Integrated woodburner, solar tubes, oil combi and underground heatstore.

[noelsquibb]

 
It all started a couple of years ago when I discovered Peak Oil ( bit slow, I know )  and realised that assuming the 'govment' would take care of everything might be a risky way to proceed.
 
So, starting off with a self built timber framed house, that we completed in '02 on a pretty tight budget ( 2200 sq ft, detached, 2 story, built for under £90k ) I wanted to be able to heat the house and DHW independent of oil and use the wood that grows all around me, plus some of that elusive sunshine that exposed solar tubes seem to scare away.
 
I tried talking to a couple of local eco plumbers but they seemed to have preferences that I could not afford or see working as retro fits.  Pellet or woodchip boilers that needed a plant room and fuel store, big expensive pressurised cylinders needing somewhere to sit ....
 
One suggestion that really was helpful, was that I check out this wonderful forum.
According to the stats I have now been logged in for 5 days and 9 minutes !  
Over a period of 15 months that's err..  hardly any time at all really.
 
And what a great time I've had. I've learned loads and even been allowed to pretend to be knowledgeable myself .
 
As my understanding built, so did the questions and I soon realised that you could get pretty confused as you got deeper in.
Blimey, the hours I spent studying and thinking about stratification and it seemed that no one really understood what goes on at a molecular level.  
The best advice I got was "put hot in the top, cold in the bottom. Anything else gets a bit complicated."
So all those stratification devices and pretty coloured vids of water getting hot, while helping a bit, didn't really answer the question.
 
Anyway after asking several questions and eventually getting a schematic drawing posted via Billi in Ireland ( thanks mate ), cos I could not get any images past the Navvi Picture Thief, I got a few useful suggestions and a general something that felt like a 'cautious silence' from the ranks of the Navvi folk.
 
Why cant it go underground ?
What's wrong with it being 1400 litres ?
Why cant I integrate the WBS and the Solar Tubes so I only need one input heat exchanger and one return line ?
Why cant I reverse a TMV to act as a thermostatic flow diverter ?
Why cant I feed hot water into my oil combi boiler ?
etc.
 
 
So, slowly the master plan evolved. Apparently I should retain the oil boiler cos a neighbour said that I might not always be up to cutting and carrying wood.
Fair enough I suppose but a lot more complicated.  Sadly weve got no underfloor heating, cos a distribution manifold cost more than a full set of steel radiators... so somehow Ive got to get pretty hot water into the radiators and the old woodburner, a second hand but pretty large space heater was miles from the oil boiler with no way to bring large bore pipes through the house .... das ist verboten ...  all modifications had to be totally concealed or a visual improvement with no disturbance whilst installing.
 
Eventually I had it nailed down enough to make a start and hit my first snag.
Permission was given to build the south facing veranda whose primary function as far as I was concerned was to locate the solar tubes, in fact why had I not already done this, but permission was not given to dig a big hole by the house, as close as I could get to the oil combi boiler, because this would require moving several potted plants that were flowering nicely.
I tried to explain that I needed to complete all underground work before I could build the veranda but this was not considered to be reasonable.
Any other permissions that I may have needed will be probably done on a retrospective basis, cos the Planning Enforcement Officers round these parts seem to be a bit more professional and sensible than some of the Planning Officers I have had to deal with. Nuff said ?
 
I had to establish the dimensions of the heatstore accurately, so I could get best use of insulation materials and work out how to build up the array of heat exchangers.
I spent hours looking at various tanks on the internet and pondered scrap fuel tanks.
I identified some precast concrete sections from Milton, that would do the job nicely but the nearest builders merchant that carried their products quoted me nearly £1000 delivered, so I decided that I would make my own sections. Based on cellotex sheet and ply sheets sizes, I came up with a concrete tank that was 1.2 wide, 1.8 long and 2.1 m deep, measured externally. Yeah I know, round is nice and concrete manhole rings are reasonably cheap but I wanted square because that's the shape that works with the insulation sheets.
 
So a casting yard was set up in front of the log shed, cos it was reasonably close to the hole I wanted to dig and just a straight track line with a digger between the two locations.
 
I'm very fortunate in having been able to purchase some old mine land that adjoins our property ( Barytes )  and to my delight I have discovered a buried seam of washed gravel that, when mixed with the finer washings in the settling ponds, makes good concrete. Obviously a bit of cement helps as well. So cement, ply and reinforcement were the only costs ( if you don't count my time and who here would dare to cost their time )
I found a few strips of reinforcing mesh but I still needed some reasonably thick reinforcing bar, no calculations but I've seen what shows up in those big rectangular concrete sections when they break, A few phone calls to various sites were disappointing and it looked like I was obliged to purchase a few lengths of 10mm. The bundle could be easily carried on a shoulder and cost me nearly £80 !!!!  Max oil and iron ore prices worldwide were to blame. Talk about bad timing.
Should I forward purchase anything else in case prices go up even higher ? Hmmm,  things weren't looking good on financials and the economy but would prices come down ? Easy with hindsight innit.

more soon ...

noel
 
 

[Rhea View]

Well, that was disappointing! 

Got right to the end.....and it's only the first installment!!!! You've had since midnight too! 

Seriously though, looking forward to Part 2 plus pictures.

[desperate]

Noel
Quote
As my understanding built, so did the questions and I soon realised that you could get pretty confused as you got deeper in.
Blimey, the hours I spent studying and thinking about stratification and it seemed that no one really understood what goes on at a molecular level. 
The best advice I got was "put hot in the top, cold in the bottom. Anything else gets a bit complicated."

Nice one mate, I know what you mean about confusion, there seems to be so much good but conflicting advice around, it is really hard to make a definitive decision, I have nearly finished my system and I still aint sure it's gonna work.

Have an applaud for your efforts.


Desp

[StBarnabas]

Noel
great stuff! Look forward to the next instalment!

[Stuart]

Looks a interesting project.Barytes Mine, not North Pennines are you?

[noelsquibb]

Thank you Rhea.  theres been a bit more midnight oil and a few more words


Cheers Desp, some old crooner once sang  " it seems the more I learn, the less I know "


Stuart, If I tell you where we are, I will have to kill you, cos Ive slagged off the local Planning Officers a bit.

East Dartmoor ( ish )

[noelsquibb]

Eventually the 100mm thick sections were all cast and were given plenty of time to harden during the long wait for the potted plants to do whatever it is potted plants do...

The base unit was made with bottom and sides as this would mean I could simply place it on sand or gravel and not need to form a concrete base in the hole.
It was strongly recommended that the insulation layers remain dry. I could see the sense in this plus the uplift on a cellotex layer 2m deep would be an issue.
so the plan became concrete sections coated with a waterproof layer externally, insulation layers, then a grp layer on the inside.
The best type of waterproofing product I have come across for this kind of application is a sheet material called bituthene, a heavy duty polythene backed by a couple of mm of sticky bitumen. I managed to track down a cheaper alternative ( cant find the name ) and with the concrete dry, I coated it with the correct primer and stuck on a continuous piece right round each section, which was fun when you don't want creases. The base unit had to be lifted up, a lap required to cover the bottom and another lap up the sides a bit. Only needs a couple of inches of well stuck material to be fully waterproof apparently.

Eventually the plants were deemed finished for the season and were quickly but carefully moved around the corner while no one was looking, By this time we were well into November ('08) and the ground was pretty wet, ideal time to be tracking up and down with diggers dumpers etc, so lawn protection was established in the form of old wooden planks, bits of ply and conveyor belting.

Digging the hole was always going to be a bit of a worry because I was digging very close to the house and -
a) might twat it with the digger bucket 
b) was going to be breaking all the rules about undermining foundations.
Ok the RC sections and gravel backfill would replace the ground that would be removed but there would be a period of time when the ground would be unsupported and I was planning on digging 8ft deep !

Hardworking wife away for the day, so ye-haa lets burn some diesel.  Couldn't get the digger to do a hole square to the house, cos it was too bl00dy big for the location, so had to sort of attack it at a jaunty angle, not to worry though, the finished article should end up flush with the ground.
Dumpered all the spoil away to the old mines and was going quite well for the first 1.2 m but then it got a bit gravelly and a bit of water started weeping in.
Just what you don't need really but we've dealt with worse than this.
1.5 m down and its getting quite lumpy and the waters coming in a lot quicker. Time to change the bucket and try to get into the harder ground then.
Lumps of rock coming out up to 0.5m dia and getting one particular lump out caused a bit of an undermine. Ive stopped worrying about the water and the house foundations and am furiously bouncing the digger around trying to get to the planned depth. Dumper now taking more water than hard material.
Offspring comes out ( must have woken him up ) and reckons he can feel the house quivering.

Hmm, time for a cup of coffee and a bit of a rethink. Ok, Ive got 1.9 m and I want 2.1m plus a bit under for blinding, so the tank will end up about a foot out of the ground if I stop the dig now. Yeah, I can pretty it up with decking and she can have a raised area for more potted plants.

Ok then its a plan. Nick the submersible pump that err... might have once pumped a very small amount of water from the stream to top up the pond, wont be needed till next summer anyway. cut some slots into a piece of pipe that the pump will  go inside and get the pump running. The hole was now half full of water but the pump was capable of getting ahead of it.

It gets a bit nasty now so any safety conscious types better look away now.

Down the hole with the shovel and iron bar to try and square it up and level it off. Best to not look at the sides, especially that undermine with the big rock above.
15 minutes was all I needed but it felt longer, put the pipe and pump in the deep end and clear of the concrete sections,  a level layer of lovely free gravel and a couple of layers of scabby old axminster carpet to protect the waterproofing layer. In with the first section and it just fitted the area I had prepared. I began to feel lucky !

A strong mix of sand cement waterproofer and section 2 was dropped on top, each concrete section had hoops cast in for lifting, with indents formed in the bottom of the next section to also act as locators.  Then it was down t'pit again with strips of sticky waterproof, working with my head n shoulders outside the sections and all the important bits safely inside the concrete box. I don't think I had rehearsed this bit very well, you know when you try to run the video in your head before you actually do something a bit challenging. A bit more primer was needed to make things a bit stickier but in the end it all seemed ok.

Tea time and its got dark but I couldn't leave it unfinished, well I could have but I told the family that I 'had to' keep going on safety grounds. That would be the house foundations safety then. Section 3 and I'm an old hand now, easy.  Bit tight by the big stikky out boulder though and hardly room for my arm to get the waterproofing band over the joint.
A piece of 18mm ply, already cut to size with cut outs so it fitted over the lifting eyes, was placed on top of section 3 and gravel loaded out of the dumper using the digger.  Once it got heaped up enough on the ply, the gravel simply flowed around the sides to backfill the sections. A bit of shovelling was required as some bits filled quicker than others but it was a good feeling knowing I was 'out of there'  even though the top section was not yet on.  Ain't gravel brilliant and self compacting too.

As I was eating my somewhat overdue tea, I reflected on what I hoped would be the most 'worrying' aspect of the project and idly calculated how much rise in standing water would be needed to create uplift in the concrete box.  Bu66er, I need to get that submersible pump set up so the float switch works properly. In the mean time I probably ought to get up a couple of times in the night and run the pump.

Next day dawned and all was well with no water inside the sections, almost no gravel spilt and the hole no more than a recent mightmare, so on with the top section, a final band of waterproof across the joint and backfill up to ground level.

Did I mention that no one apart from me was put as any risk at any time ?  In fact I don't recall having any help at any time but do I sound downhearted ??

[desperate]

Noel

He he he , dontcha love working underground?? I've done it once, we had to stick a ground beam on 2, 3 metre deep columns to build over a public sewer, I've never sweated so much. Yours looks like it's gonna be a right result,don't fancy digging one for me do ya??

Good fun

Desperate

[frotter]

Heh - that Noel. Luvs his digger, he does. Specially with new (old) seat scrounged off of a scrap Frot Towers mobility scooter.
That heat store is troglodyte-tastic old boy!


 

[noelsquibb]

Yup underground work is cool.  Most people, sensibly, give it a wide berth but I'm in my element working with deep n difficult ground conditions - motorway bridges, huge underground storm tanks, big high pressure water mains, reservoirs, deep drains. All sadly no longer required cos we dont really like big infrastructure projects anymore.  Plus I love pi55ing around with water .....    So obviously having a DIGGER ( or 2 ) is not so much a big boys toy thing, as a way of dealing with the post traumatic stress of,  errr... not having any more big infrastructure projects to play on.... Obviously.
As to why the seats all needed replacing, the obvious explanation must be   -  hmmmmm  -  I usually work on my own so its off the digger and onto the dumper or into the trench to lay a pipe or tidy something and obviously this means its a bit like a postmans van seat ... Hey, I gave up eating milk chocolate ....

So back to the project -


Once the heatstore sections were installed and backfilled it was on to the underground plummin to connect the sources of heat to it.

A trench about 0.5m deep and about the same width was dug, tidied with gravel and made ready for the insulated duct boxes that would contain the three insulated copper pipes.
The duct boxes consisted of 2.4m long 50mm thick cellotex strips joined together with our old favourite, expanding foam. These were placed in the trench foamed together and copper tube with that all singing Armaflex HT slid over it gradually built up to create the runs.  A 22mm run to deliver heat from the woodburner a 10mm to deliver heat from the solar tubes and a 22mm common return pipe.  Tubes were bent where possible and thought given to expansion, as straight runs of 8m and temperature variations of 95c, meant some potential for significant movement in the pipes. I used non lead solder and all the runs were air tested more or less as I jointed, cos I really didn't want to try and find a bad joint hidden inside two layers of insulation and buried below ground.  I took the view that the gravel under the duct and its connection to the heatstore excavation with gravel backfill, meant that any water would drain away to house foundation level as it was all connected by gravel, so dryish cellotex wrapped around 19mm thick armaflex. Cosy.

Lids foamed onto the duct boxes, a layer of thick polythene, backfilled with gravel up to just above lid level, some bits of featheredge over the polythene,  because we are only a few inches deep and finally backfill with the top material that seems to have strange qualities. If you do nothing to it at all it produces wild pansies and some rare grass plants.  Hmmm, wheres that knapsack sprayer, perhaps I should preplan my external works a bit better.

Anyway there it is, a lot quicker to describe the process than to actually do it, a blank area finally ready to build a veranda.
I was told that this time we would not be using tanalised gate posts. Oak posts were specified ! Got away with the crucks and all the rest of the structure though.
Well everybody else thought the car port looked ok.   Used some old 9"x 3"  to chainsaw rough blanks for the crucks and polished them up with a belt sander. Also belt sanded all the other tanalised timber to pretty it up, as it would all be exposed. Weird having to select the best face down on the battens but with no felt and exposed slates underneath these details are important.   

[noelsquibb]

2 more pics

[desperate]

Noel

I've sussed ya... Its Oil Drum Lane..... geddit?

Desp

[noelsquibb]

Are you referring to one of my favourite websites ?  http://www.theoildrum.com/

Those lovely oil drums were only there to create a convenient shelf height for pencils and other occasionally used items.

[noelsquibb]

Eventually it was time to get back to nightmare pit, which has had a waterproof concrete box sitting in it for several weeks. Although its been kept fully roofed with a couple of sheets of ( really quite pretty ) galvanised sheets on top of the ply cover,  Im astounded that its stayed dry. I maintained dewatering as I didnt want to risk the box floating up and down if the groundwater level gets high enough.
The first layer of insulation was done  using lightweight celcon building blocks, all laid and backed with expanding foam.
New skills were developed to try and maintain vertical walls as the expanding foam, err, expanded.
The innermost layer of insulation is foil covered foam insulation board. The total insulation should be 300mm of dry material ( foam board / lightweight building block / concrete ) with waterproof layers on the inside and outside keeping these layers dry.

Whilst waiting for the ambient temperature to raise enough for GRP to set off, I had a go at the heat exchanger array that will hopefully sit in the pit.
Using four cheap CH rads at jaunty angles, I'm hoping to be able to distribute the incoming heat fairly evenly. The hot incoming, from woodburner or solar tubes, will start at the top and warm will be diverted to the second rad down.
Ply templates were just to locate the plastic legs during assembly. Pressure tested ok to 2 bar for a couple of days then ruined it by jacking up to 2.8 bar. Sorted with a bit of brutal spannering on the radiator inserts though.
Probably not ideal pushing the output from a woodburner through the 15mm fittings that insert into the rads but no choice if I am to use cheap commercially available CH rads.

There are two copper 'coils' that will extract the heat, the DHW coil is the longer one with more coils at the top that hopefully will pick up enough heat to supply the taps. There is a CH coil that sits in the lower part of the heatstore, that can only draw heat for the CH rads up to a certain level, leaving a couple hundred litres of hot above.
The copper pipework all tests solid to 5 bar and should be up to the job but the rad connections are a bit less reassuring as the fibre 22mm tap connector washers and ptfe tape seem a bit less 'solid'.


The ambient temp never did raise up enough to use GRP so in the end everything was done by laying up the glass mat, slaping on the resin then applying heat. The Cellotex foam board got coated with a couple of layers of fibreglass whilst laid up on the flat in the shed, with the glass mat oversailing the edges to make corner joints when installed. I set up another sheet of cellotex  4 inches above the wet resin, with a hairdryer stuffed into a central hole.  I stuck a deflector plate an inch below the incoming hot air, monitored the temp with a cooking thermometer shoved into some predrilled holes and was able to get the air temp up to 40deg c on max with the lower heat setting on the hairdryer maintaining around 25 deg c. Cooking was slower than laying up and resin or gel coating, so I got the panels ready in a day by starting at around 11.00 am ( as good as it gets for me ) and finished 12 hours later, admittedly with plenty of tea breaks. The picture shows the  foam boards installed with the high temp ( nice and pink ) expanding foam bedding and backing and the unresined glass mat nicely sat in the corners, with a fine collection of pre cut sticks to ensure the foam does not expand the boards into the pit.

Once the foam was nice and crisp it was time to do the bit I was not looking forward to. The pit is 2.2m deep and now its only 2 ft wide and 4ft long. Ive got to get in there and apply the resin and final gel coat . By the time Ive put a ladder down and climbed down it there's not much room.
So with safety in mind, I assembled an in-line extractor fan, set to blow, on the end of a length of  'elephants trunking', a lemonade bottle reducer and a short length of 30mm flexi duct foamed into a standard dust mask    Course it worked !   I wouldn't be able to write and tell you if it didn't. It was hard at times trying to look through the lemonade bottle though.

Stupidly I tried to use a roller paint tray and as I climbed into the pit  with the second resin mix .  I managed to dump the entire mix onto the bottom panel so now I'm sliding around in all directions and just chucking brushfulls anywhere that I can reach. I realised that I would have to get this lot to set off hard before I got back in so I hung a 300watt halogen lamp centrally at the top and put a piece of cellotex over the whole lot. Then an idea that I had cunningly planned  was used to monitor the temperature  -

Last week in a moments stupidity, I purchased a radio weather station from Lidle's for £5. Its supposed to transmit the outdoor temp to the base unit and pick up a radio transmission to get the time.  So there it was set up indoors with the external temp sender sat beside the base unit and apparently its 3deg c warmer outside. Oh well.
I set up the outdoor temp sensor in the car port about 50 ft away and no signal was received. Pah.
So then I tried to get it to pick up the accurately transmitted time and after several resets and holding it pointing in the direction of north Germany, I eventually got the time signal.  German time is exactly an hour wrong and will always remain so. Doh !
So I took the remote sensor indoors, took the batteries out briefly and got it talking to the base unit again. While the two bits were being friendly I snuck them out to the pit and dangled the remote sensor on a bit of wire to a point just above the bottom of the pit. Bu66er me if it didn't work a treat and I was able to monitor the pit temp at the bottom registering 35deg c, ideal.

Before going back down the nice warm pit, I had to put the cold wet ladder in, only to discover that it was covered in unset resin, bound to get snags.
A quick whiz around with a carborundum faced disc, an awkward sweep up and I finally got the resin finished. Cooked it whilst having tea then did the final gel coat by  brushing all the corners  whilst standing or kneeling in the pit  and using a long handled roller to coat the big areas  once me and the ladder were out. Lost the roller off the long handle a few times but soon developed the necessary skills to reconnect it. 8.00 finish and I was done in, sweating and stinking. I sincerely hope I never have to go back into that orrible stinking confined space again.

[noelsquibb]

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