no longer works as a timer, hence explaining why it sometimes tripped at a time otherwise than 6am.
Should I be concerned at the two inches of sludge in the bottom of the tank?
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>> Should I be concerned at the two inches of sludge in the bottom of the
>> tank?
>>
Up to you, you have to use / drink the water from it. Also is it liable to get into your boiler (if you have one) and what is causing it? Corrosion in the system somewhere?
Last edited by: Old Navy on Mon 11 Jul 11 at 10:36
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>> >> Should I be concerned at the two inches of sludge in the bottom of
>> the
>> >> tank?
>> >>
>>
>> Up to you,
yup, leave it there its not going anywhere. Clearly it will come back if you syphon it out. see last comment.
>>you have to use
for hot water only - shower, bath washing up.
>>drink the water from it.
Its not drinking water... Never drink hot water from a house system,
>> Also is it liable to get into your boiler (if you have one)
No its not, the boiler circuit is sealed.,
>>and what is causing it? Corrosion in the system somewhere?
Hard water area, limescale, caused the element to fail probably.
>>
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>> >> Should I be concerned at the two inches of sludge in the bottom of the tank?
>> >>
>> Up to you, you have to use / drink the water from it. Also is it liable to get into your boiler (if you have one)
>> and what is causing it? Corrosion in the system somewhere?
If the OP's immersion heater is in daily use run from a timer that would suggest it's his only method of water heating, i.e. there is no boiler.
Most (but not all, Zero!) boiler-fed hot water storage systems in the UK are indirect, that is the water passing through the boiler (primary) is kept completely separate from the water that comes out of the taps (secondary).
The sludge is likely to be a combination of scale from the heater element and years of dissolved carp in the water supply - as long as the hot water at the taps isn't discoloured then there's no need to worry.
>> Its not drinking water... Never drink hot water from a house system
Wrong. All tap water has to be potable in a UK domestic installation. I fill pans and the kettle from the hot tap to save a small amount of energy as the water is already partially heated.
Last edited by: Dave_TDCi on Mon 11 Jul 11 at 11:01
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>> Wrong. All tap water has to be potable in a UK domestic installation. I fill
>> pans and the kettle from the hot tap to save a small amount of energy
>> as the water is already partially heated.
Right!
If you ever drink hot water from the domestic system without boiling it you are in severe danger of poisoning yourself. Thats just the bugs, let alone the dissolved rubbish in the water. Don't ever run a food outlet Dave.
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>> If you ever drink hot water from the domestic system without boiling it you are in severe danger of poisoning
>> yourself. Thats just the bugs, let alone the dissolved rubbish in the water
Just as well I don't bathe in it then, or wash up all my crockery and cutlery in it. Oh hang on, I do.
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>> Just as well I don't bathe in it then, or wash up all my crockery
>> and cutlery in it. Oh hang on, I do.
Try drinking it. It would save all your money worries, as long as you have a burial policy. And as I say, whatever you do don't go into the catering game.
Last edited by: Zero on Mon 11 Jul 11 at 14:28
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>> Try drinking it. It would save all your money worries, as long as you have
>> a burial policy. >>
Drag yourself up to date, we don't all have wildlife swimming pools in the loft, and those that do have insulated lids.
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I am up to date my old fruit, you try doing a little research.
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>> Right!
>>
>> If you ever drink hot water from the domestic system without boiling it you are
>> in severe danger of poisoning yourself. Thats just the bugs, let alone the dissolved rubbish
>> in the water. Don't ever run a food outlet Dave.
Only true if you have a hot water cylinder fed from a tank in the loft surely? Though having said that our our hot water comes from an unvented cylinder (mains fed), so in theory there's no reason not to drink it or use if for cooking. Doesn't seem right though, so we never do...
Peter
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Probably the biggest risk in drinking from the hot supply is lead. In older houses where there may still be lead plumbing or where lead is present in soldered joints the lead can be leached into the water. This effect is considerably more pronounced with hot water and so the hot supply can sometimes contain comparatively high concentrations of lead.
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That's precisely why we were warned against this as kids - my dad knows a thing or two (or three even)
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>> This effect is considerably more pronounced with hot water and so the hot supply can sometimes
>> contain comparatively high concentrations of lead.
The most likely source of lead contamination is the consumer supply pipe from the main in the street to the stop tap in your property, if the house was built before the 1950s and the supply pipe hasn't been replaced with a blue PE one yet.
I'd be very surprised to find a modern DHW system with a copper cylinder and an immersion heater still using lead pipework.
Last edited by: Dave_TDCi on Mon 11 Jul 11 at 15:27
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"I'd be very surprised to find a modern DHW system with a copper cylinder and an immersion heater still using lead pipework."
Probably true for pipework but lead bases solder was still being used into the nineteen eighties when it was banned for use in domestic water systems
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>> The most likely source of lead contamination is the consumer supply pipe from the main
>> in the street to the stop tap in your property, if the house was built
>> before the 1950s and the supply pipe hasn't been replaced with a blue PE one
>> yet.
>>
I'd be very surprised to find a a lead supply pipe that left undisturbed for decades has not got a lining of hard deposits.
>>
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My new boiler was fitted last week, the water in the heating system had been there for five years with a corrosion inhibitor, it was last drained during a bathroom refit. The water came out of the system clean and not discoloured. The water that came out after a high temperature chemical clean also came out clean. We do not have limescale in this area.
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>> Its not drinking water... Never drink hot water from a house system
>Wrong. All tap water has to be potable in a UK domestic installation. I fill pans and the
>kettle from the hot tap to save a small amount of energy as the water is already partially
>heated.
It may be supposed to be potable, but it doesn't mean it is. Rats have a habit of falling into water tanks in the roof. All water drunk should come straight out of the rising main.
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I am with zero on this - never would drink the water if fed from a storage tank! Dead birds dead rats common place despite having a 'proper' cover on the tank!
What would concern me is the fact that you say the wires on the element were exposed. I would have expected that the RCD should trip out.
Have you checked it as normally instructed ie quarterly?
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>> RCD?
>>
Residual Current Device, ELCB, or whatever acronyms are in vogue
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he hasn't got an RCD, just an MCB that's why it tripped rarely. If he had an RCD (or ELCB) it would have tripped all the time.
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>> he hasn't got an RCD, just an MCB that's why it tripped rarely. If he
>> had an RCD (or ELCB) it would have tripped all the time.
>>
Where did he say there was no RCD? I would have thought that most sensible installations would have had them retro fitted by now. RCD save lives - MCB just prevent fires.
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>> never would drink the water if fed from a storage tank! Dead birds dead rats common place despite
>> having a 'proper' cover on the tank!
The cistern in the loft should have a Byelaw 30 kit, i.e. a sealed lid on top and mesh screens on the inlet and warning pipe. If you're getting dead animals in the loft I'd want that sorting out pretty quickly, especially if they're clever enough to get in the cistern!
Houses in mountainous areas sometimes have an indirect cold cistern in the loft to supply their cold water taps when their mains pressure is too low to allow a decent flow direct from the supply. The same Byelaw 30 sealing kit is used to keep insects etc. out as with indirect DHW systems.
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As a combi boiler owner, I have no fears about drinking the water from the hot tap.
But most of my water consumption is tea or coffee, and my understanding is the best brew is made from freshly drawn cold water.
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its got nothing to do with the dead rats in the water, its do with water that may not be hot enough to kill bacteria, but may instead be incubating them in nice warm stagnant water over night.
But hey you lot drink your hot water from the hot water tank. I like a good funeral, make sure you have corned beef sarnies at the wake.
Last edited by: Zero on Mon 11 Jul 11 at 19:19
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>> The cistern in the loft should have a Byelaw 30 kit, i.e. a sealed lid
>> on top and mesh screens on the inlet and warning pipe. If you're getting dead
>> animals in the loft I'd want that sorting out pretty quickly, especially if they're clever
>> enough to get in the cistern!
Your header tank cant be sealed, if it was sealed it would create a vacuum and collapse.
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Sealed does not mean airtight. It can vent through the warning (overflow) pipe.
Last edited by: Old Navy on Mon 11 Jul 11 at 19:23
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Its not sealed then is it.
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Goodness, you like to live dangerously Zero. What about clostridium perfringens type A?
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>> Goodness, you like to live dangerously Zero. What about clostridium perfringens type A?
Branston pickle is an antidote.
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>> The cistern in the loft should have a Byelaw 30 kit, i.e. a sealed lid
>> on top and mesh screens on the inlet and warning pipe.
etc.
This is the sort I most recntly fitted
www.calveshill.com/water-tanks/below-ground-water-storage-tanks/paxton-below-ground-water-storage/
Bylaw 30 kits are very cheap - £5 - £10 upwards and pretty easy to fit providing the existing tank can be fitted with a proper lid so the tank will almost certainly be plastic.
For those who are not up to speed
www.norscreenfilters.co.uk/insect_screens_en.htm
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>> It was the element. Twisted and corroded beyond belief, the element split with the wires
>> showing along more than half of the length of the element.
>>
See my earlier advice on which replacement to get
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>> See my earlier advice on which replacement to get
Thanks, that's exactly the sort I fitted.
Any recommendation for a new timeclock? (Cheap and cheerful will be perfect, but not so cheap that it has no life.)
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Hot water problem - Zero
