Is my electric boiler safely grounded?

Discussion in 'General Home Brew Equipment Discussion' started by MrT, Jan 5, 2014.

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  1. Jan 5, 2014 #1

    MrT

    MrT

    MrT

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    Hello all,

    I've been wondering about this for a while now and not really found a definitive answer anywhere.

    I'm using a backer-style 2.4kw kettle element on my 70 litre boiler, with a self-made silicone washer on the inside, the rubber washer that came with it on the outside, a healthy dosing of ptfe tape and a KM8 nut. It works a treat and doesn't show any sign of leaking, which it does without the silicone washer on the inside, even with a load of ptfe.

    My question is this; Is the boiler grounded and safe? There's no real metal connection between the stainless pot and the element, is this okay?

    I always use an RCD plug and correctly rated leads/extensions with the boiler but I'm not entirely sure if that's safety precaution enough.

    Here are a few pictures of the boiler inside and out.

    outside

    [​IMG]

    and in

    [​IMG]

    Look forward to hearing your thoughts (and hopefully not a huge telling off...)


    Cheers.
     
  2. Jan 5, 2014 #2

    GAZ9053

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    easy way to test if you have a multi-meter, set it to continuity, touch one probe to earth pin on the plug and touch other probe to the boiler, if you have continuity it is all earthed.
     
  3. Jan 5, 2014 #3

    winnywood

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    Looks like the element will be earthed but probably not the boiler casing.
    Use multimeter to confirm.
     
  4. Jan 5, 2014 #4

    bobsbeer

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    Assuming the element is earthed, any connection of the element or water to live would be earthed via the element earth. So while the pot may be isolated at present, were this to change and the element fail you would be okay.
     
  5. Jan 5, 2014 #5

    nobyipa

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    :thumb:
    test with the element covered in water
     
  6. Jan 5, 2014 #6

    MrT

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    Cheers guys! :thumb:

    Nobyipa - great idea, that's thinking outside of the box! (well for me it is anyway)

    Multimeter has been bumped to the top of the 'want/need' list. (we all have that list right!..)

    Cheers all :cheers:
     
  7. Jan 5, 2014 #7

    nobyipa

    nobyipa

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    if you havn't a multimeter you can put the negative of a battery on your boiler a wire from the other battery terminal to your earth with a bulb in-between
    if the light glows your ok
    :thumb:
     
  8. Jan 5, 2014 #8

    GAZ9053

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    I would not rely on the water to earth the boiler. What if it has a fault before you fill it. You would not do a pass on a portable appliance test if you had to put water in it for an earth fault loop test.
     
  9. Jan 5, 2014 #9

    bobsbeer

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    That's true, but hopefully you wouldn't turn the element on if there was no water in there. And were that to happen it would ground via the element earth connection. This should cause the rcd to trip.
     
  10. Jan 5, 2014 #10

    MrT

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    Thanks for the replies chaps, it's interesting reading your replies and thoughts on this.

    It's very easy to add an extra earth cable into the elements that have screw/solder elements at the power end (the kind of elements used in the US "electric brewery" build) but this one terminates in a standard IEC so it's harder to add an extra earth line in.
    I really don't have much idea about this stuff I'm afraid (so sorry if it's a ludicrous idea) but would something like running a thick earth wire from the top of boiler to a nearby radiator pipe (which I'm assuming is very well grounded) a possibility? Again, sorry if that's talking cr*p!

    Perhaps I'm worrying too much about this (a reoccurring theme I'm afraid). I would say that I definitely won't ever be switching the boiler on without water covering the element if that helps with answers/discussion.

    I'll buy a multimeter anyway, useful for upcoming build plans I think.

    Cheers
     
  11. Jan 5, 2014 #11

    GAZ9053

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    Equipotential bonding on the heating system is not always that reliable.
     
  12. Jan 5, 2014 #12

    RobertP

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    I used to be involved in the manufacture of electrical equipment. If basic single insulation (ie the red or blue insulation visible when 3 core cable has the sheath cut back) is all that protects metal parts that could be touched from becoming live in the event of a fault then the metal must be earthed.

    With electrics in a metal drum that you are likely to have your hands on it makes sense to bolt an earth wire to it (the pot itself) even if its not strictly necessary. Connect the wire to the mains earth or the earth bond on incoming metal gas or water pipes. Existing earth bonds on pipes will have a wire running back to the incoming mains bond. Don't just connect to a pipe and hope its earthed.
     
  13. Jan 5, 2014 #13

    winnywood

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    The very idea of earthing metal appliances is to ensure that the fuse in the system trips when a fault condition occurs.
    by providing a very low resistance in the earth circuit a large fault current will develop ensuring that the fuse trips within the specific times allowed.

    Using water would not provide a suitable low resistance for a fault to occur in fact pure water has a very high resistance and only gets lowerd by including impuritys.

    The way elements are made (a steel tube filled with a mineral with a wire inside forming the heating element) When elements pack up it is usally through corrosion or fatigue to the outer tube causing a fault witch will be picked up by the earth to the element.
    The best way to protect yourself and others from electric shock is the use of a rcd.
    As pointed out that equipotential bonding is not that reliable another method would be to attach a wire to the metal casing of the boiler and then fit a three pin plug to that wire using only the earth stud and then plug it into a plug outlet.
     
  14. Jan 5, 2014 #14

    MrT

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    Okay, we're really getting into it now - thanks for all the info guys.

    This seems like a really good solution - thanks for the idea winnywood.
    I'm assuming that there's no chance of introducing more risk by doing this? Should I remove the L & N pins from the plug or no?

    I could quite easily connect the earth cable via a compression lug to the bolt at the the top of sight glass assembly and connect that to the earth pin on the spare plug. Sound like the right idea?

    It's interesting to hear a little bit more about the construction of heating elements too.

    Cheers all! :cheers:
     
  15. Jan 6, 2014 #15

    winnywood

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    You could remove L + N pins but i wouldnt bother ( it will help with stability of the plug in the socket ) you dont need to switch socket on either.
     
  16. Jan 9, 2014 #16

    pogierob

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    Considering liquid is conductive and metal is conductive.
    Assuming your heating element(internal or external) has an earth pin in the plug.
    Any short or potential leak will cause a few possible things most likely before zapping you.

    1. Electricity takes the fastest route to ground.
    If this is through the earth in the power cable then you might get a minor zap, if it doesn't go through the cable but goes through you then you are in trouble depending on the current.
    Will blow fuse on circuit your element is connected to.

    2.
    A short will most likely blow your element and then the fuse of the circuit it was plugged into. If there is a fault in your home wiring. Refer to option 1.
     

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