Will switching off geysers prevent loadshedding?

[gbyleveldt]

Your element runs at full tilt every time it switches on - I don’t get what you are trying to say. 1 hour a day vs on 24/7 and who knows how many times it turns on in that period to maintain temperature.

so, my 4kw element runs 100% to maintain a set water temperature? when it reaches the temperature, it continues to run at 100% ? it never turns off and the thermostat used to set the temp does what?

like i said, i'm no electrician, but logically it cant maintain a 100 % output or the water in the cylinder will boil, triggering the pressure release valve

the duration of runtime is the thing that you need to look at, if it takes 1 minute to push the temp up one degree vs 60 minutes to reach desired temp each day

Weather you leave the breaker on or if you manually control the breaker it's the same thing. Either you control the temp using the breaker, or the thermostat in the geyser controls it. The element itself is resistive so it draws a constant current when power is supplied to it till the thermostat turns it off.

While a geyser draws a substantial amount of power, it's a much more friendly load to the grid than inductive loads (think fridges, freezer, pool pump, traditional AC, computer, TV, etc). Inductive loads has a substantial inrush current when power is applied to it and can sometimes be 8 times more for a few milliseconds when it's initially turned on. Now extrapolate this to a whole neigbourhood(s) when loadshedding ends and you understand why substations blow up.

 

[wingnut771]

Weather you leave the breaker on or if you manually control the breaker it's the same thing. Either you control the temp using the breaker, or the thermostat in the geyser controls it. The element itself is resistive so it draws a constant current when power is supplied to it till the thermostat turns it off.

While a geyser draws a substantial amount of power, it's a much more friendly load to the grid than inductive loads (think fridges, freezer, pool pump, traditional AC, computer, TV, etc). Inductive loads has a substantial inrush current when power is applied to it and can sometimes be 8 times more for a few milliseconds when it's initially turned on. Now extrapolate this to a whole neigbourhood(s) when loadshedding ends and you understand why substations blow up.

How many kWh does a geyser use per day to maintain set temp with no water being used?

 

[gbyleveldt]

How many kWh does a geyser use per day to maintain set temp with no water being used?

That depends on many factors, mostly how big your geyser is and how insulated it, and the piping from it, is. In my case I've actually measured that turning on the geyser for 2 hours in the morning and afternoon (if the ev tubes didn't do their job) is cheaper in a 24 hr cycle than leaving it on so the thermostat maintains a 55c temperature during the day. If memory serves is was around 8kWh/pd for me controlling it vs. just under 10kWh/pd if I just leave it to do its thing. Not a massive difference, but a difference none the less

Interestingly, running two freezers and a fridge uses about the same amount of power per 24hr as my geyser does over that same period. My server rack (using a constant 300W'ish base load draws the most power of everything in my house)

 

[wingnut771]

That depends on many factors, mostly how big your geyser is and how insulated it, and the piping from it, is. In my case I've actually measured that turning on the geyser for 2 hours in the morning and afternoon (if the ev tubes didn't do their job) is cheaper in a 24 hr cycle than leaving it on so the thermostat maintains a 55c temperature during the day. If memory serves is was around 8kWh/pd for me controlling it vs. just under 10kWh/pd if I just leave it to do its thing. Not a massive difference, but a difference none the less

Interestingly, running two freezers and a fridge uses about the same amount of power per 24hr as my geyser does over that same period.

Regarding fridge and freezers. I heard they use more power if they’re empty so I keep old 2l milk bottles filled with water to take up the empty space and they end up becoming thermal batteries which slows down the cycling of it turning on and off.

 

[gbyleveldt]

Regarding fridge and freezers. I heard they use more power if they’re empty so I keep old 2l milk bottles filled with water to take up the empty space and they end up becoming thermal batteries which slows down the cycling of it turning on and off.

Hmmm, that I'm not sure about. I suppose it could make sense as an empty freezer needs to maintain cold air without any mass, where a full freezer has solid frozen mass inside. I never tested it myself so I'm just speculating.

 

[chuckles_the_cnt]

insulation and usage plays a large part in maintaining internal hwc temperature (when offline) shortening the runtime of the element. again, i'm no electrician and i dgaf

empty space in a fridge? unheard of, filling the fridge with old milkbottle water, i'm guessing you are single? or your wife gave up and let you do what you do

 

[Nerfherder]

No that not what I said.

All I’m saying is if it uses 2kWh for that one hour vs 4kWh for the whole day, surely that is a saving? I have not measured mine so this is speculation on my side.

it uses the same amount of power to heat up a geyser as it does to keep it warm, its designed to work like this.

 

[Nerfherder]

Okay 60 then.

needs to be above 65.

Also if you are letting it get cold like that then you should be getting the temp up to 70+ before using.

 

[Nerfherder]

Your element runs at full tilt every time it switches on - I don’t get what you are trying to say. 1 hour a day vs on 24/7 and who knows how many times it turns on in that period to maintain temperature.

If you leave it on all day with without using it runs for a few mins every hour.

 

[RudderVator]

If you leave it on all day with without using it runs for a few mins every hour.

Wouldn’t say thats normal to lose 10C every hour due to standing losses. Seems a little high.

I am assuming you dont touch the warm taps at all?

 

[wingnut771]

Hmmm, that I'm not sure about. I suppose it could make sense as an empty freezer needs to maintain cold air without any mass, where a full freezer has solid frozen mass inside. I never tested it myself so I'm just speculating.

I have a killawatt, will do some tests.

 

[Nerfherder]

Wouldn’t say thats normal to lose 10C every hour due to standing losses. Seems a little high.

I am assuming you dont touch the warm taps at all?

i'm saying worse case - its probably less than that with modern geysers. Its built to hold the temp

 

[The Darkness]

Look at your geyser this way: if you boil your kettle, make tea, and then leave the water left over to cool down, next tea you need to boil again. Now imagine you put that originally boiled water into a thermos flask, next time you use it, it's only lost a tiny bit of that original heat.
Modern geysers have excellent insulation though, so you should rather be focussed on how you make that heat. If you're using a conventional geyser/element, you're going to use way more power than a heat pump for instance. This would be the first thing to do.

 

[maumau]

I do switch mine off and only turn it on 1 hour a day. Feel like a lone candle bearer though because I'm sure nobody else does. Maybe my 0.001% mw will make a difference somewhere LOL. I do it anyway. It's something positive to do I guess.

I do the same but leave it on 2 hours a day.

 

[The Darkness]

I do the same but leave it on 2 hours a day.

You're likely using the same if not more power doing this.

 

[wingnut771]

You're likely using the same if not more power doing this.

Please explain the logic of it using more power? If you use 100 litres a day, it's heating 100 litres regardless.

 

[maumau]

You're likely using the same if not more power doing this.

The geyser is very well insulated and in the ceiling under a north facing tiled roof.

 

[gbyleveldt]

needs to be above 65.

Also if you are letting it get cold like that then you should be getting the temp up to 70+ before using.

55C is fine. You want it hot to prevent legionnaires disease, which has a "favourable range between 77-113degF - (25-45degC)". This directly from the CDC so I'm inclined to believe their data as correct.

https://www.cdc.gov/legionella/wmp/monitor-water.html

 

[Nerfherder]

55C is fine. You want it hot to prevent legionnaires disease, which has a "favourable range between 77-113degF - (25-45degC)". This directly from the CDC so I'm inclined to believe their data as correct.

https://www.cdc.gov/legionella/wmp/monitor-water.html

Sure - but if you are letting the geyser get cold I'd probably force it up (and make sure it maintains that temp)

 

[The Darkness]

Please explain the logic of it using more power? If you use 100 litres a day, it's heating 100 litres regardless.

because to boil water from room temperature takes more energy than to maintain its current temperature. It's moot though, because unless you have a geyser from the 50's, a normal modern geyser does a great job at insulation, which is why these blankets for them is a scam (go and put your hand against your geyser in the roof, it's cold = really well insulated).
Again, it's HOW you make that heat that counts the most.