About ready for a kiln

[JoshNZ]

I've finally got my hands on some logs I can mill into kiln framing and cladding, and my shed pad is nearly down, will finally have somewhere to build it.

I just wanted to check.. for drying hardwoods it is definitely a DH kiln I am wanting, and wouldn't get away with a conventional kiln?

My walnut supply won't last forever but that is pretty well all I have cut since I got the mill running. Bunches of it air drying everywhere from yesterday to 12 months. I figure there is no point competing with pine mills so it will always be hardwoods.

I've sourced a DH/heater/fan unit combo but I did wonder if you can get away with just heating the kiln and air movement, if you've air dried the timber reasonably well first. Not unlike a solar kiln, I suppose, but with a reliable consistent temp cycle

[doc henderson]

with a heated kiln, the compromise is loosing heat as you vent moisture.  the heated air goes out as you vent.  that is the advantage of a DH kiln.  it generates some heat, and the water is taken out without so much heat loss.  at least with solar the heat is free, and it cools down at night.  takes longer, but you do not see dollar bills floating out the vents.  all have pros and cons.

[firefighter ontheside]

In the winter I have to add some heat, but at other times I just have a couple fans circulating air and the little DH running.  The DH got it up to 107 recently, so I have it plugged into a thermostat that turns it off at 100 and back on at 95.  The first week or so, the RH in the kiln was about 35%, but now that I'm three weeks in the RH is about 20%.  The wood was about 18% when it went in.  This is working well for me, but at some point I will buy a Nyle L53 to put in there.

[JoshNZ]

Right that all makes sense.

What if you fuel the kiln from waste slabs, would a system like that need constant babysitting? That's the only reason you'd chose a conventional kiln is if the energy was free?

[YellowHammer]

Any kind of heat would work, and some places will do double duty with a DH kiln for "backup" and fine tuning, and use waste slabs or wood for augmented or even primary heat.  

If I was going to build a new system, I'd use a Nyle DH unit with built in moisture probes (those things are really nice), set it up as a good base system with fans, spacing, and airflow, as if it was going to be a true DH unit.  Especially important are the automatic vents to regulate the interior heat.  I might even buy and wire in a second set.  Then I would plumb in a heat exchanger from an outdoor wood boiler and use that for primary heat and then at some pint I would be able to hit a point on the learning curve where I could pump in enough heat to never run, or only rarely the DH compressor or strips, and the only thing that would be used to control the system would the heat controller on the OWB and the automatic vents from the DH unit.

If I had a cranky load, or there issues, I could always fall back to using the system on full DH cycle, but for long term use, I would only use the OWB and free wood waste from my operation.

[JoshNZ]

How often does a system with an OWB need monitoring? I assume it's not like a log burner in your home where you'd throw wood on every few hours.

[YellowHammer]

It depends on how much you want to spend.  Years ago I priced one out where  it would run 24 hours on a load of wood If course, it also had a big door to load it with a loader and took full loads of 8 foot pieces of wood.