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Where to keep the temperture sensor in the solar kiln

Started by Tree Dan, July 26, 2015, 06:09:20 PM

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Tree Dan

Where is the best spot to place the remote sensor...In the shade near the bottm...In the Sun or the shade?

I hear some from the south getting up to 170 F...Is that in the shade or the sun?

Cheers
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

Ianab

I'd think you want the sensor sitting beside the stack of wood. It's the temperature that you get the wood to that matters most , not how hot the collector gets.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Tree Dan

Quote from: Ianab on July 26, 2015, 06:20:00 PM
I'd think you want the sensor sitting beside the stack of wood. It's the temperature that you get the wood to that matters most , not how hot the collector gets.

Thanks, I do have it sitting on a slab in the shade behind the black tarp.
It hit 112F max.  I dont think I will get even close to 170f in this neck of the woods.

I would just think that there would be more energy in the kiln to dry wood if the sun is in the kiln compared to no sun...but at the same temp.


Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

The answer to your question depends on why you want to know the temperature.  To impress people with how hot your kiln is, then put the sensor where it will see the sun.  If you want to know the temperature of the air just before it goes into the load of lumber, put it in a shady location where it will not get sun and where it will get good air flow on the entering air side of the load.  As the air goes through the load, it will cool off, so the exit side of the load will give you the coolest.  Of course, the best location would be not directly inline with a vent.

Ok?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

xlogger

I'm in the south but not deep south. I just got my thermo hygrometer put in Sunday and put it over the wood not in the sun. The high temp so far was right under 120°. I was surprise more in the late afternoon that the temp stays up near 100° even after the sun sets behind the west trees for awhile. My RH is running between 40-50 not sure if that is where it should be? Ricky
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

Ianab

Sounds sensible sort of numbers.

The kiln stayed warm because you have a big stack of wood in there that had heated up to ~100F during the day. It will take hours for that mass to cool off again. The ~50% humidity means the warm wood is able to release moisture to the air, and the water hence escapes through the vents.  Over night the temp will drop, the humidity will go up, and the wood will naturally "recondition", which avoids most of the problems you may get from drying too fast.

Next day, you get another heat and vent cycle to get more moisture out.   Repeat until the wood is dry.

As the wood dries you will probably get higher temps and lower humidity as you aren't vaporising as much water, but almost dry wood is much more forgiving to heat and low humidity.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Tree Dan

I have also noticed the temps up high in the kiln at 8pm
That explains it...the mass in the kiln.

The hottest time of the day these days seems to be around 4 in the afternoon around here.

The wood is drying thats for sure.
We have a heat wave 90F outside :o
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

For fairly wet wood, a solar kiln operating at 50% RH is a bit low. This low RH indicates that the wood is not drying vary fast (or else the RH would be higher) or that there is too much venting.  When first starting out, we generally like more heat and that means a little bit higher RH.  For pine and other softwoods, 65% RH is a good initial value to target.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

xlogger

So on the RH being in the 40-50% range, all wood in kiln is in the low teens on moisture. Would that be in the range?
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

GeneWengert-WoodDoc

At 50% RH, the wood will eventually dry to 9% MC.  So, the air has an EMC of 9% EMC.

At 30% RH, 6% EMC.

At 65% RH, 12% EMC.

Ok?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Tree Dan

My stack of 8/4 Maple is at 12% now, and it dosent seem to get any lower.
The RH has been low in the kiln around 30%....I may put another meter in the kiln and make sure the #s match...like the temps and the Rh.

I also have some 4/4 in the kiln but not sure of the MC ...Im wired up to the 8/4 slab.

Im tempted to pull some of this wood out and use it for a coffee table.

Being up north im not getting the same amout of energy in the kiln as my friends on here from the states.
Maybe I need to run a part time dehumidifier...
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

Solar kiln?  Running the fans 24/7 ?  If so, you will average 12% EMC.  Run the fans only when the kiln is warmed from the sun...about 9AM to 8 PM.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Tree Dan

Quote from: GeneWengert-WoodDoc on August 07, 2015, 06:22:42 AM
Solar kiln?  Running the fans 24/7 ?  If so, you will average 12% EMC.  Run the fans only when the kiln is warmed from the sun...about 9AM to 8 PM.

The fans are not running all the time, they come on a 10am and shut down at 8pm.

My point is running a kiln in the mid or south US compared to Ontario Canada.

Im thinking it may need a bit of help with a D-H.
Its August now.
I know I just got the kiln running will I just get 1 load done this season?
or do I pull this load out at 12% and start the next load?
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

You should not have it stop at 12% MC as you do shut off the fans and your measured RH is low.  A DH will not get much lower than 30% RH anyway.  Are the vents 99% closed, in order to maximize the heat?  Are you certain about the MC measurement?  This could be the reason that you have the indicated high MC.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Tree Dan

Quote from: GeneWengert-WoodDoc on August 07, 2015, 09:38:25 PM
You should not have it stop at 12% MC as you do shut off the fans and your measured RH is low.  A DH will not get much lower than 30% RH anyway.  Are the vents 99% closed, in order to maximize the heat?  Are you certain about the MC measurement?  This could be the reason that you have the indicated high MC.

Good point about not getting any lower RH with a DH.
Most of this load has beed running with the vents closed, and the odd time with the vents cracked open about a inch.
I have 2 nails driven into a 2" slab  1" deep
I have a wire coming off each nail to 2 screws outside the kiln.
I then contact the moisture meter probes to the 2 screws,
This is how I get my MC.
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

Question:  where does the moisture from the lumber go if the vents are closed?

Note that 12% MC means 65% RH.  Yet, you indicate the RH is lower, so the RH and the MC do not agree.  I suspect it is your moisture measurement.  The moisture measured with the moisture meter is really the electrical resistance.  The resistance is really high.  It is possible that the insulation in the wires is not good enough and so you are measuring that resistance rather than the wood's resistance.  Can you measure the moisture with the meter and its probe, with insulated needles?  Drive the needles 1/4 of the thickness.  Also, what reading do you get if you disconnect one of the wires from the screw?  Finally, The MC in the early morning is probably quite high, as the kiln has high humidity then.  So, the screws are measuring the highest MC anywhere along their length and not just at the core or the average along their length.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Tree Dan

Quote from: GeneWengert-WoodDoc on August 09, 2015, 05:32:11 AM
Question:  where does the moisture from the lumber go if the vents are closed?

Note that 12% MC means 65% RH.  Yet, you indicate the RH is lower, so the RH and the MC do not agree.  I suspect it is your moisture measurement.  The moisture measured with the moisture meter is really the electrical resistance.  The resistance is really high.  It is possible that the insulation in the wires is not good enough and so you are measuring that resistance rather than the wood's resistance.  Can you measure the moisture with the meter and its probe, with insulated needles?  Drive the needles 1/4 of the thickness.  Also, what reading do you get if you disconnect one of the wires from the screw?  Finally, The MC in the early morning is probably quite high, as the kiln has high humidity then.  So, the screws are measuring the highest MC anywhere along their length and not just at the core or the average along their length.

Answer: Most of the moisture will stay in the kiln, but some will leak through the kiln.

Its 11.am
MC Reading on the 2 screws outside the kiln 12.8%
MC Reading with 1 wire off the driven nail in the slab and meter probes on the 2 screws outside the kiln 12.4%
MC Reading taking from inside the kiln by 1 meter probe on 1 driven nail, the other on 2" of wire from the nail 8.2%

New indicator in the kiln reads 81F and 46% RH
Old Remote Indicator reads 77F and 55RH

I will take a set of readings late in the after noon
Vents are all open 6"

Thanks for the help!

If the meter is measuring resistance, the distance between the 2 nails...or the 2 probes is important ?
The further apart the nails are the more resistance there will be , and indicating a lower MC ...am I correct on this?
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

beenthere

The meter reads your resistance, but you likely need to calibrate that reading to some known moisture contents for various species, as the moisture along with density of the wood (along with distance between pins) will affect the meter reading... I'm thinking.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

LeeB

Temperature of the wood also factors in there somewhere. I believe most meters are calibrated for 70°. Se if you can find a calibration chart for your meter. Other than that I know nothing about kiln drying.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Tree Dan

Thanks guys,
Here's my readings at 5pm.

Remote thermometer reading 99F and 27%RH.
New in the kiln thermometer reads 101F and 24%RH

I bent the driven nails inward so I could take a reading from my moisture meter and I got 10.7 MC.

I then hooked up the wires witch are solid 18gauge x 4 feet long
to the outside screws, my reading on the screws are now 11.1

The meter that I'm using is a General.

Dan
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

I do believe you have wire issues and also perhaps meter issues.  If you can disconnect the wire from the screws or nails and still get a reading, your wires have a short in them...poor insulation between them.  With the wires off, you should read zero, unless the wires are shorted, or perhaps a better term is "leaking."  Step 1 is to get highly insulated wires from a company that sells MC meters and the remote probes. 

As we believe you thermometers, you could also put two wires in a thin piece of wood and then use that reading of MC to give you the EMC.  Is the EMC measured in agreement with the thermometer and humidity reading?  Do this at several different conditions.

One other test is to try your meter when it is not in the wood but it is just in the air.  You should get zero. 

We do know that a 22 megohms resistor will give 12% MC for any meter.  So,  buy one and then use this to calibrate the meter- - the the resistor on the meter and then at the end of the wires.  But if you can get a reading from the wires when not connected to a nail or screw, then the resistance between the wires is not high enough...it is low enough to indicate a MC.  You need the two wires to either be separated or to be very high resistance.

The spacing between the nails is not real critical.  In fact it is the resistance right around the pin that is critical.  In fact, you can cut a groove between the pins and it will not affect the reading.  However, calibration is based on 2-1/16" I believe.  Do not leave the meter on, as electrolysis occurs.  Take the initial reading and do not wait for the meter to drift.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Tree Dan

Quote from: GeneWengert-WoodDoc on August 09, 2015, 06:20:56 PM
I do believe you have wire issues and also perhaps meter issues.  If you can disconnect the wire from the screws or nails and still get a reading, your wires have a short in them...poor insulation between them.  With the wires off, you should read zero, unless the wires are shorted, or perhaps a better term is "leaking."  Step 1 is to get highly insulated wires from a company that sells MC meters and the remote probes. 

As we believe you thermometers, you could also put two wires in a thin piece of wood and then use that reading of MC to give you the EMC.  Is the EMC measured in agreement with the thermometer and humidity reading?  Do this at several different conditions.

One other test is to try your meter when it is not in the wood but it is just in the air.  You should get zero. 

We do know that a 22 megohms resistor will give 12% MC for any meter.  So,  buy one and then use this to calibrate the meter- - the the resistor on the meter and then at the end of the wires.  But if you can get a reading from the wires when not connected to a nail or screw, then the resistance between the wires is not high enough...it is low enough to indicate a MC.  You need the two wires to either be separated or to be very high resistance.

The spacing between the nails is not real critical.  In fact it is the resistance right around the pin that is critical.  In fact, you can cut a groove between the pins and it will not affect the reading.  However, calibration is based on 2-1/16" I believe.  Do not leave the meter on, as electrolysis occurs.  Take the initial reading and do not wait for the meter to drift.

Thanks Gene,
Yes the meter and wire setup that I have going here is not the best and should be upgraded.
These General Moisture meters are sold for around 35 bucks
I do hear good reviews about the Delmhorst 2000 with the slide hammer.
When I got a reading this am ,It was with just 1 wire off the nail.
Perhaps the lose wire was touching the wood, but with the wires off the meter yes I get a 0 MC reading.
Dry wood around here is between 7% and 11% depending on the time of year.
The load of wood has been in the kiln now for close to 5 weeks,
and was milled in and around Dec to Feb and stickered then air dryed in the dome(Coverall)
There has never been any raining efect inside the kiln due to high moisture content from the start.
Im thinking the wood is ready to come out of the kiln now or very soon.
Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

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