Solar water panel problem

borland

I have 2 solar water heating panels fitted on my roof. the temperature last thing at night at night is 60+ C but when i check it in the morning before the gas kicks in its down to 33C.
The company who supplied it have replaced the control panel to try and rectify the problem but it didnt work.
Personally i think the pump to the panel is running constantly, replacing the control panel was supposed to fix that.
Has anyone had a similar problem and found a solution or can anyone offer a solution
Cheers

saibhne

Hi Borland,
We had a customer with an issue like this a few months ago. It turned out that the bottom sensor on the cylinder was not installed correctly and was constantly reading a low (ambient) temperature which made the controller think that the panel could offer some heat to the cylinder. Doesn't make sense if your pump is running at night though but could be worth checking.

You could also check the temperature reading on the sensor at the panel to make sure there is no issue there - most controllers work on a 6 degree differential as default, meaning when the panel is 6 degrees hotter than the bottom of the cylinder the pump will turn on. The pump should turn off when the difference in tempertaure between the panel and cylinder drops to 4 degrees. These are default settings on the Resol series of controllers and they can be changed easily enough, also different brands could use different temperature settings but the operating method is the same.

One last thing that might be happening is that the controller is set to manual control and the pump is set to always be on - unlikley but you never know..


S.

homer911

Not an expert, but based on my own experience, I had this problem in the first few days after my system was installed. I do remember that the overheat valve was mounted 90 degrees off, which meant the heat was spilling into the radiator in the attic..

Another possible issue may be the pressure in the system when running - if there is a leak, the collector may not be properly cooled, making the pump run on much longer.

quentingargan

borland wrote: »

I have 2 solar water heating panels fitted on my roof. the temperature last thing at night at night is 60+ C but when i check it in the morning before the gas kicks in its down to 33C.

I presume you have the usual configuration with a probe at the bottom of the cylinder and one at the top, and that you are talking about the top of the cylinder being 60 at night and falling to 33 in the morning?

If that is so, remmber that the coil for solar is in the bottom of the cylinder - because heat rises, even if it ran 24/7, it wouldn't change the temperature at the TOP of the cylinder. The only thing that can do that is either a running tap, or more commonly, poor insulation.

I'm also assuming that you don't have a secondary return system. This runs hot water around the house so you have instant hot water at the taps (like the posh hotels)

There are a few questions;

1) Is this an open vented system (fed by an attic tank). I have sometimes found that the vent pipe (coming up from the top of the cylinder) is hot. This will cause the cylinder to cool overnight. The pipe should come out of the cylinder, and then run horizontal for about 50cm before going up to the loft. It should be insulated along its length.

2) Is there any pipework bare in the hotpress that is hot, or even warm? There shouldn't be. I often find that the pipework to the boiler isn't insulated. This will cause the cylinder to lose heat.

3) All fittings to the cylinder should be over-insulated. I like to use short lengths of 1.5" armaflex over the insulation and butted right up to the cylinder to cover these fittings.

4) Check all the pipes coming from the cylinder - especially those that rise from the cylinder. They may be insulated in the hotpress, but not insulated any further along the way.

Q

ccsolar

Hi Borland
I have to agree with Quentin gargan, this problem might not have anything to do with your solar system.
There has to be somebody or something using using the hot water for such a drop in temp.
ie; showers or washing machine
How long is your solar system in as the problem might have been there long before the system was installed.
What type/make of controller is installed?
Dose it have a holiday/frost protection setting?

CC

bertie1

Some controllers have a setting on them that circulates hot water up to the panels at night when the temperature drops to freezing to prevent the panels freezing up ( I know there is glycol in the Irish systems to combat this but the setting is in the controllers in any case) , is there any chance this is happening.

quentingargan

bertie1 wrote: »

Some controllers have a setting on them that circulates hot water up to the panels at night when the temperature drops to freezing to prevent the panels freezing up ( I know there is glycol in the Irish systems to combat this but the setting is in the controllers in any case) , is there any chance this is happening.

Yes, and another "holiday" setting which cools the cylinder at night while you're away, but both these would only cool the bottom of the cylinder (assuming that the solar coil is at the bottom of the cylinder, where it should be...).

I assume from Borland's original post that it is the temperature at the top of the cylinder that is falling. But at this stage in the post Borland would need to respond to suggestions to date.

apc

Just to let you all know after trying various solutions such as isolating the gas boiler incase it was acting as a heat sink, it turned out to be a faulty mixer valve that controls the temp of the water from the tank ( also known as an anti scald valve). It allowed the hot water from the tank to heat the cold water tank in the attic. result hot water in the toilets and no cold water in the cold taps. Hopefully fixed now, a common enough problem. Thanks for all the help, sorry about delay in getting back:D

buttercup20

Hi,

Can I ask for some advice please on a Solar panel. In my home I have one solar panel on the roof. During the last few weeks of great weather I arrived home on one of the warmest days and the kitchen was full of steam from the boiler in the hot press. I don't think this should have happened.

On a further note is it possible to regulate the temperature (say 40-50 degrees) of the water for the taps in the kitchen and bathrooms. As a couple of times again with the hot weather the water was nearly boiling coming out of the taps.

Any help is greatly appreciated!!!!!!
Thanks,
Buttercup20

Outkast_IRE

buttercup20 wrote: »

Hi,

Can I ask for some advice please on a Solar panel. In my home I have one solar panel on the roof. During the last few weeks of great weather I arrived home on one of the warmest days and the kitchen was full of steam from the boiler in the hot press. I don't think this should have happened.

On a further note is it possible to regulate the temperature (say 40-50 degrees) of the water for the taps in the kitchen and bathrooms. As a couple of times again with the hot weather the water was nearly boiling coming out of the taps.

Any help is greatly appreciated!!!!!!
Thanks,
Buttercup20

its sounds like your installation is potenially very dangerous and something is wrong, get a reputable company out ASAP and if your installation was funded by a grant make sure you report any bad findings to the SEAI about the inital installer .
It honestly sounds potentially dangerous . get pictures taken before the work is rectified

quentingargan

buttercup20 wrote: »

I arrived home on one of the warmest days and the kitchen was full of steam from the boiler in the hot press. ...a couple of times again with the hot weather the water was nearly boiling coming out of the taps.

At the very least, you have a faulty controller. I prefer to see a thermal mixing valve as a backup in case the cylinder overheats, but in any event, there should be three probes, one at the panel, one at the bottom of the cylinder, and one at the top. The one at the top should prevent the cylinder from overheating. That may have fallen out. It should be properly secured.

You may also have a faulty controller.

As regards the steam, all blow off valves should be either sent to a drain (if from the cylinder) or to a holding vessel if coming from the solar fluid. This is downright shoddy work. Of course, the blow off valve is a last resort - If your system is pressurised (no attic tank) then it probably came from the same problem of lack of control of water temperature.

I have seen people have their faces steam cleaned when they opened the hotpress - As Outkast said, your system is quite unsafe in this condition. Steam can cause severe burns... Get someone out...

ccsolar

Hi
I would think the problem is that your solar controller has no max tank temperature set or it has been set to high.
The tank would have a pressure release valve (PT Valve) with a built in stat.
When your tank reaches 90 degrees the PT valve releases the hot steam, this valve is normally piped to a drain on a pressurised system OR would be fitted with a Blank on a vented system.
You would first need to check your controller for the tank setting and adjust according then you need to sort out the PT valve.
What make of controller have you on the solar system?
Have you contacted the installer?
If you have a heat dump fitted it would also help to prevent this problem.
With regards to the hot water in the taps, you also need an anti scald valve.
If your job was an SEAI grant then the anti scald valve should have been fitted as standard.
Where are you located?

Cc

buttercup20

Thanks to everyone who replied to my post. I now know a lot more than I did. Yes the solar panels was done with an SEAI grant. As far as I can see no anti scald was fitted. Trying to contact the installer.The make of controller on the solar panels is viessmann.

I am located in the East. Can I ask one further question? If I run into problems with the installer do I contact SEAI with my problems or will I have to check their list of "recommended" installers and contact one of these companys myself?

Thanks again,
Buttercup20

quentingargan

buttercup20 wrote: »

I am located in the East. Can I ask one further question? If I run into problems with the installer do I contact SEAI with my problems or will I have to check their list of "recommended" installers and contact one of these companys myself?

Thanks again,
Buttercup20

The SEAI warranty is only with the installer. Since they're in liquidation, I'm afraid you are on your own.

The brand of panel you mentioned is available in two types - one is a direct flow, while the other uses a heat pipe. I have come across problems with direct flow systems before - they are more pernickity about their layout because they can thermo-drive when they over-heat. If you think you have a "direct flow" system rather than heat pipes, then I would go back to the manufacturer and look for one of their installers.

Check the pressure gauge - if the pressure has fallen, this may be part of the problem. Otherwise, it would seem that the steam came from the hot water in the cylinder, rather than from the fluid in the solar circuit. In that case, you can look to any other installer, but I would look for someone with good references...

ccsolar

Hi Buttercup20
Can you check the SMX setting on the solar controller as this setting could be too high and causing the problem.

Cc

Mrdarcy1

We have Viessman solar panels to heat our hot water, they have been installed for a year and they have never worked properly, our plumber has been back to them on many occasions and cannot figure out what is going on. The water in the tank does not stay hot. Our house is a new build 5 bed house, which is super insulated with heat recovery and is A rated for the SAP calculation, with under floor heating.

The system is a pressurised sealed system, backed up with a gas boiler. We have a 300 litre stainless steel tank, all pipe work is insulated. There is solar stat at the top of the tank, and it has a heat probe at the base of the tank, where the solar coil is situated. We have a control panel which is set to a 5 degree tolerance so the pump does not work if the temperature on the roof is 5 degrees lower than the temperature at the bottom of the tank.

Our plumber fitted a non return valve so there is no back syphoning, we have taken readings from the tank that show the temperature falls over night from about 65 degrees to about 32 degrees, with no water having been used in the evening. The gas boiler comes on at 5.00 pm every evening and starts to heat the tank up, regardless of what the weather has been like, even though the panels have got up to 90 degrees on a very hot day, with the pipe to the tank having got that hot it has melted the insulation around the pipe.

We have checked the panels at night and they are not hot and the pump is not running, so it doesn't appear to be sending the heat from the tank to the panels, there is no back syphoning either. Our towel rails do work off the hot water, but only operate when the pump comes on with the hot water from the gas boiler, they do not come on when the gas boiler is not on. The boiler is on for 3 hours in the morning and the same in the evening. In the winter quarter we used £750 in gas and in the spring it was £450 and the summer quarter it was £200, the spring and summer quarter was just hot water cost as there was not heating on. This seems way too much gas to be using, so it appears that whatever is sending the water cold is costing us a lot of money. It is really frustrating as the system cost a lot of money to install and appears to be actually costing us money to have rather than saving us any money. In fact I would go as far as saying it is a load of rubbish, and we are thinking of ripping it out and going back to just using gas, so the water we have paid to heat actually stays hot, so we can use it.

Anyone got any ideas on what is sending our water cold and costing us a fortune in gas???

freddyuk

Mmm, if your plumber used ordinary foam insulation on the solar circuit it is a concern.
Also the solar system should pump when the temperature at the panel is 8c hotter than the cylinder and cease when it drops to 4c hotter.
You are saying the pump will not pump if the panel is 5c colder? In that case if it is 4c colder it will pump?? Please recheck your controller settings.
Then post back. These controllers can be very confusing and if your plumber never managed to set it up correctly that could be much of the problem. There may be a factory default setting which should be OK to make it work. What make is the controller?

Mrdarcy1

Thank you for the quick reply.

The insulation that melted is not on the pipes from the panels, this has a different insulation on it which is sort of black and rubbery, sorry I know that is not very technical, the bit which melted is on the pipe that goes into the big stainless steel tank.

Also didn't quite explain the bit about the five degree difference on the panels. I should have said the pump cuts off when the the panels are five degrees hotter that the tank. The pump does not run at night or when the tank is five degrees hotter than the panels.

The plumber wondered if the controller was set on a holiday mode, so that it dumped heat from the tank back to the panels, as a safety feature, to prevent it over heating if it was not in use, but this would need the pump to run and we have checked at night and the pump was not running, so we don't think it is that and it does cut off when the tank is five degrees hotter than the panels. Viessmann talked our plumber through some settings on the contold panel, to ensure this wasn't happening a few days ago, but it has made no difference at all, the boiler is still chugging away in the morning and in the evening.

Also I thought I should mention that if we shower after the hot water goes off in a morning, there are three of us in the household, we have no hot water in the day, just tepid water, so it doesn't appear the two huge panels we have on the roof do very much anyway, and they also seem to send the water cold we heat up using the gas. The system really is useless.

The controller is a Viessmann Vitosolic 100 and we have two Vitosolic 100 panels on a south west facing roof.

Thanks again for the speedy reply, we are really desperate to get this sorted.

ccsolar

Hi
Can you check the pipes at the back of your gas boiler before it comes on and see if they are warm?
Sounds like you have some sort of thermosiphining going on with your tank.
You might also want to check any water storage tanks in the attic as the heat could also travel up the pipe to these tanks, have seen this on 1 job a few years back but was noticed when the home owner flushed the toilet and the water was warm.
Where was the NRV fitted?
You should try and trace the pipes from the tank and see which ones are warm and where they are going to.
Cc

freddyuk

The pipes from the pump unit to the storage cylinder are still part of the solar circuit and run at the same temperature but I guess as the kit did not come with extra solar pipe insulation your plumber decide not to bother going and buying some.
As ccsolar says trace the pipework and check orientation of the NRV. It could be on the wrong circuit or back to front. If the system is getting that hot it is not the boiler so the solar thermal heat must be going somewhere. You say it is a sealed system so hopefully all safety details are in place.
What size panels have you got for 300 litres?

Mrdarcy1

Hi

We don't have any water storage tanks, it is all mains, I don't think it is back syphoning as there a non return valve fitted and if it was wouldn't the solar panels be hot at night and they aren't when I've checked. It really is a puzzle.

freddyuk

No, I know you havn't! That was not my suggestion. The heat has to be going somewhere if it is actually in the cylinder during the day. I suggest you turn the boiler off and monitor the pipes to see what is hot and what is cold. Are you using water? IE. is there a leak somewhere and the system is constantly drawing in fresh water. Is the filling loop closed and pressure constant.
What is the pressure of the solar system and the boiler system?
Is there water going into the tundish?
Is the cold inlet at the bottom of the cylinder?

Mrdarcy1

I will check non return valve with plumber, but if it was going the wrong way wouldn't the solar panels be hot at night, which when I've checked at night they aren't. Size of the panels I am not sure of exact size but I would say they are about 1 metre wide and 2 metres high each.

Mrdarcy1

freddyuk wrote: »

No, I know you havn't! That was not my suggestion. The heat has to be going somewhere if it is actually in the cylinder during the day. I suggest you turn the boiler off and monitor the pipes to see what is hot and what is cold. Are you using water? IE. is there a leak somewhere and the system is constantly drawing in fresh water. Is the filling loop closed and pressure constant.
What is the pressure of the solar system and the boiler system?
Is there water going into the tundish?
Is the cold inlet at the bottom of the cylinder?

Hi

I know you didn't mention a storage tank, my reply on that was to someone else's post, sorry for the confusion. I will check the other points with the plumber to see if that could be the issue, as he hasnot mentioned any of these points before. Yes the cold water inlet is at the bottom of the tank.

We've had the boiler off on a previous occasion and the water in the tank just gets tepid, even on a reasonably sunny day.

Many thanks again for these points I will check them with the plumber this week.

shane0007

Follow these steps and report back:
1. Bring cylinder to temperature in evening and note the temperature at T3 (temperature at top of cylinder)
2. Turn off the cold feed valve to the cylinder. This will be on the pipe from the cwst to the bottom of the cylinder. It refills the cylinder as you draw off hot water.
3. Leave overnight and in the morning check and note the T3 temperature reading.

If the temperature is within 5 - 6C, you have a leak on your domestic hot water pipework. If the temperature still has a substantial drop, come back to us.

freddyuk

Mrdarcy1 wrote: »

Hi

I know you didn't mention a storage tank, my reply on that was to someone else's post, sorry for the confusion. I will check the other points with the plumber to see if that could be the issue, as he hasnot mentioned any of these points before. Yes the cold water inlet is at the bottom of the tank.

We've had the boiler off on a previous occasion and the water in the tank just gets tepid, even on a reasonably sunny day.

Many thanks again for these points I will check them with the plumber this week.

Ah ha! So you are saying the solar system is getting hot but the cylinder is not hot?? Then the circuit is not heating the cylinder via the solar panels is all I can conclude although it is heating the hot flow possibly by convection. And that suggests an airlock possibility which prevents the water getting around the circuit. You also say there is a "stat" at the top of the cylinder and a "probe" at the bottom. There should be 2 "probes" on the cylinder at the top and bottom which measure the temperature. If it is daylight is there heat in the incoming solar pipe? Is the return pipe to the panels cold? Test this on the outlet side of the pump station but beware of very hot pipework. Try the easy stuff first.
Is the pump station quite close to the panels?
Is there a heat dump circuit?

X20DTL

Looking for some help with my solar system problem.
I have a 2-panel (flat panels) system which lately seems to struggle to get the tank (200L) up to 50 celcius even on the best of sunny days.
I have noticed that it seems to charge the tank Ok up to this point but after that is simply cannot transfer the heat from the panel to the tank and subsequently the panel rise above the 110C limit and the controller then circulates no more.
I have noticed lately that there now seems to be air in the system however the gauge still reads just under 3BAR.
I bled some air from the pumping station and on the flow/return of the lower coil going into the tank but it seems to get air locked again.
i don't believe i have a leak as the pressure would be falling however there is still air in the system.
I wonder is the circulation pump on the way out? Would the pump be good enough while the fluid is not too hot i.e. under 50C but as the system heats up that it loses efficiency and simply cannot pump up to the panels?
One other factor that might not be helping it is the pump is a 3-4meter Wilo unit however my panels are on the roof of my 2-storey house but the pumping station and tank are on the ground floor, maybe the pump is'nt good enough for the height distance to pump any longer?
Lastly, the sensors & control panel seem to be working as it circulates perfectly normally until you get near 50C so the problem must be somewhere else.
Could a failing pump churn the fluid in the circuit and liberate gas/oxygen from the fluid?
It's really confusing to think it's getting airlocked but there doesn't appear to be a leak anywhere.
Any ideas out there as to what might be the problem?

John.

maurice1

That is a puzzler!!
The pump is not really pumping the weight of the water up to the roof as the weight of the return water is nearly equal and opposite so it is just circulating it.

On some Wilo pumps there is a screw cover at the end of the drive shaft (Opposite end of the impeller). Sometimes these come loose and air can get in.

I presume that your over pressure relief device is normal. If it is easy maybe throw a rag over its output and see if it gets moist.

Perhaps some joint on your pipework expands at 55 degC and leaks and lets air in and as it cools it reseals.

Expansion vessel, Is the rubber diaphram still good.

Just some ideas that spring to my mind. Presuming it worked once you just have a small fault and finding it can be trial and error.

X20DTL

maurice1 wrote: »

That is a puzzler!!
The pump is not really pumping the weight of the water up to the roof as the weight of the return water is nearly equal and opposite so it is just circulating it.

On some Wilo pumps there is a screw cover at the end of the drive shaft (Opposite end of the impeller). Sometimes these come loose and air can get in.

I presume that your over pressure relief device is normal. If it is easy maybe throw a rag over its output and see if it gets moist.

Perhaps some joint on your pipework expands at 55 degC and leaks and lets air in and as it cools it reseals.

Expansion vessel, Is the rubber diaphram still good.

Just some ideas that spring to my mind. Presuming it worked once you just have a small fault and finding it can be trial and error.

Thanks for the suggestions & ideas. I'll have to have a look for the pressure relief valve as I'm not sure where it's located. There is a valve close to the pump and if I remember correctly this is where the contractor filled the system day one, that was nine years ago! The valve is like a gate valve and there is a little plastic screw cap over it and there is a tiny weep from that, when I say tiny I mean just you'd see the threads only damp, maybe over the nine years this has lost enough to let in air?
I know the pump screw you're talking about and I'll check that, it's in the centre of the cover and is slotted to take a flat screwdriver if I am correct.
On the expansion vessel, what pressure should be in this when cold?
If there was a leak in this would it cause air to get into the glycol circuit?

dathi

X20DTL wrote: »

Thanks for the suggestions & ideas. I this is where the contractor filled the system day one, that was nine years ago!

after nine years would say you need new antifreeze and top up