measure geyser temperature?

Hi everyone,

I hope someone can help me with this, since I can't find anything on google. How do I measure the water temperature inside my geyser? I want to know build a "smart geyser controller" which can sense water temperatures and then heat-up the water as needed.

In South Africa we have a device called "GeyserWise" (http://www.satchwell.co.za/geyserwise.asp) which basically connects to the back of the Geyser's thermostat and you can program it to come on at certain times of the day. But I want to extend this and add a GSM based controller, which will allow me to turn the geyser on when I return from a long trip and I know I'm say 2 hour's drive from home.

So, I need to know how to measure the water temperature inside the geyser, without cutting it open to add a temperature sensor. Has anyone done something like this and can share some ideas?

If your geyser controller has mechanical buttons which can be used to turn it on manually, perhaps you could wire those switches up to an Arduino and operate them electrically as required. Making something which is a functional replacement for your geyser controller and accepts SMS commands would be technically feasible and not especially difficult, but making it as presentable and user-friendly as the commercial product would be the hard part. However, here in the UK these things work at mains voltages, and combining electronics with mains voltages can be very dangerous without specialist knowledge.

With heating control systems, the controller usually has an air temperature sensor and can be configured to vary the target temperature during the day.

With a hot water heater, I would expect the target temperature to be fixed by a thermostat attached to the hot water cylinder, and all the controller would do is turn the heater power supply on and off. You could attach a temperature sensor to the outside of the cylinder if you wanted, but I don’t see any need.

If you can get at the existing thermostat you could probably epoxy a temperature sensor like These to the metal tank and cover it with a little insulation. That should be very accurate.

At first I was visualizing running 100 meters of wire into Old Faithful, the famous USA Geyser 8) But NO..

DISCLAIMER: Mentioned stuff from my own shop...

PeterH:
If your geyser controller has mechanical buttons which can be used to turn it on manually, perhaps you could wire those switches up to an Arduino and operate them electrically as required. Making something which is a functional replacement for your geyser controller and accepts SMS commands would be technically feasible and not especially difficult, but making it as presentable and user-friendly as the commercial product would be the hard part. However, here in the UK these things work at mains voltages, and combining electronics with mains voltages can be very dangerous without specialist knowledge.

With heating control systems, the controller usually has an air temperature sensor and can be configured to vary the target temperature during the day.

With a hot water heater, I would expect the target temperature to be fixed by a thermostat attached to the hot water cylinder, and all the controller would do is turn the heater power supply on and off. You could attach a temperature sensor to the outside of the cylinder if you wanted, but I don't see any need.

Our home geyser is operated from 220V, which I can easily turn on and off using an Arduino + a relay (SSR for better protection) but I want to be able to measure the water temperature as well. It has the following thermostat in, "kwik therm t105 " (__K W I K O T______________________) which has a dial at the end where I set the temperature. This fits into a small tube housing on the side of the geyser. Look at option #2 in this photo for a sample: http://www.vaalsteel.co.za/LAY_OUT__Large_.jpg

There are many "Geyser" hot water heater types.

Does your have a storage tank or is it "On Demand" type with almost no storage?

If it is a storage type, think about the stratification of hotter water near the top (output). You may want to measure temperature both at top and middle / bottom of such a tank to predict how much energy will be needed to bring the temperature up for what length of time.

Using a lot of water quickly on a tank heater makes the bottom water much cooler and there is less reserve capacity left. If very little water is used, the tank slowly becomes more uniform in temperature and there is more 'reserve' capacity. You still pay for the energy, the dynamic performance is just different.

terryking228:
There are many “Geyser” hot water heater types.

Does your have a storage tank or is it “On Demand” type with almost no storage?

If it is a storage type, think about the stratification of hotter water near the top (output). You may want to measure temperature both at top and middle / bottom of such a tank to predict how much energy will be needed to bring the temperature up for what length of time.

Using a lot of water quickly on a tank heater makes the bottom water much cooler and there is less reserve capacity left. If very little water is used, the tank slowly becomes more uniform in temperature and there is more ‘reserve’ capacity. You still pay for the energy, the dynamic performance is just different.

It’s a 150L storage type, like this one: http://www.vaalsteel.co.za/LAY_OUT__Large_.jpg / http://www.housecheck.co.za/wp-content/uploads/2011/12/Geyser-horizontal1.jpg

The cold water enters in the left lower corner and the hot water exists the top right hand side. The current heating element and thermostat sits in the middel, on the left side where the cold water comes in. It’s No #2 and #3 on that image

The GeserWise design uses a custom made adaptor that adds on to the thermostat.
They then use one of these to measure the temperature

Hope this helps!

Blender:
The GeserWise design uses a custom made adaptor that adds on to the thermostat.
They then use one of these to measure the temperature
http://robotics.org.za/index.php?route=product/product&path=57_123&product_id=279

Hope this helps!

Thanx Blender,
I thought of getting one of those thermistors, but where do I connect it to, without drilling a hole into the geyser? That's where I'm stuck..... Do you simply stick that small thermistor into the same hole as the normal long thermostats?

It's No #2 and #3 on that image

It looks like there is a removeable cover in that area. Have you taken it off? Can you touch the inner metal tank? If so, you could add a temperature sensor.

Info on the widely-used DS18B20 type electronic temperature sensor is here:
http://arduino-info.wikispaces.com/Brick-Temperature-DS18B20

terryking228:

It's No #2 and #3 on that image

It looks like there is a removeable cover in that area. Have you taken it off? Can you touch the inner metal tank? If so, you could add a temperature sensor.

Info on the widely-used DS18B20 type electronic temperature sensor is here:
http://arduino-info.wikispaces.com/Brick-Temperature-DS18B20

Yes, there's a bit round metal plate, about 10" - 12" with a rubber seal that houses the heating element and thermostat. So, do I just drill a hole in, put a plug in, and insert the thermistor? The storage tank holds 150L water, which I guess has a lot of pressure once it's heated upto about 50degrees celcuis so I don't want to flood the house with experiments. I was hoping someone has done this already and could give me some tips on how they put a thermistor inside, without causing a water leak or electrical short.

Yes, there's a bit round metal plate, about 10" - 12" with a rubber seal that houses the heating element and thermostat. So, do I just drill a hole in, put a plug in, and insert the thermistor?

Can you touch the OUTSIDE of the metal plate?

How about the metal of the inner tank next to the round plate?

I don't think it's highly important to have the Temperature Sensor in DIRECT contact with the water. After all it (usually) has a metal covering itself.

Metal-to-metal contact and a little epoxy (epoxy putty, especially metal-filled type) might be easy to use.

terryking228:

Yes, there’s a bit round metal plate, about 10" - 12" with a rubber seal that houses the heating element and thermostat. So, do I just drill a hole in, put a plug in, and insert the thermistor?

Can you touch the OUTSIDE of the metal plate?

Yes I can but it doesn’t feel warm, probably due to the thick rubber gasket inbetween the water and outside of the plate.

terryking228:
How about the metal of the inner tank next to the round plate?

I don’t think it’s highly important to have the Temperature Sensor in DIRECT contact with the water. After all it (usually) has a metal covering itself.

Metal-to-metal contact and a little epoxy (epoxy putty, especially metal-filled type) might be easy to use.

Fair enough it’s fairly easy to put epoxy on the outside but I don’t know if the reading will be of any use. The geyser’s temperature is set to about 60 degrees Celsius but when I touch the metal plate it’s like a luke warm cup of coffee that’s been standing for a while. Not nearly as hot as the water that comes our of the tap

RudiAhlers:
Fair enough it's fairly easy to put epoxy on the outside but I don't know if the reading will be of any use. The geyser's temperature is set to about 60 degrees Celsius but when I touch the metal plate it's like a luke warm cup of coffee that's been standing for a while. Not nearly as hot as the water that comes our of the tap

Not familiar with SA geysers, but US water heaters have two metal layers separated by insulation. If you can open an access panel on the outer shell and pull aside some insulation, using thermal epoxy (the type used to mount LEDs to heatsinks) to attach your sensor to the inner vessel should be reasonably good. Software can compensate for the offset after some empirical measurements (60° output temperature = 50° sensor temperature).

There should be an access panel of some type where the 220V heating element enters the inner tank. Perhaps the sensor could be squeezed in near this point.

Apart from the dangers of working with 220V, isn't this a case of hacking your existing controller? You have an existing thermostat that's already reading the temperature and all it controls is whether the heating element is on or off. Is there a way to read the temperature data from the existing hardware and then control the power through SSR or a powerswitch tail (or whatever equivalent you can find that switches your higher voltage)?

Hi Rudiahlers

want to know if you managed to build your custom geyser controller with the arduino?

I have simpel solution for your original post on how to read the temperature in the geyser, although by now you maybe managed?

please let me know if you did build a controller

Hi Jaco,

I haven't spent any time on this again, but I'm rather curios to know what you have to offer?

Hi Rudi
the solution is actually simple. i have been working with geyserwise a few times with solar installations.
you actually remove the whole thermostat out of the element base plate. then you insert the ds18b20 sensor into the tube where the thermostat probe lied in. that is it. this way you can read the tank temp without modifying anything on the geyser.
i have wrote some code to do similar to the geyserwise controller but actually need help on some of the code.
maybe you can help with some pointers?

jacobotha:
Hi Rudi
the solution is actually simple. i have been working with geyserwise a few times with solar installations.
you actually remove the whole thermostat out of the element base plate. then you insert the ds18b20 sensor into the tube where the thermostat probe lied in. that is it. this way you can read the tank temp without modifying anything on the geyser.
i have wrote some code to do similar to the geyserwise controller but actually need help on some of the code.
maybe you can help with some pointers?

Hi Jaco, I kinda “brushed off” this project, since the geyserwise was already installed and doing it’s job.
I also only started playing with temperature sensors recently and you’re right, the DS18B20 could do the job pretty well. Together with a SIM900 shield it would be a breeze to setup something like this. Maybe next time, when I’m bored and want to hack something :wink:

What help do you need though?

P.S. Where in ZA are you?

Hi Jaco,

By any change, have you made any progress in this project. I want to know the challenges you have/had with the temp prob DS18B20 or what every you used.

I have a good mind in buying the geyserwise, but it will be more fun and rewarding if I can do this completely myself. I'm ok with programming in Arduino, Raspberry PI/JAVA, or even the microchip. I have a few types of temp sensors that I have played with.

Please let me know where you are at in this project so far. By the by I stay in Woodmead, Gauteng.

Regards
Sanjay Mistry

I design and manufacture geyser controllers akin to the Geyserwise and all we do is replace the electromechanical thermostat running down the centre of the element with a DS18B20 inside a sealed brass tube