Kristen's 60kW Log Batch Boiler and 5,000L Thermal Store

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Kristen

New Member
Jan 4, 2016
80
UK
Hi all,


Stumbled over this site whilst looking for something to do with stacking firewood and spent several hours reading threads ... as you do ;lol. Before joining some discussions I thought it might be helpful to describe where I'm at.


In January 2009 I installed:


60kW HDG Turbotec batch (log, gasifying) boiler

2,500L Primary Thermal Store from Akvaterm with 2 x DHW coils, 2 x Solar coils, 2 x 9kW immersions.

2,500L "Unsophisticated" Secondary Thermal Store from HDG


(2,500 Litres = 660 USA Gallons)


(2 x Thermal Stores because we did not have enough ceiling-clearance for the tipping-angle of a single 5,000L tank but, actually with benefit of hindsight!, 2x tanks is better for us as in Summer we disconnect the Secondary and use just the Primary as heat-dump for Thermal Solar thus getting 2,500L up to "hot" water, rather than having 5,000L of "tepid" water).


Original central heating system was oil boiler & radiators, open-vented. New boiler / thermal store / accumulator is pressurised, so due to worry about whether existing radiators would cope with being pressurised we left the central heating circuit open-vented and put a heat exchanger where the old boiler had been - thus we have two (Wilo low-energy) pumps, first from Thermal Store to Heat Exchanger, second from Heat Exchanger around the radiator circuit.


We also have a pool, and added a second heat exchanger in place of where the pool (oil) boiler used to be. The first Wilo pump is used to get hot water to the pool heat exchanger, and the pool's filter pump gets the pool water to the heat exchanger. (Actually we have since moved the Boiler and Thermal Stores from the garage, which adjoined the house, into the main part of the house and both heat exchanger are now in the new boiler room, rather than the pool room as previously, so that we bring the "cool" pool water to the heat exchanger, rather than the "hot" thermal store water to the heat exchanger, as the heat losses in transmission are less. (In Winter I don't care, it's all within the envelop of the building, so heat losses become space-heating). Moving the boiler / thermal stored INTO the house has resulted in a significant reduction of fuel, so "subjectively speaking", as no two winters are identical :), the heat loss from having the boiler / thermal stores in an "outhouse" was significant. This is, of course, obvious but over here in UK I see lots of installs being recommended in "outbuildings", as not many houses have space for all this lot within the envelope of the house, and my Number One Top Tip would be to ensure that the boiler / store is INSIDE the house envelope.


Originally we had 2 x coils in the thermal store for DHW (Domestic Hot Water). The first low in the tank as a "pre heat", the second at the top for a final heat. There is then a mixer valve (joined to the cold feed) that regulates the output hot water (to 65C / 150F I think). The thinking was that if the tank was hot, top-to-bottom, the output from the bottom coil would be close-to 65C, and thus there would be no/little additional heating at the top coil, and thus no/little impact on stratification. If the tank wasn't so hot then I'd have to live with stratification in order to be sure to get DHW. Top part of the primary tank is "reserved" for DHW - i.e. the feed/flow to central heating Radiators is lower in the tank.


There are then 2x Solar coils (also in the Primary thermal store). If the top half (of the primary) thermal store is below 60C / 140F then solar heating only goes to top coil (and solar panels have to get hot enough so that their dT is 10C-or-so higher). Once the top half reaches 60C then solar heating switches to bottom half (at which point the dT is more easily achieved as it only has to be 10C higher than the (cooler) bottom of the tank)


The electric immersion heaters are an emergency fall back in case the boiler breaks. Previously our oil tank was inside the house (no longer permitted in UK, or at least not with the old-style tank we had) so to continue to use oil we would have had to have a new tank, out in the garden somewhere, and pipe that across the drive to the house. Big job, lots of collateral damage to make good, and our primary objective was to be more Eco Green ... so Oil was out ...


In Summer it was quite difficult to get top half of 2,500L tank to be consistently above 60C to provide DHW at 60-65C. So we added a separate DHW tank, which has Solar Coil (top-to-bottom), Boiler Coil (top half only) and two immersions - boost at the top, and another at the bottom for "full tank" mode. In principle we want to leave some "cold" water at the bottom of the tank so that the Solar has something to heat.


We use the original 2x Coils in the Thermal Store, previously used to provide DHW, to pre-heat the water going into the hot water tank (so, in principle, the hot water tank should be refilled with water at 60C in Winter, maybe as low as 40C in Summer during any not-very-sunny periods)


Once Solar has heated the DHW tank it switches to dumping heat into Thermal Store. If there is enough of that then it is available to a) pre heat water for the hot water tank or b) to dump into the pool.


We thought long-and-hard about stratification of the thermal store, and considered buying a fancy tank with all sorts of baffles and devices to mitigate the problem. In the end we went for "simple" instead and that saved me a lot of money; Looking back: I'm happy with the decision.


Since then we have added an extension to the house, and that has under floor heating (lower temperature). The extension is built to Passive House standards, so needs very little heat (although we have chosen to keep it warmer than we used to have the main house so it is very cosy, and reduced the temperature of the main house, so the Passive House extension does use some heat).


We have also added more thermal solar panels dedicated to heating the swimming pool. The swimming pool filtration circuit can now pass the water through a) the dedicated solar panels then optionally b) through the Thermal Store heat exchanger (either taking heat from the thermal store, if there is some spare, or I light the boiler at the same time). In practice the Solar Panels are sufficient except for the very start / end of the swimming season (for us that is late March to early November - which is probably 4 - 6 weeks longer than would be normal for a pool in this area without serious commitment :) )


For Winter Heating we evolved a method that suits us over the first couple of years. We found that lighting the boiler in early afternoon, which then ran for about 6 - 7 hours on a "batch", heated the house nicely in the evening. The boiler stopped at about the time we went to bed, which seemed ideal. There would then be enough heat in the thermal store for the morning heating run (before we get up), and any "boost" in the morning if it was cold (I work from home). In the afternoon we would load the boiler between half-and-fully-full depending on how low the store temperature had fallen. Below 40C / 105F it then has no "guts" for heating the house via radiators; in practice in the UK the day temperature in Winter is 5C and night temperature 0C, so with a reasonably sunny day there isn't a need for much top-up heat until afternoon / early evening. Of course we also get Arctic conditions at times (we get -10C to -15C for perhaps a week's duration about once a decade) and on those occasions we light the boiler in the morning, and top-up the "burn" during the afternoon, but it is rare to need to do that - mild winters not at all, average winters maybe 5 days of the year, cold winters maybe 10 days. In mild winters we get away with a full-load every-other-day, as we do in Autumn / Spring (maybe only having a burn 1-in-3 days in early Autumn / late Spring).


We found control using convention thermostats wasn't getting us what we wanted. Thermostats wanted to heat the house when the temperature fell below X-degrees, but that might compromise the Thermal Store if its temperature was getting low. OTOH if we put too much wood in the boiler the house would heat up in the evening, the thermostat would cut off, the thermal store would heat up and, at around 85-90C / 185-195F the boiler would damp-down, and we'd just smoulder the remainder of the fuel "wasting it".


So we changed the controls so that we now have a "forced central heating on" timer. If the Thermal Store is down to 40C we load the boiler full, and force the central heating on for 6 hours. That will heat the house well, in 6 hours, and leave the thermal store at Max just as the fire goes out - if we judge it right! (if not I can just put the central heating on for another hour to lower the Thermal Store temperature and then the boiler fan will resume). If the Thermal Store is nearer to 60C then we half-load the boiler and set the force central heating timer to 4 hours.


If, by this means, we heat the house hotter, in an evening, than the old thermostat setting would have allowed, then we go to bed one or two degrees warmer, and wake up with less heating required in the morning (house has very little air leakage [about 2-3 ACH @ 50 pascals, or whatever the test is!] and reasonable insulation + double glazing). The house has concrete 1st floor and flat roof, since augmented by pitched roof and lots of "loft insulation". In the Passive House Extension all the internal walls are dense blocks, so the thermal-mass of the building is very high indeed, and thus over-heating the house is "slow" and stored well by the building's fabric. I guess this approach won't work for everyone :cool:


The Solar Thermal for the Pool doesn't need to heat the pool in winter (and I regard it as a waste running the filtration pump just to dump solar heat), so we have a bare pipe around the Conservatory as a heat dump. It gives off very little heat in Winter (but it is not good for the Solar Panels to overheat), and we just switch the plumbing over to heating the conservatory in winter, and turn the Pool Pump "solar switch" off. I have some plants in the Conservatory and they are happy with any boost heat they get.


In case of interest the full installation details are on a UK Forum:

http://www.navitron.org.uk/forum/index.php/topic,5875.0.html
 
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Some photos:

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First Light :)

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What 5 tons of almost boiling water looks like on a cold January day when flushing the pipes :)

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Left to right:
Boiler
Secondary / Primary Thermal Store (at the back)
2x (red) expansion vessels

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Flow directions (Solar Coils were not plumbed at that time)

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Fuel Delivery :)

img_2368_logbarn-jpg.171442.jpg

Log store barn (prevailing wind is from the opening, behind camera, and about 30-degrees off to the right, which angles the air flow through the length of the stacks)

Oh ... forgot to mention in my earlier post. I bought a couple of handfuls of 1-Wire temperature sensors and hooked them up using a BUS wiring structure, and used them to monitor temperatures up and down the thermal stores, and at various flow & return points on pipes. Found them invaluable in the early stages (and cheap), locating things like within-one-pipe thermal siphoning, valves coming on in the middle of the night for no good reason, and so on. They've gone into retirement at the moment (a bit too "boy's own" for longer term usage), but I could really do with a new, better, system that allows monitoring of lots of temperature points (around the house and greenhouse, let alone around the boiler) so I'm on the lookout for something suitable, and cheap-ish.

index.php?action=dlattach;topic=5875.0;attach=2407;image.jpg
 
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Nice looking system! Welcome to the Hearth, we all enjoy seeing how wood is used for fuel around the world.

BTW: what species of trees are being delivered in the picture? Looks like what we call American Beech.

TS
 
Looks like what we call American Beech.

Not sure what American Beech translates into over here :) and not sure what that wood was either, but we mostly burn Chestnut (and I don't know which variety that is either, but I presume it is Sweet Chestnut - Castanea sativa - rather than Horse Chestnut - Aesculus hippocastanum) Castanea is in the Fagaceae family, which also includes (what we call!) Beech, and also Oak ...

We have burnt some Pine (mixed with hardwood, such as Chestnut) as sometimes my supplier says he can't find a hardwood. I think he's bored of trying to tell me that now, so perhaps that was just a Newbie thing to shift the pine! He tries to tell me that Pine is cheaper ... but ... it burns quicker, and I reckon overall we get less heat (maybe more goes up the chimney?) so that means buy more, split more, cart more and, on really cold days, have to make more actual fires so, for me, the highest calorific wood is the best value because it reduces work.
 
You'd get overall less heat out of the pine because it weighs less (assuming both are dried the same amount). So less BTUs per given volume. But it still might be good value if the higher calorific wood is significantly more expensive.

Very interesting project! Looks a bit complicated, but that's what some say when seeing mine, and I think mine is pretty simple. :)
 
I'm going to have to read the first post 5 time before I begin to understand!

Interesting to me where the barometric damper is located. It seems that most installs here are located near the boiler. I would think farther from the boiler, like yours, would be less dusty, at the least.
 
Looks a bit complicated, but that's what some say when seeing mine, and I think mine is pretty simple.

Me too. I have no difficulty explaining what pipe does what to anyone who is interested enough to ask, without having to get all Geeky about it ...

Interesting to me where the barometric damper is located.

I found reading your Boiler Install thread fascinating :)

From this picture (in the UK Forum thread I linked to) perhaps?

index.php?action=dlattach;topic=5875.0;attach=2338;image.jpg

Since we have moved boiler inside house envelope there is lots of dust within boiler room. Trying to think of a way to "Vacuum" this up once in a while - but it sits on top of pipe insulation etc. so is fiddly to "collect". Alternative would be to quarantine the boiler, itself, in its own room, to contain all dust there, but we don't really have enough space to achieve that. I presume it is mainly clearing out the ash which is causing the dust.
 
How is the availabilty of the wood and what is the cost over there?

Can only speak for myself, dunno about rest of UK: I found a Forestry Management Guy. He looks after woodland for lots of different people, I suppose you'd call him a "consultant". He also seems to arrange for felling / disposal for these clients, so I have become one of his clients. Each year he includes me in his list of people needing wood, and juggles who-gets-what. His clients who sell firewood take many, many, loads, so one less to allow me to have a load seems to fit his planning system, thus he tries to arrange a load for me that is as near as possible, thus reducing haulage cost.

From memory I am paying GBP 1,000 p.a. for about 18 tonnes (green) of forestry logs. That is delivered, and I think about 30%-40% of the total cost is haulage. Since installation the price of Oil, based on my previous usage, would now be around GBP 6,000 p.a.

I work on the basis of having the barn full (it stores a little over 2 years requirement) at the start of the heating season, and also a year's-worth of logs delivered and sat outside. During the winter the new logs are cut, split and stacked - in the space made vacant as seasoned wood is used in the boiler. Wood splitting takes my "Oddjob" man about 5-10 days and, other than some painting, other Winter jobs are far fewer than Summer jobs, so it fits his work schedule well. I have a small farm tractor log splitter which runs a cone-shaped screw off the PTO (rather than hydraulic, as I never found anything hydraulic [and affordable for my log volume] that had a fast reset-speed for the splitter, whereas with the cone you can just put logs on it as fast as you like as there is no recover time once a log is split. It would be unforgiving though, if you lost concentration whilst using it).

And must be nice to have no smoke rolling out with the primary door open. Negative draft I presume?

There is a "bypass" lever. That causes the combustion chamber to connect direct to the flue, instead of through the gasification re-burn chamber. If there is a need to open the loading door, during a burn, it is essential to pull that lever first, to stop the fire coming out of the door! but it also helps to get a direct draught during lighting.

Lighting procedure has changed since Day One when we did it by the book, which said something like:
  • Cover base with cardboard from an old box (to cover the gaps in the floor which draw gas downwards into secondary combustion chamber)
  • Load with kindling / small wood for lighting
  • Make a fire
  • Load logs on top
The combustion chamber is 1 Metre / 39" deep. Its hard to get logs in there over the top of a roaring fire!

New, evolved, procedure is:
  • Cut logs to 1/2 Metre, instead of 1 Metre, and load the combustion chamber back-half-first, and then the front-half. Much easier to get the logs tightly stacked, and 1M logs were never perfectly straight!
  • Start by fully loading logs into the back half of the boiler
  • Lay one layer of logs at the front
  • Cover with small sticks / bark (that has fallen off the logs and can be swept off the log store floor :) )
  • Cover that with a generous handful of shredded paper (we have lots of confidential paper from the office)
  • Light the paper and immediately release the flue-handle. The fire in the paper is drawn, downwards, through the sticks / bark, and then down through the single layer of logs. Push the door "to" to increase the draught.
  • After a short while, to allow the logs to "catch", pull out the handle (to prevent smoking into the room), open the door, fully load the front half of the boiler (on top of the fire).
  • If the fire is slow to "catch" then pull the handle out so that the fire is drawn through the logs in the back-half. However, we find this increases flue temperature very quickly (usually before the logs have "caught") and that causes the Max flue temperature sensor to "trip" and the fan goes off, smoke comes into the room, and red lights start flashing and alarm bells ringing - I presume that's not good for the equipment!
  • The other thing I find is that if the fire is slow to catch I can both a) pull out the flue handle and b) open the bottom chamber door intermittently. Having zero draught thought the bottom means that any fire in the top chamber burns flames directly upwards; those flames die down quickly (pls note that the fire is, at this stage, "weak"). But they tend to cause some bark on the logs above to "catch". The re-closing the bottom door creates a strong downward draught, whatever sparks have ignited start to glow strongly, and then re-opening the bottom door will cause another burst of naked flames, A few repeats of that cycle causes enough wood to be ignited that the whole load then catches quickly.
We find that there is usually some unburnt "charcoal", so this is raked to the front / separated from the ash (when the ash is emptied, about once a week), and becomes part of the easily combustible materials at the front of the boiler which is easily lit by the starter-fire and the downward-draught.
 
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I was thinking of this pic

Ah, OK. In that case I'm not sure that, from this side of the pond :), I've understood your earlier comment:

"Interesting to me where the barometric damper is located. It seems that most installs here are located near the boiler. I would think farther from the boiler, like yours, would be less dusty, at the least."
 
I think I just initially misunderstood your reply. Your is farther away from the boiler than ours. That's all I meant.
 
Wow, nice setup....I will go back and read the OP, I went right to the pictures...just like the old school days..LOL
 
Oh ... forgot to mention in my earlier post. I bought a couple of handfuls of 1-Wire temperature sensors and hooked them up using a BUS wiring structure, and used them to monitor temperatures up and down the thermal stores, and at various flow & return points on pipes. Found them invaluable in the early stages (and cheap), locating things like within-one-pipe thermal siphoning, valves coming on in the middle of the night for no good reason, and so on. They've gone into retirement at the moment (a bit too "boy's own" for longer term usage), but I could really do with a new, better, system that allows monitoring of lots of temperature points (around the house and greenhouse, let alone around the boiler) so I'm on the lookout for something suitable, and cheap-ish.

I use the Vesta system for monitoring and control... I dont know what cheap is to you
after checking all those pics of your expensive system.. check it out http://96.54.66.117/public/huff.html
 
You'd get overall less heat out of the pine because it weighs less (assuming both are dried the same amount). So less BTUs per given volume. But it still might be good value if the higher calorific wood is significantly more expensive.

Very interesting project! Looks a bit complicated, but that's what some say when seeing mine, and I think mine is pretty simple. :)
Here in the northeast you can get all of the pine you want for free, in most cases even delivered. I had a giant white pine get fried by lightening which needed to be taken down but they wanted a fortune to remove it. I told them to leave it and I would burn it. I found it incredibly difficult to split, so much so that when you factor in the extra splitting time, the extra splitting volume, all the extra work associated with larger volume to get the same weight/btu's I rather pay for a truckload of log length. Fortunately or unfortunately I always seem to find "free" wood. free is defined as need to go get it, sometimes cut it, load the trailer and unload it. When I factor in the value of my time, my wood gathering makes as much economic sense of many of the other things I am doing around my wood burning hobby.
 
I dont know what cheap is to you
after checking all those pics of your expensive system

I'm funny like that ... spend lots of money on good systems and then resent spending "that little bit extra" on an accessory that I think should be cheaper.

As I get older I get more like my Father, who's advice was always "The best quality is the cheapest" ... I now have several things, including my ski trousers!, that I bought decades ago that were best-quality, some, bt not all, of them very expensive at the time, and have saved me "buy-cheap, buy-twice" many times over.

Our house thermostats are a joke / case-in-point. We have Heatmiser thermostats in lots of rooms (including usually unheated rooms such as Conservatory). They are hooked up to some fancy Home Automation system, which overrules the Stats. I have no idea why I need to do it this way, the stats are probably GBP 50-100 each, whereas a simple temperature sensor (like 1-wire) is probably GBP 5. Then there is the Heatmiser motorised-valve controller (actually I think it heats some wax to control flow, rather than actually turning a motor). It works by associating a thermostat with a valve. There is no way (as far as I know) to control a valve directly. For example, we have two heating circuits in the conservatory (UFH and Radiator). I have plants in there during the winter, the UFH is used if we get cold weather, just to keep it at 5C / 40F, but on a cold night that won't be enough / have a fast enough response time. So we have a radiator too. What I want is if temperature is 5C bring on UFH, if it falls further to, say, 4C bring on radiator too. But I have to have two, separate, thermostats to achieve that. Daft. And whilst I'm having a moan I cannot download data usefully from Heatmiser. I bought their "Data Integration Package", its total rubbish. Have to hook up a USB device, and then download the data. I suppose that's OK, although I would prefer a Network IP address. It uses Round Robin for 31 days, sorted by 1-31 (not by today-to-oldest date). So on the 5th of the month you have 1-5 from this month and 6-31 from last month. Of course if it is 5th March then 6-28 is February and 29-31 is January. The download format is not a simple CSV where I could sort this all out in Excel / SQL, its a formatted output, so has to be pre-processed. For goodness sake! this is 2016, not 1850! AND it only logs to whole degree (but thermostats display to 0.1 degree). I am logging data from my Passive House extension, if we turn everything off and go away for the day I would be surprised if it loses more than 1C per day. So to detect when "heating demand" is requested is impossible, as there is only ever a 1C toggle, and the point at which it rises 1C may well be sun on the window, or heating that came on some time before that point. The logged data doesn't bother to include "calling for heat", just "current temperature". Useless. And it does not work at all now I have added Home Automation unit (can't deliver data to more than one source), and Home Automation has no Download of data, only on-screen APP graphs ... WTF?? :(

I'd like to just stick Cat-5 temperature sensors everywhere, and have a central control unit read the data and then "CONTROL" the valves.

We have Elan Home Automation which talks to the Heatmiser heating thermostats (all it does is set / change the temperature, and the thermostats then change the Valves), and it also talks to the Lutron lighting and some alarm system that I can't remember the name of. Its all fine, the other bits work really well, just the heating seems Stone Age by comparison.
 
As the old saying goes "Warm's you twice" ... or maybe five-times?!!
I am definitely in the 5+x category. As I sort out my woodshed and different areas to store wood I am hoping to cut it down to 3 - 4 x:).
 
I use the Vesta system for monitoring and control

First search on Google for "Vesta Temperature" didn't go well! I did lean that it is -4C in that part of Minnesota, and -123C on a "huge asteroid" of that name :). Second search didn't go much better - "Vesta Temperature monitoring" gave me companies in Vesta that providing monitoring equipment and services. Could some kind person give this poor old codger a helping hand pls? Thanks

EDIT: I've now seen it in Nofossil's sig: http://www.vecs.org/ :)
 
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First search on Google for "Vesta Temperature" didn't go well! I did lean that it is -4C in that part of Minnesota, and -123C on a "huge asteroid" of that name :). Second search didn't go much better - "Vesta Temperature monitoring" gave me companies in Vesta that providing monitoring equipment and services. Could some kind person give this poor old codger a helping hand pls? Thanks

EDIT: I've now seen it in Nofossil's sig: http://www.vecs.org/ :)

Try this link Kristen.. http://www.vecs.org/ if you have any questions message this guy
Nofossil he's the owner.

The vesta looks like a great match for your system in my opinion
 
Hi Kristen
Nice system.
Could you tell me what you were paying a liter for oil last year and what the price has come down too now?
Here in the Great White North last year was around $1.20 CD and now it is $.85 CD a liter.Last year our dollar was par with US,and now we are down to a $.70 CD to 1 UD
 
Could you tell me what you were paying a liter for oil last year and what the price has come down too now?

Sorry, can't help on that point as I'm pleased to say that I haven't used oil since 2009 :)

From this site

https://www.boilerjuice.com/heating-oil-prices/

looks like it is GBP 0.2851 / L at present, and was twice that in January 2014 ... Last year January 2015 was about GBP 0.40
 
oil-price-chart.png

This graph is supposed to be interactive, covering the last 5 years, but it might be that the forum will cache it ...
 
3.785 Litres per US Gallon ?

I make GBP 0.2851 = US$ 0.41 so, yes, US$ 1.55 a gallon.

Both Gasoline and Diesel over here are GBP 0.99 / L which is US$ 1.45 - so $ 5.49 per gallon - I'm guessing your vehicle fuel is cheaper at the pumps? :)

I *think* the only tax on Heating Oil here is VAT (Sales Tax) at 5%. Vehicle fuel has its own special tax, and then VAT / Sales tax of 20% is added on top of that, so my guess is we are paying around US$ 4.00 in tax per US gallon of Gasoline / Diesel
 
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