Sparer man pellets med Ack-Tank?

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Nemo
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Blev medlem: tor 30 jan, 2014 23:28

Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

Hello (feel free to answer in Swedish)

I´ve been thinking about this for a while and it seems that there is no clear answer. I know people with on/off pelletburners with and without ack-tank and the only thing there seems to be a given is that the number of starts are reduced relatively to the size of the ack-tank.

But does that necessarily mean that the consumption-levels of pellets drops?
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
FRS05
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Re: Sparer man pellets med Ack-Tank?

Inlägg av FRS05 »

It is better to avoid a ack-tank. The short summary is that there is more heat losses if you have more hot water.
Ulmapannan
Ulma 2000 TCA
Dragbegränsare
Mafa Midi
140m2 + 90m2, 1909, 22grader
Nemo
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Blev medlem: tor 30 jan, 2014 23:28

Re: Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

So basically only ack-tank if You have solar heating, brænder ved etc.

But what if the ack-tank stands in a place where the spild-värme is used, and not just lost?

We do agree that a burner start costs xtra pellets and thats why it is good to have few starts (and long heating/burning times for high efficiency)

Keep in mind I´m only talking about on/off pelletburners at a fixed kW-level (be it 8, 10, 15, 20, 30 etc).

Full-modulation burners are a different story in my opinion.
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
rod02
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Blev medlem: lör 20 dec, 2008 02:01

Re: Sparer man pellets med Ack-Tank?

Inlägg av rod02 »

I want ack-tank. When the system stopps it whould keep my house warm for longer. I have a boiler termometer in my bedroom. If it¨s ok, a ack-tank would keep my bedroom warm all night. Now it does´nt :-( . For ex if you forget to fill up the weekstorage. Poweroutage and so one. And my combinationboiler sometimes gets a few pieces of fire wood... And maybe it saves the electrical parts. Fewer starts saves electricity. And i rather waste pellets :-) .

Är det någon som förstår min engelska :-p ?
Egor duplomat D1F 1978 Pellx 2001 7.0 Tigex25 Bulkföråd Termomatic ERA
Nemo
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Blev medlem: tor 30 jan, 2014 23:28

Re: Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

sure - your english is fine :D - and you are welcome to reply in swedish as I read the language reasonably well.

My starts have been halved by the use of a buffertank, which allows me to delay my starts by 135 mins, and the burning time have increased from 25-40 mins to 60+ minutes. Roughly this adds up to 3-7 starts a day (from mid October to mid April). So as You say the electrical parts have an easier time, and the burning-efficiency must be better overall.

But I don´t think it saves pellets in any dicernable degree - or I am not sure.
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
rod02
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Blev medlem: lör 20 dec, 2008 02:01

Re: Sparer man pellets med Ack-Tank?

Inlägg av rod02 »

Jag har inte räknat på det, men tädelementet drar nog en hel del ström.

Om du vill skriva med en blandning av danska och svenska, så funkar det nog för de flesta här.
Egor duplomat D1F 1978 Pellx 2001 7.0 Tigex25 Bulkföråd Termomatic ERA
Nemo
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Blev medlem: tor 30 jan, 2014 23:28

Re: Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

I see the reduction in electricity use already (which actually allows me to keep the boiler shut down completely from mid April to mid October due to the extra electricity my solar cells generates. There is an 6kw El-patron/charger in the ack-tank and I have heatpipes for solarheating).

I can write in Danish but not in Swedish as I´m part English (I haven´t got the knack for it - sorry, but I can read the language).
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
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Honda
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Re: Sparer man pellets med Ack-Tank?

Inlägg av Honda »

Hello Nemo.

It's regarded as "common knowledge" around here that a buffer tank decreases the overall efficiency due to increased heat losses. I think it might be because of this white paper by Äfab: http://www.afabinfo.com/pdf_doc/rapport ... apport.pdf.

There is a lot to read there to make up your own mind, but here's a quote: "Trots ökade förluster menar vi att bra installerade- och isolerade ackumulatortankar på max 750 liters volym ändå ger fördelar som överväger ett verkningsgradstapp på några procentenheter. En ackumulatorvolym på 500- 750 liter är därför ett bra alternativ. I synnerhet då det även öppnar dörren för kombinationssystem med solvärme."

As a side note it's also regarded as common knowledge around here that on/off burners has a higher overall efficiency than fully modulating burners, and some people can't really be convinced that a fully modulating burner can work at all. It made me smile when I came across a thread on one of the danish forums (possibly about your 'strange foreign system' :D ) where the consensus seemed to be that on/off burners have lousy efficiency if they even work at all...

A main difference is that over here a "normal" boiler contains at least 150 liters or water and has integrated hot water production. This kind of boiler can easily run on/off all year around without excessively short burn cycles. Browsing the Danish forums it looks like a 'normal' boiler over there contains at most half of that water volume and hot water is always produced externally, which completely changes the requirements on the burner. NBE went the route of a fully modulating burner adjusting to the current power demand of the building while hot water is batch produced on demand with the boiler output diverted to the buffer tank by an electrically controlled valve. Looks to me like a much more complicated system, with possible higher efficiency when the power demand for heating is really low.

Could it be these differences in system design are mostly due to tradition? Or possibly optimized for a longer period with low or no heating demand? Maybe even different water quality is a factor, the integrated hot water production requires soft water to work well I think. I suppose it's always easiest to sell a system resembling what people are used to seeing.
Termax 25Cr med spaksotning, Bio Comfort + lambda + kompressorrengöring, 10m skorsten med 125mm insatsrör. 8t bulkförråd. Matene vertikalskruv. https://github.com/motoz/PellMon open source pelletlogger
Nemo
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Blev medlem: tor 30 jan, 2014 23:28

Re: Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

Honda I love your answer - thank you so much! :D

I been on a Danish forum but left it because I almost exclusively got grief and harsh words from my choice of heating system.

I saw the strength of the more straight forward on/off system early on, and when I opted for solar heating there was just no contest. There seems to be only a small group of danes that share my perspective. There is however still a minor market for the on/off approach as the Atmos with a25 burner (an Iwabo copy from the Czech Republic) as they can be purchased from roughly 22000 dkr and upwards, also with buffertank included in some instances. Some Swedish burners are here as well mostly Pellx, iwabo, bioline/ctc - but not many complete sets - boiler + burner. I agree with your thoughts about this being a cultural thing - NBE dominates the Danish market for sure (I doubt that there are much more than 40-45 liters of water in a scotte-boiler).

I appreciate the durability and the stability more than the prospect of saving perhaps 200kg pellets per season. And with solar heating the issue of buffer or not becomes a non issue - I suppose you could use large insulated plate exchangers instead of a larger waterstorage - but in my case it seems inconsequential, where the heatloss from the buffer is used by the room it stands in, and the buffer is only 300 liters.

The more complex NBE-burners also seem more prone to problems either with the increased complexity in the burner itself or the electronics - so basically it comes down to choice because the downside of on/off burners are the many ignitions.

In my world if you combine with solarheating (or heat pump, or wood or ..) it becomes a no-brainer even though combined heating systems are more complex than a stand alone system.

As a sidenote: I noticed the development of the Vølund/Nibe Pellux 100 - it seems to be a hybrid between the two systems. It has some of the sturdy Iwabo qualities, but it has a larger modulation capacity 5-19kW where it still show good efficiency. And then they went for the Polish fuzzy logic electronics third generation, and placed it directly in/on the boiler. I have heard both good and bad things about the latter.

once again thank you for responding, the link is brilliant. thanks!
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
Användarens profilbild
Honda
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Blev medlem: fre 14 jan, 2005 11:17
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Re: Sparer man pellets med Ack-Tank?

Inlägg av Honda »

Yep, the groupthink is strong on both sides of the pond... I have a biocomfort 'scotte' myself so over here I belong to the small minority with a strange foreign burner.

My boiler is a finnish termax 25 with a volume of 190 liters so I could run it completely on/off if I wanted to, but I do like that it runs continuously when it's below zero outside. That's the best quality of the nbe burner controller in my opinion, it's very flexible and you can adjust almost everything. Some would say that's a drawback I suppose, but I like it that way.

Before that I had a kmp PX20 (very similar to a PellX) for 10 years, which gave me lots of trouble. I think that the main reason was that my power demand was just more than it could handle, just because it says 20kW on the plate it apparently doesn't mean it can take 20kW continuously for long... With the new modulating burner I have about 5% lower pellet consumption, but since I also switched out the old boiler at the same time that does not really say anything much. Possibly one could say that at least there are no huge differences between running on/off or 100% modulating. The electricity cost for the ignitions are in any case completely negligible.

I googled 'denmark hard water' and it really seems to be a big problem in large parts of the country. That might explain why hot water production is mainly external to the boiler since a heat exchanger wouldn't last very long and the temperature needs to be kept as low as possible. And with an external hot water tank and a longer summer season I suppose it makes sense to keep the boiler volume down to minimize the waste heat left in the boiler when no heating is needed. Different needs, different solutions and everything has it's own set of drawbacks.
Termax 25Cr med spaksotning, Bio Comfort + lambda + kompressorrengöring, 10m skorsten med 125mm insatsrör. 8t bulkförråd. Matene vertikalskruv. https://github.com/motoz/PellMon open source pelletlogger
Nemo
Gallringsobjekt
Inlägg: 26
Blev medlem: tor 30 jan, 2014 23:28

Re: Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

You make som very good points. I never thought about the issue with 'hard water' but it makes sense that one adapts the technology to the surroundings.

Also I would like to clarify, just because NBE´s products isn´t something for me, they are still very good and very conservatively priced products (at least in Denmark). And no one can argue with the success the little company in Northern Jutland have had.
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
FRS05
Energiprofet!
Inlägg: 595
Blev medlem: mån 21 nov, 2011 17:08
Ort: Halmstad

Re: Sparer man pellets med Ack-Tank?

Inlägg av FRS05 »

A question off topic, but what are the price for pellets in Denmark? Interesting to know. :)
Ulmapannan
Ulma 2000 TCA
Dragbegränsare
Mafa Midi
140m2 + 90m2, 1909, 22grader
Nemo
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Inlägg: 26
Blev medlem: tor 30 jan, 2014 23:28

Re: Sparer man pellets med Ack-Tank?

Inlägg av Nemo »

well there are some variations according to season and where in Denmark You live. People closer to Germany often drive to get pellets from there, or even hire a larger truckload.

where I live, Northern Jutland, the price pr kg is roughly 1.7 to 2.4 kroner. Depending on season, and if you pick them up yourself or have them brought to you.

I have bought 3600kg high quality Tpi Supreme for this season for 1.97 dkr pr kg - they are kept in a larger storage hall but I am hauling them my self - 900kg at a time.
Regards from Nemo
Denmark (Northern Jutland)
Värmebaronens Pellmax UB w. Viking Bio 20
300l buffertank, 60 Heat Pipes, 6kw charger, external heat exchangers (Vvfs.dk)
6.5 kw Solarcells (Energetica)
132m2 + 10m2 cellar, 1952 brick house, partly modernized
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