The case of the mysterious Immersion heaters....

Discussion in 'Electricians' Talk' started by sparky Si-Fi, Jan 30, 2004.

  1. The Trician

    The Trician New Member

    A clip-on ammeter (clamp meter finds it every time. Current or no current!!
     
  2. leeds spark

    leeds spark New Member

    "A clip-on ammeter (clamp meter finds it every time. Current or no current!!"

    HOW??
    I may be stupid here,city and guilds 2361,2362,2380,2391,national electrotech AM1+2,12 years experience,and would hate to dissagree with anybody,but a clamp meter is simply an ordinary ammeter with a current coil wound into the jaws,no current in primary(eg,the jaws,no current in secondary,so how do you work that one out??
     
  3. The Trician

    The Trician New Member

    "A clip-on ammeter (clamp meter finds it every time.
    Current or no current!!"

    HOW??
    I may be stupid here,city and guilds
    2361,2362,2380,2391,national electrotech AM1+2,12
    years experience,and would hate to dissagree with
    anybody,but a clamp meter is simply an ordinary
    ammeter with a current coil wound into the jaws,no
    current in primary(eg,the jaws,no current in
    secondary,so how do you work that one out??


    EXACTLY! Surely, as you have made me acutely aware of your esteemed qualifications, you should henceforth be aware that if you know the current rating of the equipment, and this equipment is not doing its job, - heating up the water in this case - despite what the Main metering is telling you, then you can check this with an ammeter. 3KW Immesion heater at 230V = 13.04A or thererabouts. So, you clip the ammeter onto the Live first to see if the heater is pulling 13A. Place it on the Neutral and the reading should essentially be the same. If the readings differ, then you know you have a problem with the heater element/connection/whatever.
    Measuring current when fault-finding with a voltmeter yeilds no results is sometimes a good idea - Savvy?
    Sometimes it is a good idea to test under load conditions to see if whatever you suspect is faulty, is, or is not doing 'as it says on the tin'.

    This comes from 25 years in the electrical industry working on many different types of plant/machinary/environment. I hold similar qualifications to yours but I find my experience to be the more useful of the two:)
     
  4. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Well,Well,Well, this has certainly started an interesting post..will be back later
     
  5. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    I use a clamp meter quite often,usually use the tails as a good source,isolate everything else aprt from the circuit you are on

    (I did this as well BTW)

    used insulation tester also to check elements.
     
  6. lastword

    lastword New Member

    It could be a dodgy thermostat in one or other of the IH's. They tend to jump back into action (for about a week) at the slightest touch. Even just taking the lid off can do it.

    If it's the bottom element then your customer only gets hot water from the top of the tank which soon runs out. So he concludes that the element has gone.

    If it's the top element the whole tank will eventually get hot, but it takes much longer than usual (about 2 hours). Again, your customer concludes the element has gone.
     
  7. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    ok just to recap....

    Supply from board to both separately supplied DP switches ok(neons on btw)but tested anyway!
    Insulation tested both elements...'bout .15 megs between live conductors...........200+Megs between live conductors and earth..to me ok

    tested cont thru stats.ok

    clip on ammeter think was about 24/25 Amps and watching supply boards meter belt round like a fiddlers elbow.

    Oh one other thing,tried persuading him/her that he got no RCD's on his TT supply and he wants them like he life depended on it!.

    That is half of our trouble,persuading the general public that what they need will save their life,but it always comes back as 'this bloke is trying to roll us over!'

    Oh well,yet another non-compliance to BS 7671 on the cert!
     
  8. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    .................oh and still have not heard a dickie-bird from 'em!,weird this!
     
  9. supersparky

    supersparky New Member

    evnin sifi
    metal expands when hot, prehaps a crack in metal which opens whan at a certain temp, but element is covered in scale so traps air, preventing water rushing in for a while
    thats one of my recent anyway...

    ss
     
  10. The Trician

    The Trician New Member

    .................oh and still have not heard a
    dickie-bird from 'em!,weird this!

    You don't think they're dead do you???

    Anyway, on to a much more important question

    Why DO egg & bacon butties taste better when eaten outside? Just had 2 and they were belters:)
     
  11. leeds spark

    leeds spark New Member

    Hey,The Trician,a split element can pass around 13a to earth,so how do you tell where its going?And btw,your right about the bacon butties,must be something to do wtih the outside air,ever noticed how much betterfish'n'chips tste t the coast? :).

    Sparky SiFi,in my experience with immersion heters,if it int the thermostat,leave it to a plumber.If youare lucky enough to be able to completely drin an old cylinder,then it'll invariably getyou bck by refusing to let go of it selement.If you are extremely lucky and get the element out without the cylinder breaking,then make sure you clean thread up before inserting new one,they can be a c* to seal.Good luck with it....wanna borrow my bargepole? :)
     
  12. leeds spark

    leeds spark New Member

    gonna have to get a new "a"key.....
     
  13. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    I am just about convinced its a plumbing fault.

    Bloody give up now!

    Still as I keep saying,still have not heard nothing,maybe Tric is right,perhaps there dead.

    Find out soon as put an estimate in for some little stuff he wants sorting.
     
  14. The Trician

    The Trician New Member

    Hi Leeds!
    If it was passing 13 A to earth at 240V I think you'd feel it! OR the fuse/protective device should blow.

    You're right about fish'n chips though - Marvelous on the sands:)

    You're also dead right about trying to remove a knackered immersion heater - and you can keep hold of your barge-pole - I've got my own when it comes to these things. Usually it ends up as 'Time to buy a new cylinder guv':)
     
  15. leeds spark

    leeds spark New Member

    If it were passing 13a to eath then its would only be passing its rough design current anyway,an IH is usually on a 16a breaker which will carry tht indefinately.Although i have to admit,if this blokes on a TT system as pointed out then yes one would expect to feel it.
     
  16. The Trician

    The Trician New Member

    I see your point here but I would expect the fault current to be higher than 13A. As you say, its not impossible for a faulty element to pass the equivalent of its design current to earth but it surely is unlikely?

    To eliminate any doubt you could drop a clip-on ammeter onto the earth cable and see what's flowing......:) :)

    Still reckon a clip-on will find it see!!
     
  17. ban-all-sheds

    ban-all-sheds New Member

    SS - I hope your elusive customer appreciates all the behind-the-scenes work you've been doing - how long before your hourly rate exceeds the cost of new IHs?
     
  18. Puterfixer

    Puterfixer New Member

    Had something simular with a Wickes unit was a faulty Stat that showed as working till it had been on for around 15 mins and just cut out dead when the water got to 30 degs when it was cold put meter on and all ok

    Hope it helps
     
  19. supersparky

    supersparky New Member

    its not the hardest thing in the world to work out when you can see a hairline crack in the element!
    think about it, a small crack will hold air untill it is forced out when the pressure pushing putwards exeeds that of the surface area of the air buble...simple, yet again, think about it sheds use ur noodle!
    cant help but think that now you think im gone your still trying to get one over on me :eek:

    ss
     
  20. Damocles

    Damocles New Member

    Just remembering that theres two elements, so both must be faulty?
     

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