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Author Topic: Just got my solar running and want some re assurance and guidance  (Read 1454 times)
harveymushman
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« on: September 03, 2019, 09:20:39 PM »

ok...so this is all new to me. Finally loaded my 30 nr 58mm tubes into my collector and my system is up and running...wow what a great feeling as I started the concept some two years ago while extending the house.

I have a worcester gdi 35 gas boiler running underfloor and radiators with my solar connected to a 300l telford tempest solar tank. traditional wet system. The solar is using a glowworm pump unit and I have a navitron supplied sorel stdc controller. I have a temp sensor on the collector at exit and another in the lowest point on the tank just under the stat.

Since loading the tubes I have observed the controller activate the pump and watched the collector temp rise and then as if by magic the tank sensor temp rise accordingly. As the last few days have been typical late autumn i have witnessed a max temp of on the collector of approx 55 deg and the tank temp rise from say 21 to 45 degrees. So am happy it's working and doing its bit. The temp differentials are pretty much factory set with a 10 degree temp difference being the activation point etc.

Now I'm a non tech person who understands the basic principles but now I want to know a bit more and convince myself its all been worth it so have some basic questions..


1. should i be measuring the tank at a higher level so if the water temp at the bottom is rising then surely its achieving hotter at the top? ( is this necessary)
2. My gas boiler still kicks in as I have it set on timer. Should i witness my boiler working less or shutting off as in theory the solar is doing the majority of the work.
3. how do i get refinement so the solar is giving me the hot water and the boiler is only boosting when needed as we approach the end of summer and enter dark nights this is vital as i see it for saving wonga....
4. Do i have to worry that if the pump is running and the weather isn't giving the solar much energy am i burning power for not much benefit?
5. Should I be going insulation crazy around the pipework to prevent heat loss or enjoy the benefit of a warm cupboard for airing clothes ...like the good old days...

Please be kind with technical jargon  as I'm no techno nerd but am keen to understand the best set up at all possible so I can be smug in the knowledge that I'm on my way to getting something for nothing....

Look forward to some comments from anyone who thinks they can give re assurance..

Thanks

Harvey
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Countrypaul
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« Reply #1 on: September 03, 2019, 11:18:45 PM »

I dont havw solar or gas so I cant comment on most of your queries.

The forum Mantra is insulate insulate insulate, so on point 5 the answer is YES.
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todthedog
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« Reply #2 on: September 04, 2019, 07:10:06 AM »

As a fellow  non techie.
The temperature that the water is heated is set by the controller and can be altered (see your manual). We had ours set much higher and used a radiator to dump the hot water if this was exceeded. Rarely used 2 or 3 times in 10 years.
We were two adults and made sure not to scald  ourselves in midsummer.

The pump is activated when there is a temperature differential between the tank and collector again this can be adjusted a reasonable differential is good, if not the pump is continually switching  on and off.

Even in midwinter the solar does it's  work, for us water arrived at 7C the solar heated it to 30C ish even on cloudy winter days. The boiler in your case then only has to raise the temperature to your usable temperature much less energy used. In Spring Summer and Autumn our source of traditional heat was switched off completely for up to 8 months.

Insulate everywhere, then insulate some more. When bored insulate and check your draught proofing.

Well done and good luck





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JohnS
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« Reply #3 on: September 04, 2019, 07:28:08 AM »

Again, I am not a solar thermal user, although I nearly installed a system ten years ago but am glad I waited for PV.

Does your tank just do not water or is it a thermal store that acts as a buffer for the UFH as well?

If the former, I would adjust the HW timer so that the boiler supplies heat only in the late afternoon/
evening after the sun stops.  That is what I do with my system in the summer as the Solar immersion heats the cylinder.

Modern solar thermal cylinders are designed so that the boiler coil is not at the bottom, which leaves cold water at the bottom for the solar to heat up, even in winter.

Your system appears to be working well.  As the cylinder heats up, the collector temperature will rise as the return water to the collector is warmer.  The 10 or so degree differential sounds good.

Insulate well, even in the airing cupboard.  There will still be some heat loss.
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harveymushman
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« Reply #4 on: September 04, 2019, 12:27:12 PM »

Thank you for your comments and it appears I am on the right track to successfully running a solar thermal system.

Back to the benefit side if the gas boiler is kicking in on a timer and heating water which in effect is already heated by solar what tells the boiler " your work here is done my friend and hence it isn't burning away trying to heat the water beyond what is necessary...
I suppose this is more of a traditional plumbing question as to be honest I don't fully understand the control side of things. My tank is a 300 litre pressurised type with the main boiler heating coil on top and the solar coil at bottom so the whole point of the solar is to gainon the hot water side as the boiler looks after the underfloor and radiators on the heating side.

But also when installed and running I suppose its given me the appetite to understand the science and further my knowledge on solar thermal, so the control and mechanical side is important.

Interestingly the comments on here with heat dumping interest me as I openly admit having missed the peak of the summer heat I probably wont know how the system will fair in really hot  periods like we had over the last bank holiday weekend. When the hot water kicks in from the boiler I have noticed since its install one radiator in the bedroom gets warm and hence can I presume this is a heat dump for the boiler tank hot water. If this is so and the solar gets the water really hot will this radiator act the same or am I missing something quite obvious here??





Again any comments tips advice would be most welcome.
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JohnS
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« Reply #5 on: September 04, 2019, 12:50:55 PM »

The boiler output to the hot water is turned on and off by a thermostat.  When the water cools, it switches the boiler on (timer permitting) and once it is heated up it switches the boiler off.  The on and off temperatures are several degrees apart to prevent rapid cycling.

The water in the cylinder is also stratified.  As the water warms up, it rises to the top.  When a tap is opened, the hot water at the top is drawn off and is replaced by cold water at the bottom.  There will be some mixing, but not too much. 

300 litres is a decent amount of hot water and depending on hot water demand should last all day.

Thus, you should aim for lots of hot water by early evening to cope with the demand for evening showers and baths.   You might need a boost at 6am for morning showers.

The aim is to have a relatively cold cylinder for the sun to heat up and then some help to finish the job late afternoon from the boiler if necessary.
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brackwell
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« Reply #6 on: September 04, 2019, 02:04:02 PM »

The rule often banded on here yrs ago was that the tank size should be 5L per tube or in your case 150L.  The efficiency of the system is very much enhanced by the tubes being fed cooler water.  If the tank is smaller the temps get higher but the fficiency goes down and vice versa and therefore the 5L/tube was thought of a good compromise.

In your case for a large part of the yr, say 6 months, you will end up with a large tank of warm water below say usable 45C. even though you are catching all the energy available.  This scenario therefore requires further water heating to make it usable and here you need to think of "just in time" ie just before you need it and this may be morning or evening depending on usage, but by how much is only just enough. This can be adjusted by adjusting the tank themostat on the side of the tank situated perhaps 1/2 way up one side.  I would initially start by setting the temp to 45C and the boiler for 1/2 hr and go from there.  If you overheat the tank with the boiler you will loose efficiency from the tube and have wasted your gas.

For the summer 6months you probably do not need the boiler to come on but like all these things it depends on your usage and experience over time.
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harveymushman
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« Reply #7 on: September 04, 2019, 03:17:49 PM »

Thanks again,

Yes and that's how I always intended it to be used. I had the same thoughts and as my standard boiler settings are morning and evening I think I will see and adjust the boiler times. I am going to reduce the timer slots in time first and see what effect that has. Ideally most showering in the house is done towards the evening hence on a good day I would like to think the solar has provided enough but maybe a top up still late afternoon will be the solution.

Again in the morning a boost for a period just for early morning demands....

Agreed this will be easier in summer and through the winter months probably more assist from the gas boiler......

I'm more than happy with it so far and appreciate all the comments as I'd like to think it's been worth it. Like all things in life it's the little tips and knowledge you pick up on the journey that helps with getting the most out of it.

Many Thanks.

Onto PV'S Next as with the solar running i'm twddling my thumbs!!!
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harveymushman
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« Reply #8 on: September 16, 2019, 12:36:32 PM »

ok update from the weekend.

Saturday was a glorious blue sky sunny day and I witnessed a high of 62 deg on the Collector and 54 degrees on the tank.....mega happy especially when everyone showered later and no hot water issues...( no gas boiler input all day)..

Yesterday with a lot of cloud lesser figures but still 38 degree on the tank at the afternoon point....While doing some final insulation wrapping on the connecting pipework on the collector I noticed a very minor weep on one of the compression fittings so minor infact it was just a trace on the finger when swiped across...

When the system is running in the middle of the day the pressure gauge reads 2-2.5 bar...when it stops in evening it drops off..... Is this normal and could this minor weeping be the contributor......When I released the high level air valve there was no evidence of air in the system just fluid so in escence am happy the system is working fine...

Any comments hints advice greatly appreciated.

Happy Solar days
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Iain
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« Reply #9 on: September 16, 2019, 02:03:03 PM »

Hi


Quote
. When the system is running in the middle of the day the pressure gauge reads 2-2.5 bar...when it stops in evening it drops off..... Is this normal and could this minor weeping be the contributor......When I released the high level air valve there was no evidence of air in the system just fluid so in escence am happy the system is working fine...

Check your expansion vessel precharge pressure. If you run at 1 bar the pre charge should be about 0.8 bar. (0.2 bar below system pressure)
A lot of expansion vessels come precharge to 3 bar so much too high.

If ithe pre charge is set too high your system pressure has to exceed the pre charge in order for the expansion vessel to work.

Had similar issues on. I run at 1 bar system and 0.8 bar precharge.

You will need to drop the system pressure in order to set the precharge.( the shrader valve on top of the expansion vessel) or could be 0 precharge. Either way needs testing and setting

Iain
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dimengineer
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« Reply #10 on: October 12, 2019, 09:04:30 PM »

Thanks again,

Yes and that's how I always intended it to be used. I had the same thoughts and as my standard boiler settings are morning and evening I think I will see and adjust the boiler times. I am going to reduce the timer slots in time first and see what effect that has. Ideally most showering in the house is done towards the evening hence on a good day I would like to think the solar has provided enough but maybe a top up still late afternoon will be the solution.



I've had a similar setup to you for the last 10 years so here's my thoughts.
In the winter, its not that important. It will act as a top up - on really good days you'll get a good amount of energy, but those days are rare. So stick with your standard water heat timings -  perhaps an hour in the morning and evening. Do not have your water heating on all day - very inefficient and really does not help the ST performance.

In the summer you will need to experiment. What I found works (and my setup is bit undersized) is to just have a reheat in the evening on the thermostat. If the water is hot enough, the boiler does not kick in. If it isnt, it does briefly, adn you then have enough in the morning as well. If the forecast is good, just turn the boiler off. There will be occasional times when you need to just give a quick manual boost.

In the spring/autumn, it will be suck it and see. Something in between.

As others have said - insulation is key.
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