[Closed] DIY (Kit) Solar Thermal - hints and tips?

I put the tank above the panel and use 18mm pipes so it thermosyphons with no pumps or electronics.

Double or triple insulate all the pipe rums and add a jacket even if you buy the highest standard insulated tank. If you don't the temperature loss overnight will lead to a tepid shower in the morning.

Plumb the solar tank so you can use it as a preheater for a second conventional tank in Winter. My solar tank has been around 28°C this very sunny week which obviously isn't hot enough for a shower but means the conventional tank only has to add 15° rather than 33°.

I made my panel myself, double-glazed and with a very well insulated back.

Strip the lagging off the return pipe run in mid Summer so the primary circuit doesn't boil.

Thanks Edukator, unfortunately I don't think I can do most of what you suggest given my house layout: It's a very "British" design of house and the panel will have to go on the pitched roof so a HW cylinder above the roofline isn't very practical - the neighbours would probably complain too!

Nice idea for the pre-heat tank, but my cylinder and my gas/immersion system all points to utilising a single tank: the top 1/3rd (~70 litres) would allow for gas top-up in the early evening if the sun hasn't cut it, the immersion is about half way down so would allow for overnight heating of 125 litres if needed, and the Solar coil is in the bottom so heats the whole volume (~250 litres)to whatever it can during the day. It's just about the timing I think, i.e. not firing up the 'leccy or gas until after the sun has had a go.

kit is fine - navitron are a well known brand of panels.

numbers - assuming you have a 210litre cylinder and that you use it daily (if you have kids and a wife then you can pretty much say that you will), and that the thermal panel is sized correctly for the tank, you'll get half your hot water for free over the course of a year. 200(litres) x 365(days) x 13 (kWh needed to heat a full tank) x 0.5 = 2100kWh of energy saved in a year.

If you'd normally heat that overnight at 5p/kWh you'll save £105.00per annum, same for gas right now. if your tariff changes (and Octopus can withdraw the Go tariff if it suits them) then the numbers change dramatically.

Don't bother buying a jacket if your cylinder is already insulated - you'll not get one to fit well enough to make a difference that can be measured, but do over-insulate any pipework and fittings. Don't plumb the tank as a preheat you'd be looking at another £1000 plumbed in, adding a further 10 years to any payback.

edit: yes - control of your backup is key. you'll get to know your usage but i just leave the solar to do its stuff and have the DHW come on at about 6pm - it either tops up or it doesn't depending on the weather/time of year.

This is of no help whatsoever, but why solar thermal (which is a one trick pony) when you could install solar PV which would also heat your hot water but wouldn't cost anything to run nor {potentially} involve introducing more liquids into your roofspace?
I know you've already made your mind up as you've installed a solar thermal unvented tank but I'm just interested.

Thanks @smudger666. Good to hear all that, matches my own understanding.

@sharkbait - I have a solar PV on the bigger section of my roof. Unfortunately due to the location of a chimney stack it’s only got about 1.25 kw output max. I can, of course wire it all up to heat the water, but I currently use the output (such as it is) to heat an extension with u/f heating (the element is below the 100mm thick screed so it charges it up rather like a storage heater and keeps the room warm well into the evening).

One thing I’d like to have used the output of the PV for is charging our electric car BUT despite the charging point having a sensor so I can charge at the rate the panels are producing, I find out (after the installation and the increased cost of the sensor install) that it needs more than 6amps to be produced before charging will take place.The output of the panels absolute maximum is about 5amps(1250watts/220volts = 5.6amps, minus losses). Pants 🙁

In addition to above - I’m not sold on the idea of utilising solar PV generated electricity to heat water. One solar collector panel about the size of 1.5 solar PV panels would heat more water in my tank than a full day of sun on my PV panels which are 6 times the size.

Using the PV to run the household base load during the day whilst charging a battery on the remaining juice for nighttime base load seems a better idea.

Here is a trick for you. My parents system manufacturers required the system to be charged to 3 bar. I needed to do this during a drain, clean and recharge. You can buy really expensive pump / system to achieve this with powerful 3 bar pumps. I used a 1.5 bar shower pump (second hand) plus a plant sprayer as a supply for the punp. 1.5 bar in header + 1.5 bar from pump gets you to 3 bar. Message me if you need more photos and information.

Unfortunately due to the location of a chimney stack it’s only got about 1.25 kw output max.

Ahhhh - I thought the solar thermal was your only 'alternative energy' system.... makes much more sense now.

I guess over time you will get to know how much hot water you need each day. Then you can dial in the immersion heater on a stat or basic plc control to fire between say 0100 and 0500 only from say 50c or below
So if the plc pick up point is at half full each day would start with 100 ltr of hot water regardless of pv input.
Obvs it will be more than 50c at the top and less than 50c at the bottom.
Set a wide differential on the plc so it doesn't cut in and out at or nearvthe cut off temp