The small things get you

[rick]

Undertook a significant bit of plumbing .... To make more efficient use of my PV array have installed a diverter switch pumps unused electricity into immersion.

I have Underfloor Heating and a thermal store, to make sure mains pressure DHW still functions correctly need to install a shunt pump across the boiler primaries.

So with a lot of pre-thought, assembled pump, isolation valves, non-return valve, and a whole bundle of end feed Tees & elbows.

Drained system down .. store has a baffle so there is upper & lower drain c*ck .. unscrewed the bypass valves & pressure gauges.

With trepidation cut into 28mm primaries, and commenced to dry fit the new pieces. The 28mm electrical zone valve on primaries was weeping from actuator shaft when 'open' .... so had to replace that as well during drain down. Also the store has a automatic air bleed valve that looked sorry for its self so replacing that as well.

To fit zone valve, simplest way was to cut off pipe above olive, and fit a new piece of pipe below direct to new T piece (shunt connection).... Easy enough reduced number of joints.

All joints done, reassembly .... and found that I could not now reinstall pressure gauge as it fouled the new pipe run ... could nut turn it to screw it into male bsp fitting.

The fitting was a Kuterlite cast bronze fitting 28x 28 x1/2" bsp

As time was after 6pm ... thought best approach heat up fitting and rotate by 30 degrees - gauge will then fit .......... bad choice. Heated up OK and rotated ... but try as I might I could not get the joint to remake ... even good quality flux ... just looking black & cruddy ... no nice ring of solder.

OK .. plan B .. remove fitting clean it all up and remake joint. Top piece popped out easily, but bottom would not come out ... after much effort pipe collapsed.

So small thing No.1 was screwing in gauge failed !

No DHW that night ... OK next day decided to get new fitting - nobody has one in stock .... so will have to use a 28 x 28 x 22 Tee, reduce 22 to 15 put in a small piece of 15mm pipe and then fit a 15mm to 1/2" BSP union.

Annoying things is, I could have added an extension to exiting Kuterlite fitting and avoided replacing it .... trying to finish in one day caused me a lot of extra work.

Put it all back together ... including remaking all the tank connectors, bypass valve ... 22 individual joints.

Started to fill .. and load noise of escaping air ... found that the lower of the drain c**ks was not sealing. Found the rubber washers had disintegrated on both drain c**ks ... cost pennies - but didn't have any ... So small thing No.2 was drain c*ck washers failed !

It was after 6pm ... but took a chance phoned my mate (Manager at local PTS) he was just leaving and would take a pack with him .. and meet me at a half way point.

Replaced washers, filled, pressurised ... one slight weep at tank primary connection ... 1/4 turn of nut fixed that .... drained flushed, refilled & added inhibitor.

Job done ...... overall very pleased no leaks no bad joints ..... just caught out by 2 unexpected events.

Need to make changes to the Underfloor heating take off next, going to install a 28mm temp mixing valve, currently direct connect to heat exchanger - it can wait a week I think .

[Graham.]

Get with the program Rick, the deal was to sell that electric to *me* at an exorbitant price, not to use it for something useful. ;-) ;-)

[rick]

I still get paid for it even if I don't export ..... great idea. So by dumping in in the immersion I get twice the benefit.

[harry]

Totally uneconomic. It's not possible to store a significant amount of energy as heat (unless you have a swimming pool sized store. And when you need heat, there is little PV power available. Home insulation is the answer. Keep it stupid simple. Hi tech often fails.

I have almost 8Kw of PV, I export around 80% of it. I heat my hot water with solar thermal which is almost four times as efficient as PV in terms of energy gathering ability.

[rick]

you may be missing the point I think.

I generate X amount of energy..... I can use any of that for free. The rest gets exported. My payments are based on my generation 'not' on my export, therefore any I use is effectively free, wherever I use all or none of it. There is only so much I can use on a summers day.

You mention you export 80% of your generation ... well that is 80% you could be using ... for free.

I don't intend it to replace my heating, I intend it to supply my DHW needs in the summer ...... that will be significant saving on gas. The system will be able to be topped up by boiler if required.

I put system in 3 weeks ago, and since then boiler has been switched off, left controller on but boiler power off so de-stratification pump still operated with flow switch. .... and water has been hot 'almost' every day.

This is in a pretty poor June.

So it is economic to store all of my DHW needs in a thermal store.

The store is there, the PV array is there, and it works.

To make it even more efficient the cost is a pump (installed yesterday) and the TMV valve so I can increase store temp thereby storing more energy.

There are loads of guys on Electricians forum who have fitted these systems and they have produced full logs of kW stored in the DHW .... very impressive. It is a proven system, it works.

I don't dispute liquid based solar is more efficient, just no way I wanted water above my roof. Even more efficient would be ground heat pumps - but cost for me is prohibitive.

[harry]

"Water above your roof"????? ? Doesn't it rain where you live?

The point is that the money saved on heating water is trivial compared with the cost of saving it.

The means you have adopted is foolish. All you needed was an immersion heater (which may be existing) and a "solar/smart switch". Eg:-

There are cheaper ones than this available too.

[harry]

Additionally, thermal heat stores are a waste of time. By the time the heat is needed, it has leaked away after only a short period of time. Especially on small systems.

You need to heat domestic hot water and use it right away to be efficient.

[rick]

"> The means you have adopted is foolish."

Think you missed the point. I don't want water being stored on my roof, same as I don't want cold water tanks in my loft ......my choice, accept it may not be yours.

As to your other points - you have jumped to wrong conclusion.. I do have an immersion (fitted in Thermal store) I do have a solar diverter switch so I am well aware of these and the benefit and pay-back for them.

To allow immersion based DHW, the existing thermal store needs a de-stratification pump to work - hence the reason for installing the shunt pump.

By installing said pump I can now have boiler totally off and let PV powered immersion provide my DHW during summer months. Needed to install shunt pump to make it work.

So not foolish at all .. and certainly not money lost.

[rick]

I'm sorry but you are simply not correct. If you can heat your water at no cost (i.e. PV and solar switch) Keep it in well insulated store ... use it when you need it.

My DHW heated by immersion during the day is still hot enough the next morning for showers etc.

[dennis]

Solar power is really efficient at that especially at night!