Are you all pleased with your solar panels for hot water heating

John T Carroll

Jakey Rolling wrote: »

Thanks for that - I will have to quiz my plumber on this, as you say, the system components are being stressed by this continual stagnation.

What I can't work out is what size radiator would be needed to effectively dump the excess. Given that the aperture of the tubes is approx 3m2 then at most you would expect continuous 3kW heat to be transferred, if solar radiation is approx 1kw/m2. However the controller often shows power up to 20kW, presumably based on temp difference, flow rate and specific heat capacity. I'm not so keen on plumbing a rad in a cold attic. Wouldn't it need glycol in the circuit too?

I would say that a 2 Kw Dump Radiator would be adequate even with an ambient temperature of 20C, you can do your own calculations on the attached spreadsheet. Yes there would be glycol in the system as it becomes part of the whole primary circuit and would also include a three way diverter valve and a suitable solar controller, quite alot of controllers have this facility, your's may already have it. The central heating system itself can be utilised but is a bit messy especially with systems with zoning, there are some posts out there regarding this.
The 20 Kw power indication may wrongly be a "12 or even a 24 hourly" number, power as distinct from energy is based on an hourly calculation. A 3 M2 evacuated tube array wouldnt give, in my opinion, more that 2.2 Kw even in a very sunny day.

freddyuk

Don't forget you need a solar rated diverter valve not a simple 3 way motorised valve. A 60 x 40 double rad finned should give you about 1kw under normal conditions and cost under €50. You don't need rad valves just male - 15mm compression.

Jakey Rolling

Having had a look through the solar controller menu, and downloaded the manual it doesn't seem my controller has the option of operating a divert valve for heat dumping. The only related option for "Collector protection" is to force the pump on at predetermined temperature, but this just feeds to the normal storage tank - suitable if you had a swimming pool or large accumulator possibly!

It looks like this would be a pain + cost to change, as the controller is integrated into a "Solar Station" package. FYI, the controller is an "STDC" made by Sorel Mikroelektronik, rebranded as "ModvSol".

Jakey Rolling

John T Carroll wrote: »

The 20 Kw power indication may wrongly be a "12 or even a 24 hourly" number, power as distinct from energy is based on an hourly calculation. A 3 M2 evacuated tube array wouldnt give, in my opinion, more that 2.2 Kw even in a very sunny day.

The power seems right enough, as with a temp difference of 20C and flow rate of 12litres/min that gives about 16kW (using c * m x dT ). The pump is switched on once the temp difference is >9C, but it seems there is some initial overshoot in collector temp after the pump has started circulating. Steady state it is closer to 2kW as expected.

Anyhow, I'm happy that the controller's calculations are ball-park correct as it's giving approx 10kWh over a day, with 5 hours operation and average 10C temp difference between collector and storage. That works out at an average of 2kW while in operation, so about right.

John T Carroll

In view of that you might consider using the Central heating as a dump, I use mine very occasionally in a "manual" mode to see how it functions. I have no problems with stagnation as I have a Flat plate set up and I have the max cylinder temperature setting at 80C, I have soft water so no scaling problems. The cylinder (oil fired) heating coil is 0.65 M2 which is probably typical of a lot of installations. When "dumping" I have an isolating switch on the electrical suppy to the oil burner which I switch off. I manually open the oil fired coil motorised valve to the hot water cylinder, I put the Timer to constant ON and then simply turn the room stat to its maximum setting of 30C which starts the C.Heating pump, I have two radiators (approx total 3 kw output) which do not have thermostatic valves so the water circulates through them. It seems to have no problem in removing excess heat from the cylinder. It wouldnt be too difficult to "automate" this. You could fit a simple differential temperature controller with a cylinder surface mounted sensor about a 1/4 to 1/2 way "up" the heating coil to give
a fairly representative temperature measurement. It may be worth looking at the heating coil area, in lots of cases. this is now 1.0 M2.

freddyuk

Jakey Rolling wrote: »

Having had a look through the solar controller menu, and downloaded the manual it doesn't seem my controller has the option of operating a divert valve for heat dumping. The only related option for "Collector protection" is to force the pump on at predetermined temperature, but this just feeds to the normal storage tank - suitable if you had a swimming pool or large accumulator possibly!

It looks like this would be a pain + cost to change, as the controller is integrated into a "Solar Station" package. FYI, the controller is an "STDC" made by Sorel Mikroelektronik, rebranded as "ModvSol".

You seem to have the most basic version but there is a heat transfer option? Maybe this can be used to dump heat rather than transfer it to another cylinder? Instructions seem a bit lacking unless you have a complete operators manual. If it will transfer heat at a set temperature then just put this through a radiator as it is simply a TDC.Is there a terminal for this purpose?

Jakey Rolling

freddyuk wrote: »

You seem to have the most basic version but there is a heat transfer option? Maybe this can be used to dump heat rather than transfer it to another cylinder? Instructions seem a bit lacking unless you have a complete operators manual. If it will transfer heat at a set temperature then just put this through a radiator as it is simply a TDC.Is there a terminal for this purpose?

I have downloaded what appears to be the complete operation manual - as above, no mention of heat dump facility, or any heat transfer to anything other than the primary storage (in my case a 300l pressurised cylinder).

My plumber said he has similar sized systems working 4+ years without a problem. To be fair, pressure seems well regulated when stagnating, due to the expansion vessel. Stays between 2 and 3 bar.

I'll look at costs of suitable controllers. Can I assume that another unit would work with the same thermocouples that are in place?

John T Carroll

Jakey Rolling wrote: »

I have downloaded what appears to be the complete operation manual - as above, no mention of heat dump facility, or any heat transfer to anything other than the primary storage (in my case a 300l pressurised cylinder).

My plumber said he has similar sized systems working 4+ years without a problem. To be fair, pressure seems well regulated when stagnating, due to the expansion vessel. Stays between 2 and 3 bar.

I'll look at costs of suitable controllers. Can I assume that another unit would work with the same thermocouples that are in place?

Personally, I wouldnt even dream of allowing any system stagnating which can result in collector/system temperatures of up to 250C. This was the main reason I didnt go for E.Tubes at the time. After x years when the system starts degrading for whatever reason, one will say I wonder would it have done y more years if I had had a heat dump fitted.

If you do decide to retrofit a Controller capable of dumping then you might find one that looks at the STORE temperature as its measurement (for dumping only) and not the cylinder temperature. Quentingargen explains the problem with using the cylinder temperature quite well in one of the "Solar Heat Dump" posts. It probably would be prudent to change the solar fluid as well as this may have degraded even though this would not have reached 250C, its more than likely that it would have reached temperatures roughly corresponding to the saturation temperature as this is the temperature that the panel starts blowing down into the expansion vessel, the remaining vapour is then superheated on up to say, 250C. The saturation temperature at 2 Bar (gauge) is 134C, at 2.5 Bar is 139c & at 3.0 Bar is 144C.

The new controller should be compatible with the existing sensors if they are PT1000. I think most modern systems use PT1000 probes now. Its quite easy to measure the resistance on one probe by disconnecting it, if not sure. In any even, check with the supplier of the Controller.

Caracol

sinnerboy wrote: »

I'll sticky this awhile and add

Please indicate

cost
year of installation
m2 area
orientation
flat plate or tubes
cylinder size
summer heat dump strategy ( if any )

Reminder - no trade / company names please

.

cost : 6570 euros (including scaffolding)
year of installation: 2014
m2 area: 40 tubes (Kingspan thermomax)
orientation: South West
flat plate or tubes : tubes
cylinder size: 300L copper triple coil
summer heat dump strategy: 2 heat dump radiators in attic
Controller: Resol C4

House currently has 3 zones
Zone 1 upstairs rads
Zone 3: downstairs rads
DHW

Very happy so far:
On a sunny day in May temps go up to 50s in bottom of cylinder and high 50s in top of cylinder
On a mixed / cloudy day in May, temps in the 40s which is ok for bath and showers.

mickrick1

Hi Guys - I installed solar panels in our bed and breakfast back in March 2011. Everything seems to be fine, although I have no scientific data to back this up.

Just wondering do I need to ensure that heat transfer fluid is still at the same level as when panels were installed. How can I check this? Do I need to get a professional in? I have a drum of the fluid in the garage.

Any suggestions would be much appreciated.

Mick.

josip

Mick, I'm a user not a professional, but my understanding is that it's usually a closed system with an expansion vessel. I think the fluid only vents in extreme situations.

Any time we've had a bubble in the system, I've called in the installers since the system had to be drained.

Very open to correction from pros

ccsolar

mickrick1 wrote: »

Hi Guys - I installed solar panels in our bed and breakfast back in March 2011. Everything seems to be fine, although I have no scientific data to back this up.

Just wondering do I need to ensure that heat transfer fluid is still at the same level as when panels were installed. How can I check this? Do I need to get a professional in? I have a drum of the fluid in the garage.

Any suggestions would be much appreciated.

Hi Mick
Check the pressure gauge at the side of the pumping station
If it's between 1-2 bar your system should be fine
Best to check it late evening.

Cc

mickrick1

ccsolar wrote: »

mickrick1 wrote: »

Hi Guys - I installed solar panels in our bed and breakfast back in March 2011. Everything seems to be fine, although I have no scientific data to back this up.

Just wondering do I need to ensure that heat transfer fluid is still at the same level as when panels were installed. How can I check this? Do I need to get a professional in? I have a drum of the fluid in the garage.

Any suggestions would be much appreciated.

Hi Mick
Check the pressure gauge at the side of the pumping station
If it's between 1-2 bar your system should be fine
Best to check it late evening.

Cc

Cheers CC.

I checked pressure gauge last night and it was at 0. Can you tell me how to reset it. I have reset pressure gauge before on our hot water system by using a flat screwdriver. Can I do something similar here?

Thanks

Mick.

ccsolar

mickrick1 wrote: »

ccsolar wrote: »

Cheers CC.

I checked pressure gauge last night and it was at 0. Can you tell me how to reset it. I have reset pressure gauge before on our hot water system by using a flat screwdriver. Can I do something similar here?

Thanks

Mick.

Hi Mick
0 pressure basically means you have a small weep/leak in your system
Check all joints for signs of a leak possibly staining on insulation but you need a special pump to fill system and flush out air
Try hiring at a plumbing shop or get an expert to service and repair leaks
Sorry it's not better news

Cc

John T Carroll

ccsolar wrote: »

mickrick1 wrote: »

Hi Mick
0 pressure basically means you have a small weep/leak in your system
Check all joints for signs of a leak possibly staining on insulation but you need a special pump to fill system and flush out air
Try hiring at a plumbing shop or get an expert to service and repair leaks
Sorry it's not better news

Cc

Before re filling the system, ensure that the expansion vessel pre pressure is checked, it should be around 1.5 to 2.5 Bar.

My system pre pressure was 2.5 Bar (cold evening) and the installer continued pumping until he had 2.8 Bar on the liquid side pressure gauge. This should have pumped about 1.4 litres of water/glycol into the 18 litre expansion vessel, this should serve two purposes, it will act as a cool buffer for the expansion vessel in the event of stagnation and it will make up any small air pockets that might remain after commissioning. I got tiny quantities (bubbles) for about 10 days when I cracked open the manual vent on the Deaerator or the Air Catcher as they call it in the USA. Make sure that too much liquid is not pumped into the expansion vessel as it wont hold the blowdown contents in the event of stagnation.

mickrick1

Any ideas on a good person to look at my system in Galway?

championc

Got my RPi outputting the data once again

https://xively.com/develop/Y9cJha4J1gxxCijlJKkW

John T Carroll

championc wrote: »

Got my RPi outputting the data once again

https://xively.com/develop/Y9cJha4J1gxxCijlJKkW

It's asking for a Login+Password.

championc

https://xively.com/feeds/1928576781

calum22

Great thread!!!

I was talking to a company at last years SelfBuild show in Dublin and was unsure. This thread has definitely reinvented the possibility of solar panels at my house

jiminho

This question is more for new builds that have "passive haus" or almost PH standard so air tight, very insulated and good natural space heating capabilities.

Has anyone on boards used their solar thermal panels to heat their hot water and central heating? Underfloor heating would be sufficient to heat a PH and as these require to be on all the time (hot days excluded) would only need water flowing thru them at approx. 30C. This temperature is obviously well suited for geothermal where it can be produced consistently all year round but sounds like this would be well within the capabilities of solar panels. Obviously a bigger system would need to be installed but as any system gets bigger, surely it would become more cost effective. Has anyone ever heard of this been done in Ireland or UK?

I am in the process of installing a system that consists of 2 x 20 tube collectors in a SE & SW configuration, I don't expect it to provide sufficient heat for the UFH but I hope to offset some of the energy required so that I'll need to load the turf boiler less.

BryanF

jiminho wrote: »

This question is more for new builds that have "passive haus" or almost PH standard so air tight, very insulated and good natural space heating capabilities.

Has anyone on boards used their solar thermal panels to heat their hot water and central heating? Underfloor heating would be sufficient to heat a PH and as these require to be on all the time (hot days excluded) would only need water flowing thru them at approx. 30C. This temperature is obviously well suited for geothermal where it can be produced consistently all year round but sounds like this would be well within the capabilities of solar panels. Obviously a bigger system would need to be installed but as any system gets bigger, surely it would become more cost effective. Has anyone ever heard of this been done in Ireland or UK?

This thread is about solar water heating?
Solar panel space heating is not suitable for Ireland. Start a new thread if you want further discussion.

ccsolar

[Deleted User] wrote: »

I am in the process of installing a system that consists of 2 x 20 tube collectors in a SE & SW configuration, I don't expect it to provide sufficient heat for the UFH but I hope to offset some of the energy required so that I'll need to load the turf boiler less.

Hi
2x 20 tubes in SE/SW is ok but I wouldn't get over excited about the performance if connected to a 300 litre tank
You would be better off in the long run to spend a further €600 and fit 2 x 30 East / West system
Might also want to consider the Nous system or thermodynamic system
Before you proceed you should really talk to someone that has an east west system installed and get there opinion.
Cc

championc

IMO - To add, the main months of gain, where you will have excess heat, will be during the summer months, the one time of year when I would expect that you would not be using your UFH. So complexity in controls and maybe pipework may indeed outweigh the benefits. You might do a bit better during Spring and Autumn if you have a dual coil buffer tank with a diverter valve and top load it. Obviously, the buffer tank would need three coils then, with the top one connected to your CH / UFH

jiminho

championc wrote: »

IMO - To add, the main months of gain, where you will have excess heat, will be during the summer months, the one time of year when I would expect that you would not be using your UFH. So complexity in controls and maybe pipework may indeed outweigh the benefits. You might do a bit better during Spring and Autumn if you have a dual coil buffer tank with a diverter valve and top load it. Obviously, the buffer tank would need three coils then, with the top one connected to your CH / UFH

Very true, it's just something i'm looking into as it would be great to have a single system. I've looked back thru the pages but I don't think you've mentioned it, can i ask how many people are in your household? Would the norm be each person has a single shower per day - in the morning or at night? I've looked at your graphs (which are great data btw) but what's your opinion of winter time - do you have a gas system that needs to "top up" during the cold months and if so, how much i.e. 20%, 50%? Lastly, what's your opinion of the temperature of the water when having a shower - are you ever cursing to yourself that it could be a bit warmer or is it the same as a normal shower? Cheers

Iamhere

Hi,

Looking for some advise if possible, looking into solar tubes at the moment and finding it hard to get a clear idea on the best setup for our house.

House was built in 1999, it has 2 en-suite showers (1 mixer shower, 1 electric shower) and an electric shower in the main bathroom.

I have got two quotes so far, both have suggested 20 tubes, with 240/250 litre copper cylinder (dual coil).

We are currently heat water for the likes of a bath using the oil central heating as the immersion is faulty and i have been advised it would be best to replace the current copper cylinder.

There are 2 adults and 1 2 year old in the house at present but we would be hoping this would change to 2 or 3 small people over the next few years.

The house is west facing so i am wondering would 20 tubes and the cylinder size above fit our needs, also id prefer to get a stainless steel cylinder but this is just based on how they look rather than anything serious

Thanks in advance.

ccsolar

ccsolar wrote: »

Hi
2x 20 tubes in SE/SW is ok but I wouldn't get over excited about the performance if connected to a 300 litre tank
You would be better off in the long run to spend a further €600 and fit 2 x 30 East / West system
Might also want to consider the Nous system or thermodynamic system
Before you proceed you should really talk to someone that has an east west system installed and get there opinion.
Cc

I had already started the installation so no going back really, anyway finished it at the weekend and so far so good.
Saturday(just the late afternoon), despite it being mostly overcast did bring the tank up to 50c since then the weather has been awful and the panels are only getting up into the low 40s, so no useful heat there.

josip

Deleted User wrote: »

panels are only getting up into the low 40s, so no useful heat there.

Panels at low 40s would give a cylinder temp of mid 30s in our config.
Which is almost 20 degrees of lift over incoming water temp.
Is it because your cylinder temp was up to 50C on Saturday that you don't consider it useful?
If you've used any water since Sat, then the 40C+ at the panels should have heated the bottom of your cylinder to mid 30s?

josip

josip wrote: »

Panels at low 40s would give a cylinder temp of mid 30s in our config.
Which is almost 20 degrees of lift over incoming water temp.
Is it because your cylinder temp was up to 50C on Saturday that you don't consider it useful?
If you've used any water since Sat, then the 40C+ at the panels should have heated the bottom of your cylinder to mid 30s?

I meant in the sense that I couldn't use it for a shower or the like, but it did raise the temperature of the tank here is a screenshot of the system right now.
Note that both pumps are running and the system is providing low level heat.
The backup turf boiler is firing up and will heat the tank instead.