Can things get worse ?
Course they can -
Sunday ( 20th Dec ) saw my weekly pump out of the insulation layers and another top up inside the heatstore. About 30 litres each side, so pretty balanced.
Then it started to cold and I wondered if the solar manifold could freeze, after all I haven't actually fitted the pretty Navvi toobs yet.
Several reasons -
Because everything is integrated, I needed to be confident that all aspects were functioning before generating heat.
The fire was brought on line first and to start with I had too much hot water in the store that DHW demand wasn't getting rid.
This has been rectified by connecting the heatstore into the CH circuit. The WBS is just about keeping up with heating and hot water although when it drops below -2c overnight, we have to work the fire harder and try to keep the top boiler at around 70 - 75c to add a few degrees to the water flowing through the rads.
And if the temp at the bottom of the heatstore is over 50c, which it generally is with the WBS running continuously, the toobs have got to be cooking water at a few degrees more, otherwise there's no gain and as I don't expect this sort of solar gain until spring, there seems to be no hurry to install the toobs ....
So rather than try and make sense of all that delta T stuff you lektronic experts go on about and use the frost protection circuit that is apparently lurking in the Navvi TDC 3 controller, I thought I would manually switch on the solar pump whenever sub zero temps threaten.
So I did. I felt the heat pulse through the flow control thingy, so was confident that heat was moving through the solar circuit. Pressures in the EVs ok, no worries.
Monday night there was a bit of noise coming from the plumbing behind the WBS, so, I opened the bleed valve at the high point behind the fire and NOTHING CAME OUT !
Checked the pressure in the system and its at zero. Great, its 10.00 pm, the air temp is about -3c and there's no pressure in the circuit that takes heat from the fire. Oh well, best run the fire pretty quietly and take a look tomorrow.
It didn't thaw out on Tuesday until late morning and I considered the solar manifold area to be the best source of leak because it had been run hot for the first time and perhaps some thermal stresses had opened up one of my favourite joints ( compression ). Everything had been up to pressure for months and had held up ok though.
So, ever the optimist, I pumped half a can of inhibitor and another three litres of antifreeze into the circuit, then another 5 litres of water and we've got pressure.
A quick bleed round, another 3 litres of water and up on the veranda roof to open up the, very well insulated and protected, above roof pipework.
No visible leaks unfortunately but interestingly, if you poke yer finger up into the manifold when the solar pumps running you can feel the heat in the header pipe.
Which means I'm heating the sky and if I don't, freezing cold air can get to the header pipe through the holes where the toobs should sit.
So either got to fit the toobs and possibly sort the programmer, or cut 30 bits of pipe lagging and stuff em in the holes with a bit more lagging to fill the central hole.
Options, options ....
1. Will Noel fit the toobs and sort the TDC3 programmer ?
2. Will Noel cut and fit 30 bits of lagging into the holes in the manifold ?
3. Will Noel switch the solar pump on and off depending on air temps ?
4. Will Noel drain down everything and go on a long holiday ?
Cast your votes now ! heh, did I mention votes ?
Coming down the scaffold board on the veranda roof at around 3.00 pm, I couldn't help noticing that the wet part of the board has suddenly got all slippery as the air temp dropped. Luckily the upstand of the ladder was enough to slow me down to an acceptable rate of descent though. Phew.
So pressure down a bit but still a bit of pressure, no visible leaks, all a bit inconclusive really.
Last night the air temp dropped to -4c so we were running the fire quite hard.
Around midnight I filled the fire and opened it up to give it a bit of a blast before a final top up and shutdown to minimum burn through the night.
Bl00dy Navvi forum distracted me and the fire got well hot, up to over 85c on the top boiler and the side boilers kettling loudly.
Shut it all down hard, checked the circuit pressure and we are back to zero, then fretted while it continued to make quite a lot of noise and wondered if there was enough water to allow everything to keep moving. Really didn't need the solar circuit to stop circulating with the air temp now approaching -5c.
Eventually fell asleep to the sound of BBC world service and got up quite early to see what the fire was doing.
Wife had de-ashed and stoked it and the top boiler temp was well past 80c yet the fire just getting going.
Clearly something was wrong and it got to 90c before the pump cut in. The bubbling and gurgling confirmed it, so the fire was shut down hard.
The boiler temp continued to climb and eventually topped out at 110c. I was able to stay calm and logical though and reckoned that we were seeing the fire temp rather than the water temp and the top boiler was empty. Nothing I could do, except keep the fire shut right down and let it slowly expire.
The kitchen / diner where we spend most of our time was pretty cold by now and the heatstore temp was a few degrees lower than normal so time to switch the oil combi boiler on I reckon.
Lovely warm radiators now ?
Well .... for a couple of hours they were, then they got cold.
Max demand on the wall stat, max temp on the boiler knob, no circulation though.
Great ! Coldest day for 15 years, WBS bu66ered oil boiler happy to cook but wont circulate ! "
and two days till Christmas.
Wife helpfully suggests "what about that bloke that did the service / commissioning check last year ?"
Yes dear, I would imagine he is sat at home right now waiting for my call !
Or, more likely turned his phone off cos he's already had a dozen emergency callouts .....
Hey I've got a spare CH pump, how hard can it be ?
Looks like the Bosch pump fitted is configured differently from a standard pump though.
Anyway, a quick lekky check from your very local certified expert, showed that the pump was not getting energised, which seemed to point towards electronics / switching / controllers and not something I am too confident about.
But I can 'hotwire' the pump. So the boiler pump got a direct feed from the plug point that I wasn't using to run the CH through the heatstore and the heating was back on line. Another phew moment then.
Oddly, as the day progressed the live to the pump seemed to be doing exactly what it should as I played with the room stat and tonight the hotwire was removed and the internal feed wires reconnected.
It worked perfectly for about 5 minutes then the pump stopped again.
So what is the logic / flow circuit that switches the pump, I wonder
Meanwhile, back to this morning -
Outside, everything was frozen solid and covered in 12mm of ice, including the garden tap and the hosepipe that would be needed to feed water into the WBS circuit.
So, once the trauma of the boiler pump was sorted, I put the hose reel in the boiler cupboard and poured a few kettles of hot water onto the garden tap to eventually get it flowing. Then off on an adventure to collect the organic turkey from a distant farm before all the ice had melted and back in time to hunt the leak in heavy rain showers.
Filled the circuit and bled everything but seemed to be putting a fair amount of water in.
Had sussed that I could isolate the solar bit by closing the ball valve on the flow gauge and noted that the solar EV was showing no pressure drop while the WBS EV was showing a drop from 1 bar to zero in about 10 minutes. This confirmed that the leak was not in the solar pipework and as there were no visible leaks in the control cupboard the best place to look was the 'gravy store'.
The covering planks had ice on both sides. Between the tri-iso10 layer and the 100mm cellotex layer was nice and cold, so not a lot of heat escaping I reckon.
The cellotex had to have the garden spade treatment to de bond it, even though it was only removed 3 days ago. Odd how that expanding foam gets livened up by the hot wet atmosphere.
Cover off and quelle horreur, the water level is UP ! So the leak is in the gravy store.
I repressured the circuit and went back to the heat store, hoping to find a high level compression fitting had failed but not really expecting much and immediately saw a disturbance that could only come from water escaping into water.
Investigation required that I bail out the top foot or so of lovely hot steamy water with a dash of inhibitor, antifreeze and as yet unidentified brown stuff. Good job it wasn't heated by the oil boiler, eh ?
And there it was, a pin hole in the top skin of the top radiator.
how am I going to fix it ?
how long before the next pin hole opens up ?
will I be able to access it ?
will Screw-fix honour the radiator warranty ?
With a self tapping screw and a bit of inner tube.
Pretty soon, probably Christmas Day or Boxing Day.
Not without lifting the entire heat exchange array out of the gravy pit.
Be fun trying, there's nowt in the instructions about running em immersed in an acid vat
Hole plugged, system repressured and holding, random bits of aluminium bolted together and strapped to the circuit with the radiators, gravy pit topped up with freezing cold mains water, fire lit and off we go...
Hmmm not quite, there's some suspicious gurgling noises coming from the plumbing behind the fire and the pump hasn't cut in yet.
Top boiler temp rising, pump cuts in, gurgling noises continue, temp continues rising .... WTF is going on ?
Shut the fire down hard and wonder if the diverter valve is stuck again.
Both pumps are running though, so we should be able to transfer heat to the store as per burn no 2.
Had tea and checked the fire. It had quietened down, the gurgling noises had stopped and the top boiler temp was back near 60c. Yet another phew moment.
If there's pressure in the circuit tomorrow morning and its not freezing, I will stop the solar pump and see if the top boiler temp rises.
If it does, I will be obliged to conclude that the replacement reversed TMV has failed.
Perhaps it would be safer and simpler to remove this component and rely on the pipe stat to switch the pump on and off and accept that there will be times when the water in the boilers is below 60c.
Plummin tomorrow ? Probably.
Stay tuned.
pics -
pin holed rad
hole, a bit fixed
