Truth About Switching Geysers Off?

[Zoomzoom]

So swop the pipes...it takes 20 minutes.

Or just use your memory.

I don't know who "they" are though. Sounds like a spastic plumber to me.

Even as a lefty I put my hot water on the left. And when I bought this house one of the taps was inverted and I swopped it around in the first month.

But ultimately you should be washing your hands with warm water...otherwise not bother washing them at all really.

Spastic plumber because the taps say 'hot' on the LHS but it is installed on the RHS on ALL the taps. Thankfully am moving to my own house soon with all new plumbing (cos there literally wasn't any previously installed - ditto on electricity) so no old pipes, no old wiring, no old geyser ...... an old house with nice thick wall with NEW everything else = best of both worlds.

 

[SauRoNZA]

Well flipping the logo around should be even easier.

 

[Zoomzoom]

Well flipping the logo around should be even easier.

not my house, not my problem.

 

[selby]

my problem is these damn mixer taps - they put the hot water on the RHS (dumb!) which...

What if you're left handed?

 

[Zoomzoom]

What if you're left handed?

well I am, but I was forced to be a righty, I find that I tend to hold things in my left hand (it feels more secure) and use my right hand to turn the taps on. I personally would prefer the hot on the left and the cold on the right, but that is my choice. I am pretty sure there is no set rule for it.

 

[richjdavies]

Wow - maybe you guys should start your own thread about left-hand taps - May I suggest "you know what really grinds my gears... taps"

So savings can only be achieved on the standing losses portion, which can be a maximum of 2,59 kWh a day for a 150 litre geyser.

Well, yes and no... we're being careful to state that part is TINY and not worth it!

If your geyser has no leaks, no pipes and you don't use any hot water at all; then yes, the only saving you'll get is from standing losses from the geyser. You also get 'losses/savings' from:
A. Losses along the pipes - i.e. every time you run the tap and wait until it's warm, that water is being taken from the geyser and left in the pipe to cool again. I worked it out for me once, and it was quite small, but I live in a flat...
B. Any leaks/drips are better at 40 degrees, than at 60 degrees... although yes, sort out the leaks!
C. Standing loss performance likely IS NOT like the standards, often worse... if there's a draft, or the insulation is broken, or pipes aren't lagged coming out etc...
D. Apart from showering, bathing etc, most of the times you use hot water (or at least turn on the hot water tap) the temperature isn't critical; so generally people happily use water at 40 degrees rather than 60 degrees, thus reducing the amount of energy they are washing down the drain.
[PS - on this point, why are you washing dishes in scolding hot water?? you know it doesn't 'kill the bacteria' right? just hurts you...http://goo.gl/HtZXeD]

As an engineer - I know where you're coming from - the difference in heat-loss on a well insulated geyser between it being at 55 degress or 60 degrees is VERY small... and not worth the effort.

But as an energy user - and as someone who helps other people with their energy use - I know from experience that leaving my geyser on my electricity bill was R500/month, but with it only on when it got too cold, it was R300/month (small flat... Century City... 2 years ago...)

 

[Geoff.D]

Wow - maybe you guys should start your own thread about left-hand taps - May I suggest "you know what really grinds my gears... taps"



Well, yes and no... we're being careful to state that part is TINY and not worth it!

If your geyser has no leaks, no pipes and you don't use any hot water at all; then yes, the only saving you'll get is from standing losses from the geyser. You also get 'losses/savings' from:
A. Losses along the pipes - i.e. every time you run the tap and wait until it's warm, that water is being taken from the geyser and left in the pipe to cool again. I worked it out for me once, and it was quite small, but I live in a flat...
B. Any leaks/drips are better at 40 degrees, than at 60 degrees... although yes, sort out the leaks!
C. Standing loss performance likely IS NOT like the standards, often worse... if there's a draft, or the insulation is broken, or pipes aren't lagged coming out etc...
D. Apart from showering, bathing etc, most of the times you use hot water (or at least turn on the hot water tap) the temperature isn't critical; so generally people happily use water at 40 degrees rather than 60 degrees, thus reducing the amount of energy they are washing down the drain.
[PS - on this point, why are you washing dishes in burning hot water?? you know it doesn't 'kill the bacteria' right? just hurts you...]

As an engineer - I know where you're coming from - the difference in heat-loss on a well insulated geyser between it being at 55 degress or 60 degrees is VERY small... and not worth the effort.

But as an energy user - and as someone who helps other people with their energy use - I know from experience that leaving my geyser on my electricity bill was R500/month, but with it only on when it got too cold, it was R300/month (small flat... Century City... 2 years ago...)

It is the little things that add up .....
In a 4 bedroomed home (older house, the geyser is typically located between the 2 bathrooms), and the pipe run to the kitchen is long. So the water wastage before hot water comes out of the tap in the kitchen is the most. Then the "savings" can be more than one would think by simply making the engineering calculations. If your savings amounted to R 200/month in a flat then the savings in a home would larger.

Washing dishes in "hot water" is not about killing bacteria, it is about food removal especially fats. ....

So as is borne out by the formal study in the reference in this thread shows that changing hot water usage pattern does make a difference.
Keeping a geyser at its set temperature 24 hours a day, when hot water is required only once a day is just wasting energy.

 

[furpile]

Wow - maybe you guys should start your own thread about left-hand taps - May I suggest "you know what really grinds my gears... taps"



Well, yes and no... we're being careful to state that part is TINY and not worth it!

If your geyser has no leaks, no pipes and you don't use any hot water at all; then yes, the only saving you'll get is from standing losses from the geyser. You also get 'losses/savings' from:
A. Losses along the pipes - i.e. every time you run the tap and wait until it's warm, that water is being taken from the geyser and left in the pipe to cool again. I worked it out for me once, and it was quite small, but I live in a flat...
B. Any leaks/drips are better at 40 degrees, than at 60 degrees... although yes, sort out the leaks!
C. Standing loss performance likely IS NOT like the standards, often worse... if there's a draft, or the insulation is broken, or pipes aren't lagged coming out etc...
D. Apart from showering, bathing etc, most of the times you use hot water (or at least turn on the hot water tap) the temperature isn't critical; so generally people happily use water at 40 degrees rather than 60 degrees, thus reducing the amount of energy they are washing down the drain.
[PS - on this point, why are you washing dishes in scolding hot water?? you know it doesn't 'kill the bacteria' right? just hurts you...http://goo.gl/HtZXeD]

As an engineer - I know where you're coming from - the difference in heat-loss on a well insulated geyser between it being at 55 degress or 60 degrees is VERY small... and not worth the effort.

But as an energy user - and as someone who helps other people with their energy use - I know from experience that leaving my geyser on my electricity bill was R500/month, but with it only on when it got too cold, it was R300/month (small flat... Century City... 2 years ago...)

It wasn't me talking about the scolding hot water for dishes, but anyway. So we can agree that timers don't really save you a lot of electricity, it just enforces a behaviour change that people are not willing to do themselves?

 

[Geoff.D]

It wasn't me talking about the scolding hot water for dishes, but anyway. So we can agree that timers don't really save you a lot of electricity, it just enforces a behaviour change that people are not willing to do themselves?

Yes agreed. Indirectly the timer therefore does save energy costs. The savings are larger for installations that include low grade geysers, and poorly insulated pipes, leaks, dripping taps, long pipe runs that cause more cold water to be drawn into a geyser etc.

 

[Alain Craven]

The point by furpile is correct in my experience.

We do the same - set times for the geyser to go on and if all the water is used, too bad.
People learned and adapted and it works smoothly now.
A couple of really cold days (where ambient water temp is very low) I manually override timer. Maybe 4 or 5 times a year.

 

[Splinter]

But ultimately you should be washing your hands with warm water...otherwise not bother washing them at all really.

Where do you get this pearl of wisdom from?

 

[richjdavies]

I'm with Splinter on this...
http://lifehacker.com/cold-water-and-regular-soap-kills-germs-just-as-well-as-1488847107

You don't need hot water to wash your hands... (although it's nicer!)

 

[richjdavies]

Yes agreed. Indirectly the timer therefore does save energy costs. The savings are larger for installations that include low grade geysers, and poorly insulated pipes, leaks, dripping taps, long pipe runs that cause more cold water to be drawn into a geyser etc.

100% ^this...

I'm not sure a 'timer' is the thing that does it... but switching off does. A timer won't save you any money if you switch it so that it's on just as much as it was before (e.g. 3-4 hours per day!)
** but it certainly won't cost you more **

Also about the pipes and what they call 'hot-lag' (i.e. how long it takes for hot water to reach the tap), I started doing some analysis just basically trying to figure out how much water is in a pipe... it's not hard to work out.

e.g. 25mm diameter pipe = c. 500sqmm cross sectional area = 0.5L of water per meter of pipe
so if you have a 10m run of pipe before your tap that's 5L of water
If there's a 50 degrees drop, then you've wasted about 0.3kwh for each time you fill that pipe*

So if you do that 5 times per day, then I guess that would be getting on to 45kwh/month?

This will change ALOT if the temperature is lower, degree drop is less, distance from geyser is shorter, number of times you run the tap... etc.


* 50 degree drop = 70 degrees at your geyser, 20 degrees ambient, and it's cooling ALL the way down;
5 Litres (=5kg) x 50 degrees x 4.2 kJ/kgK (specific heat capacity of water) / 3600 (kwh/KJ) = 0.292 KJ

 

[Zoomzoom]

so lagging better than switching it off ...

I'm really amused by this thread - its 5 bits of anecdotal evidence followed by a few 'this is the science' posts and no-one agrees. It is precisely this combo of science that doesn't quite seem to actually reflect real world conditions and anecdotal evidence that ranges from one extreme to the other that lead me to post this question in the first place.

 

[furpile]

so lagging better than switching it off ...

I'm really amused by this thread - its 5 bits of anecdotal evidence followed by a few 'this is the science' posts and no-one agrees. It is precisely this combo of science that doesn't quite seem to actually reflect real world conditions and anecdotal evidence that ranges from one extreme to the other that lead me to post this question in the first place.

Not quite, that lagging is wasted energy, you cannot save it unless you frequently use hot water. After you have used hot water, the amount that is left in the pipe cools down, this is lost energy. The geyser has to heat that amount of water in the geyser again. It just means that you shouldn't use hot water if you don't need to, many people use the hot water tap to wash their hands, and it does not even reach the tap by the time they are finished. That hot water in the pipe is wasted. Usually pipes inside the house will be 15mm diameter, so that is a third of the volume that richjdavies worked out. But still a lot.

The problem with getting a single answer is that it depends a lot on your circumstances, what works for someone else will not necessarily work for you.

 

[Zoomzoom]

The problem with getting a single answer is that it depends a lot on your circumstances, what works for someone else will not necessarily work for you.

well that is the nub of the problem. theoretical science is all very well, but it fails to take into account specific circumstances. Anecdotal evidence is all very well, including the theories on why someone thinks they got a saving, (or why they didn't) but none of it actually has a firm definitive answer. There is always a question left in your mind.

 

[Geoff.D]

Not quite, that lagging is wasted energy, you cannot save it unless you frequently use hot water. After you have used hot water, the amount that is left in the pipe cools down, this is lost energy. The geyser has to heat that amount of water in the geyser again. It just means that you shouldn't use hot water if you don't need to, many people use the hot water tap to wash their hands, and it does not even reach the tap by the time they are finished. That hot water in the pipe is wasted. Usually pipes inside the house will be 15mm diameter, so that is a third of the volume that richjdavies worked out. But still a lot.

The problem with getting a single answer is that it depends a lot on your circumstances, what works for someone else will not necessarily work for you.

Yes it is a systems engineering problem requiring a complete solution not a piece meal solution. In other words you can't just do one of the things required, you need to do them all.

so lagging better than switching it off ...

I'm really amused by this thread - its 5 bits of anecdotal evidence followed by a few 'this is the science' posts and no-one agrees. It is precisely this combo of science that doesn't quite seem to actually reflect real world conditions and anecdotal evidence that ranges from one extreme to the other that lead me to post this question in the first place.

No lagging the pipes as far as possible does not eliminate the need to only switch on the geyser when hot water is required, the combination is what works.

100% ^this...

I'm not sure a 'timer' is the thing that does it... but switching off does. A timer won't save you any money if you switch it so that it's on just as much as it was before (e.g. 3-4 hours per day!)
** but it certainly won't cost you more **

Precisely. Before I installed the instant hot water under the sink, I did in fact set the geyser at 70° C to ensure the water would reach the kitchen tap at 50° C, and the water that had to flow out of the pipe was measured at 4.78L before the water reached 50° C.

After lagging the pipe leading to the kitchen ( about 18m that could be reached), it was possible to lower the geyser temperature to 60° C and reduce the water "loss" to about 3L ( with the water now at 58° C in Winter. The 60° C setting ensures that all the bathroom taps also maintain a temperature of above 50 °C.

The in line heater in the kitchen sees to it that the 3 L water "wastage" is now entirely eliminated, as the water runs hot immediately, meaning even if someone was to draw water out of the geyser from the hot tap indiscriminately, the savings are not "wasted".

I agree also what works for one situation will not work in another and may not work as efficiently for everyone either. that is why in my post further down I said IF one is serious about this whole business, one has to take plenty of measurements and truly understand what will work for you.

The biggest savings comes from "training" persons in the household to use hot only when needed and to do so intelligently. And that is where a "timer comes in, it "forces" the training to becoming a habit.

BTW, The longest I require in mid winter to heat the water is only 1 hour and 15 minutes per 24 hours ... In summer it is 59 minutes.

 

[richjdavies]

I'm really amused by this thread - its 5 bits of anecdotal evidence followed by a few 'this is the science' posts and no-one agrees. It is precisely this combo of science that doesn't quite seem to actually reflect real world conditions and anecdotal evidence that ranges from one extreme to the other that lead me to post this question in the first place.

I sense frustration, but you're asking asking a complex question where we don't have any data. It's a bit like dieting... everyone knows the science bit (less calories...) but the problem is there's this complex system (a person) who's doing the eating, doesn't keep any reliable data and has emotions and feelings... bleh! The same goes for saving electricity, some people think "I've been good and switched the lights off last night, so I can have a nice long shower this morning"

Anyone who says they used more energy by switching off their geyser is just plain wrong (sorry whoever it was...) -- probably their bill was creeping up as it was getting into winter, then they switched the geyser off and used up more than that by using a kettle to heat the water, or heaters to heat the room just cause it was cold.

If you want your hot water usage to be 100% the same after you switch it off, then you likely won't save much [assuming small-ish standing losses, lags etc.] But why not give it a go and find out. It's a good start to figuring out if maybe you do have a leak. You don't need to get a timer, just go and switch it off at the breaker board. See how long until you get complaints from the rest of the family

You could always get a data-logger (PLUG ALERT --> I'd personally recommend a Homebug <--) -- and then figure out from that how fast your geyser is dropping temperature, how much power it is using etc... Then you can start arming yourself (and the people trying to answer your question) with a bit more data.

 

[Zoomzoom]

I am switching from a system where my electricity is included to municipal metered electricity. I wanted prepaid, but there are no meters available for the foreseeable future. So no point in trying to give details I don't have.

I have the habit of switching the geyser off overnight - have done for years - having heard it saved electricity. Then in the process of investigating solar (seriously the pricing on that is INSANE!) I discovered some info that said not only does switching the geyser off not save electricity, but also shortens the life of your geyser. Then you get another site that says nope it doesn't harm your geyser, and switching off does save.

Reading through this thread I'm no closer to knowing if switching your geyser off for 8 - 12 hours a day does save, if only because it is not recycling through the reheat process during that time, or not.

How can a simple question be so damn complicated to answer.


Take any geyser - turn it off during non-usage period (so no water loss) for between 8 - 12 hours save enough on the reheating cycle to justify doing it? Or is any saving immediately off-set by the heating it will do when you put it back on?

 

[richjdavies]

Take any geyser - turn it off during non-usage period (so no water loss) for between 8 - 12 hours save enough on the reheating cycle to justify doing it? Or is any saving immediately off-set by the heating it will do when you put it back on?

Okay - that's a specific example, that I think we can answer. Lots of people have done that test, and it's actually what's done by SABS to work out the losses for every geyser (over 48 hours rather than 12 like you say).

If you don't use any water during that time, and assuming your geyser isn't cooling all the way down to ambient... then...

YOU WILL NOT SAVE ANY ENERGY!

You're letting it cool down partially (from say about 70 degrees to about 65 degrees), then heating it back up again... why do you think you'd save any? In fact your geysers own temperature controller will be doing this itself...

The people who are saving are switching their geyser off for 20-24 hours a day, not just the 12 over night.

** PS: before I get flamed for this --> yes, the geyser will lose slightly slower at 65 degrees say rather than 70 degrees, but it's marginal until it gets much closer to ambient.
So reasons why you might save on 'switching geyser off overnight' include:
- There's a leak... so you ARE using water, you just don't realise... better to use that water at 60 degrees than 70 degrees
- Your geyser's insulation is screwed -- so it cools down significantly overnight... so it will cool down to say 30-40 degrees -- i.e. closer to ambient
Way to test this... switch your geyser off... if it's COLD in the morning, then you'd have saved energy; if it's still pretty much as hot as it was, then your geyser probably doesn't have leaks/bad insulation

The savings people talk about aren't from switching it off overnight, they are from switching it off for 24 hours a day, and only switching it on for a couple of hours to heat up before a shower (when heat matters)