Controlling Overheating in a Dehumidifying Kiln
How to cool off a dehumidifier kiln that is overheating just from the compressor heat. March 4, 2009
Question
What would be the best way to lower the temperature of a DH kiln from 48 degrees Celsius to 30-35 degrees Celsius? I do not use any heating this is the heat off the humidifier only. I have eight fans total in a bank. The kiln is eight feet wide x 14 feet long x 3 feet, 6 inches wide and it is a truck insulated box.
Also, which would be the best way to control the r humidity? The unit is based on an EBAC and it will dry 90 cubic feet max. Any input would be appreciated as the manufacturer is no longer in business.
Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
Energy is used to evaporate water, so if you have extra heat you are not drying the wood. The wood is probably already dry. If you need lower temperatures so the compressor works, then install a fan that is thermostatically controlled. Are you saying the EBAC is out of business? Interesting indeed.
From contributor J:
As far as I know EBAC is still going strong.. Eight fans sound like a lot for a kiln that size unless they're very small. If the ambient temperature is high the kiln will overheat and an over temperature vent is required. The EBAC kilns will normally shut the compressor off when the temperature reaches three degrees over set point and remain off until the temp lowers. It sounds like your outside temp is high or exposed to the hot sun. With that many fans their motors would be giving off a lot of heat also.
From the original questioner:
Just a note to reply this is an EBAC copy – not an actual EBAC. Further to your response - would I require an inlet fan as well?
From contributor J:
Not a fan just a louvered vent (kind of like a dryer vent in reverse).
From the original questioner:
Yes all the fans are ten inches diameter and all eight in a bank with the dryer central mounted on one side of the unit in the top corner. I might try disconnecting half the fans and see what effect that has on the temperature first, then I’ll look into the vent idea. You boys are some years ahead of us on homemade kilns - maybe ten years.
From contributor S:
I used to run a small EBAC. The kiln chamber I used was an insulated box made of plywood. High temperature was never a problem. Trying to run it in the winter was a losing proposition. I'm wondering if your truck box is out in the hot sun? If it is, perhaps moving it to a shady location would help. Or you could build a simple frame and put up shade fabric. The humidity on my EBAC was controlled by the compressor going on and off, as well as the temperature. I believe you weren't supposed to go more than a five degree C increase a day when starting. The compressor "on" time was started at 10% and then gradually increased as the temperature went up. It seems to me you could control this yourself either manually or with some type of timer.
From the original questioner:
Believe me we don’t have a problem with heat outdoors here just rainfall! The truck body is a proper fridge container lined with glass fiber six inches in thickness. I have a central four inch thick partition down the middle - from floor to ceiling which reduces the compartment to14 x 4 x 8 feet. I have thought of removing this but would the humidifier work effectively in that volume? In theory it will only dry 90 cubic foot of timber.
From Gene Wengert, forum technical advisor:
The amount of moisture in the air is so small that it will not matter if it is open or not. However, you would increase heat losses with more wall exposure. You might also not have as good air flow as desired.
