Like Tree2Likes
  • 1 Post By Raccon
  • 1 Post By talllatte

technical electricity question

Closed Thread
  1. #1

    Join Date
    May 2008
    Location
    New Territories
    Posts
    320

    technical electricity question

    I just had a new german-pools 6000w under-sink water heater installed. My place is fairly new, and it had the switch on the wall, and the plumbing/wiring under the sink ready with dedicated wiring (in three phase, though). I just added the heater to complete it. However, it's not working at correct capacity (ie, the temp per flow rate is low - really low).

    I thought I had single-phase power in the house, but I don't - I have 3-phase. And apparently this unit is designed for single phase (and I bought it on that premise). The electrician who came out said no problem, and made a few wiring changes, either in the breaker box, or under the sink. Not sure exactly how he hooked it up. But I do know you can wire single phase appliances into three phase - that's how whole houses connect to the grid in many parts of the world - single phase is run from the pole into the house. but here in HK, at least in some places, 3 phase comes right into the breaker box, and runs around the house, for big things that need it, like water heaters.

    My question - is it possible he hooked up the heater wrong? his explanation for why it's not very warm is because of the wattage (6kw)combined with the phase switch-ery he had to perform. My friend's mom just had a similar unit installed - and it runs reallly hot.

    My technical knowledge is limited, but I think there is a phase balance problem or something like his hook up is faulty....

    Any recommendations? Like a good *HONEST* English speaking electrician that won't charge a fortune just to talk to me and see if something can be done?


  2. #2

    Join Date
    Sep 2008
    Posts
    3,677
    Quote Originally Posted by AsiaJason:
    I thought I had single-phase power in the house, but I don't - I have 3-phase. And apparently this unit is designed for single phase (and I bought it on that premise). The electrician who came out said no problem, and made a few wiring changes, either in the breaker box, or under the sink. Not sure exactly how he hooked it up.
    Normally not a problem since each phase against Neutral gives you 220-240VAC, but if there isn't any Neutral in the outlet under the sink it won't be easily possible to connect single-phase equipment; wiring across two phases would provide a higher voltage and likely damage the heater, not to mention the safety issues this would cause.

    But I do know you can wire single phase appliances into three phase - that's how whole houses connect to the grid in many parts of the world - single phase is run from the pole into the house.
    If you have 3 phases in the house then typically those come also from the pole, it's not possible to make 3-phases out of one by wiring alone.
    Instead a converter is needed, but it's not something most people would have unless you really do need 3-phase supply, the converters are bulky and not cheap, especially if you want to supply a whole house from it.

    ... but here in HK, at least in some places, 3 phase comes right into the breaker box, and runs around the house, for big things that need it, like water heaters.
    3-phase supplies make more sense than single ones, and will hopefully become more common.

    My question - is it possible he hooked up the heater wrong?
    Seems like it, though ....

    his explanation for why it's not very warm is because of the wattage (6kw)combined with the phase switch-ery he had to perform. My friend's mom just had a similar unit installed - and it runs reallly hot.
    I am wondering how he did this; since it doesn't heat properly it must be running at a lower voltage than specified but I can't quite figure out how that can be done with a 3-phase supply.
    AsiaJason likes this.

  3. #3

    Join Date
    Jun 2007
    Location
    Ex Sai Kunger Sunny Qld for now
    Posts
    8,318

    Raccon, I was thinking how they did this also, without seeing a wiring diagram of how the heater elements are configured/switched. From what I was reading off the German Pool website, these 16kw + heaters draw 26 plus amps, and am assuming when he disconnected the other 30 amp breakers ( assuming there were a bank of 3 ) Now only one active conductor ( 220V) L1 and Neutral are providing power to the heater. If the OP has a 380V 3 PHZ power supply, then why aren't they connecting the heater to its proper wiring config ? If you have a 380V 3 phz appliance, it should be wired to a 380V 3 phz supply for maximum efficiency, which will provide lower running cost.

    Converting a 3phase appliance to a single phase is a bit like fitting a tow ball to the front bumper of your car, trying to push a trailer, instead of pull... Very illogical as to whats happened here.


  4. #4

    Join Date
    May 2008
    Location
    New Territories
    Posts
    320
    Quote Originally Posted by Raccon:
    I am wondering how he did this; since it doesn't heat properly it must be running at a lower voltage than specified but I can't quite figure out how that can be done with a 3-phase supply.
    Hmm. what you say makes sense....

    I'm not sure, but in your opinion, is it worth it to have someone come out? Do you know anyone?

    Anyone know an electrician that they trust?

  5. #5

    Join Date
    May 2008
    Location
    New Territories
    Posts
    320
    Quote Originally Posted by Skyhook:
    Raccon, I was thinking how they did this also, without seeing a wiring diagram of how the heater elements are configured/switched. From what I was reading off the German Pool website, these 16kw + heaters draw 26 plus amps, and am assuming when he disconnected the other 30 amp breakers ( assuming there were a bank of 3 ) Now only one active conductor ( 220V) L1 and Neutral are providing power to the heater. If the OP has a 380V 3 PHZ power supply, then why aren't they connecting the heater to its proper wiring config ? If you have a 380V 3 phz appliance, it should be wired to a 380V 3 phz supply for maximum efficiency, which will provide lower running cost.

    Converting a 3phase appliance to a single phase is a bit like fitting a tow ball to the front bumper of your car, trying to push a trailer, instead of pull... Very illogical as to whats happened here.
    My heater is the smallest - a 6Kw - HERE

    It does say it's for a single phase power. and our outlets is definitely 3 phase.

    Also - the indicator light on the switch (outside the kitchen) barely lights up - but the electrician said it's because of the switch to single phase( and it's a 3 phase switch). so it sounds like he's only using one wire.... but he did some work in the breaker box (yes, there are 3 banks) so I'm not sure what he could have done. Unless there's no neutral under the sink, and he turned one of the colored wires into a neutral. But that doesn't explain the possible low voltage situation, does it?


    I guess I just need someone reliable to come out. Any suggestions?

  6. #6

    Join Date
    Sep 2008
    Posts
    3,677
    Quote Originally Posted by AsiaJason:
    But that doesn't explain the possible low voltage situation, does it?
    Nope, if he did that the heater should work correctly.

    I guess I just need someone reliable to come out. Any suggestions?
    Sorry, dunno anyone.

  7. #7

    Join Date
    May 2008
    Location
    New Territories
    Posts
    320

    Thanks for your input guys, I do appreciate it.


  8. #8

    Join Date
    Dec 2005
    Location
    south pacific region
    Posts
    517

    Also you might want to double check that the house water lines in & out are connected respectively to in & out on the heater.

    ((this had actually happened to a water heater i had installed, same effect; the water was not so hot))

    Last edited by WalkAbout; 26-11-2010 at 07:04 PM.

  9. #9

    Join Date
    Jun 2006
    Posts
    123

    I've seen some shockers (no pun intended) installations over here!

    All supply in HK in 3 phase, you should to have it up to your unit, otherwise it is certainly on each floor.

    So the 220V 1PH appliance is running "cold". Since it is 1PH it is quite unlikely how it could get wired incorrectly. 26A 1PH is a big old chunk so it could be (as Skyhook was leading to I think) the old boy has possibly disconnected a heater inside to lower the power - if it was say 3 x 2kw elements.

    All conjecture but a simple fix for any not a cowboy.

    Skyhook likes this.

  10. #10

    Join Date
    Jun 2007
    Location
    Ex Sai Kunger Sunny Qld for now
    Posts
    8,318
    Quote Originally Posted by talllatte:
    I've seen some shockers (no pun intended) installations over here!

    All supply in HK in 3 phase, you should to have it up to your unit, otherwise it is certainly on each floor.

    So the 220V 1PH appliance is running "cold". Since it is 1PH it is quite unlikely how it could get wired incorrectly. 26A 1PH is a big old chunk so it could be (as Skyhook was leading to I think) the old boy has possibly disconnected a heater inside to lower the power - if it was say 3 x 2kw elements.

    All conjecture but a simple fix for any not a cowboy.
    Yep I was thinking that the coils were divided into 3 elements, so it does sound like only one coil is active, which cant produce enough heat on its own to cope with the rate of water flow. Thus never actually getting hot, just warmish.

    I would call the distributor of German pool and have them send a service tech out, even if it costs a few $$$ to finally sort this problem out.
    Last edited by Skyhook; 27-11-2010 at 09:05 AM.