Posted By: Ed DaviesFor the low power pump to work a syphon would need to be held in the collectors. So how does the drainback work, then?

I don't know. Rotex specialise in drainback systems & there's no mention of motorised valves or air-bleed paths in their installation instructions:

http://www.rotex-heating.com/service/techdoc/current/solaris.html

Posted By: fostertomSo why can't both be PV powered, as both are only reqd when the sun shines?

They can, but if dedicated PV panels are used, its not an efficient use of PV capacity because most of it would only be used during ST panel charging.

David

I was obviously reading too much into the following:

Posted By: fostertomDrain back can mean that all the warm water drains out of the panel when the sun goes in and the PV-powered pump stops

Pump stopping when sun goes in implied dedicated PV to me.

David

When the sun goes in the pump is welcome to stop pumping, and drain-back to happen if that's what the system is designed around.

If it's just pump head, against a restrictor, that keeps the the panels full of thermofluid, then that implies a big pump running continuous (while the sun's out), bigger than the pump needed to circulate a sealed circuit without restrictor (syphon held in the collectors, as davidfreeborough says) once re-priming (by big pump) has happened.

Ed/wookey: Solar thermal is a notifiable installation, as it involves not just electrical work, but also elements of L1 and G3. The IDHE desribe it thus on their site:

"All solar water heating work normally involving additional hot water storage is therefore notifiable to a building control officer unless a competent person can self-certify and issue a commissioning certificate. Requires minimum levels for insulation, time and temperature controls for hot water storage. Also, water storage vessels to have a minimum performance. A commissioning certificate is required to be left. Note that different rules apply in Scotland and Northern Ireland.

"The Building Regulations (G3) 2000 www.odpm.gov.uk Applies to hygiene in buildings, particularly unvented hot water storage. Requires only competent operatives should install such certified equipment along with associated safety equipment." End of quote.

Notifiable. Certified equipment. Competent operatives to sign work off OR go BCO route, who have certain requirements of their own, as already quoted from a BCO. Doesn't sound like the professionals find it nonsense wookey.

There's also the element of RHI when it comes along of course. Non-approved kit means no RHI.

As for the element of buying everything from one place, that is just common sense. Nowhere did I suggest wookey that it was illegal to pick and mix, as you suggest, or that you had to get everything from one place. You are misreading what I am saying, which is that it is much safer for a DIYer to get approved, compatible components from one source.

Especially as even experts on here are showing confusion over something as simple as a drainback system. But you want to advise an ingenue to somehow pull it all together, with your advice? Save me.

For clarity, the actual quote was: "Buy a proprietary (ie tested/approved) kit. Unless you are a solar designer/accredited installer. Anything else and you will be outside building regs and safety standards". I clarified this in my second paragraph of the very first post.

Non-approved kit is, as I showed above, unacceptable to a BCO. He will require a certification of conformity from a testing body employed by the manufacturer for this purpose. Kit may not be banned but it may also not get approval. Like my home made car. What's so hard to grasp?

David - sorry, just re-read your precis above, I think it's just about spot-on.

My plumbers concerns of overheat were before he convinced me on drain-back system.

we will take your advice Crusoe and use PAW drainbloc system its one less thing to worry about in a much much larger project, as for cost, if you add up all the pumps valves controller, suitable drain back vessel etc. and plumber fiddling time you could easily afford the plug and play PAW unit.

Plus if they ever get the RHI out of the starting blocks, the PAW unit would qualify

Were the solar thermal installation to be "plugged in" to a socket via a 13a or lesser fuse then I dont think it would fall under part P unless it involved an immersion heater circuit alteration.

Posted By: crusoeUnless you are a solar designer/accredited installer.

I possibly meet the first part of that criteria. What actually is a solar designer?

Like most of this legislation there is a lot of 'should' and 'may' and very little 'must' and 'will'.

Posted By: crusoedjh - point taken, although I did asy it was from the IDHE site, and you found it.....if I was cherrypicking...also a notifiable occupation soon... :)) ...why would I give the reference?

Yes, you said it was from "the IDHE site", but no I have not found that site - what made you think I had?
You haven't given a reference yet, just vague assertions. Please do give the reference now, including a URL.

Posted By: crusoeI think you are missing the point djh. You can't have solar thermal unless you HAVE 'additional hot water storage' - ie a new cylinder fitted (for this purpose I am ignoring sidewinders/solar inserts into the 2.25" immersion heater boss or Solartwin (now defunct) type apps, as most people simply do not go there

Lets see, you're now saying "You can't do X without Y, except in the case where you can, so I'll just ignore that". And you missed out another important case, which is where people have already had a suitable storage tank installed in advance.

If it's not notifiable, the BCO doesn't have to pass it!!!!

Posted By: crusoeAlso can't have solar thermal, quoting from B Regs above - unless they conform as follows...

That doesn't make it notifiable.

Again, it appears you are twisting words to try to make the regulations appear more onerous than they are. It's a common ploy of some tradesmen but it's not something I would expect of you, or anybody else here.

djh: I have never - yet - found a solar-ready hot water tank. That may come, hopefully it will, but for now your point is hypothetical and not worth the paper it isn't written on. As solar thermal and DHW storage - as a minimum - go together, your other point fades somewhat too.

And vague assertions, come on, the quote is there if you want to find it. Google IDHE and solar thermal and I'm sure it will appear :)

From 'A Buyer's Guide to Solar Water Heating' at www.energysavingtrust.org.uk

"When installing a solar water heating system
building regulations will apply. This is to ensure
that your property can support additional
load, both internally and on the roof. Before
proceeding with the installation, you must
check with your local authority building control
officer that all proposed work is compliant
with current building regulations unless your
installer is qualified to self certificate the work.
Please note that there may be additional costs
associated with building control notification."

Not overly technical or addresses all points of notification, but it makes the point - notify or self cert.

Or there's 'An introduction to Solar Thermal at cumbriagreenbuild.org.uk, viz:

"Building regulation approval is required for solar panel installations, which will consider the suitability of
the building for the installation and electrical installation. It is advisable to contact the local authority
Building Control Department in the initial stages of the project."

Make what you want of it. Or ignore it. I know what I have to do to comply.

It appears these guys do too - unless they are twisting words too perhaps....

Two weeks away and doesn't the old GBF move along at a fair clip when you don't get on regularly. NOw I'll never catch up

Anyway, I thought I'd get a BCO's input to clear up what appears to some to be a confusing issue. I called BC here in Cornwall to ask, if I was a DIYer, if I would need to notify building control of a solar thermal installation. The young lady (not a BCO) was pretty sure I did. she checked and said yes, I would need to submit a building notice, at a cost of £133. Buuut, she said, we haven't done a DIY solar thermal installation yet!!! Hmm I thought, so the competent persons scheme has either put a stop to DIY installs, or the DIYers simply aren't telling anyone

I had some further questions which she couldn't answer, so she referred me to another office. Nobody qualified there either but he would call back (yeah, right!). Gobsmacked when he did about two hours later, a genuine BCO. He confirmed the first lady's comments. And, on being questioned further, he said that on the inspection visit, to sign the installation off, he would be looking at roof loading, electrics, hot water under G3 and suitability of equipment for purpose. What did that mean? Solar Keymark or other recognised approval.

I then phoned a very well known supplier in the solar industry, (all panels keymarked) and he said pretty much the same. What would be the point of the competent persons' scheme, he said, if any T, D or H could install it without any kind of check on their competency, endangering not only themselves but also their neighbours. Big bang re-visited.

So there is no further confusion, I would suggest, in light of some of the things being suggested here, that if YOU are planning a DIY install, get your BCO - or a competent person - involved at an early stage. And unless you know well what you are doing, avoid buying possibly incompatible components piecemeal from different suppliers.