What to expect from solar panels.

[ericmark]

Father-in-law has two solar panels on the roof and a DeltaSol BS Plus controller and SolarBloC® midi 3-line station (2 roofs) pumping station in the airing cupboard reading the instructions it says if the water on roof is warmer than water in cistern then water should circulate and the coil is right at the bottom of the cistern so water should be cold and in theory even if it does not heat the water to 60°C at least it should reduce how much gas is used.

However the central heating S plan has a problem, the micro switch in the motorised valve for domestic hot water is stuck on, so the orange wire has been temporary removed to stop the pump running with valves closed, so domestic hot water is only heated when the house central heating calls for heat, however he has no radiator in living room just a gas fire, and if this is left on the central heating will not fire up.

The net result has been no domestic hot water, now I understand maybe not to 60°C but hot water nearly same temperature as cold water.

Before paying out for some one to repair the solar water heating, question is what is it reasonable to expect from a pair of solar panels, at this time of year with only one person in the house what temperature can one expect solar panels to heat the water to?

 

[Hot&Cold]

Who installed the solar products ?

 

[flameport]

what temperature can one expect solar panels to heat the water to?

Entirely depends on the amount of sunlight. In November = next to nothing.

repair the solar water heating,

Don't bother wasting money on that - the repair costs will be far more than just using the gas boiler or even the electric immersion heater.
Solar hot water is a failed concept, as the cost of installation is orders of magnitude greater than the very small cost of heating hot water.

 

[ericmark]

I know my daughters flat in Turkey has a good solar water heating system, but I do not really expect it to work quite the same in the UK, the losses are too great, brother-in-law also had solar powered water heating but the panels were electric not water filled. However I think if it will not work, why does anyone fit it?

And the second question is if it does work, what happens if the water is not circulated? Could the water boil in the panels? Can it be safely switched off, or would it need removing from the roof?

So it would seem there are two pumps and three sensors if either panel has water in it hotter than the bottom of cistern a pump should run, it was short of water so I will guess in the summer my father-in-law has turned it off thinking it was the immersion heater as they have used the immersion heater supply the water has either expanded or boiled and as a result that's why when we looked at it there was a shortage of water.

I don't know how much power the pumps use, but not keen on switching them off, neither am I keen on spending money to get it repaired or removed, but however we proceed it will cost, best option would be to remove it and replace immersion heater, but that would cost a lot of money, he is 91 now and when he dies house will be sold so it's some one else's problem then.

So if the heat gained equals the cost to run pumps then likely best idea is to swap the switched FCU for an un-switched version so he can't turn it off, so it would be nice to hear from some one else with the system so we know what to expect.

 

[bernardgreen]

There are several type of water filled solar collector for roof mounting, The simplest and least effective are water filled panels behind double glazing panels. In the UK these are generally a waste of money.

Evacuated glass tube with the rear half silvered to reflect heat onto a fluid filled tube at the from to the glass tube

The most complex ( in my experience ) is a small bore pipe at the focal point of a cylindrical lens formed as part of the evacuated glass tube around the pipe.

Provided the pump can run fluid into a heat store or heat dunp then in the UK boiling is seldom a problem. Freezing is a problem in the UK and either antifreeze has to be added to the fluid or a dump system fitted to drain the fluid when freezing is likely.

Or you could go over the top

the big heat

 

[ericmark]

Who installed the solar products ?

Tower Windows they would ring my father-in-law up annually and get him to have more work done, starting with double glazing, then conservatory, then front door, garage door, and one year they got him to fit the solar panels.

 

[JohnD]

I heat my HW with gas, and the usage costs in the region of 25p per day (have a look at the meter in summer when CH is off)

so even if solar could halve my annual HW bill, it would only be £45 a year. Not worth "investing" in solar. Very doubtful if it is even worth buying an Immersun or similar if you have PV panels.

I suspect the salesman will project savings on electrical water heating, which might cost £1 a day, plus standing charge. But only the foolish or unfortunate heat their HW with peak-rate electricity.