What to do when wet bulb reading is too low to kick on compressor?

[TBrown99]

Okay, I spoke with Stan. 

The big message is that below 25% moisture, you can't damage the lumber by more aggressive drying. So, instead of the "raise temp to 140" approach, it will be good to adjust WB lower and heat higher (but be mindful that the compressor may cut near 130 which would require manual switch reset). 

So, here's goes... 

Will catch up further later on...

[doc henderson]

Nice.  keep us in the loop!  thanks.

[TBrown99]

I pinned moisture levels two days ago after seeing no drip flow after tweaking the DB higher to 125 & WB down to 80 per Stan's advice.

The single 1" board was dry (below 8) but the 9/4 were still often in high teens. (So, after 4 days...) I was expecting to see lower numbers. (Everything else is 9/4)

After 24 hours, no sign of moisture. Therefore, I reset to "boil it out" for half a day reaching 138 degrees for several hours. (Last time Stan advised 2 full days.). I let the temp come down expecting to see moisture once compressor came on. Nothing.

Moisture levels on my Govee sensors are getting quite low 11.4% now at 120 db.

So, I was at a loss as to what to try next. I decided to just let it go at 120/80 for several more days. Full air flow.

What's happening then is the exhaust fan is kicking on in 12-20 minute heating cycles from the L53 box controls. So, moisture is exiting. But this isn't how I was expecting this to work. And I'm not sure if that's a bad scenario.

Perhaps I should have done a 48 hr "boil it" try. But I don't sleep as well at night when the room is maxing out temperature, though it's probably in irrational concern.

I still need to work on sealing the unit and adding insulation from 13 r to 30 r.

My basic feeling is that I just need to give it a bit more time. 4 days is probably too short.

Thanks

[doc henderson]

so, you have varying thickness of wood in the kiln.  is that what accounts for the range of MC.  are they all the same species?  If you drop the DB to 80 the RH will go up, and you might condense water, but that would serve to further lower the RH in the kiln when the temp goes back up.  can you check the wood with a pin less to see what it reads.  very frustrating and interesting problem.  

[doc henderson]

so, is the moisture content still decreasing each day?  what is your target.  I am sorry if you already said.  I am remembering parts of this thread with an oak thread.

[TBrown99]

No, I only had one test piece of 1" basswood in this charge. Everything else is 9/4, mostly basswood, some pine & poplar.

I took the poplar out because it could stand more air drying. (It was serving mainly to hold plywood top.)

I removed the top.

I'll check levels maybe tonight. RH by my Govee sensor continues to fall, 10.5 now.

My target is 7-8.

[doc henderson]

If it continues to drop at a decent rate, you may be losing enough moisture to keep going.

[TBrown99]

I shut off the aux heat last night and temp fell from 120 to 115 overnight. So, L53 can't maintain heat even after 4 days of warm up. So, I need to return to insulating and sealing leaks. This will have multiple benefits.

[Hamajama]

What moisture meter are you using? I ran into a very similar issue with this a few months back with a charge of 16% air dried 9/4 Magnolia. Called Stan, tried to boil the moisture out, seemingly nothing. The Delmhorst J2000 has a temperature setting to adjust the measurements outside of normal temps.

From the manual: 

The J-2000 defaults to a temperature of 70ºF. As wood temperature increases, its electrical resistance decreases and indicated moisture content rises. Lower wood temperatures result in lower indicated moisture content. A correction is necessary if the wood temperature is outside the range of 50ºF (10ºC) to 90ºF (32ºC). Set the temperature accordingly and the meter will make the correction.

It might be completely unrelated, but when I realized this and made my adjustments, I was getting much more accurate readings and the wood had already reached 6-7%.

[TBrown99]

Thanks for sharing this experience. 

I do adjust my Delhorst temp. And I've started using the longer pins given this is 9/4.

[TBrown99]

Are you monitoring the actual EMC of the lumber?  At 120F and 20% RH, your kiln is just below a 4% EMC condition.  That is fine if the kiln condition is at 4%, but I don't let the actual lumber get below 5% EMC.  I monitor my lumber in the kiln real time with Lignomat probes.  If your driest lumber is getting close to 5%, you need to remove it or start adding water to the kiln. 

What are the options with the Lingomat probes? Which product do you use?

I already own the Delhorst 2000 so perhaps there's a similar product in that line..

[blackhawk]

What are the options with the Lingomat probes? Which product do you use?

I already own the Delhorst 2000 so perhaps there's a similar product in that line..

I use the Lignomat K2-33M system:  K2-33M  You can buy the PK probes separately and they offer many different lengths.

The K2-33M comes with a Ligno K meter, which is a pin only meter.  If you don't have a pinless meter already, they have a VersaTec model that is both pin and pinless.  You would just need to call and ask if you could substitute in the VersaTec meter in the K2-33M package.

[TBrown99]

I'm documenting the following as I use this single thread for future feedback instead of starting new threads all the time.

As I mentioned, last night I turned off the flow of hot water to my kiln which feeds about 17' of radiant baseboard fin heaters, which I train independent fans on to increase release of heat. (BTW, short of fitting my boiler lines with t-stats, Stans advice, I rec'd an InkBird device to control the fans instead ITC-308 Wifi. Excited to test this...)

Temps held last night until 1:00 am. Perhaps the residual heat in the boiler lines finally faded out... but the drop from there was pretty steady so I'm not sure whether something else occurred. Anyway. The L53 was unable to maintain 120. Temp went from 118.4 to 114.7 at 10:46, so about 10 hours.

Does this represent rapid heat loss? Does it indicate that I have lots of insulating work to do? The chamber is inside a heated chamber, 80 degrees. The outdoor temp is now 50 F. The decline seems to finally be settling out at this level. 

[TBrown99]

I ended the basswood drying session. Everything looks to be 10-12% with long probes. 9/4. simply leaving it in for a few more days would help but this level will be fine for these pieces for now. There's no major unexpected checking / cracking. Looks good.

I did the heat treatment 130 degrees (higher actually) for 30 minutes (actually a lot longer).

[doc henderson]

well insulation only acts to slow movement of heat so you may need more.  If I understand, your kiln container is inside of a conditioned space, so that makes the temp gradient less (like being summer all year long).  I do not know if that temp drop over that time is normal or not.  the initial holding of temp is from residual heat in the radiant heat, but also the wood and kiln mass as well.  If you further insulate and seal things up, it may save on heat loss and increase your ability to finely tune your kiln and follow schedules.  leaks will bleed heat and moisture and make it hard to keep temps and humidity up.  Would you say it is minimally insulated now?

[TBrown99]

yes, the drying chamber is inside a larger yet small drying chamber which has heat too so it can get up to 90+ (I'll be drying 4' stickers in here). But no condenser this outer area. 

The manual says minimum r-30. I'm at r-13 (1-2" foamboard layer. So, I can add 13 more or 3 inches to bring me to 30. I expect that a good job here and more sealing would make a big difference in holding heat & humidity.

Given that Nyle sells supplemental heaters, I expect that maintaining 120 with the L53 isn't uncommon. Anyway. I'm guessing that some math on that heat loss rate would help evaluate but that's beyond my pay scale.

[blackhawk]

I think that you need more insulation.  My kiln is outside as a stand alone structure and I can hold 120F with just Nyle's built in heater element.  It will hold this way as long as outdoor temps are 35F or above.  I have R25 in my walls, R10 foam under the concrete, and R42 in my ceiling.

For heat treating, you need to be up to at least 140F.  The core of the lumber must reach 133F and be held there for a minimum of 30 minutes. Once I reach 140F, I hold there for 24 hours just to be safe.  I have a thick block of wood that I keep in the kiln with a temperature probe embedded in it so that I can monitor the temperature of the actual lumber.

[TBrown99]

Updates: 

I received the Lingo-Versa system with 3 pins and 1 EMC line. Very excited to get this setup / in use. 
My next charge will be 9/4 white pine.

My top priority now is to insulate / seal more. The key here will be to make my inserts between studs easy to remove for Summer operation (to avoid overheating issues). I'll use some poly sheet between fitted layers so I can easily pull out.

I've setup the InkBird ITC 308 to control auxiliary heat (basically a switch control for fans trained on radiant fins to accelerate heating). Very easy to deploy and use with a nice app interface to control remotely with. (I'll still need to control fluid flow via the hand valves. Perhaps I'll eventually get some controls there as well.) FYI, the InkBird ($35) temp probe tracks closely to the Nyle probe so I'm now suspecting the Govee (& Sensor Plus) sensors as tracking too low. I'm searching for a way to get a solid reading on the temperature... and then calibrate sensors from there.

Thanks    

[K-Guy]

@blackhawk 
You said:
The core of the lumber must reach 133F and be held there for a minimum of 30 minutes.

The USDA requirement is 133°F for 45 minutes at the core of each board.

[blackhawk]

@blackhawk
You said:
The core of the lumber must reach 133F and be held there for a minimum of 30 minutes.

The USDA requirement is 133°F for 45 minutes at the core of each board.

Stan - I was going by these two documents from the USDA.  Both of them call out 133F for 30 minutes at the core.  

https://www.fpl.fs.usda.gov/documnts/fplrp/fpl_rp626.pdf
https://www.fpl.fs.usda.gov/documnts/fplgtr/fplgtr282/chapter_20_fpl_gtr282.pdf

[K-Guy]

@blackhawk 
I stand corrected but would still the 45 minute time frame as a bit of overkill. 

Also, whenever you see them talking about ISPM-15, they are talking about international regulations for packaging(pallets, etc.) used in overseas shipping.

[TBrown99]

Okay, this kiln room is suddenly getting more real, as my neighbor manufactures these lamp posts, 50 at a time, via his bending process,

https://www.roomandboard.com/catalog/lighting/floor-lamps/streeter-wood-floor-lamp/

He normally let's them air dry for 2 weeks (1x2 walnut, oak), from 20% to dry, and has asked if I can dry these for him, he believes in 1 day.

I deployed my Ligno-Versa 3-probe, 1-emc but the switch box wasn't made properly so they are sending a replacement. (The dial was set to 9-12, not 1-4 and it turned roughly, not clicking into positions.) Regardless, the manual doesn't seem to explain the actual operation. I have more information from Grete here but still I need help understanding... I've appealed to her for further assistance, waiting to hear back, but I'll now contact Blackhawk above, as he has a similar system...

I'm dragging it on insulating. 

My intention is to mill some white pine 5/4 and do a 4th test load with probes. 

I've realized that I still should move my exhaust line as Stan suggested... While the fan works fine, reduces temp quickly when necessary, I'm guessing that with heat rising, it provides an escape for heat even though the fins work.  

 

[beenthere]

Toby
What country are you from? Would help if you would click on your profile and update some information. Helps to understand your posts. 
Thanks

[TBrown99]

Done!