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Adding Geyser To Inverter Circuit.


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Hi, i did mention this plan in some other post , but at that stage is was only a plan with some spares ordered.

I know this will not work for everybody, but in my situation it will. I do have spare PV capacity 95% of the day, Before this plan, I ran my geyser on a timer from 2 to 4 every afternoon. That was sufficient for our demand and even left enough hot water for a morning shower. I tested the geyser and saw that it only switched on for 1 to 1and half hours a day, so I decided on the following solution. 

I had a company build me a 1 KW element. Had another company modify a spare plate for my current geyser to fit the1KW element (company number 2 messed their part up completely and left the plate in a perfectly useless condition. So i collected another plate from the scrapyard and modified it myself. Further more I increase the allowed running time to about 5 hours on the timer to allow sufficient heating.

Spares used:

1 x Custom build 1Kw element          = R360

1 x Scrap plate                                  = R15

1 x Thermostat                                  = Recovered from existing Geyser.

 

Modification was done as follows.

Original plate.

a.jpg

Scrap Plate:

b.jpg

As you could see, there is a difference in the type of element, as well as the holes in the 2 different plates. I did not want to ask someone to weld/braze a 1.25 inch nut to a plate again as that way of doing it did not work. (i am sure it can, but the guy I asked, returned the plate in a different shape than the one he received from me) so for my second attempt I went for a plate with a nut to fit the element. Last mention plate comes standard with 8 Holes and the original comes with 6 holes. the diameter of the plates were the same and 2 holes (Marked with a red line) matched perfectly. So i bolted the two plates together and used the 4 open holes as pilot holes to drill new holes in the 8 hole plate. 

c.jpg

That left me with cleaning up the plate a little and screw in the ! kw element. You can see the 8 hole plate now has a few holes more. The element that I bought included.d.jpg

Almost ready to go in, only saw this picture is blurry after the element was installed in the geyser.

e.jpg

 

The newly drilled holes fitted perfectly, I ran the geyser for some time from the battery and it did well, takes about 26 Amps from my 48V bank.

When the sun comes out in the morning Will see how the PV handles the element, but I can not foresee any problems. My current system should handle it with ease.

And if all goes well, there goes my last 3 to 4 units I still had to buy from the council on  daily basis.

 

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My plumbing "mechanic" recently had to replace my element in the 150l Kwikhot (a 2kW originally) due to an earth short... normal for a 10 year old geyser, so no issue there...

But, he got a "good" deal on a 4kW element which "was great for solar installations"... Ummmm, my geyser is connected to a single Axpert!!! So although geyser element only used in exceptionally bad weather days, turn it on and the Axpert shits itself!

I like the new element, because the water heats up faster than hell, but the rewiring exercise (to connect to municipal power only) and cost was huge... could've bought more water heating panels/tubes for that and negated the electrical connection completely!

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  • 1 month later...

This geyser is a great source of confusion. Before I made the modification, I use to monitor it by watching usage on the prepaid meter, With a 3 KW element it use to be one for 1 to 1 and a halve hours per day. (3 - 4.5Kwh) per day.

I replaced that with the 1KW element and allowed it (by using a timer) to run from 10H15 to 15H00 every day.

I started Using AICC this week and was keen to see how long the geyser really takes to heat up the 150litre geyser, and I was shocked by the results.

Some other facts that might be taken into consideration:

  1. The 3 to 4.5kwh was in winter time.
  2. The geyser is exposed to direct sun this time of the year from 12H00 till about 16H00
  3. It is a new geyser that was installed in February (Kwickhot 610 duel ) witch is rated for 2.25kw heat losses over a 24hour period.
  4. Used by, 1x baby in baby bath, two small girls taking separate bathes, Mom taking a shower directly after work and then again late night, me taking a shower at night with enough hot water left for a shower in the morning. 
  5. No pre-heating of water
  6. No additional heating methods.
  7. Nice hot ambient temperatures most of the year.

My confusion comes in with the actual kwh usage as recorded by AICC over 3 days.

  1. Aicc shows that it is indeed a 1kw element.
  2. Day 1 it ran from 10H15 to 12H30 (2.25Kwh)
  3. Day 2 it ran from 10H15 to 12H45 (2.5Kwh)
  4. Today it ran from 10H15 to 12H45 (2.5Kwh)

Does anybody have an idea what can cause this low kwh consumption? Its only slightly bigger than the standing loss rating.

Can it be that with our hotter climate in Phalaborwa,  the standing losses is so greatly reduced that I actually just have to heat up the replaced water?

 

 

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1 hour ago, Jaco de Jongh said:

Can it be that with our hotter climate in Phalaborwa,  the standing losses is so greatly reduced that I actually just have to heat up the replaced water?

The measured standing loss is done at standard conditions as specified by SANS 151: Ambient is 20 Celsius and the geyser is heated to 65 Celsius.

If you do the usual thing of setting it for only 55, and your ambient is above 20 much of the day, then the standing loss will be less.

You can actually work out a formula for your geyser. Newton's law of cooling says it cools down at a rate proportional to the difference between the current temperature and ambient. This means (I cannot remember the calculus to derive this, so you'll just have to trust my memory) that the formula is of the form T = c*e^(kt), where T is the temperature, e = 2.7182 and t (lower case) is time in whatever unit works for you. c and k are constants you have to solve for.

If you plug in t=0, then T = c. Since the starting temperature for the test is 65, that means c = 65.

It takes 1.16Wh to heat one liter of water by one degree centigrade. If you also know the standing loss over 24 hours is 2.25kwh, you know this represents 2250/1.16/150 = 13 degrees centigrade, and 65 - 13 = 52. So you know T = 52 when t=24. So now you can solve for k.

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13 hours ago, AndewJ said:

where do you get the 1Kw and 1.5Kw geyser elements? I have been looking for one all over but no one seems to stock them.

My local electrical hardware shop has 1kW elements without a pocket. I got 1.5kW elements with a pocket from TecsaReco (branches Durbs, CT, Jhb, Pta and PE and Bloem + some other places). 

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On 17/09/2016 at 10:41 AM, Chris Hobson said:

My solution was a twin port plate also for Kwikot geyser  and 2x 1500W elements which are reasonably easy to source.

 20160123_084111.jpg

Addition: When the photo was taken I had a 1kW and a 1.5kW elements now we have two 1.5kW elements.

why do you use dual elements? 

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1 hour ago, Fritz said:

why do you use dual elements? 

I suspect it's because you want to use the surplus power to heat water, and you're more likely to have 1.5kw surplus than to have 3kw surplus. Even if you have an array big enough so that you do have 3kw surplus at some point in the day, you will have that peak for a much shorter time. Since water heats more or less linearly over time and you have all day... using a smaller element is the ticket.

The second one you put on a time switch and connect it to the grid. If the water isn't hot enough by the time time timer switches on, it takes it the rest of the way on the second element (or both at the same time if you put it in late afternoon).

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3 hours ago, Fritz said:

why do you use dual elements? 

 

1 hour ago, plonkster said:

I suspect it's because you want to use the surplus power to heat water, and you're more likely to have 1.5kw surplus than to have 3kw surplus. Even if you have an array big enough so that you do have 3kw surplus at some point in the day, you will have that peak for a much shorter time. Since water heats more or less linearly over time and you have all day... using a smaller element is the ticket.

The second one you put on a time switch and connect it to the grid. If the water isn't hot enough by the time time timer switches on, it takes it the rest of the way on the second element (or both at the same time if you put it in late afternoon).

Plonky has the gist of it.

I have a 3 phase generator and two phases come into my home. One powers the inverter and all the inverter fed circuits. The other powers a few non-essential lights, occasionally a small pump and the 2nd element in the geyser. 

So during the day I power one element with excess solar energy and then in the evening when the gennie goes on I can power both using separate phases. I could have 2 or 2.5kW for the second one but the phases are better balanced with 1.5kW.

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On 10/27/2016 at 9:22 PM, Jaco de Jongh said:

This geyser is a great source of confusion. Before I made the modification, I use to monitor it by watching usage on the prepaid meter, With a 3 KW element it use to be one for 1 to 1 and a halve hours per day. (3 - 4.5Kwh) per day.

I replaced that with the 1KW element and allowed it (by using a timer) to run from 10H15 to 15H00 every day.

I started Using AICC this week and was keen to see how long the geyser really takes to heat up the 150litre geyser, and I was shocked by the results.

Some other facts that might be taken into consideration:

  1. The 3 to 4.5kwh was in winter time.
  2. The geyser is exposed to direct sun this time of the year from 12H00 till about 16H00
  3. It is a new geyser that was installed in February (Kwickhot 610 duel ) witch is rated for 2.25kw heat losses over a 24hour period.
  4. Used by, 1x baby in baby bath, two small girls taking separate bathes, Mom taking a shower directly after work and then again late night, me taking a shower at night with enough hot water left for a shower in the morning. 
  5. No pre-heating of water
  6. No additional heating methods.
  7. Nice hot ambient temperatures most of the year.

My confusion comes in with the actual kwh usage as recorded by AICC over 3 days.

  1. Aicc shows that it is indeed a 1kw element.
  2. Day 1 it ran from 10H15 to 12H30 (2.25Kwh)
  3. Day 2 it ran from 10H15 to 12H45 (2.5Kwh)
  4. Today it ran from 10H15 to 12H45 (2.5Kwh)

Does anybody have an idea what can cause this low kwh consumption? Its only slightly bigger than the standing loss rating.

Can it be that with our hotter climate in Phalaborwa,  the standing losses is so greatly reduced that I actually just have to heat up the replaced water?

 

 

You could install a Geyserwise timer to measure the temperatures before, and after heatup. Or you could hookup the thermostat to a Raspberry Pi or Arduino and measure it that way as well. What will show whether the water entering the geyser is much hotter than you expected it to be. 

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  • 1 year later...
On 2016/10/27 at 9:22 PM, Jaco de Jongh said:

This geyser is a great source of confusion. Before I made the modification, I use to monitor it by watching usage on the prepaid meter, With a 3 KW element it use to be one for 1 to 1 and a halve hours per day. (3 - 4.5Kwh) per day.

I replaced that with the 1KW element and allowed it (by using a timer) to run from 10H15 to 15H00 every day.

I started Using AICC this week and was keen to see how long the geyser really takes to heat up the 150litre geyser, and I was shocked by the results.

Some other facts that might be taken into consideration:

  1. The 3 to 4.5kwh was in winter time.
  2. The geyser is exposed to direct sun this time of the year from 12H00 till about 16H00
  3. It is a new geyser that was installed in February (Kwickhot 610 duel ) witch is rated for 2.25kw heat losses over a 24hour period.
  4. Used by, 1x baby in baby bath, two small girls taking separate bathes, Mom taking a shower directly after work and then again late night, me taking a shower at night with enough hot water left for a shower in the morning. 
  5. No pre-heating of water
  6. No additional heating methods.
  7. Nice hot ambient temperatures most of the year.

My confusion comes in with the actual kwh usage as recorded by AICC over 3 days.

  1. Aicc shows that it is indeed a 1kw element.
  2. Day 1 it ran from 10H15 to 12H30 (2.25Kwh)
  3. Day 2 it ran from 10H15 to 12H45 (2.5Kwh)
  4. Today it ran from 10H15 to 12H45 (2.5Kwh)

Does anybody have an idea what can cause this low kwh consumption? Its only slightly bigger than the standing loss rating.

Can it be that with our hotter climate in Phalaborwa,  the standing losses is so greatly reduced that I actually just have to heat up the replaced water?

 

It dependes on the ambient temperature, isolation and water "in" temperature.

 

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  • 2 months later...

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