Solar performance

bkb

Hi,
I'm doubting the effectiveness of our solar installation (and have being for the last 2 years).

Last week the system was running for 5-6 hrs per day but only reaching a tepid tank temp (300 L tank) of about 37-39 degrees. I say tepid as the water was just about comfortable for taking a shower. I turned off the UFH so that only the solar would be heating the water.

The controller is a Sorel TDC3 and we have 60 tubes on a South facing roof. The controller draws from the tubes when the tank temp differs from the tubes temp by 20 degrees.

Could users with Solar installs post what their recordings were for the past week and in general how their system performs over the course of the summer months. When we installed this I was under the impression that the panels would be supplying all of our hot water over the summer months.

cheers

quentingargan

You have something wrong here. Sixty tubes of any sort should do better than that, though you don't say what size the tubes are.

My own system has been bringing the cylinder up to its maximum of 80 degrees most days this last week, and after that our heat dump has been operating.

You say the controller waits until the panel is 20 degrees hotter than the cylinder. The normal setting here would be 6 degrees to 10 degrees, but even that shouldn't cause the problem with tubes. But if the settings are that far out, I wonder what else is wrong...

I'd also check that the pipework is entirely insulated from end to end, that there is no incidental heat loss along the pipe run etc. Is there any heat coming from pipes leading away from the cylinder? If it is open vented, is there any heat escaping up to your attic tank?

So many things to check, but I would start with these ones and come back. It could be that your system has faulty heat pipes. You would have to take out one of the tubes and test the heat pipe.

But first of all, I would assume that the panels are producing the heat, and that it is being lost en route. If that turns out not to be the case, then it is down to the panel.

bkb wrote: »

Hi,
I'm doubting the effectiveness of our solar installation (and have being for the last 2 years).

Last week the system was running for 5-6 hrs per day but only reaching a tepid tank temp (300 L tank) of about 37-39 degrees. I say tepid as the water was just about comfortable for taking a shower. I turned off the UFH so that only the solar would be heating the water.

The controller is a Sorel TDC3 and we have 60 tubes on a South facing roof. The controller draws from the tubes when the tank temp differs from the tubes temp by 20 degrees.

Could users with Solar installs post what their recordings were for the past week and in general how their system performs over the course of the summer months. When we installed this I was under the impression that the panels would be supplying all of our hot water over the summer months.

cheers

bkb

cheers for that.

The tubes look standard (when looking at other roofs!!!!) The default temp diff was 10 degrees but I changed this to 20 as I found the heat dump was happening at panel temperatures that were too low.
i.e. if our tank was 26 degrees, the system was drawing when the roof reached 36.

By changing it, I was trying to achieve what your system does, transfer the heat at a high temp.

quentingargan

The heat dump is a different thing really. This is a divert valve which re-directs the flow from the panel into a "dump" radiator when the cylinder goes above its maximum temperature.

The only reason to change the standard temperature differential is when there is a really long pipe run. The default is usually to come on at a differential of about 6 to 8 degrees, and off again when that differential falls to less than 4 degrees.

But I think your problems lie elsewhere...

homer911

with 40 tubes and 300l, my collector reached over 70C at one point yesterday with the tank reaching 59C. My temp differentials are currently 9C on and 6C off. Some might argue against this but based on my usage and pipe run, I find this effective

dathi

hi i have a sorel controller which is set at degrees 10 i have 30 tubes and 200ltr tank the tank has been up to 65 all week and has dumped into the central heating 2 or 3 times have it set to dump at 65 because of limey water

bkb

Daithi, is the solar the only means of heating your water tank? Mine is set to dump at 75 but I doubt it has ever done that.

dathi

hi bkb as i said i have 30 tubes into 200ltr tank. the central heating is connected to the other coil and i have independent control of that .which means that if the solar does not heat the water to a high enough temp i can turn on the boiler and raise the temp of water in tank.the last week with the clear sky the solar heated the entire tank to 65 every day. thats with 4 of use having showers out of it. and on some days it dumped heat. on my setup i have a relay switch that opens the two port valves on central heating and turns on the central heating pump. (but not boiler)this pulls some heat out of the tank and dumps it into the central heating circuit.quintan system uses a 3port valve to open a circuit to a spare rad to dump heat there.that is what people are talking about when they talk about heat dump.what you were talking about was heat collection .allowing the collector temp raise so high before it is transfered to the tank is not necessary with your sorel controller .as it modulates the speed of the pump slowing it down if there is less heat, speeding it up if there is more. hope this is of some help

Mothman

Even in my 13 year old flat plates system, 6sqm, 300l tank, the bottom of my tank was above 60 during some of the past week with no supplementary heating.

My settings are similar to what Quentin suggests.

Quentin also suggests there is a problem elsewhere.

Could there be an issue with the temperature sensor at the collectors?

My brother had this issue for a while.

ccsolar

Hi
I have seen 60 tubes with a 400 ltr tank reach 75 degrees in the last week, that's with 5 kids and 2 adults drawing off the system.
I would check the heat-pipes, if there was a problem with the controller the temp on T1 would have reached 150-200+ degrees every day for the last week.
What is the maximum temp T1 has reached this week?
Is there an anti-scald valve fitted ?
Check the cold tap in the bathroom, is the water warm ?

You could always shut down the solar system and see what temperature your collector reaches during the day.
This will give you a better idea if your heat pipes a faulty .
Cc

bkb

cheers CC,

T1 only ever reaches 20 degrees above the tank temp, so typically the tank would start off at 27 degree and reach maybe 37 degrees by the end of the day. That would mean the max temp T1 is allowed to reach is 57.
The Sorel Controller has recorded an operation time of 5/6 hours.

The tank is meant to 'spill-over' into the ufh tank

Finally, all cold taps work as they are meant to.

Mike2006

Even if the pipe work was not insulated, over the last couple of weeks, I doubt that you could 'lose' that much heat through the pipework.

I would look very closely at the 'electrical' side of things. You can interrogate this in 30 mins and it would rule out any electrical/control problem.

Firstly, I would check the 2 RTD's at T1 and T2.

I am going to assume that these are either PT100 or PT1000 rtd's.

Check T1 when your solar contoller says that the temp in the collector header is 40 DegC. Your PT100 should have a resistance of approx 123 ohms across it. If you have a PT1000, it should read approx 1230 ohms.

Same with T2. Check resistance again using a multimeter.

If these are ok, then you could have a problem with your controller.
You could check the T1 and T2 channels on this with a decade box but I doubt that you have one of those so you could use a set of resistors which would be cheap to buy from maplin.
If you have PT100's, buy a 100, 110 and 130 ohm resistor and these should roughly equate to 0, 28 and 80 DegC on your controller. Using these, check that your relays are coming in and out as configured on the controller.
If you have PT1000's, 1000, 1100 and 1300 ohm resistors will give the same temp readings on your controller.

(If they ask you in Maplin for a wattage rating on the resistors, just tell them that the smallest they have will do. You will not be putting any load on it.)

If all this works out and shows up no problems, then verify your pump at the solar station. Then check that all solenoid/electric valves (if any) are operational.

If all this is clear then it is most likely that you have a mechanical issue.

Also make sure that your solar system has not leaked out all of its glycol and that it is running dry...

Apologies if this is over complicating things for you, but if you want to troubelshoot the controller and verify it, you will need to be able to interrogate it like that.

Mike.

fressatty

i'm having a mare with mine. The setup i have is for hot water and space heating. It's completley inconsistent, since the weather got decent there in february i increased the store temperature to 80 degrees because i noticed the solar pump was shutting down when taank got to 60 degrees. Myself and the missus take bets on wether or not we can have a shower or bath, more times than not the water is luke warm at best and that runs out after 2 minutes. I've even had the oil boiler on for longer and more regularily but this is inconsistent aswel because it seems to heat the water but then we get the same issues when having shower or bath. The tank readings are 67Celcius at the top and on a good sunny day it will we 65 plus degrees at the bottom and up to 70 in the top. I thought it was air locks so i bled the tank, even drained it and refilled it at one point to no avail.

I have a Sonnenkraft Comfort setup, evacuated tubes, south facing garden, theres myself the missus and a newborn so its not like we;re heavy on the hot water usage.

I dont know if this is a thermostat failure/ mixing valve failure/ temperature sensor issue or where to start.


Anybody else having similar issues i.e. Hot water in the tank but inconsistent warm to hot water in the shower and bath and running out of hot water completley after about 5 minutes or less?

championc

bkb wrote: »

cheers CC,

T1 only ever reaches 20 degrees above the tank temp, so typically the tank would start off at 27 degree and reach maybe 37 degrees by the end of the day. That would mean the max temp T1 is allowed to reach is 57.
The Sorel Controller has recorded an operation time of 5/6 hours.

The tank is meant to 'spill-over' into the ufh tank

Finally, all cold taps work as they are meant to.

Check what temperature difference between the roof and the bottom of the store your controller is set to shut off at. I nearly sounds like they are too even and so cooler roof temp is being transferred back into your store after heating it up. The diff should be no less than about +4 deg C. So if the bottom of the store is 60 and your roof temp falls to 63, the pump should shut off immediately and stay off unless the roof increases above 68 or 70 (since pump activation would be 8 to 10 above the bottom of the store).

I'm sure the 5/6 hours is the time the pump has been running.

Here's my stats from 26 March