Electric Water heater

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ronw

1222 posts

Uber Geek

#222914 3-Sep-2017 19:36

I have a Solar/Electric Water Heater with two elements bottom and top. I don't need both elements going so want to turn one off but no sure which is the best one to leave off. Should it be the bottom element where the cold water enters the tank that stays off or the top element where the hot water is drawn from.

Any help please?

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pipe60

127 posts

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#1857721 3-Sep-2017 20:11

Turn the bottom one off this will leave you only heating a smaller amount of water at the top of the tank.

if you turn off the top element the bottom will try and heat the whole tank.

sparkz25

750 posts

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#1857724 3-Sep-2017 20:37

how many liters is the tank?

i personally wouldn't turn off the bottom element, seems stupid to me as you will only be heating half the cylinder and it wouldn't retain the heat as long as it would if the whole cylinder was hot,

it would potentially also use more power and you would have less hot water to use,

a dual element setup is usually good if there are high volumes of water needed to be heated or if you wanted to use night rate and economy power rates where the bottom element would be on night rate and the top element would be on economy rate or both are on normal rate

ronw

1222 posts

Uber Geek

#1857728 3-Sep-2017 20:44

Tank is 300 litres and I am advised that the top 150 litres are more than enough for a two person household. Don't forget its a Solar tank so it's always getting some heat from the outside panels. From September to April it never seems to use electricity anyway and in the colder months it has enough energy from Solar to get temperature up to around 40 degrees and electricity supplies the rest.

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larknz

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#1857736 3-Sep-2017 21:26

Are both elements on day rate or is one on night rate?

ronw

1222 posts

Uber Geek

#1857768 3-Sep-2017 22:15

We don't have any night rates All power is single rate

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Aredwood

3885 posts

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#1857780 3-Sep-2017 23:07

Since you have solar - turn off the bottom element. As you will get way better energy efficiency from the solar system. And the top element will heat up partially heated solar water far faster than stone cold water anyway.

I have solar hot water myself - and even on days in winter with little sun. I will often still get 10-15deg of heating from the solar. You wont get that if the bottom of the cylinder is constantly heated to 60deg.

larknz

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#1857809 4-Sep-2017 06:58

Turn off the bottom element as a trial. If you run out of hot water water then turn the bottom on and leave the top off.
The top element is normally used for quick recovery.

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Shoes2468

785 posts

Ultimate Geek

#1857914 4-Sep-2017 09:53

ronw:

Tank is 300 litres and I am advised that the top 150 litres are more than enough for a two person household. Don't forget its a Solar tank so it's always getting some heat from the outside panels. From September to April it never seems to use electricity anyway and in the colder months it has enough energy from Solar to get temperature up to around 40 degrees and electricity supplies the rest.

You have to be mindful of legionella, tank should regularly heated to above 60 degrees to kill any. Turning off the bottom element wouldn't be a great idea as it may leave a permanent lukewarm bit for bacteria to grow. If you want to increase efficiency and whilst being safe and for maximum efficiency the best case would be for the bottom or both electric elements to come on for 3/4 hours when the cylinder is likely to be at its hottest point from the solar (late afternoon?). Especially if your power if flat rate and no night rate. This way the element only has to raise the temp if its not already greater than 60 degrees, and if it is it's only a little below has the least amount of work to do.

ronw

1222 posts

Uber Geek

#1857935 4-Sep-2017 10:07

Thanks for that I am aware of the dangers of Legionnaires. In the Summer and Autumn seasons the solar can push the temp up to 75 which is the maximum. In the Winter I keep an eye on the Temperature but the system has some pretty fancy software that will ensure that it goes above 65C at least once a week. With just two using the hot water it rarely drops below 60C at the top and even after showers hardly drops.

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