Truth About Switching Geysers Off?

[Sinbad]

It should take about 30 minutes to heat from completely cold to 55.

If it takes longer, something isn't right.

So on at 04:00 and off immediately after the latest shower.

If you have an actual temperature reader on the thing it helps a great deal.

In summer mine doesn't go on in the morning at all. So from off at 23:00 the night before I can shower happily the next morning and when walking out after a it's refilled with cold water it's about 35-39 degrees.

Assuming a 200l geyser and a 4kw element, heating your water by 25 degrees will take 90 minutes.
100l geyser 45 minutes.

30 minutes? smoking something mate...

 

[SauRoNZA]

Assuming a 200l geyser and a 4kw element, heating your water by 25 degrees will take 90 minutes.
100l geyser 45 minutes.

30 minutes? smoking something mate...

It might be that it's 30 minutes up to a certain point otherwise it triggers the error.

I agree it does seem a bit quick.

I'll find the manual and check exactly what it says. Only remember thus because it had an error due to the thermal probe pulling out if it's housing.

 

[Polly101]

People who claim noticeable savings from switching off a normal 100-300 litre domestic geyser are either not measuring correctly, or their large geyser has zero insulation (extremely unlikely), in which case bigger savings are to be had were they to insulate the geyser.

There is no way the current configuration of the universe allows one to save energy by bringing water to a certain temperature (say 60 degrees), letting it cool, and then heating it up to that temp again.

I'm on a phone and can't now type out the maths. But maybe an engineer will. All you need is Grade 9 physics.

It takes a precise amount of energy to raise the temp of say 150 litres by say 10 degrees. There's no way around that. Period.

If the claims were real, one must account for the loss in energy to that extent, even allowing for <100% efficiency in heater element and dissipation from geyser.

All else being equal, if the claims were even vaguely true then science as we know it collapses completely.

Factor in the cold water entering the geyser. Make sure the geyser is turned off just before you allow cold water to enter (ie just before you turn the water on). Then switch the geyser on the next morning an hour before you shower. You save on the temperature maintenance when geyser is not in use.

 

[spiff]

https://90by2030.wordpress.com/2010/06/25/your-geyser-–-does-it-help-to-turn-it-off-and-on/

 

[Nerfherder]

Factor in the cold water entering the geyser. Make sure the geyser is turned off just before you allow cold water to enter (ie just before you turn the water on). Then switch the geyser on the next morning an hour before you shower. You save on the temperature maintenance when geyser is not in use.

Will cost you more in maintenance when the seals break. They are not designed to go hot and cold like that.

 

[Necropolis]

Geyers @ my place is on for +-2 hours a day only.

I switch it on @ 6pm - then turn it off at around 8 before the GF and I shower / bath.

Have noticed a drop in how much we pay for electricity on a monthly basis.

Edit:

And in the hot summer months we sometimes go a few days without turning the geyser on.

 

[thehuman]

Ok, something is wrong then. It's a geyser wise with the temp display. I bumped it up to a max of 55 with a low of 45. After 90 minutes it didn't get above 50 and wouldn't seem that it didn't want to go above 50 cause it sat there for a long time. During that 90 minutes I chowed roughly 10kw of electricity.
What's interesting with my normal household and the geyser not heating, I was going through a tenth of a kilowatt every 30 seconds. Now as we get ready for bed and everything is off, going through the same amount every 95 seconds.

Think I will get an electrician out.

let him check the element could have a thick layer of scale
the thicker the buildup the less effective the element

 

[me_]

Hehe.

What is staggering is that people who can vote to elect a government can't get their head around the basic junior high school science. This is such basic stuff. You use the same energy whether you heat it in one go or whether you heat it in a thousand little spurts over ten hours. The dissipation loss happens when the water temp is above ambient atmosphere temp, irrespective of whether you heat in one go in 10 minutes or a thousand little ones over 10 hours.

The only possible saving is when your geyser water temp is in equilibrium with ambient, ie there is no energy loss through dissipation. So, you can save a very little bit if you leave the geyser power off for more than 24-36 hours, say. And then only after the water temp is same as air temp.

Or maybe what you are failing to factor in is Newton's Law of Cooling:

Newton’s Law of Cooling states that the rate of temperature of the body is proportional to the difference between the temperature of the body and that of the surrounding medium. This statement leads to the classic equation of exponential decline over time which can be applied to many phenomena in science and engineering, including the discharge of a capacitor and the decay in radioactivity.

While it may be a linear equation to calculate how much electricity will be used to heat the water, it's not a linear equation for how heat is lost.
Basically the larger the temperature difference, the greater the heat loss. As the difference narrows, the rate of cooling slows. This is mostly the same reason running the geyser hotter uses more electricity.

So our geyser is on a timer that heats up our geyser to 55 degrees in the morning before we wake up. We then shower after which the geyser temp is only about 30. If you take average temperature to be 20 degrees, then our differential is around 10 degrees which will not lead to much loss at all. If the geyser were at 55, there would be a difference of 35 degrees which would loose a lot more heat.
Even with a well insulated geyser, we are saving about 2kw per day.

 

[SauRoNZA]

Or maybe what you are failing to factor in is Newton's Law of Cooling:


While it may be a linear equation to calculate how much electricity will be used to heat the water, it's not a linear equation for how heat is lost.
Basically the larger the temperature difference, the greater the heat loss. As the difference narrows, the rate of cooling slows.

So our geyser is on a timer that heats up our geyser to 55 degrees in the morning before we wake up. We then shower after which the geyser temp is only about 30, but it doesn't switch on again till the night when it runs for a short period.
Even with a well insulated geyser, we are saving about 2kw per day.

So your logic is to already have it off by the time you shower so you don't heat the cold water unnecessarily?

Wouldn't the best saving be had then by having the geyser NOT adding cold water to itself until it's run empty?

 

[me_]

So your logic is to already have it off by the time you shower so you don't heat the cold water unnecessarily?

Wouldn't the best saving be had then by having the geyser NOT adding cold water to itself until it's run empty?

No, that's not quite what I was saying. The issue is the temperature differential between the geyser temp and ambient. By not adding cold water, the remaining body will still loose heat faster than if it had been cooled by adding cold water.

I would also be very hesitant to run a geyser dry because I'm sure it wouldn't be good for the element if it ran completely dry. All the geysers I've had won't allow you to run them dry - they rely on the cold water pressure to provide hot water.

 

[Arthur]

Or maybe what you are failing to factor in is Newton's Law of Cooling:


While it may be a linear equation to calculate how much electricity will be used to heat the water, it's not a linear equation for how heat is lost.
Basically the larger the temperature difference, the greater the heat loss. As the difference narrows, the rate of cooling slows. This is mostly the same reason running the geyser hotter uses more electricity.

So our geyser is on a timer that heats up our geyser to 55 degrees in the morning before we wake up. We then shower after which the geyser temp is only about 30. If you take average temperature to be 20 degrees, then our differential is around 10 degrees which will not lead to much loss at all. If the geyser were at 55, there would be a difference of 35 degrees which would loose a lot more heat.
Even with a well insulated geyser, we are saving about 2kw per day.

I did in fact recognise that above.

Here's the quote:

Indeed, the rate of loss generally decreases the closer you get to ambient. But in everyday household situations the diffs is insignificant, amounting to cents not Rands.

I'd be interested to see how this accounts for 2kW of savings in a day.

 

[Geoff.D]

Wow, I see the emotion about this whole matter never ends.

A few things I picked up in this thread that are strange if not incorrect and others that are totally dependent on hot water usage patterns and how many persons there are in a household.

(1) Legionaire's Disease: There is NO way that a geyser that never get above 55° C can combat this virus. It is only a matter of time and how healthy the persons exposed to water below 55° C are. It is a recognised fact that if you want to kill off bacteria in a hot water system, that the water MUST get above 60° C for a reasonable amount of time every day.
(2) Improving the insulation of a geyser AND the pipes leading to and away from the geyser is critical. This one single move reduces the heat loss from the hot water system to the minimum possible. Geyser blankets are less effective with modern geysers than with older geysers so it may not have the same effect these days as it did in the past.
(3) Identifying where other possible places where excessive heat loss occurs is equally critical. The biggest issue is the distance of the geyser from the place where water is drawn. Drawing hot water from the geyser in our place in the kitchen means we have to run the tap and fill a 5 litre bucket before the water is hot. I solved this problem by installing a water heater on the line to the kitchen below the sink, not only saving on the amount of water used, but also ensuring that hot water is instantly available and thus reducing the amount of hot water drawn out of the geyser to a minimum.
(4) You cannot turn off the cold water supply into a pressurised geyser system, only into a low pressure gravity fed hot water geyser. This is a very dangerous practise, as a geyser should never be allowed to run empty anyway.
(5) Changing a family's water usage pattern is very important! The smaller the geyser, the more important it becomes. Coupled with this is the amount of water used out of the hot water system at lower temperatures is very significant. This is where a timer has a physiological effect on everyone using water in the system. Subconsciously, everyone knows that hot water is only available at certain times, and that they must use it sparingly so everyone will get some works wonders! This is a major benefit of a timer ! ( or any other geyser control system for that matter). In bigger families, you need a larger geyser, and the temperature must be set hotter. In smaller families (2 adults say), you can go smaller but and possibly lower temperatures but never below 60° C.
(6) Ripple relays and municipality controlled timers DO NOT help anyone save money, they only allow one to load balance or shift load from high usage times to low usage times. I use a simple ECU, which will switch off the geyser when ever the stoves are on.
(7) All the scientifically correct calculations cannot account for hot water usage patterns in a household, so while those that argue about the formulas and whether they work or not are really wasting their time. Of course the formulas are correct. It is the water usage pattern that influences what persons measure as a "saving". There is NO point in keeping the geyser going if there is no demand for hot water. Just switch on when you know there is going to be a demand for hot water, it works!
(8) You cannot do any short term measurements either. One has to know what the "normal" situation is with accurate measurements (unaffected by other power usage), then implement a timing sequence and again measure until one gets the optimum savings.

I KNOW that with a timer, I can reduce the power consumption of MY GEYSER by 40% with the twice a day sequence I have that is different between winter and summer. I have a different temperature setting based on how many persons in the home as well, as a different setting for summer and winter. It is a bit of a bastard having to climb into the roof to change the temperature setting so a more modern geyser control system does help.

 

[SauRoNZA]

No, that's not quite what I was saying. The issue is the temperature differential between the geyser temp and ambient. By not adding cold water, the remaining body will still loose heat faster than if it had been cooled by adding cold water.

I would also be very hesitant to run a geyser dry because I'm sure it wouldn't be good for the element if it ran completely dry. All the geysers I've had won't allow you to run them dry - they rely on the cold water pressure to provide hot water.

Yeah it was more a hypothetical question regarding a more intelligent geyser that would monitor it's own levels before filling up.

 

[SauRoNZA]

Wow, I see the emotion about this whole matter never ends.

A few things I picked up in this thread that are strange if not incorrect and others that are totally dependent on hot water usage patterns and how many persons there are in a household.

(1) Legionaire's Disease: There is NO way that a geyser that never get above 55° C can combat this virus. It is only a matter of time and how healthy the persons exposed to water below 55° C are. It is a recognised fact that if you want to kill off bacteria in a hot water system, that the water MUST get above 60° C for a reasonable amount of time every day.
(2) Improving the insulation of a geyser AND the pipes leading to and away from the geyser is critical. This one single move reduces the heat loss form the hot water system to the minimum possible. Geyser blankets are less effective with modern geysers than with older geysers so it ay not have the same effect these days as it did in the past.
(3) Identifying where other possible places where excessive heat loss occurs is equally critical. The biggest issue is the distance of the geyser from the place where water is drawn. Drawing hot water form the geyser in our place in the kitchen means we have to run the tap and file a 5 litre bucket before the water is hot. I solved this problem by installing a water heater on the line to the kitchen below the sink, not only saving on the amount of water used, but also ensuring that hot water is instantly available and thus reducing the amount of hot water drawn out of the geyser to a minimum.
(4) You cannot turn off the cold water supply into a pressurised geyser system, only into a low pressure gravity fed hot water geyser. This is a very dangerous practise, as a geyser should never be allowed to run empty anyway.
(5) Changing a family's water usage pattern is very Important! the smaller the geyser, the more important it becomes. Coupled with this is the amount of water used out of the hot water system at lower temperatures is very significant. this is where a timer has a physiological effect on everyone using water in the system. Subconsciously, everyone knows that hot water is only available at certain times, and that they must use it sparingly so everyone will get some works wonders! This is a major benefit of a timer ! ( or any other geyser control system for that matter. In bigger families, you need a larger geyser, and the temperature must be set hotter. In smaller families (2 adults say). you can go smaller but and possibly lower temperatures but never below 60° C.
(6) Ripple relays and municipality controlled timers DO NOT help anyone save money, they only allow one to load balance or shift load from high usage times to low usage times. I use a simple ECU, which will switch off the geyser when ever the stoves are on.
(7) All the scientifically correct calculations cannot account for hot water usage patterns in a household, so while those that argue about the formulas and whether they work or not are really wasting their time. Of course the formulas are correct. It is the water usage pattern that influences what persons measure as a "saving". There is NO point in keeping the geyser going If there is no demand for hot water. Just switch on when you know there is going to be a demand for hot water, it works!
(8) You cannot do any short term measurements either. One has to know what the "normal situation is with accurate measurements (unaffected by other power usage), then implement a timing sequence and again measure until one gets the optimum. savings.

I KNOW that with a timer, I can reduce the power consumption of MY GEYSER by 40% with the twice a day sequence I have that is different between winter and summer. I have a different temperature setting based on how many persons in the home as well, as a different setting for summer and winter. It is a bit of a bastard having to climb into the roof to change the temperature setting so a more modern geyser control system does help.

Pretty sure Legionnaires is sorted from 45 degrees and up.

Which is why Eskom and most energy saving resources recommend 55 as an optimal setting.

****

Oh I see wiki says it thrives below 45 not that it dies above it.

Still one can argue how would it ever come to exist in the first place if the geyser operates at 55.

And one has to question why that is then the recommended temp?

Personally 55 is (physically) safer option to me with a baby in the house anyway.

The bacteria grows best at warm temperatures.[5] It thrives at water temperatures between 25 and 45 °C (77 and 113 °F), with an optimum temperature of 35 °C (95 °F).[21] Temperatures above 60 °C (140 °F) kill it.[22]

 

[Geoff.D]

Those recommended settings were made before LD hit the news and before our on Health authorities got in the Act. Suggest you look at Eskom's webpages for the latest. In the mean time the SABS has drawn up regulations regarding hot water systems.

In other countries such as the UK, legislation specifies a minimum temperature by law.

 

[bwana]

Pretty sure Legionnaires is sorted from 45 degrees and up.

Which is why Eskom and most energy saving resources recommend 55 as an optimal setting.

****

Eskom recommends 60°c. http://www.eskom.co.za/sites/idm/Residential/Pages/hotwatermanagement.aspx

 

[Neo_X]

going on all the feedback in this thread, it really seems like it comes down to the fact that we have VERY crappy geysers here in south africa.

my personal experience is the same - timer did drastically improve my usage - by a factor of about 10 units a day, even after i added a geyser blanket ( Builders R300 version).

 

[Seriously]

Pretty sure Legionnaires is sorted from 45 degrees and up.

Which is why Eskom and most energy saving resources recommend 55 as an optimal setting.

****

Oh I see wiki says it thrives below 45 not that it dies above it.

Still one can argue how would it ever come to exist in the first place if the geyser operates at 55.

And one has to question why that is then the recommended temp?

Personally 55 is (physically) safer option to me with a baby in the house anyway.

Yep, but 65 degrees is still better and the recommended limit as I know.

Prevention[edit]
Although the risk of Legionnaires' disease being spread by large-scale water systems cannot be eliminated, it can be greatly reduced by writing and enforcing a highly detailed, systematic water safety plan appropriate for the specific type of facility involved (office building, hospital, hotel, spa, cruise ship, etc.)[15] Some of the elements that such a plan may include are the following:

Keeping water temperature either above or below the 20-50 °C range in which the Legionella bacterium thrives.
Preventing stagnation, for example by removing from a network of pipes any sections that have no outlet (dead ends). Where stagnation is unavoidable, for example when a wing of a hotel is closed for the off-season, systems must be thoroughly disinfected just prior to resuming normal operation.
Preventing the buildup of biofilm, for example by not using (or by replacing) construction materials that encourage its development, and by reducing the quantity of nutrients for bacterial growth that enter the system.
Periodic disinfection of the system, by high heat or a chemical biocide, and the use of chlorination where appropriate.
System design (or renovation) that reduces the production of aerosols and reduces human exposure to them, for example by directing them well away from building air intakes.
An effective water safety plan will also cover such matters as training, record-keeping, communication among staff, contingency plans and management responsibilities. The format and content of the plan may be prescribed by public health laws or regulations.[15]

http://www.hse.gov.uk/healthservices/legionella.htm

Using temperature control
The primary method used to control the risk from Legionella is water temperature control.
Water services should be operated at temperatures that prevent Legionella growth:

Hot water storage cylinders (calorifiers) should store water at 60°C or higher
Hot water should be distributed at 50°C or higher (thermostatic mixer valves need to be fitted as close as possible to outlets, where a scald risk is identified).
Cold water should be stored and distributed below 20°C.

 

[Zoomzoom]

https://90by2030.wordpress.com/2010/06/25/your-geyser-–-does-it-help-to-turn-it-off-and-on/

BEST ANSWER YET!!!

 

[Zoomzoom]

This leads me to the next question - does boiling a kettle use more or less electricity than drawing the water for dishes from the geyser?