Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tankless, instant hot water heaters

  1. Aug 12, 2010 #1
    I have got an electrical problem!!! Could you respectable electrician experts please give me some much needed advice?
    On eBay I bought a couple of these tankless, instant hot water heaters for use on 220VAC:

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300454789352&ssPageName=ADME:X:RTQ:US:1123 [Broken]

    Towards the bottom of this page they says that it has to be earthed (not on Neutral).
    It heats up OK, yet the problem is that I measured about 100V between the water and (water input) copper pipe and (only) when I try to connect the earthing wire from the heater to the copper pipe, the automatic fuse goes off. The same happens if I try to connect this earthing wire on Neutral of 220V.
    This hot water heater uses an open (uninsulated) resistor/ heating wire as element and water conducts. How to earth out the residual 100V?
    Here it shows the inside of the heater:
    http://www.productoracoral.com/repuestos_eng.html
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Aug 12, 2010 #2
    Whoa...that looks pretty scary. I'd make a guess that they are meant to be run on a single phase 220v circuit that has one end at neutral/ground. US household 220v has each leg at 110v in opposite phase, so 220v between them and neither is at ground potential.

    Rather than electrocuting your dog and family I'd try to re-sell them to someone else.
     
  4. Aug 12, 2010 #3
    Yes... I don't know how they can get away with offering it on eBay... "40 years of experience" etc. They must have electrocuted more naked people in their showers than Hitler! No wonder their victims don't complain... :(
     
  5. Aug 13, 2010 #4

    MATLABdude

    User Avatar
    Science Advisor

    That's standard: you should never connect neutral to ground except at the junction box (at least, not in most parts of Canada and probably the US). If you look through older threads in this forum (ground versus neutral, etc.) you'll find that ground is used as a protective measure, to ensure that casing, parts you touch, etc. are never 'hot' relative to ground.

    Schip666, you are correct that standard household electricity is 2-phase (i.e. two legs 180 degrees out of phase). If you crack open your panel, you'll usually find double-sized breakers (or two adjacent breakers tied together with a tie bar) that straddle the two legs. Standard practice is to run 3-wire (technically, it's 4 if you count the bare copper grounding wire, but everybody refers to it as 3-wire) to whatever 220/240V appliances you have. That's the two 'hot' wires, the neutral, and the ground.

    This is probably the setup you have for your oven, if you have an electric one. Long story short, it's probably legit--you just have to make sure the case of this thing is grounded.

    The less legit part of this are the wiring requirements that are sort of glossed over. Every one of these tankless water heaters (the ones that are meant for showering, and not, say, making tea) that you might buy at Home Depot or Lowe's require something like 30 to 80 A. Then again, they can probably deliver more than 3 L per minute. Still, you're unlikely to just happen to have a disconnected 3-wire connection (of whatever ampacity) going to your bathroom. Unless you're experienced (and your jurisdiction allows it) you should probably call in an electrician to put in the appropriate breakers, the wiring, and the hard wiring of the heater.
     
  6. Aug 13, 2010 #5

    russ_watters

    User Avatar

    Staff: Mentor

    I was thinking that too - does this mean a lot of those Brazilians are using these on standard circuits with #12 wires? :surprised
     
  7. Aug 13, 2010 #6

    MATLABdude

    User Avatar
    Science Advisor

    #12 is usually good for household 20 A. #14 is used for 15 A, which is conveniently (maybe a little too conveniently) what this heater takes.

    Note that the numbers in the link below probably represent maximum allowable current (and probably not what's allowed by code in most jurisdictions)
    http://en.wikipedia.org/wiki/American_wire_gauge
     
  8. Aug 15, 2010 #7
    Today I got a message from the technical support of this dangerous water heater:

    "These units are very safe if properly installed, there are thousands installed for over 40 years and not a single casualty.
    Your local water probably has a high mineral water an conductivity, however please try the following:
    Do not use a circuit breaker with residual current protection as this will shutoff the unit., USE NORMAL CIRCUIT BREAKER 20 AMPS
    and Ground the Unit.
    You should only detect about 30 to 36 volts between the running hot water and the tap/
    Try with another unit"

    How should I respond to their letter? As a reply I prepared something like this, but maybe you have a more professional reply and so, I better wait and send the reply tomorrow (Monday 15th):
    "Yesterday I called my electrician, who installed the whole electrical wiring and he explained to me: that the RCD is tripping for a good reason. I should not put my hand anywhere near that water because I could end up dead! The reason they're meant to be earthed is for safety, so that if a fault develops the current has somewhere to go. There obviously is a fault, because as soon as you connect it to earth the RCD trips. If there wasn't a fault, I would measure 0v between the water & copper pipe.
    Thus, I am seriously compromised and don't dare to ask him to remove the RCD. He also mentioned that if for any reason the ground wire comes off, I won't survive the shower. Therefore, this water heater is in deed life threatening.
    I have an installed Chinese tankless, instant hot water unit and no such problem with it. I trusted your product to be equally safe, but as it turns out it's not the case. Please be so kind to compensate me for the shipping losses".
     
    Last edited: Aug 15, 2010
  9. Aug 15, 2010 #8

    russ_watters

    User Avatar

    Staff: Mentor

    I keep forgetting that residential is 15A/#14 - commerical general power circuits are 20A/#12. Anyway, I was still thinking of something else - thinking they were going to run 30A through it:

    There is a discrepancy between the ebay page and the homepage (linked from the OP). The sentences that have the voltage, amperage, and Brazil in it in the homepage say:
    whereas the same sentences on the ebay page read:
    Googling, it looks like Brazil uses 110/220. What I was wondering is if there are really two different products or not: are people running the 110V/30A version from standard household circuits.
     
    Last edited: Aug 15, 2010
  10. Aug 15, 2010 #9

    russ_watters

    User Avatar

    Staff: Mentor

    Ask them if it is UL listed or has been tested by any such uderwriting lab/agency in any country they sell it in.
     
  11. Aug 15, 2010 #10
    Yes, that sort of questions I should include in my reply to their email... Thx for that! :)
     
  12. Aug 15, 2010 #11
    Hitler did not electrocute, but gas people. Also, Godwin's Law.
     
  13. Aug 15, 2010 #12
    Here's, yet another model of their range of "lethal products": http://www.productoracoral.com/electron_eng.html
    In that video you can hear the (low volume) voice of camera man telling him to put the finger into the glass... to prove how safe it is. I am just amazed that they can they get away with this?
     
  14. Aug 15, 2010 #13
    True, but here I tried to rather focus onto "killing naked people in the shower"... whatever form is particularly macabre.
     
  15. Aug 15, 2010 #14

    MATLABdude

    User Avatar
    Science Advisor

    jjj333, have you tried earthing using the bare copper wire that comes out of the electrical box instead of the copper pipe? Having just reread your original post (edited?) it seems as if you've already installed this unit, and the breaker is going as soon as you flip the breaker.

    It's possible that your plumbing isn't properly grounded (or grounded at all) if it's significantly above 'ground'. That or you have a short somewhere, and one of your 'hot' wires is making contact with the plumbing. The old standard was to run a thick copper conductor and clamp it to the pipe near where it enters your building. Over time, corrosion can prevent good electrical contact between the clamp and the pipe, allowing for your plumbing to be at a different potential than 'ground'.

    If you don't have a ground conductor in the cable that you have in the washroom (and can't do what I recommend above), this may also indicate that your neutral is disconnected from your ground at the panel. This is easy to check: measure the voltage between the neutral and ground prongs in any outlet. This assumes, however, that your house actually has the standard 3-prong outlets (this isn't always the case in north american houses that are older than 40 or 50 years):
    http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#Type_B

    Lastly as Russ points out, the manufacturer's website states very clearly that this product uses 30 A at 110 V (I'd trust them over the guy hawking them on eBay), and thus around 3 kW. Hooking this unit up to 220 V doesn't halve the current, it actually doubles it (assuming no significant resistance change due to temperature, or there isn't a second model which is actually designed for 220 V / 15 A). If the breaker only blows once you hit the switch on the unit (i.e. not a grounding / wiring fault as outlined above) then it's blowing for the very expedient reason that you're trying to pull 60 A from a 15 A breaker.
     
    Last edited: Aug 15, 2010
  16. Aug 15, 2010 #15

    MATLABdude

    User Avatar
    Science Advisor

    It's fine, assuming that the electrical bits are (electrically) insulated from the water. This is the case with aquarium heaters, and (usually) the heating elements on electric ranges (i.e. if you touch them while they're operating, they may burn you, but they won't electrocute you)
     
  17. Aug 15, 2010 #16
    Thank you MATLABdude for your reply... :)

    Yes, you are right, that got to be measured not just assumed and so, I just tested it: I put the multimeter to 750VAC and measured 0V between neutral and water pipe and 0V between neutral and the copper pol (hammered) in the ground. That means all three, i.e. the Neutral and Ground Pol and the water copper pipe are grounded. Besides, I discovered the difference of potential between Neutral and the plumbing when I was a 16, starting my hobby in electronics. It was, when I wondered when I touched a hairdryer of which metal casing was earthed on Neutral. When I touched the tap I felt a low current voltage. I then measured it and it showed 90V. I then held a piece of wire between the metal housing and
    the tap... et voilà, the 90V disappeared! That's how I taught myself shocking electricity!
    My house wiring is only 2 years old. Chilean plugs have got 3 prongs: A, N & Earth.
    ...and that's of course the one I bought:
    http://cgi.ebay.ca/Electric-220V-Tankless-Water-Heater-SHOWER-HEAD-10105P1-/300451636441?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item45f45024d9
     
  18. Aug 15, 2010 #17

    MATLABdude

    User Avatar
    Science Advisor

    Okay, good that these are now eliminated. Odd that they only have the 110V version on their main page, but have a 220 V version on their sales page... Perhaps it's as simple as the resistance (or the contacts for the resistance) are shorting out against the casing somehow? Can you do a continuity check between the three (disconnected) wires of the device, with and without the water switch activated?

    ...And you have really, really good English for somebody in Chile (unless you're an ex-pat from the US or the Commonwealth countries)
     
  19. Aug 15, 2010 #18
    Now the units are already packed up and sealed in the box to be shipped back, first thing tomorrow... :) Yet, I opened them before and as you can see in their Pic, it has got a neoprene membrane onto which the element is screwed on and the top cover houses the two copper contacts with the two wires; looks rather neat. The ground connector consists of a screw inserted into the side of the container, touching the water. The only thing I could have measured would have been the resistance of the heater element itself. It worked O.K.; i.e. as soon I opened the water tap, the water started to heat up and when I closed the tap, the heater element switched off. Yet, I/it failed to remove the measurable 100V between the water and earth.
    Yea...you guessed it right... I lived 35 years in .au and now I'm a young pensioner (68) in Chile. Besides, I'm a "whistler-musician" and self-styled philosopher. My books are on LULU (see preview) and my whistling Demo, here:



    http://www.live-styler.de/home/images/jjj-DEMO.wma

    Enjoy! Johannes K. Drinda ("Made in G") :)
     
    Last edited by a moderator: Sep 25, 2014
  20. Aug 15, 2010 #19

    Averagesupernova

    User Avatar
    Gold Member

    Not likely. A 15 or 20 amp breaker would trip quickly.
     
  21. Aug 16, 2010 #20
    Today I sent them back... but received yet another message from their technical support, saying:
    "You have to use a regular breaker, and do not worry you will not be electrocuted, thousands have been installed in Brasil, Colombia nad USA and not a single electrocution, so Chile should not be an exception.
    All the electric showerhead manufacturers use this exposed wire element, such as Lorenzetti Brasil, Coral, Bocherinni, with an exceptional safety record".

    So, they badly want me to step under this shower, albeit my electrician wants to save my life... :rolleyes:
    I'll let you know how this saga will end.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook