Vacutherm iDry input

[Stephen1]

Treadsactual, I think that wood was in the kiln way to long for 4/4. HM needs to be dried fast! 
I am drying loads of it now, 2 weeks off the mill and into the kiln , full power, 160F and then after 6 days turn it up to 163F and I will pull it out tomorrow morning or Sunday morning, depending on the water coming out of the kiln. That is big in IMHO , moisture coming out, when it drops it is either dry or you need to crank the temp. I do that with walnut and Oak, start low, 105F, then turn it up when the water changes. 
Jim was right in the 12 hr drain cycle for sure, get the moisture out of the kiln. 
I collect the water in a 45 gallon white plastic barrel. When the amounts drops, ( I'm looking for a 4"- 6" drop in volume of water or more with maple, cherry, popple , pine) its time to do something else. Take the wood out, turn up the temperature if its a slow drying type of wood.
I do not like to open the Kiln to check moisture content as then your wood cools down, moisture comes out of the kiln. you are also testing Hot wood, 150F so the meters are not that acurate, and you take away the conditioning aspect of the partial vacuum kiln. It also add 2 days to the drying time. You have to get the heat back up. You have to have confidence in the process for the Accelerted Air Drying System the IDRY is. 160F and 8" of Vacuum. It works. Leave the doors shut for your cycle time. 

I have determned my cylce as 2 weeks with everything 6/4 and thicker, under is  7 days. Water output determines shorter or longer.  I only open my kiln on those timelines, giver or take a day or 2. My Heater is running at 207 volts because of what my utility delivers instead of 240 which your element and the kiln are designed for. It affects the drying times. 
Cheers

[Stephen1]

The maple I dried was sawn in February and March. I did reach out to Jim Parker and the only recommendation he had was to change the drain cycle from 24 hour to 12 hour.

I started at 105 degrees, and adjusted the temperature up based on the moisture readings with my Delmhorst pin meter. I raised it to 160 only when all my readings were under 15% (15 days after starting the load). It took 11 more days at 160 under vacuum to get it all around 7% moisture. 4/4 maple took 26 days by that schedule.

Luckily we do a lot of stained maple stair treads, so we are able to use the “cherry maple” for those.

I have 10 loads of Hard maple to do from a customer. A great experiment. 
The 1st 2 loads and previous 6 loads from 4 months ago were done at regular press start and wait. 160F 24 hr drain cycles.
They were all dry in 7-8 days. 
I am doing the next 4 loads at full power but set the drain cycle to 12 hrs,  24 hrs at full power to get the temp up and then 12 hr cycles. So far in 2 days the water draining out is the very close to the same amount as in a 24 hr cycle. 
I am hoping this will reduce the kiln time by a day or 2. 
I'll keep you posted.

[nativewolf]

How'd you end up with your experiment on the 12 vs 24 hour cycle?

[Stephen1]

How'd you end up with your experiment on the 12 vs 24 hour cycle?

Well in my 'scientific' way I am still running my experiment. I have 4 bundles of maple left to dry. I believe it saves a day in the kiln. But then the bundles are air drying so that probably takes a day off right away. And now the wood is coming in cold, not quite frozen yet, that will start in a couple of weeks. Then I will have to make room in the shop to bring the wood into thaw for a day.
What I have noticed is the 12 hr cycle takes the kiln longer to get to 160F , the magic number. At 160 the temp in the kiln will hit nere 155 and that is when the last of the water in the core is forced/boiled out. The boiling point of water at 8" of vacum is 153.5F.  With maple the faster to 160 is key. Especally once it's air dried down to 15%. I will see more wood show up to be sawn and dried probably around Febuary sometime so we will keep the 'science' going. 
I keep recording what I am doing and will read up on it when things slow down around here. 
Right now I believe my science is based on how I feel that morning when I load the kiln. 

[Log Dawg]

Looking for opinions on the following.

I am fixing to Idry some,

Pecan 5/4 , 8-12 ft long, and 4 to 8 inches wide.
Majority has been air drying over a year.    I am thinking full setting to 160 at 24hr drain?

8/4 honey locust that is 18 inches wide and 12 feet long that is currently at 25% moisture content on surface, 32% or above, in the middle
I am thinking 1/2 power 24 hr drain setting for a week then move to full setting 160 with 24 hr drain?

Fresh 6/4 boxelder that is running the same moisture content as the honey locust
I am thinking 1/2 power 24 hr drain setting for a week then move to full setting 160 with 24 hr drain?

Look forward to hearing your opinions.

[Stephen1]

I am able to record/watch my water draining each drain cycle. 
I started using 120F as a start temp. I understand that over 125F. And over 25% moisture. more movement occurs. 
When the amount of water drops off, I start to increase the temperature and increase the drain cycle time to keep the wood conditioned. It is ussually only 2-4 days to get to 160 and the wood is dry. 
The box elder would be like maple, dry it fast. 
THe others I do not know. 

[NC Daniel]

I'm a little late to the maple darkening subject...

My understanding is that one of the major factors to maple darkening is exposure to oxygen which is why the vacuum kilns are able to produce "whiter" lumber. It sounds to me like the individual who was having trouble with the maple darkening was opening the kiln door often to check the moisture content, in turn exposing the wood to more oxygen. Like Stephen1 says hit start and try to keep the door closed. Just my $0.02.