Using a DC powered PTC element to heat water (successfully) - Page 3




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  1. #41
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by FreeLander2 View Post
    Could you not achieve the same result by using a simple timer or change some settings, eg the geyser element is not allowed to switch on until the batteries are fully charged and if the solar is powering the element only?
    Yea, my question too!!!
    You can even change to a 1kw or 500w standard element if the load is too much on your batteries.
    Then you use the timers on the Geyserwise to only switch on after 12:00 till say 18:00 when your batteries is fully charged.

    For me the cost of solar PV is still too high to use for heating water in a dedicated system.
    Then I still rather stick to my evacuated tubes.

    I think as the cost of PV comes down, this is a better option, but then I would combine it with a hybrid invertor to better manage the PV.
    But then again experience have shown me to stick to standard off the shelf equipment.
    Doing anything custom, tends to come back at you in the worst of times.


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  2. #42
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by Wetkit View Post
    Yea, my question too!!!
    You can even change to a 1kw or 500w standard element if the load is too much on your batteries.
    Then you use the timers on the Geyserwise to only switch on after 12:00 till say 18:00 when your batteries is fully charged.

    For me the cost of solar PV is still too high to use for heating water in a dedicated system.
    Then I still rather stick to my evacuated tubes.

    I think as the cost of PV comes down, this is a better option, but then I would combine it with a hybrid invertor to better manage the PV.
    But then again experience have shown me to stick to standard off the shelf equipment.
    Doing anything custom, tends to come back at you in the worst of times.
    <Mine is Titanium more sexy. The method is the same though.

  3. #43
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by TonySwash View Post
    Hi all,
    I thought I would share my story about heating my 150 litre geyser from a DC source.
    I have 20 265 watt panels producing 135VDC into an Axpert 5KVA inverter and charging 28 110AH batteries.

    The brief was to be totally off grid using only PV. I installed a 2200w 220VAC element in my geyser. The problem was that after showering, the water temp would drop to 35 Deg and would only get heated at 6h30 the next day after dropping to 27 Deg overnight.
    This put a massive drain on my batteries and when microwaves and kettles came on in the morning we went below the low voltage threshhold and Eskom kicked in.

    I then installed a 400 watt 48VDC PTC element next to the 220VAC one. It is connected directly to the batteries via a manual on off switch. No thermostats although I use the geyserwise display for reference.

    So now when I have showered the temp is still 35 Deg and around 9h00 I switch on the DC element. The inrush is about 18 amps for one or two seconds and then it settles at 380 watts at 52 volts. At around 4pm the water is between 54 and 60 degrees and the element is switched off. My geyser is triple lagged and in my garage. The temp in the morning is between 48 and 52 degrees.
    The 220 Volt element will only switch on if the temp is below 48 Deg and runs from 6h30 until 8h00 using a geyserwise.

    This set up has been running now for the past 8 months in Robertson and I rarely see the 220 element coming on. Being PTC it is super efficient over a standard unit but more pricey. I am still using the same amount of power every day to heat the water but it is spread out over the solar day. My batteries are normally charged by 13h00 anyway so I have excess power.

    So no more low voltage outages, and the batteries are not enduring a 2200 watt drain for 90 minutes every morning.

    The 400 watt element is not available commercially but I suppose if there was enough demand it might be worth it. Beware of low cost PTCs though. They are not reliable and I only used them for the prototypes.

    I hope this goes to show that PV heating is possible and cheaper than the horrible looking things stuck on roofs.
    Rgds
    Tony
    I just use a 12L/minute gas geyser, and only pay for energy while I am using it, with endless supply of hot water. Have you thought of this option?

  4. #44
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    the geyserwise is an awesome tool but if every1 showers I fail to see why 1 would ever heat water above 37 deg C.
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  5. #45
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by ryzen View Post
    the geyserwise is an awesome tool but if every1 showers I fail to see why 1 would ever heat water above 37 deg C.

    I believe that the water should be heated to about 55 degrees in order to eliminate bugs that may thrive in lower temperatures.
    I think that legionaries was mentioned.
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  6. #46
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by WalterK View Post
    I believe that the water should be heated to about 55 degrees in order to eliminate bugs that may thrive in lower temperatures.
    I think that legionaries was mentioned.
    Would that he a problem in pipes as well? Since I installed the Paloma geyser we set the temp to 46C since there is no need to add cold water. My thinking is overheating just to add cold water again is wasting gas.
    Last edited by Karoo Klong; 2018/12/03 at 08:25 PM.

  7. #47
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by Karoo Klong View Post
    Would that he a problem in pipes as well? Since I installed the Paloma geyser we set the temp to 46C since there is no need to add cold water. My thinking is overheating just to add cold water again is waisting gass.

    Honestly cannot say with certainty, I just have the number 55 linked to Legionaries disease rattling around in the back of my mind. So just to ease my OCD, my temperature is set to reach 55 degrees at least once a day.
    Sorry that I cannot be of assistance.
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  9. #48
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by ryzen View Post
    the geyserwise is an awesome tool but if every1 showers I fail to see why 1 would ever heat water above 37 deg C.
    You would need a big geyser to compensate for such a low temp setting. Legioneres comes to mind but I have never heard of a case in S Africa. Thats not to say it hasnt happened.

  10. #49
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    There was a case reported not so long ago about a cabinet minister (Edna Molewa?) who succumbed to legionare's disease. Whether accurate or maybe something else (HIV??) - who knows?
    Eggie.

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  12. #50
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by WalterK View Post
    Honestly cannot say with certainty, I just have the number 55 linked to Legionaries disease rattling around in the back of my mind. So just to ease my OCD, my temperature is set to reach 55 degrees at least once a day.
    Sorry that I cannot be of assistance.
    Here you go sir. Above 55C
    https://www.google.com/url?q=http://...qACK8NeicCIB7g

    Also see this article.
    https://www.treehugger.com/green-foo...mperature.html
    Last edited by Karoo Klong; 2018/12/03 at 10:29 PM.

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  14. #51
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by Wetkit View Post
    Yea, my question too!!!
    You can even change to a 1kw or 500w standard element if the load is too much on your batteries.

    But then again experience have shown me to stick to standard off the shelf equipment.
    Doing anything custom, tends to come back at you in the worst of times.
    Where can a 500 or 1000W element be bought as I have only seen the normal 2kW, 3kW and 4kW elements for the flange and screw mounted elements. Kwikot don't show such elements on the web.

  15. #52
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    anyone tried using peltier elements they can be got prety cheap off ebay ad as they act as heat pumps you get 1.5 times the heat out as you put in so your 400w equivlent would be 266w i see one add for 5 50w peltiers for R140 throw some old cpu heatsinks on the cold side and you should have a prety eficient geyser for cheap. thinking now about making up an eficient travel kettle for the car. a single 50w peltier should boil a cup of water for coffy in 15 min using only 4 amps which is well within a cigarette lighter sockets capability.

  16. #53
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Quote Originally Posted by ekkekan View Post
    Where can a 500 or 1000W element be bought as I have only seen the normal 2kW, 3kW and 4kW elements for the flange and screw mounted elements. Kwikot don't show such elements on the web.
    See attached.
    I found this is the AEE Solar catalogue
    Google: 2018-AEE-Solar-Catalog
    Attached Images Attached Images  

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  18. #54
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Thanks a lot Richard. This is quite a wide selection that can be used from DC. Will follow up where to source it from. Then just a matter of finding a means of getting the thread cut in a flange or another flange.

  19. #55
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    Default Re: Using a DC powered PTC element to heat water (successfully)

    Wireohms in Durban

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