Compressor not kicking in

[logbyr]

 

 Started my L200 up today after a few pointers from K-guy.    Kiln hit 80deg but compressor didnt engage.    When I looked at controller it shows humidification is on but compressor is not.   I don't have humidification.     Checked the wiring inside the unit and it's all hooked up correctly.   What am I missing here?

[Southside]

What are your set points?

[logbyr]

Set to come on at 80.    120 dry and I believe 98 wet bulb

[YellowHammer]

The compressor and the humidity function is controlled by the wet bulb set point.

The compressor will only operate when the dry bulb is over 80F (as a freon safety) and the wet bulb is above your WB set point - in this case, your compressor won't be commanded to come on until the reading gets above 98.

Your wet bulb set point is higher than 70.7 so the controller is calling for more humidity, trying to reach your higher setpoint.  It doesn't matter if a humidity injection device is hooked up, the controller doesn't know or care.

You system is working correctly, it is trying to inject humidity to hit your WB set point while running the heater to hit your DB set point.

[Southside]

80°F is the lowest dry bulb temperature the compressor will come on at.  As YH said your unit is operating correctly.  What are you drying?  

[logbyr]

Thanks for the answers.   
Load is curly soft maple, cherry and and walnut 4/4.

[YellowHammer]

When the controller is calling for the compressor to come on, there will be a little "o" under the compressor label on the display.  Typically, there is a 6 minute delay from when the compressor is commanded on and when the controller lets it come on.  

[K-Guy]

Yellowhammer and Southside are correct.

For the L200/KD250
The Dry Bulb will not let the compressor start below 80°F to prevent freeze up. At that point the control of it is turned over to the wet bulb which will start the compressor when the wet bulb actual (the wet bulb temperature in the kiln) is 2 degrees above your setpoint after a 5 minute delay to prevent short cycling damaging the compressor.

I hope this helps to explain the operation of the unit.

For the L53/KD150 the Dry bulb is set to 85°F 

[WDH]

As the air gets heated and causes evaporation of water from the wood, the water vapor in the air will increase the humidity which increases the wet bulb temp.  As the humidity and the wet bulb temp continue to rise, a point will be reached when the wet bulb temp gets up to your set point. When the actual wet bulb temp exceeds the wet bulb set point by a full 2 degrees and stays there for a full 6 minutes, the compressor will kick on. As the compressor runs and water is removed from the chamber, the kiln humidity will drop which means the wet bulb temp will drop.  When it drops below the wet bulb set point, the compressor will shut off until the humidity and wet bulb temp rise again to 2 degrees over the wet bulb set point for 6 minutes, and the compressor will come on again and water will be removed from the chamber again.

  The wet bulb set point prevents the unit from drying the wood too fast if the moisture content of the wood is above fiber saturation point (about 25% moisture content).  

[GeneWengert-WoodDoc]

If the chamber is tight and the vents are closed tightly and the doors are also tight, then for each 100 BF of lumber, when they lose 1% MC they will release about 3 pints of water, which can raise the humidity of the air substantially.  So, you should not have to add moisture to the kiln, the lumber's moisture will do it.  If the wood is so dry that it does not have lots of moisture, then a lower humidity would be fine.

[logbyr]

Again thx for all info.   Kiln got up to temp sat evening and has been pumping out water ever since.    When compressor kicked on heat rose much faster.  
My chamber is 24 x 12 x 12.    3 fans across top.   I'm not real happy with air flow coming back thru the stack.   It's well baffled.   No leaks anywhere Handkerchief test only shows about a 10 deg movement.   I was expecting a noticable air flow.    Need to address this and some supplemental heat as winter is coming.

[K-Guy]

Your chamber is quite large for a L200, how many fans do you have? I would think you should have at least 6 for the extra length and width.

[logbyr]

Inside width is 23'     
12' deep.   (48" wide lumber stacks)
12' tall

 

[WDH]

Perfect stickering! 

[JoshNZ]

How does a compressor remove water, mind a newbie asking?

All of my Google searches only turn up results about draining water from air compressors =/

[Don P]

Search;dehumidifier.
As the temperature goes up the air can hold more moisture vapor. If  that air is then passed over a cold coil that moisture then condenses to liquid and can be drained away. The compressor drives that cooling coil. The heat produced by running the compressor is used to help heat the chamber.

[WDH]

Yes, there is also a condenser with fins like on an air conditioner to condense the water in vapor form back to liquid form so that it can be removed. 

[YellowHammer]

How does a compressor remove water, mind a newbie asking?

All of my Google searches only turn up results about draining water from air compressors =/

Those are two different mechanisms.  

Draining water from a standalone air compressor is due to the amount of water vapor in the air being compressed past its saturation point and falling out as a liquid in the bottom of the tank.  As cycle after cycle occurs in an air compressor, the liquid water accumulates in the bottom of the tank and must be drained periodically. 

When moisture laden air is passed over a cold surface, like a glass of iced tea in the summer, the moisture in the air will condense on the cold surface as water droplets and leave a water ring on the table the glass is on.  In a refrigeration cycle, freon in a gas state is run through a compressor, but then that is run through a small orifice which chokes the flow and on the the downstream side of the orifice, the gas expands and cools down as it expands.   The cold, low pressure gas is run though a pipe with cooling fins, which act as the cold glass of iced tea, and the water vapor in the kiln chamber air condenses on the cold aluminum fins as water droplets, and falls into a catch pan and run out of the kiln.

Here is picture I took years ago showing how the water condenses and drops off the cold fins near the bottom.


 

[JoshNZ]

I see, I didn't realise it wasn't an air compressor in question. Thanks!