karmacoma
Member
I'm looking at my Hills Solar hot water storage tank, which is ground-mounted with a circulating pump housed on the side. I can see two wires leading into a plug at the bottom of the tank. It would have to be a tank temperature sensor, used as input to the pump controller. I'd like to somehow take leads off this to a temperature display indoors.
Has anyone done this kind of thing? How did you do it?
I've googled around but no luck -- is there any good-how-to on the web?
Morbo
Member
http://www.ebay.com.au/itm/like/252021535617?limghlpsr=true&hlpht=true&ul_noapp=true&hlpv=2&chn=ps&lpid=107&ops=true&viphx=1
remote wireless thermometer?
karmacoma
Member
So it seems the better idea is to have an independent sensor rather than risking disruption of voltage or whatever to the existing sensor circuit. I wouldn't be able to fit a second sensor into the same plug at the bottom of the tank, which is just a 3/4" brass cap on a tee where the mains water comes in. But there is the inlet from the solar hot water just above it, and I could get a tee onto that, to mount an new sensor.
I see various thermocouple probes on eBay that have a hex screw termination between the probe and the cable, and it looks like I could get a neat watertight fitting of probe into cap with that. So I guess I'm looking at getting the right thermocouple and a display for it.
karmacoma
Member
I am finding that every active system I have is breaking down. I suspect the solar hot water system isn't working well either. It might be, but I have no way of knowing. I suspect, because even last summer the gas booster would fire up if anyone drew water from the hot tap. So I want a temperature display I can keep an eye on. If it reads 18oC in the tank on a sunny summer afternoon, I know I've got something else to fix. A sensor in through the top outlet would indeed be best, but the pressure relief valve has baggsed that spot already.
The tank is insulated, so I wouldn't have thought a sensor on the outside of that would tell me very much. Haven't taken the top cover off (that will require emptying the tank and moving it out of position), maybe there's a bald spot there for a surface sensor. Guess I originally thought I could just take off a display from the existing sensor but unless it's done electronically off the right transistor legs on the controller circuit, I now guess not.
Greg
Member
I have digital temp sensor / displays on inlet and out let pipes. All I did was dab a bit of thermal paste on the pipe, zip tie the sensor on and recover with the insulation. Admittedly mine are just on 1.5m of wire but it works well enough when the water flows and the temps look realistic. Would that be good enough for you?
Morbo
Member
how is the SHW controlled? The controller should have a bunch of sensors? mine has 3, tank on top, tank from pump, solar collector. The sensor on top of the tank is for the pump to switch off, when the tank is at 80 deg. Panel and pump out is for pump comes on at 14 deg difference and off at 7 difference. Plus when the panel is 3 or so deg on winter nights, the pump comes on so the panel does not freeze.
All these temperatures can be checked on the pump controller.
Your trouble maybe is, the pump is dead. Happened to me last summer. I realised that, when after 3 days of sun the tank was still at 50 or so deg insted boiling point.
Its not a good idea to use the sensor on 2 inputs. Then the resistance the sensor sees is halfed and the voltage out of the sensor would be lower, because a higher current would be drawn. If its amp based sensor, each input would see 1/2 the current / 1/2 the temperature. Lower voltage would also mean, lower temperature. You would mess up the whole system.
fixed it up recently, pushed it in next to the socket so it touches the tank.
the picture comes up 1st when you do image search for apricus sensor .-)
Really?Its not a good idea to use the sensor on 2 inputs. Then the resistance the sensor sees is halfed and the voltage out of the sensor would be lower, because a higher current would be drawn. If its amp based sensor, each input would see 1/2 the current / 1/2 the temperature.
If you just measure the voltage between the two leads to the sensor, you will not change anything if the inner resistance of your second temperature meter is high enough. Any digital volt meter would do.
However the correlation between temperature and voltage is possibly not linear and it will then be necessary to produce a conversion table from volt to degrees.
Making that is not so hard. Remove the sensor from the tank. The sensor is usually not wet, but sitting dry in a thin tube with a closed end. Then take the sensor and put it into water of different temperatures. Measure temperature and voltage and write down the data. The produce a xY chart from these data. After that create a table for voltage and temperature in whatever steps you want by interpolating data from the chart.
Using Excel or any other spreadsheet will speed up the process. There might even be a decent curve fitting possible which will allow then to calculate the temperature from the measured voltage data.
Morbo
Member
your voltage meter has a very high resistance, so it does not draw too much current out of the device you want to measure. Plus you are not putting it in parallel.
If you do D/A conversion, you have a pull up resistor. Otherwise with the circuit opening, it would just pull the voltage out of the sensor down. If you do audio, you put some resistors in and the former component should be able to produce some current. If you make a Y piece and say hook up a CD player to 2 amps, you would half the signal.
karmacoma
Member
If I'd gotten Apricus instead of Hills it might have been better - I see Apricus has a range of sensors and displays you can buy, while Hills just died. Would be nice if the pump had a sensor to circulate like the Apricus on winter nights -- here in -6degC Canberra -- might have saved the air vent from freezing and bursting. As it did.
I will have to go out and have another look, but first take I only saw two sensor wires - one disappearing off in the wall so presumably going to the evacuated tube collector, the other going into what I assumed was the mains inlet, but the assembly instructions are calling the 'tank sensor well'. If I find out the markup for how to place images here I will add a pic.
All I can say about the controversy over whether tapping in on the tank-sensor-well sensor leads (in the last two posts) is 'yoiks'. Unless that's resolved, I'm not able to act because I haven't got enough knowledge on such things personally.
karmacoma
Member
Only problem with the meat thermometer (or a more sealable thermocouple) I now realise is that there's nowhere to insert it properly. Now that I know what I thought was the mains water inlet is actually a sensor well (not sure why it has to have mains water around the sensor, as well as the sensor apparently going into the tank), one thing is cleared up. That is, I couldn't see why a sensor probe wouldn't just obstruct the water flow at the inlet. Of course it would, and that's not what the manufacturers did. So I won't put in a sensor in the solar hot water inlet, because that would obstruct flow.
So Hills manufactured a tank that could never have a thermometer attached. Well, that probably saved them 20 cents per tank, and -- lessee now -- would have returned the shareholders or Hills Family or private equity firm or whoever another 0.0000001% profit. Gee, free market thinking always works.
So unless someone's gone through the exercise of tapping into the controller for a readout (seems not) then I will just explore the idea above of a surface sensor on the inlet/outlet as per Greg's suggestion.
Sunshine
Member
I have a Hills SHWS as well.. apparently the circulating pump can fail, though mine is 7 years old.
I have previously contacted this mob, very helpful, he recommended this upgrade kit when pump does fail, and he says that controller is more programmable than the Hills.. give him a call if you want to discuss further.
http://www.solarhotwaterparts.com.au/pump-stations/solar-hot-water-pump-station-with-resol-deltasol-bs-4-1-2-sensors-1
Solgen
Member
I have had a Hills SHWS since 2008, a few years ago I replaced the controller with one of these devices. http://www.ebay.com.au/itm/CONTROLLER-of-SOLAR-WATER-HEATER-water-proof-240V-for-Australia-Newzealand-/231001268581?hash=item35c8bfa165.
Its very good, gives you an indoor display that shows the sensors temps and what the pump is doing. In addition, you can change the settings for pump start and stop, plus other aspects of operation. I recommend them.
With regard to sensors, for the lower sensor, you either have to jam the sensor up under the insulation onto to the tank or carefully drill through the outer shell and insulation until you can get a good contact with the tank. Secondly, I have purchased a couple of the NZ made sensors - http://www.ebay.com.au/itm/Senztek-Solar-hot-water-SolaStat-Tank-sensor-3M-10K-/291481342969?hash=item43dda453f9, which are very good but expensive. On installing these, I discovered that the original installers had put the tank sensor in the wrong spot which was sensing the wrong temp and causing the pump to operate at times when there was no solar gain (like at night!).
The system works very well now.
karmacoma
Member
Sunshine, interesting. The aftermarket kit is a complete redesign. Nicer pump, and the controller is a lift-out hand held module with LCD display and 3-button keypad, which includes a temperature read-out from a 'roof sensor'. Pricey though - $570 down from $880. I notice he's selling other sensor parts, and lots of aftermarket controllers. They seem to have a full-on electronics design engineer. Yes, he is worth a call. Can't do $570 bucks, but I might learn something. Thanks.
karmacoma
Member
Solgen, what a find. Seems to be called an Ultisolar SR1068. I found a few other things about it by Googling, like the manual: http://www.ultisolar.com/SR1068.pdf. At $128 it's not bad. It definitely gives a temperature read-out. But you must have been dissatisfied with the provided sensors, because you bought more expensive ones - why was that? I'm interested in this because the price is achievable for me. Are you able to post any pics of your installation?
I use one of these.
http://www.ebay.com.au/itm/Solar-Power-Energy-Digital-LCD-Thermometer-Heat-Sensor-Probe-Cable-50-150-3ft-/321527499100?hash=item4adc88495c
They are very cheap, don't require batteries and will read the required temperature range. Cut the wire to the probe and extend the wire as long as you want so you can mount the display somewhere convenient. You'll need to drill a 10mm hole into the outer casing on your hot water tank (near the top) and poke a screw driver through the insulation until you get to the inner tank. Push the sensor down this hole so it is in contact with the tank and seal up the drilled hole (with the wire coming out of it) with silicone.
They are so cheap you can add as many as you like to monitor the temperature on any part of the system. My readout is indoors, high up on a wall and it still gets enough light on its solar panel to keep it running. It has been there for about 4 years.
Morbo
Member
for the sensor:
behind that cover is a rubber ring. I pushed the sensor in, so its pushed against the socket and touches the tank. This gats me about 7-8 deg higher reading as per the picture further up. So now the pump really stops at 80 deg not at 90 and may live longer.
for the SHW: if you buy cheap, you buy twice? Wen we bought ours, the vendor did some Q&A session, and people would ask questions like, what happens when its frost and the like. Strange, that yours does not even have a controller let alone some frost protection.
Sunshine
Member
karmacoma and morbo,
I think you're incorrect about no freeze protection.. read page 9
http://www.energymatters.com.au/images/Hills/SLR_M_001_Owners_Manual.pdf
karmacoma
Member
Sunshine, good find. I'll have to get on the roof and have a look for that. In the meantime, assuming that is true for my model too, it is another bit of evidence that my pump has stopped working (the other thing being that the gas booster comes on in summer).
Morbo
Member
does it have any controller at all? Which has a status LED for pump on or something? Or manual override to switch the pump on?
http://www.solarhotwaterparts.com.au/manufacturers/aae/senztek-solastat-plus-1-2-solar-hot-water-sensor-controller
then just switch pump to manual and get a meat thermometer or just your fingers, the water temperature in the socket from panel to tank should go up.
Morbo
Member
"yes the Hills has a controller.. would look like this"
glamourous junction box.
the pump vibrating does not mean its pumping
if it looks like this
http://www.budkompleks.com/akcesoria/pompy/pompa-cyrkulacyjna-c-w-u-grundfos-up-15-14-b-80mm.html
the hot water may have demagnetised the impeller
Sunshine
Member
the pump is most likely this one http://www.solarhotwaterparts.com.au/circulating-pumps/salmson-sb-04-15-solar-hot-water-pump
another way of checking that the pump is working is to check the window in the water flow meter.. switch off the pump and the spring should move
