Moisture content measurements - logs

[cornish wood burner]

Very interesting but if someone can't tell difference between a wet log and a dry log from looking at it and picking it up then they shouldn't be burning wood. Likewise if they can't organise their log shed accordingly.

 

Probably a fair comment but it should give a little more accurate comparison if you are interested. You do get a feel for moisture as you say but for many different species, hard and soft, a meter might confirm your guess.

I sometimes buy wood chip for our boilers so an accurate meter is essential for pricing chip of different mc. I reckon to be able to predict the reading within a few percent by a squeeze, but most suppliers would not be happy with that.

[openspaceman]

Dry in a slow oven 60 deg ish for 24 hours until the wood stops losing weight.

Divide the weight loss by the original weight and you have the moisture content as a normally used wet basis.

If you do this for a few different pieces then you will get an idea of your meters accuracy throughout the range.

 

Why only 60C Ian?

 

I dry at 120C for 24 hours, I don't think I lose significant mass in VOC.

[cornish wood burner]

Why only 60C Ian?

 

I dry at 120C for 24 hours, I don't think I lose significant mass in VOC.

True. Just me being a bit too conservative. I did put 80 originally but in reality I probably dry around 100. Unpleasant to hold for long when it comes out of the Rayburn but I'm not sure of that exact temperature.

[Scotty38]

I dry at 120C for 24 hours, I don't think I lose significant mass in VOC.

 

I totally understand what folk are trying to do here but you won't catch me leaving the oven on for 24 hours, that's a fact....

[openspaceman]

I totally understand what folk are trying to do here but you won't catch me leaving the oven on for 24 hours, that's a fact....

 

It's an experiment, not everyone needs to it just gives a more accurate result then measuring the changing resistance of the electrolyte as it becomes more concentrated.

 

 

 

With an electric oven the cost is not too high as the losses are only water leaving, losses through the sides and the air bleed used to cool the fan bearing. Back in the late nineties I had a plot of electricity in against moisture loss and there was a very good correlation of electricity input being a standing loss+0,75kWh per kg of water loss for a given temperature.. I guess it costs me about the same as a pint of beer to satisfy my curiosity.

 

I've run similar tests on the delonghi dehumidifier to see what it costs to condense a kg of water.

 

My 80 mile commute to work and back is my most significant use of energy which I regret more.

[Aunt Maud]

I think that there's a massive amount of worthwhile knowledge floating about on this firewood thread and if a chap wants to know, then they should have the right to be presented with the correct information by whoever has the knowledge.

 

That way, whoever it is doing the asking will react in a positive way and make the necessary adjustments to either their storage methods or firewood buying choices.

 

With all due respect and all that, being told that they shouldn't be firing with wood because of well......stuff, won't encourage them to get to grips with the issue and sort their storage and buying choices.

 

Just saying.

[openspaceman]

True. Just me being a bit too conservative. I did put 80 originally but in reality I probably dry around 100. Unpleasant to hold for long when it comes out of the Rayburn but I'm not sure of that exact temperature.

 

OK I understand, in your case the rayburn is on anyway so there is no extra cost in drying.

 

It's interesting that once the log is dry it can be handled at 120C as the thermal conductivity is low as well as its specific heat, so the initial heat at the surface is conducted away from the skin faster than it is replenished from the log.

 

Apparently the same is true if you dip your hand in liquid nitrogen but there's no way I'm trying that.

[SamWhiting12]

A big company near me that sells logs has put me off buying logs , after repeatedly selling me soft wood logs that are 28-32%, I cannot buy again...the logs took ages to get going and produced little heat.The ton load of wet logs I had lasted me longer than a ton of dry because of the crap fire it produced did not make me want to lite it so much, and the slow burn as it was so wet made it last...in other words if this company dryied there logs right then I would have ordered more ,burnt more,and they make more money.

It took me a few years of having bad logs before I got myself a moisture meter,and since then I now find my own wood.If I go to a forest I know ,where there are some trees on the ground that were felled only 8 months ago,chop it up and measure,its 23-28%,mostly Ash...So why the hell this company has 30% really winds me up, but they are always busy.

 

Give me a ring if you need seasoned logs, Nelson isn't to far away from us

[gdh]

Out of interest do those of you drying at high temperatures in 24 hours find it only dries the outside or have you got around that?

 

We had too many issues with drying that way so we've gone to the other extreme and dry at 30-35 degrees over 3-4 weeks.

 

And in reply to woodworks, on our own log burner we'll burn anything up to 30, we just stack it by the side first. 15 is what I would like but we still see it as a luxury.

[SamWhiting12]

Recently bought a cheapo £20 digitial meter from my chimney sweep. Seems to give reasonably consistent readings for any given split log. I've been measuring various h/w cut logs from freshly cut/split, to 'kiln' dried for a coupe of days beside the stove. Have the following observations:

 

Readings are usually higher measured on the ends of the log (often a lot higher) than on the sides, including when freshly split before measuring.

 

When measuring the sides, no significant difference across or parallel to the grain.

 

The bark invariable has very high readings usually >30%. Peeling off the bark often reveals visible dampness underneath.

 

Any comments appreciated - Happy New Year

 

With the amount of rain we have had, unless they are undercover, the outside of the log is going to much wetter than the inside. Get them undercover and in a windy place will be the best way to dry these for burning this year.

 

If you cover them up in a place that gets no wind then you wont dry the logs out in this weather. You will just end up growing mold.

 

Happy New Year