Solar water heating - not working?

OmegaRed

Hey Folks,

Apologies if I explain the below incorrectly / not in the right language.

I bought a new build last year with both solar panels and solar hot water tubing on the roof.

Since the winter, I didn't really take any notice of the solar hot water tubing heating the water as there wasn't much sun, but the last few weeks I have noticed it doesn't seem to be doing much.

All I can see is what is happening on the Joule DeltaSol display over the last few days:

Temperature at the collector (solar tubing on roof) was off doing its thing from about 10am till about 4 / 5pm. Was fluctuation between anywhere between 30 and 80 degrees for most of the day.

Temperature at the TST thermostat at the bottom of the tank stayed a consistent 16/17 degrees all day, never heated up.

Temperature at the SE thermostat at the top of the tank was around 45 degrees. and slowly cooled through the day. Usually it never goes below 40 as I always give it about a 30 minute boost each morning which provides just enough hot water for me and the missus through the day.

I've checked both thermostats TST and SE and they working fine

My understanding is that if the collector temperature goes above the temperature of the SE thermostat, than the SE thermostat should rise as that starts to get heated?

The pump kicks in every so often during the day so its doing something, I just can't figure out how it should be heating the water. Any ideas?

freddyuk

No flow through the system. The temperature at the collector should rise quickly in sun and if that temperature is higher than the cylinder stat then the pump will kick in until the collector temperature drops by 8 -10c then it will switch off. This cycles every 10 - 15 minutes on average. What pressure do you have in the system? Are the pipes hot in and out of the pump when it runs? If not there may be an air lock. Is there a vent on the collector. Should be a fitting to screw a vent on to allow air out.

OmegaRed

freddyuk wrote: »

What pressure do you have in the system? Are the pipes hot in and out of the pump when it runs? If not there may be an air lock. Is there a vent on the collector.

Pipes not hot

Collector showing about 60 now


Pressure just above 2

freddyuk wrote: »

Should be a fitting to screw a vent on to allow air out.

Can I do that myself?

freddyuk

It will be on the highest point of the system if it is there so normally on the collector pipe connection. If you remove the polystyrene cover on the pump station you can check for an air scoop on the pipes and get to the in/out pipework to feel them - they Might be HOT. Your pump flow and return temperatures do not reflect the collector temperature so the heat is not transferring. It is a sophisticated pump so prone to issues in my experience.
Can you feel the pump running? Can you turn it up and try to shift any air? It is only rated for 70c so it may have overheated but the LED's suggest it is not faulty. Have you seen temperature of collector go above 80c?

John.G

The solar circ pump should start up when the collector temp is 6 to 10C higher than the "store" temperature, (the temp just above the top of the cylinder solar coil. If the pump is running then as above, probably air in system, if not, then different problem, either pump or controller. You should be able to start the pump manually but don't do this if collector temp above say 40C (thermal shock). You also have a flow gauge below the pump, you should see a little brass bobbin moving up a 1/2 ins or so from the bottom when the pump starts or is running.

dathi

https://www.resol.de/Produktdokumente/11211794_What_many_people_do_not_dare_ask.pdf

would it be a communications problem between the controller and pump as in above link ?

freddyuk

Once we know fluid is being pumped then go and look at controller. Otherwise it will take longer to solve.

John.G

I have my pump on the end of a 3 pin plug so can verify it externally, however, if the pump green LED is is illuminating on/off then maybe OK, it should also be able to switch it manually from the controller. Some pump stations also have a deaerator fitted in the flow with a venting screw, if air present maybe increase pump speed settings temporarily to try and get rid of air without climbing on the roof.

OmegaRed

freddyuk wrote: »

It will be on the highest point of the system if it is there so normally on the collector pipe connection. If you remove the polystyrene cover on the pump station you can check for an air scoop on the pipes and get to the in/out pipework to feel them - they Might be HOT. Your pump flow and return temperatures do not reflect the collector temperature so the heat is not transferring. It is a sophisticated pump so prone to issues in my experience.
Can you feel the pump running? Can you turn it up and try to shift any air? It is only rated for 70c so it may have overheated but the LED's suggest it is not faulty. Have you seen temperature of collector go above 80c?

I can hear the pump running and at times there is like a cycle of a continuous
gushing noise with the sound of what I presume is the circulation running correctly

I have seen the temperature hit well over 100 the last few days with direct sunlight

Because the top stat is showing above 40 most days (I heat it in the mornings for about 30 minutes with oil) is there some sort of differential that needs be in place between top stat and bottom? So if my top stat is always above 40 then it wont heat if the bottom stat is always hovering around 15 / 17 degrees?

Unfortunately I don't have access to the collector on the roof.

John.G

The bottom stat is called the store temperature and is taken just avove the solar coil so when the controller detects a difference of ~ 10C between this and the collector then it starts the pump and this store temperature should start rising slowly, the pump will stop when this differential falls to ~ 3C, it will also stop if the cylinder temp or the collector temp are excessive maybe 65C & say 100C.
You obviously have air in your system, unfortunately probably in the collector, have you removed the cover off the pump station to see if you have this deaerator?, if so just try venting air from it (hold a rag underneath).

OmegaRed

John.G wrote: »

The bottom stat is called the store temperature and is taken just avove the solar coil so when the controller detects a difference of ~ 10C between this and the collector then it starts the pump and this store temperature should start rising slowly, the pump will stop when this differential falls to ~ 3C, it will also stop if the cylinder temp or the collector temp are excessive maybe 65C & say 100C.
You obviously have air in your system, unfortunately probably in the collector, have you removed the cover off the pump station to see if you have this deaerator?, if so just try venting air from it (hold a rag underneath).

So I yanked out the top stat (the cylinder temp?). The temperature has now fallen rapidly and the good news is the bottom stat (store temperature) has now bumped up almost 5 degrees the last hour and and is still rising (was 15 this morning and now 20)....


Can you let me know where the deaerator is and I can try and blead it?

John.G

There you go (highlighted in yellow). You seem to have a very good flow judging by the flow bobbin on the right.

When you get a chance check the maximum cylinder temperature setting (for solar) on the controller, it should be set to 70C IMO. otherwise the solar circ pump will stop esch time the gas/oil fired coil heats up the cylinder to 60/65C?.

OmegaRed

Thank you very much. I'll try that and see what happens

Since taking the top stat (the cylinder temp) out the bottom stat (store temperature) is now showing a good increase and its "pumping away". It was 14 this morning and now 25.

liamMHoo

Hi All,
I'm having a difficult time trying to find someone to come and fix my solar water heater (installed about 15 years ago, 60 tube system, Sorel controller, etc.) It never gave a moments trouble until earlier this year when the collector temperature reading was all over the place. I assumed a bad sensor and replaced it but that didn't fix the issue. I "managed" to run it a bit over the summer by manually adjusting sensor calibration values. It's been manually turned off now for the past 2 months.
Does anyone have a recommendation for someone who will come and diagnose/fix it? Location is Meath.
Thanks!