Technical question for all you sparkies.....

#1
I did A2 Sparky in 1978, and haven't used it since except for minor domestic repairs and installations !
Question:
When I switch my immersion heater on, it trips the ELCB between the distribution board and the meter, rather than the CB in the immersion heater circuit. Why would it do this, and does this indicate a specific type and location of fault?

ta!
 
#2
My discipline is "C", but I've watched sparkies fitting plugs and feel qualified to pass on received wisdom.

The ELCB trips at a lesser current than other forms of circuit breaker, hence why it is the current (oh, dear) breaker of choice.

(edit: I could go on about the way that ELCBs work differently to RCCBs and so on, but unless you're A1 qualified, you won't understand. I certainly don't.)

Now, in return, explain to me why a calorifier isn't just called a heater, a word that all we non-"E"s understand?
 
#3
The ELCB trips when there is an earth fault (Phase to Earth) or (L/N to E) if you prefer
The MCB will trip on an overload or short circuit

The usual reason for a ELCB tripping before a MCB on an immersion heater system is that the immersion element has failed.

If you have an continuity/resistance tester of some type it is usually possible to test the element by disconnecting it from the supply and testing between the Live, Neutral and Earth. If there is a low or no resistance the element has failed.

Otherwise you are probably looking at the wiring or possibly the ELCB becoming too sensitive (not very common though)
 
#4
Leccy said:
The ELCB trips when there is an earth fault (Phase to Earth) or (L/N to E) if you prefer
The MCB will trip on an overload or short circuit

The usual reason for a ELCB tripping before a MCB on an immersion heater system is that the immersion element has failed.
Thanks - that's what I suspected. I'll test it....
 
#6
Unless one wants a faster heart beat and a very vigorous wake up feeling
 
#8
Leccy said:
The usual reason for a ELCB tripping before a MCB on an immersion heater system is that the immersion element has failed.
They trip at 40mA. You can trip one with the static or induced electricity in the wires after you have turned the isolator off.

It could be the immersion heater has split, so there's an earth leakage to the copper cylinder. However the immersion heater is mineral insulated and the mineral insulation absorbs moisture from the atmosphere. They will trip if they haven't been used for a while. I think that they're not usually connected to a RCD-protected circuit, but I am not a sparky. Try the UK-DIY forum, search the archives; many knowledgeable folks on there.

http://groups.google.co.uk/group/uk.d-i-y/topics?lnk=gschg&hl=en

And a calorifier isn't called a water heater 'cos it would cause confusion with gas-fired or oil-fired water heaters. The Yanks don't use the word they call them indirect water heaters (storage calorifiers) or heat exchangers (tube-in-shell heat exchangers).
 
#9
RCD, ELCB, RCCB, MCBO, call em what you will can be found with different operating times

10, 30 and 100ms (milli-seconed) being the most common

To protect human life a 30ms is used, for areas around cattle sheds etc it was common for 10ms breakers, 100ms and above are typically used to protect equipment or as the first RCD in a building with faster rate breakers used as protection on individual circuits (Discrimination {probably the only times it is legal to discriminate lol} this helps to prevent cascade tripping)

The immersion element is mineral insulated internally but this is not supposed to absorb moisture from the air as this will cause it to fail. The element is sealed to prevent moisture entering the mineral insulation is for insulating live parts from each other.
 
#10
Onetap said:
....but I am not a sparky....

And a calorifier isn't called a water heater 'cos it would cause confusion with gas-fired or oil-fired water heaters. The Yanks don't use the word they call them indirect water heaters (storage calorifiers) or heat exchangers (tube-in-shell heat exchangers).
My friend Google tells me that other people talk of gas and oil calorifiers.

He also found these definitions:

A device that heats fluids by circulating them over heating coils.
A storage vessel, not open to the atmosphere, in which a supply of water is heated.
http://www.answers.com/topic/calorifier?cat=technology

Neither of which contain the magic word "electric."

As the word seems to be a derivative of the Greek word "Calor" (heat), I can't see that the sparkies have a patent on it.

I'm convinced that sparkies use it just to confoozle us mere mortals. (Just as I'm convinced that live and neutral is a load of bo££ocks - they're of the same magnitude on each side of earth and, being alternating, swap between positive and negative anyway. So, as long as the stripey wire goes to the top of the plug, does it really matter which of the other two go to the fuse?)

(And neutral ISN'T neutral - if you don't believe me, span neutral and earth with your tongue!"
 
#11
putteesinmyhands said:
Onetap said:
....but I am not a sparky....

And a calorifier isn't called a water heater 'cos it would cause confusion with gas-fired or oil-fired water heaters. The Yanks don't use the word they call them indirect water heaters (storage calorifiers) or heat exchangers (tube-in-shell heat exchangers).
My friend Google tells me that other people talk of gas and oil calorifiers.

As the word seems to be a derivative of the Greek word "Calor" (heat), I can't see that the sparkies have a patent on it.
I fear I was a little ambiguous.
The term is mainly used in building services about heat exchangers, usually e.g., LTHW to DHW (low temperature hot water [up to 100 degC] to domestic hot water), MTHW to DHW, or (unusually nowadays) steam to DHW, MTHW to LTHW, steam to LTHW, etc..

Storage calorifers are/were domestic hot water cylinders which stored typically 50 or 100 gallons and would reheat in 1 or 2 hours. There'd be a heater battery, a 'tube bundle'of copper tubes expanded into a tube plate.

Non-storage calorifiers are typically used to generate LTHW for space heating. They have no storage capacity, maybe 10 or 20 gallons in the 'shell'.

I never heard the word used about electric water heaters, because only a moron or a sparky would consider using electricity if you've got boilers on the same site.

The cost of copper has made plate heat exchangers more common now.
 
#12
Neutral is a return path and its all to do with fuzes and and fault currents why you dont connect live and neutral the other way round (if you dont have and RCD and your supply is a TNC (Combined Neutral and Earth) your fuse would not operate when it should on a short circuit (could go on alot more about the theory side of it and the differnet ways your supply is connected up before it gets to you but frankly it bores me and I am a sparky)

And a calorifier has very limited electrical systems (usually pumps, valves, temp sensors) it is a heat exchanger (think a coil fed with hot water from a central boiler/heating system on a site being used to heat the water in a series of tanks locally ie barrack blocks)
 
#13
Sounds like, as has already been said, that the actual heater element itself is starting to fail/already failed.

you dont give any indication as to the age of the unit, if its an old one then it will start to break down causing the fault. you may also find that if pin holes start to appear in the casing of the element then this will allow water to seep into the MI which will cause it insualation properites to become less overtime.

If youve got access to an insualtion resistance tester or megger then this can be used to test between phase and earth, and Neutral and earth. as the kind of fault you have indicates an excessive earth leakage rather than a short which would normally trip the main mcb due to the large fault currents

if you dont have access to an IR tester, the best thing i can suggest is just changin the element, they're cheap enough i'm sure, try screwfix
 
#15
Isn't it just that sparkies use the term to differentiate between "slow" water heaters (for showers etc.) and instantaneous water heaters (for sinks)?
 
#16
In answer to the original question, I looked it up here;

http://groups.google.co.uk/group/uk...k=gst&q=immersion+heater+rcd#c2053809f406d33a

The usual cause is a split immersion heater which, curiously, can continue to work on a non-RCD protected circuit as an electrode boiler (live to earthed cylinder through the water). They usually split as a result of limescale causing overheating.

If unused for some time, the damp mineral insulation can cause tripping until it has dried out.
 
#17
mikey_sparky said:
as leccys said, the whole system earthing thing is a complicated affair and bores us sparks.. so we dont really wish to inflict it on mere mortals lol
It's time to come clean! I do a lot of bluffing, and I can recognise one of my fellows.

Just admit that when you do your sparkies course, you're told to use "special" words that a non-sparky won't recognise so that the job is left to the "experts."

....then carry out REME IAs by replacing bits one at a time until it works.

:) :) :)
 
#18
putteesinmyhands said:
mikey_sparky said:
as leccys said, the whole system earthing thing is a complicated affair and bores us sparks.. so we dont really wish to inflict it on mere mortals lol
It's time to come clean! I do a lot of bluffing, and I can recognise one of my fellows.

Just admit that when you do your sparkies course, you're told to use "special" words that a non-sparky won't recognise so that the job is left to the "experts."

....then carry out REME IAs by replacing bits one at a time until it works.

:) :) :)
EX is a Hass Been and a Spurt, is a drip under pressure, I love EXPERTS!
 

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