I am in a discussion with a fellow worker as to the going on抯 inside a Nyle Kiln. My interpretation is the heat element brings the air up to specified temperature and keeps it there cycling on and off as needed. The compressor removes as much moisture as needed to keep the RH as programmed with both switches being on auto. His understanding is that the compressor generates both heat and pulls moisture, and the heat coils are for initial heat only, suggesting the heat be turned off after reaching temp. The Nyle literature is not real clear.
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
The heat is supplemental heat and is used (automatically) whenever the air is not at the desired temperature. You do indeed have to use supplemental heat initially. Once running, you will likely have enough heat from the compressor and its activities (it is a heat pump), that additional heat will not be needed. However, if your kiln building is not well insulated or you are running really hot, you may need more heat than the unit provides. If you have enough heat, the supplemental heat will not come on even though the switch is on. The supplemental heat is usually electric, which is expensive. Using propane or other less expensive fuel to "kick start" the process may be an economic advantage.
I built my kilns and insulated with 2 layers of foam insulation 2 " thick and a layer of plastic before I put the 1/2 " OSB skin on the inside. I put two heavy coats of aluminum roof coating over that. Five years now and I have no problems. It cost me about 5 cents per bd ft to dry. My kilns will heat to 130 degrees or more by storing the heat from the compressor. I figure the R value of my kilns at about 60. Temperatures exceeding 130 could damage your compressor, unless it's mounted external with ducts (unit outside the kiln).
Check with Nyle before you make any changes. I don't know how well cargo containers are insulated, but probably not near R60. DH kiln drying is different from commercial drying kilns. It抯 hard to damage lumber in a DH unless you do something really stupid.