2 Moisture testers - 2 different readings..sigh

[Woodworks]

Why? I sell logs, they are seasoned and burn just fine, I know this because I burn them on my burner and I have the chimney cleaned every year and there is very little spot or build up according to my sweep. People are brainwashed into moisture content, just like they are brainwashed into the soft wood is crap vibe.

 

Why because some customers want to know. Picked up a new customer last week purely because I guarantee it was all below 25% and mainly below 20% not that he checked. They are not expensive bits of kit and as far as I am concerned help with knowing what is dry and what needs a bit more time.

[openspaceman]

What did cave men do to test the moisture content or Henry the 8th?? Fire has been around for thousands of years, it's been used for cooking and heating since the dawn of time, long before any fancy moisture meters. People are getting brainwashed by stove company's and the likes.

 

I take your point and I burn wood of higher than ideal moisture content but there is little doubt that drier wood will more likely burn smokelessly.

 

My personal view is that there is not much advantage in burning wood that is below its fibre saturation point (25-30%) because getting dry to that level is easy. Drying below 20% is a bit pointless in my log pile as it soon picks the moisture up again.

 

The main thing for clean burning is to maintain a high enough combustion temperature for the products all to burn out cleanly, big or sophisticated burners will do this with 45% mc feedstock.

[Mike H]

Well, I have tried to do the tests and as the wood gets below 10% the meters start to agree! Above 10% there is no consistency or logic.

 

So I tried burning some wood which showed, when freshly split, 15% on the inside with the brennenstuhl moisture meter and 40% with the Stihl.... burns well with no hissing and lots of heat.

 

I think I will stick with the Brennenstuhl!

[Stubby]

 

I think I will stick with the Brennenstuhl!

 

And you thought I was joking when I suggested that 2nd post in ..... ........

[cornish wood burner]

Why because some customers want to know. Picked up a new customer last week purely because I guarantee it was all below 25% and mainly below 20% not that he checked. They are not expensive bits of kit and as far as I am concerned help with knowing what is dry and what needs a bit more time.

You new customer might have realised that he or she will get more heat (kWh) from 20% MC wood against the same volume of 30% MC.

There is no point buying wood then burning it to boil off excess moisture. Better to source guaranteed dry wood and the way to accurately check that is with a calibrated moisture meter.

[openspaceman]

You new customer might have realised that he or she will get more heat (kWh) from 20% MC wood against the same volume of 30% MC.

There is no point buying wood then burning it to boil off excess moisture. Better to source guaranteed dry wood and the way to accurately check that is with a calibrated moisture meter.

 

Ian you are right but the difference may not be as great as you think, IMO the bigger gain is in less pollution and smoke.

 

As I see it the sums are fairly simple for a first approximation and I note you did state by the same volume, and we'll assume no volume change from 30% to 20% which is stretching it a bit as that is the region when there is most shrinkage:

 

Take 1 kg hardwood log at 30% mc wwb, it contains 0.7kg of dry wood containing 3.617kWh of heat energy and 0.3kg of water that will be lost at chimney exit temperature with 0.225kWh wasted to atmosphere, net heat released to stove 3.39kWh

 

Take the same log and instead dry it to 20% mc wwb , now the amount of dry wood is the same 0.7kg with 3.617kWh of heat energy but the water vented up the chimney is now only 0.112 kg so you have more than halved the water in the wood and are now only wasting 0.084kWh up the chimney but the net energy released to stove is now 3.53kWh a net gain of 4% usable heat.

[cornish wood burner]

Ian you are right but the difference may not be as great as you think, IMO the bigger gain is in less pollution and smoke.

 

As I see it the sums are fairly simple for a first approximation and I note you did state by the same volume, and we'll assume no volume change from 30% to 20% which is stretching it a bit as that is the region when there is most shrinkage:

 

Take 1 kg hardwood log at 30% mc wwb, it contains 0.7kg of dry wood containing 3.617kWh of heat energy and 0.3kg of water that will be lost at chimney exit temperature with 0.225kWh wasted to atmosphere, net heat released to stove 3.39kWh

 

Take the same log and instead dry it to 20% mc wwb , now the amount of dry wood is the same 0.7kg with 3.617kWh of heat energy but the water vented up the chimney is now only 0.112 kg so you have more than halved the water in the wood and are now only wasting 0.084kWh up the chimney but the net energy released to stove is now 3.53kWh a net gain of 4% usable heat.

Usual to buy logs by volume I guess but the same calc would look a lot worse by

weight. I agree driving the water off is not a huge cost if burnt in a suitable appliance but how

about in an older inefficient appliance?

[openspaceman]

Usual to buy logs by volume I guess but the same calc would look a lot worse by

weight. I agree driving the water off is not a huge cost if burnt in a suitable appliance but how

about in an older inefficient appliance?

 

Pass but it's past you bedtime and the more significant thing will be excess air