Solar Heating Question

[PullerGas]

Probably just needs the expansion vessel pumping up and some pressure adding. Sadly not worth getting anyone out as the cost savings
on solar thermal are so small not worth it. Solar thermal isn't viable in the UK.

Rubbish!! A Solar Thermal panel & system will easily have a serviceable lifespan of at least 50 years. You'll be lucky if a PV panel will maintain its output for anything more than a couple of years!!

I was looking at a flat plate panel that was fitted in 1978 & it's still providing free hot water every summer.

 

[JohnD]

No mention of cost savings and payback time then.

 

[Agile]

A reasonably priced solar thermal installation should not be very expensive.

Nothing like the cost of PV panels!

 

[PullerGas]

A reasonably priced solar thermal installation should not be very expensive.

Nothing like the cost of PV panels!

I picked up a Chinese evacuated tube panel for £280 a few months ago. The old boy down the road from me will pay close to £18K!! for his shyte PV panels.

 

[ianmcd]

To get back on track with what you are asking OP, that blue container is there to collect water emitting from your pressure releif valve and is an absolute cowboy lazy installer fix, that pipe should terminate outside, it is most probably an expansion vessel recharge that you require but I wouldnt recommend you touch any part of the system yourself as parts of these systems can reach extreme pressures when working normally

 

[TheFew]

Thanks. The install is in the loft against an inside wall, which is why the may have taken the easy option.

Finally found someone to come out next week and take a look at it.

Today under sunny conditions the dials are showing 95 degrees and 40 degrees and the system pressure is at 1.5 bar (up from 1 bar).

Lots of water noise in the loft.

 

[TheFew]

Should the system be at 2.0 bar all of the time? Even when cloudy outside?

 

[TheFew]

Now at 110 degrees and rising. Pressure 1.5 bar.

 

[ianmcd]

The reason that your pressure is different depending on temperature is because the expansion vessel needs recharging, that is what the expansion vessel does it absorbs the expansion of the water in the sealed system and keeps the pressure at a constant, when the expansion vessel is working as it should you will still get fluctuations in the system pressure but it will be minimal, to simplify things if you took a pot of cold water and marked where the level of the water was, then boiled the water the level would now be higher as the water has expanded, as the water in your system is sealed it cant do this so it increases in pressure, the expansion vessel is basically a big balloon full of air and when the water pressure increases it compresses the bladder and that keeps the pressure of the water in the system at a constant, then as the water cools and the water pressure decreases then the bladder expands and keeps the water pressure at a constant, hope this simplifies things for you

 

[TheFew]

Thanks. I had a chat with the engineer and he is going to come next week, replace the expansion tank and recharge the system. Should be all sorted in a few days.

 

[dcawkwell]

Most likely nothing wrong with the expansion tank just needs a foot pump on it and check the tyre valve that it isn't leaking.

 

[simond]

The expansion relief into the Worcester plastic drum is perfectly acceptable and is per the manufacturer installation instructions at the time. The problem is likely to be the expansion vessel, as described above. These have a very hard time in a solar thermal location because of high temps; if it is depleted, replenishing the air charge is only a temporary fix - just like pumping up a leaking bike inner tube.

Whilst I wholeheartedly agree with the total futility of solar thermal and solar PV (neither will exist without some of us subsidising the wealthy*), if you already have it, it makes sense to keep it going if the maintenance costs are within the realms of a payback.

The idea of a domestic solar thermal system lasting 50 years is naive. Many customers are shocked at the maintenance costs over the first 10 years. It's like the everlasting broom, it'll go on forever.... if you keep recharging the glycol, changing the pumps and the expansion vessels.

Solar PV on the other hand is generally more reliable; the panel performance does degrade slightly over time, but only slightly. Might need a new inverter every 10 years or so but they are easy to access and the manufacturers usually have a refurb/exchange service - those that are still in business.

*so much for people being green. Drop the subsidy and no one wants to be green anymore. All they wanted was the money. Surprise Suprise.

 

[bernardgreen]

My first "exposure" to solar heating of hot water was on the roof of an office block in Tel Aviv, it was a very simple and seemingly very safe method.

A vented cylinder above the solar panel was supplied with water from a header and expansion tank a couple of feet above the cylinder. This water was heated by circulating through the panels. Water for the building was separate and heated by being passed through a coil inside the cylinder.

It would seem that if the sun was too hot and the shade for the panels failed to deploy the worse that could happen was the water in the cylinder would reach 100°C and then boil away.

 

[Agile]

I am about to buy one of those Bernard.

Not for UK use though.

Made by Bathroom Boutique in 150 li, 200 li or 300 li. Gravity supplied with a little header tank at the top. But the float valve is only supplied with 15 mm inlet so that would limit the flow rate although the mains pressure is about 3 bar.

Tony

 

[bernardgreen]

The Bathroom Boutique one looks a lot more professional than the ones in Tel Aviv ( but it was a long time ago when I was there ).