Cordwood wanted Somerset

[mendiplogs]

Hi Jon

 

Sounds to me like they are burning wood above 20% moisture content. The more moisture in the wood the less heat comes out. That is the golden rule, get moisture to 20% or below. If the moisture is at the correct level then 100 tonnes will give 400, 000 kwh of heat which is the equivalent of 40, 000 litres of heating oil. This woild heat around 10 large detached family houses. Unless their house is huge it sounds like heat is being lost somewhere either through under ground pipe work or burning the water from un seasoned wood.

 

I know of a similar situation where they were burning about 10 times the expected volume of chip and it turned out to be deteriorated under ground insulation of the heat main and they effectively had underfloor heating in the field!

HI MATE there not it all barn dry hard wood the chaps who fitted the log boiler fitted 2x45kw for there place it a very old house mate in the winter the stoves will not keep up it all good hard less then 20% mos let me tell there place is larger then 10 large detached family house and the chip one i no of is to but it better on chip im told when your running a stove of 2 x 45kw thanks jon

[st135r]

There's your answer John.

 

Running 2 x 45 kw log boiler will only cope with about 600m2 of floor area, about 2 large detached houses. Unless they are running 24/7 then they may cope with 6 if well insulated.

 

You are dead right, a chip would've been a much better bet. Also a lot more convenient and automated.

 

Cheers

[mendiplogs]

There's your answer John.

 

Running 2 x 45 kw log boiler will only cope with about 600m2 of floor area, about 2 large detached houses. Unless they are running 24/7 then they may cope with 6 if well insulated.

 

You are dead right, a chip would've been a much better bet. Also a lot more convenient and automated.

 

Cheers

 

HI MATE it very house there it can not keep it a very old house to so not good insulated place a chip boiler im told would of been better they have job to keep up to and they have all kit they need to and a very large wood to all with good hard in and it well seasoned to thanks god only no,s what there going to do when that run out they use 100 of tons per year thanks jon

[st135r]

You're absolutely right, chip would've been more suited.

[mikeyne]

I'm in a similar situation but we have been running our boiler now for 3 months. Reading the thread is interesting as I'm living and breathing the heat calculations and seeing what reality is like versus expectations. Bottom line, you will not get 4kwh per kg of dry wood even if you have it at 20% moisture.

 

We are burning 2 year really well seasoned hardwood which is measuring anything between 16 to 20% moisture. The tested efficiency of the boiler is 90% plus, but this will be in laboratory conditions.

 

The actual tested efficiency of our boiler in a real life burn at it's hottest part of the burn was 85.7%. At the start of a burn and the end, the efficiency will be a bit lower. Then you have losses in the pipework between the boiler and the thermal store which even being super lagged will exist.

 

We manage to achieve anything between 2.7 kWh to 3.0 kWh per kg so the reality is 75% efficiency when you talk about the useful heat you actually get into the thermal store.

 

I'm curious why you have gone for such a large store for a 45kw boiler though? We have a 60kw boiler and a 3000 litre tank which work really well together.

 

I was expecting to get 4 kWh per kg when I was planning the system so the real life result is quite different, but really happy with the installation! The house is toasty warm and not a drop of oil being burned. Takes a bit of work keeping the wood pile filled up but I need something to keep me fit!

[mendiplogs]

I'm in a similar situation but we have been running our boiler now for 3 months. Reading the thread is interesting as I'm living and breathing the heat calculations and seeing what reality is like versus expectations. Bottom line, you will not get 4kwh per kg of dry wood even if you have it at 20% moisture.

 

We are burning 2 year really well seasoned hardwood which is measuring anything between 16 to 20% moisture. The tested efficiency of the boiler is 90% plus, but this will be in laboratory conditions.

 

The actual tested efficiency of our boiler in a real life burn at it's hottest part of the burn was 85.7%. At the start of a burn and the end, the efficiency will be a bit lower. Then you have losses in the pipework between the boiler and the thermal store which even being super lagged will exist.

 

We manage to achieve anything between 2.7 kWh to 3.0 kWh per kg so the reality is 75% efficiency when you talk about the useful heat you actually get into the thermal store.

 

I'm curious why you have gone for such a large store for a 45kw boiler though? We have a 60kw boiler and a 3000 litre tank which work really well together.

 

I was expecting to get 4 kWh per kg when I was planning the system so the real life result is quite different, but really happy with the installation! The house is toasty warm and not a drop of oil being burned. Takes a bit of work keeping the wood pile filled up but I need something to keep me fit!

 

HI MATE can i ask how large the house is for 60kw boiler thanks jon

[mikeyne]

Hi Jon, I've never accurately measured it, but it's going to be around 250 square meters. There is also an external building of around 100 square meters that is also coming off the same heat store so around 350 square meters in total.

 

When we were sizing the installation we looked at the 45kw model but it just seemed a little too risky. Now that we've been using it for a few months it feels bang on right, 45kw would have struggled.

[mendiplogs]

Hi Jon, I've never accurately measured it, but it's going to be around 250 square meters. There is also an external building of around 100 square meters that is also coming off the same heat store so around 350 square meters in total.

 

When we were sizing the installation we looked at the 45kw model but it just seemed a little too risky. Now that we've been using it for a few months it feels bang on right, 45kw would have struggled.

 

HI MIKE what going near me mate, with the 2x45kw if you seen the house you would :lol::lol:at it mate i fell sorry the chap having to loading the boiler it like this :banghead::banghead::banghead::banghead:just waste of good hard as it not keeping up thanks jon

[st135r]

Mikeyne

 

Great to hear the positive experience you are having with your boiler. 3kw soujds about right for the useful heat per kg of wood and good to hear no oil being used.

 

When sizing an accumulator, the calculation is fuel chamber volume in litres x 13. This will give minimum size required. The larger the accumulator however, the more flexibility you have with the use of the boiler. This is because the loading valves fitted to the system mean that the accumulator is heated from the top down, so the more cold water you have below the useful hot water, the more scope there is to store the heat generated from a full burn at full rate. It will prevent the boiler modulating down and losing efficiency and potentially extend or decrease the time between burns.

 

It sounds like your system is perfectly suited to your house and your use of the system as you are probably using some of the heat that is being pruduced during a burn as wel, as the accumulator being loaded.

 

Kw rating of log boilers is almost irrelegant to some extent, the key to sizing a system is the fuel chamber volume. Depending o what boiler you have, you mag find the fuel chamber is 250 litres which match your 3000 ltr tank. Some manufacturers will say you don't need an accumulator at all to run it. Well, it will work but efficiency will suffer massively.

 

It will be interesting to compare wood usage to oil usage over a year. Really pleased to hear such positive log boiler stories.

[hardtop110]

I've got a 20kw Stratford boiler stove mated to a dinky 300l thermal store via a laddomat load charger. The thermal store also takes oil and solar thermal feeds too and delivers heating and how throughout the house using conventional rads. We used 300l of oil last year (for when I was away working) and about 10 cube of logs which I process myself.

Sort of a middle ground between Genset Steve and full log gasification setup. Oh and its a 4 bed detached with me working from home so using heating during the day.

Edited December 12, 2013 by hardtop110