Installing a geyser timer

Trust|Nobody said:
That looks like a nice monitor.
But it really bothers me that the engineers who designed it used "KWHr", the correct SI unit is kWh.
All engineers should know the SI units.

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Quite correct. There are many examples where the manufacturers do not adhere to the standards. It is a pity that products like this are allowed to be sold in SA> Products that do not adhere to the country's standards should be removed from the shelves. It might sound trivial to be pedantic about these things but that is where the rot set sets in.

The abbrev for "kilo" is small caps "k". The abbrev for power in Watts is "W". The abbrev for hours is "h".
These things are simply bad programming.
 
More useful info:

(1) Have a look at this site: https://www.savingenergy.org.za/
(2) Look at these calculation tools on the above site: https://www.savingenergy.org.za/asl/calculation-tools/
(3) Understand the new energy labels for all appliances sold in SA.
(4) Have a look at these compulsory specs when buying appliances: https://www.savingenergy.org.za/asl/manufacturers-and-importers/
(5) SANS 151 covers geysers: The minimum rating for a geyser is now ("B"). Unfortunately, many of us are sitting with geysers in our homes that will battle to meet the "D" rating. -- These geysers all benefit from the installation of a geyser blanket.
(6) And for the really interested in water heaters, here is a thesis done on the subject! Fascinating stuff!
https://scholar.sun.ac.za/bitstream/handle/10019.1/.../reid_thermal_2016.pdf?...2...



See attached document
 

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@Geoff.D

Are you able to translate what this means, for a normal guy to understand ?

I know it's the amount of loss - but I'm unsure the actual meaning

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That is the amount of power needed to keep geyser at set temperature, with zero hot water going out and cold water going in
 
Dolby said:
@Geoff.D

Are you able to translate what this means, for a normal guy to understand ?

I know it's the amount of loss - but I'm unsure the actual meaning

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Where did you spot this please?

The explanation above is correct.

I would interpret this as meaning that the geyser consumes 2.59 kWh over a 24 hour period, with NO hot water being drawn from the geyser, and no temperature control other than a standard thermostat and on continuous power. What is missing is this would surely apply at a specific temperature setting, as heat loss is proportional to ΔT.
Presumably, the ambient temperature is also specified.
This is presumably the worst case figure.

It simplifies the calculation of heat losses as that formula is rather complicated with all sorts of proprietary information required, which presumably manufacturers would be reluctant to release into the public domain.
 
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It is quite simple to measure the value for a geyser. Simply note the kWh value on a meter connected to the geyser, as soon as the power is cut to the element when the geyser has reached temperature, and then check again 24 hours later, with no water drawn from the geyser. The difference would be an indicator of what the standing losses are.
Now you could experiment by changing the on-off times until you find an optimum (least) value.
 
Remember that your geyser should reach 65 degrees at least once a day. This will keep the Legionnaires disease at bay.
 
Geoff.D said:
Where did you spot this please?
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The spec sheet for my geyser.

I'm thinking something like 3 x 1hr sessions in the day would be the best (5am - 6am / 12pm - 1pm / 9pm-10pm) to keep the temperature high enough in the day
 
Yes, that is where one of the strengths of the Geezerwise product lies.
It offers you 4 cycles in 24 hours. You are therefore able to use one of those cycles to take the geezer up to 65 degrees and the other 3 to optimise energy savings.

With a single element controlled by one thermostat, you have to set the geezer temperature to at least 60 degrees.
All you have left is the timing and duration of each timing period.

The other benefit of the product is the 30A rated contacts on the relay.

Incidentally, a Geezerwise unit is nothing more than a multiple period timer coupled with exact temperature control.
Ordinary thermostats are very crude devices, with dubious temperature accuracy, and very little control of the time between when the element is ON or OFF.
 
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IMG_20190421_205323_928.jpeg

"A recent study has shown that it takes a 3kW (150l) geyser 2 hours to heat water to 60ºC"

Did they really need a study for that?

Energy required to heat 150 l of water from 25 to 60 °C:
Q = mCp∆T = 150 kg × 4.184 kJ/kgK × (60-25) K = 21966 kJ.

Time required for a 3 kW geyser to transfer 21966 kJ of heat to the water:
t = Q/P = 21966 kJ/3 kW = 7322 s = 2.03 h.

There's a 2 minute calculation.
 
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No, but that is what marketing is all about --- trying to make things look more impressive than it really is.
I agree that geysers should be fitted with a geysers blanket and the pipes insulated. However, I think they are exaggerating the savings. Especially with the new geyser standards implemented. With older geysers the savings are noticeable. Add to this a heat management system and you have what I have, I can run on one heating cycle for up to three days without any problems.
 
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Some facts.
1 Wh = 3.6 kJ
1 W = 1J/s
1 litre of water has a mass of 1kg (good enough for this purpose)

Specific heat of water = 4.187 kJ/kgK [Cp]
Energy required to heat water Q [kJ] = mCp(Ts-Ta); Ts= set temperature & Ta=ambient Temperature outside geyser or incoming water temperature; m=mass of water in kg. Temperature is in degrees K = degrees C
Time to heat water t [seconds] = Q/P; P = element in kW; Q in kJ
Standing losses is complicated but as indicated above could be available as an estimate of the energy required to maintain a geyser at the set temperature without drawing water from the geyser as x kWh/24 hours.

There are much more complicated formulas around, but the above works pretty well.

The heat loss is in general not a linear relationship over 24 hours, because the ambient temperature is not a constant, and very dependent on where the geyser is installed. Less heat loss occurs in Summer as compared to winter. Less heat loss occurs during the day than in the night time. The only way to truly understand what is happening is to measure the ambient temperature outside the geyser over a 24-hour period.
Incoming cold water temperature is another variable that is different between winter and summer.

All the above makes for a very interesting experiment depending on how much effort you want to put into the exercise.

Thermostats can be checked by placing the stem in boiling water and then monitoring the temperature to see when the thermostat switches On and Off. (A multimeter across the terminals is the easiest way to detect On and Off). The difference in temperature can then be used to calculate how much energy is required to keep the water at the set temperature as a proxy for the standing losses.
 
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Geoff.D said:
More useful info:

(1) Have a look at this site: https://www.savingenergy.org.za/
(2) Look at these calculation tools on the above site: https://www.savingenergy.org.za/asl/calculation-tools/
(3) Understand the new energy labels for all appliances sold in SA.
(4) Have a look at these compulsory specs when buying appliances: https://www.savingenergy.org.za/asl/manufacturers-and-importers/
(5) SANS 151 covers geysers: The minimum rating for a geyser is now ("B"). Unfortunately, many of us are sitting with geysers in our homes that will battle to meet the "D" rating. -- These geysers all benefit from the installation of a geyser blanket.
(6) And for the really interested in water heaters, here is a thesis done on the subject! Fascinating stuff!
https://scholar.sun.ac.za/bitstream/handle/10019.1/.../reid_thermal_2016.pdf?...2...



See attached document
Click to expand...

Bump. See the slat reference for an in-depth explanation of water heaters and SANS 151.
 
IMG_20190422_095547_948.jpeg

My geyser is set to 50 °C. I want to set it to 60 or 65 °C but I can't see a setting for that.

Can this thermostat be set to those temperatures?
 
signates said:
The small yellow dial can be turned clockwise to increase the temperature.
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The picture quality is low. MyBB reduced the quality. I can see numbers for 10, 30, 50 and 70 °C but no 60 or 65 °C.

Turning clockwise will decrease the temp.
 
Yes. Counterclockwise. Last time I checked mine was over 2 years ago and couldn't remember which way.
 
Estimate between 50 and 70. The newer ones now mark 60 or 65 depending on the make
I always calibrate new thermostats before installation with boiling water a thermometer and a multimeter. Mark 60 and 65 if possible or just 65 if the difference is too little. Use a permanent marker
 
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