Setting the temperature on a pt1000 sensor ?

SPAWKER · 12-01-2016 08:35PM #1

Hi all
I have a Dimplex solar system which is controlled by a Solcu1 control unit but it's acting up at the moment,the bottom sensor in the tank is only reading 12 to 14oC is there any way I can test it or set it back up so as it works again.
The sensor is a pt1000 one.
If it's gone does the tank need to be drained to take it out or can it be taken out when the tank is full ?
Thanks

air · 12-01-2016 11:35PM

They're generally set into a pocket on the panels, i'm not so sure what the setup is on the tank end. Can you trace the cable and have a look at it?
The sensors are cheap and easy to replace anyway.

SPAWKER · 13-01-2016 08:59AM

No it's the one in the bottom of the tank that's not working properly or it's knackered ,do you know if the tank has to be drained to replace it or can it be done with it full.?
Thanks

John T Carroll · 13-01-2016 12:18PM

SPAWKER wrote: »

Hi all
I have a Dimplex solar system which is controlled by a Solcu1 control unit but it's acting up at the moment,the bottom sensor in the tank is only reading 12 to 14oC is there any way I can test it or set it back up so as it works again.
The sensor is a pt1000 one.
If it's gone does the tank need to be drained to take it out or can it be taken out when the tank is full ?
Thanks

Just locate the probe on the cylinder and gently pull on the cable and the probe will come out quite easily, its installed in a pocket. It quite possibly not faulty atall and you may find that something has snagged it and partially or fully pulled it from its pocket. When you pull it out it should then read the same as the ambient temperature at the outside of the pocket and you should see some change, probably upwards depending on how hot you keep your house. Try that first anyway as these probes tend to read properly or not atall.

re testing it: A PT 1000 probe reads 1000 ohms at 0C, the correction factor is 3.85 ohms/DegC, you can leave the probe in the pocket and remove the wire tails at the nearest junction box or at the controller and test it with a multimeter, if the temperature reading was 14C before testing then the resistance should read 1054 ohms (1000+(14*3.85) ) and so on, be careful if working at the controller and switch it off as there is 230V floating around there.

SPAWKER · 13-01-2016 10:30PM

John T Carroll wrote: »

Just locate the probe on the cylinder and gently pull on the cable and the probe will come out quite easily, its installed in a pocket. It quite possibly not faulty atall and you may find that something has snagged it and partially or fully pulled it from its pocket. When you pull it out it should then read the same as the ambient temperature at the outside of the pocket and you should see some change, probably upwards depending on how hot you keep your house. Try that first anyway as these probes tend to read properly or not atall.

re testing it: A PT 1000 probe reads 1000 ohms at 0C, the correction factor is 3.85 ohms/DegC, you can leave the probe in the pocket and remove the wire tails at the nearest junction box or at the controller and test it with a multimeter, if the temperature reading was 14C before testing then the resistance should read 1054 ohms (1000+(14*3.85) ) and so on, be careful if working at the controller and switch it off as there is 230V floating around there.

Good man thanks
Will have a look at it over the weekend when I get a chance and will post back my findings.

SPAWKER · 17-01-2016 08:58PM

John T Carroll wrote: »

Just locate the probe on the cylinder and gently pull on the cable and the probe will come out quite easily, its installed in a pocket. It quite possibly not faulty atall and you may find that something has snagged it and partially or fully pulled it from its pocket. When you pull it out it should then read the same as the ambient temperature at the outside of the pocket and you should see some change, probably upwards depending on how hot you keep your house. Try that first anyway as these probes tend to read properly or not atall.

re testing it: A PT 1000 probe reads 1000 ohms at 0C, the correction factor is 3.85 ohms/DegC, you can leave the probe in the pocket and remove the wire tails at the nearest junction box or at the controller and test it with a multimeter, if the temperature reading was 14C before testing then the resistance should read 1054 ohms (1000+(14*3.85) ) and so on, be careful if working at the controller and switch it off as there is 230V floating around there.

Disconnected the sensor from the control panel which was reading 10degC and tested it with a multimeter which gave me a reading of 1029 ohms . When I connected it back to the panel it seemed to reset it. Before I went at it the minimum temp on it was 9degC and the max was 14degC now it's saying min temp 5degC and max 64 degC so hopefully it is back to normal. Will now have to wait for a bit of sun or warmer temperatures to see if it will work again.
Thanks for your help.

John T Carroll · 17-01-2016 09:09PM

SPAWKER wrote: »

Disconnected the sensor from the control panel which was reading 10degC and tested it with a multimeter which gave me a reading of 1029 ohms . When I connected it back to the panel it seemed to reset it. Before I went at it the minimum temp on it was 9degC and the max was 14degC now it's saying min temp 5degC and max 64 degC so hopefully it is back to normal. Will now have to wait for a bit of sun or warmer temperatures to see if it will work again.
Thanks for your help.

Thanks for posting back your findings, I'd say the probe is OK, 1029 ohms is 7.5C (1029-1000)/3.85, so there or there abouts. As there is very little solar gain recently that temperature will read fairly close to the mains supply if there is a big drawoff from the hot water cylinder, when no drawoff say at night it should go up a bit because of the hot water layers above it. I think mine read around 15c this morning.

SPAWKER · 17-01-2016 10:40PM

Also went to remove the sensor from the tank but it is siliconed in so didn't attempt to remove it see attached photo.
You reckon the probe is alright with the reading it gave me ?
Hopefully we get a bit of sunshine in the next while so as I can see whether it will work or not again.
Once again thanks very much for your reply it was very helpful.

John T Carroll · 17-01-2016 11:26PM

SPAWKER wrote: »

Also went to remove the sensor from the tank but it is siliconed in so didn't attempt to remove it see attached photo.
You reckon the probe is alright with the reading it gave me ?
Hopefully we get a bit of sunshine in the next while so as I can see whether it will work or not again.
Once again thanks very much for your reply it was very helpful.

I would think its ok but its probably a bit sluggish in response time as it looks as if its just siliconed onto the side of the tank. You could remove that female plug after first draining down the tank and look in and ensure that theres no obstruction inside like a coil. If clear you can buy a thermostatic pocket, a PT1000 sensor and an adaptor as both the thermostatic pocket and the cylinder connection are both male. The new location will give far quicker response time and should improve the Solar performance as well as you wont be undercooling the water that you have already heated with the solar panel.
https://www.google.ie/search?sourceid=navclient&hl=en-GB&ie=UTF-8&rlz=1T4GGHP_en-GBIE441IE441&q=picture+of+solar+cylinder+thermostat+pockets

SPAWKER · 21-01-2016 07:04AM

Just an update on this
Got the wife to check how thing's were going yesterday as we had a bit of sun,so she checked the controller and it said that the temp at the panels was 81degC and the pump symbol was rotating so she checked the bottom temp and it was at 11deg the top was at 25deg.She then checked it again in an hour or so and both temperatures were still the same.
When I got home from work I put a hairdryer onto the bottom sensor which was at 11deg and it shot up to 30deg in a few seconds which tells me that it is working. So there must be something else wrong with the system other than the bottom sensor ?.

John T Carroll · 21-01-2016 09:19AM

SPAWKER wrote: »

Just an update on this
Got the wife to check how thing's were going yesterday as we had a bit of sun,so she checked the controller and it said that the temp at the panels was 81degC and the pump symbol was rotating so she checked the bottom temp and it was at 11deg the top was at 25deg.She then checked it again in an hour or so and both temperatures were still the same.
When I got home from work I put a hairdryer onto the bottom sensor which was at 11deg and it shot up to 30deg in a few seconds which tells me that it is working. So there must be something else wrong with the system other than the bottom sensor ?.

There is something definitely wrong there, I would say that your solar system is either depressurised due to loss of glycol or that the system is full of air which may have happened during the summer! due to stagnation especially if you have a evacuated tube set up, stagnation would be unlikely with a F.Plate array due to its lower efficiency. The bottom sensor (store sensor) is/should be located just avove the solar coil, when the temperature difference between the solar panel sensor and the store sensor is around 7C to 10C (depending on its setpoint) the controller starts the circ pump. When everything is working normally, the heat from the tubes or panels is transferred to the water in the cylinder and the panel temperature will start to fall and the store temperature will start to rise, when the difference (differential) between the two falls to 3C to 6C (again depending on the controller setting) then the solar circ pump is directed to stop. There is no way that the panel temperature should rise to 81C with a store temperatrure of 11C so I would suggest checking the following. Check the solar system pressure, the minimum should be not less than 1.5 Bar, its normally around 2.5 to 3 Bar, if this is OK check that the circ pump is, in fact, running, theres a venting screw at the motor end, remove this, but either wear safety glasses or stand at arms length to avoid glycol getting into your eye and see if the pump shaft is rotating. Thers no point in me prattling on at this stage, you can tell us how you got on after first checking these points out. John

SPAWKER · 21-01-2016 01:14PM

John T Carroll wrote: »

There is something definitely wrong there, I would say that your solar system is either depressurised due to loss of glycol or that the system is full of air which may have happened during the summer! due to stagnation especially if you have a evacuated tube set up, stagnation would be unlikely with a F.Plate array due to its lower efficiency. The bottom sensor (store sensor) is/should be located just avove the solar coil, when the temperature difference between the solar panel sensor and the store sensor is around 7C to 10C (depending on its setpoint) the controller starts the circ pump. When everything is working normally, the heat from the tubes or panels is transferred to the water in the cylinder and the panel temperature will start to fall and the store temperature will start to rise, when the difference (differential) between the two falls to 3C to 6C (again depending on the controller setting) then the solar circ pump is directed to stop. There is no way that the panel temperature should rise to 81C with a store temperatrure of 11C so I would suggest checking the following. Check the solar system pressure, the minimum should be not less than 1.5 Bar, its normally around 2.5 to 3 Bar, if this is OK check that the circ pump is, in fact, running, theres a venting screw at the motor end, remove this, but either wear safety glasses or stand at arms length to avoid glycol getting into your eye and see if the pump shaft is rotating. Thers no point in me prattling on at this stage, you can tell us how you got on after first checking these points out. John

Thanks for replying
Will have a look at it when I'm off over the weekend and have more time to play around with it and will post back my findings.
Thanks again

SPAWKER · 23-01-2016 08:06PM

Hi John,
I had a look at that today and found that there is no pressure on the gauge at all so I'm wondering is it full of air or maybe it needs to be filled with Glycol ? .If it is either air or a refill is it possible to do it myself or will I need to get someone in to do it?
I have a three panel flat panel set up on the roof if that is of any bearing on it. I have also taken the vent screw off the pump and can see that it is spinning when the controller turns it on.
I have now switched the controller to the off position so as not to have the pump running so I hope that this wont affect the system in any way.
I have attached a couple of photos of the pump set up and the expansion tank and overflow that are beside the pumpstation.

John T Carroll · 23-01-2016 09:07PM

I cant view any images since the DDoS attack on Boards.ie last Sunday but it doesnt matter. The next step I would advise you to take is to remove by either twisting or prising off a plastic blanking screw at the very back of the solar system expansion vessel, you will then see a valve that looks exactly like the one on your car tyre, just press the valve stem with your finger nail or a small screwdriver, if glycol comes out then the expansion vessel diaphragm is ruptured and the expansion vessel must be renewed (not a DIY job) if there is no pressure or very little air pressure then just maybe the air has leaked out over a period of time, if there is some pressure, then beg or borrow a tyre pressure gauge or a hand tyre pump with a pressure gauge and measure the air pressure, if its anything more than say 0.5 bar and you have zero pressure on the liquid side then you have a glycol leak somewhere, if the pressure at the expansion vessel end is less than say 0.2 bar, start pumping up the expansion vessel and both pressures should be almost exactly the same if you havnt lost any glycol, pump away until you get 2.5 bar on either side, if you have no pressure at the liquid side then you have lost glycol, you should then get someone in at this stage as you dont know where the leak is, it could be somewhere on the panels or worst of all a pinhole in the solar coil. If you have a unvented (pressurised) Hot Water Cylinder then the solar coil wont be holed because you would still have pressure at the solar system.

SPAWKER · 24-01-2016 08:02PM

John T Carroll wrote: »

I cant view any images since the DDoS attack on Boards.ie last Sunday but it doesnt matter. The next step I would advise you to take is to remove by either twisting or prising off a plastic blanking screw at the very back of the solar system expansion vessel, you will then see a valve that looks exactly like the one on your car tyre, just press the valve stem with your finger nail or a small screwdriver, if glycol comes out then the expansion vessel diaphragm is ruptured and the expansion vessel must be renewed (not a DIY job) if there is no pressure or very little air pressure then just maybe the air has leaked out over a period of time, if there is some pressure, then beg or borrow a tyre pressure gauge or a hand tyre pump with a pressure gauge and measure the air pressure, if its anything more than say 0.5 bar and you have zero pressure on the liquid side then you have a glycol leak somewhere, if the pressure at the expansion vessel end is less than say 0.2 bar, start pumping up the expansion vessel and both pressures should be almost exactly the same if you havnt lost any glycol, pump away until you get 2.5 bar on either side, if you have no pressure at the liquid side then you have lost glycol, you should then get someone in at this stage as you dont know where the leak is, it could be somewhere on the panels or worst of all a pinhole in the solar coil. If you have a unvented (pressurised) Hot Water Cylinder then the solar coil wont be holed because you would still have pressure at the solar system.

Hi
I had a look at that expansion tank today and found that it has 1.8 bar of pressure in it. Also when I pressed in the valve no fluid came out. Another thing when I took the vent screw off the pump there doesn't seem to be any fluid in it or maybe I can't see it. Also there doesn't seem to be any activity in the flow meter that is below the pump.

John T Carroll · 24-01-2016 08:35PM

SPAWKER wrote: »

Hi
I had a look at that expansion tank today and found that it has 1.8 bar of pressure in it. Also when I pressed in the valve no fluid came out. Another thing when I took the vent screw off the pump there doesn't seem to be any fluid in it or maybe I can't see it. Also there doesn't seem to be any activity in the flow meter that is below the pump.

I'm afraid that means you are after losing the glycol (leak), the pre pressure in your expansion vessel was probably 2.0 Bar and if a 3 litre glycol buffer was pumped into it, it would be reading 2.5/2.6 Bar if normal. You didnt say if you have a unvented Hot Water Cylinder, if you had then the "good" news would be that the coil is definitely not leaking, even if you have a gravity fed Hot Water Cylinder, I would expect to see some sign of water around due to to 10/15 ft head so it is more than likely, in my opinion, something out on the roof panels, sealing washers or the like. This doesnt fix it for you unfortunately and I think you should call in someone who can identify the leak and recharge the system again, best of luck. John

SPAWKER · 24-01-2016 09:21PM

John T Carroll wrote: »

I'm afraid that means you are after losing the glycol (leak), the pre pressure in your expansion vessel was probably 2.0 Bar and if a 3 litre glycol buffer was pumped into it, it would be reading 2.5/2.6 Bar if normal. You didnt say if you have a unvented Hot Water Cylinder, if you had then the "good" news would be that the coil is definitely not leaking, even if you have a gravity fed Hot Water Cylinder, I would expect to see some sign of water around due to to 10/15 ft head so it is more than likely, in my opinion, something out on the roof panels, sealing washers or the like. This doesnt fix it for you unfortunately and I think you should call in someone who can identify the leak and recharge the system again, best of luck. John

Not sure if its an unvented tank or not but its a 300 litre one and there are 3 expansion tanks on it 2 red 12 litre ones and a bigger blue one can't see the size on it.
Thanks for all your help.

Setting the temperature on a pt1000 sensor ?

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