Kiln controls recommendation

[solidwoods]

I am building a 5000bf kiln.  Anyone have a  suggestion for simple kiln controls (water boiler heat) or a DIY system?

[Den Socling]

how simple do you want to get? Two process "loop" controllers are about the minimum for good control. But you need (or will want) fuses, switches, maybe solenoid valves, valve actuators (pneumatic or electrical) and indicators.

[Frank_Pender]

SW, I went very simple.  I got a Taylor Hotwater furnace and place a heat exchanger in a semi-trailer.  I palced an Ebac 800 in there to remove moisture very slowly.  It works great. 8)
Good luck with your project.

[smwwoody]

Jerry Lewis from Timber Wolf Dry Kilns markets a simple controller for a hot water kiln I will find his phone number for you

[Mark M]

Frank, how big of a heat exchanger are you using? do you have any pictures or diagrams?

Mark

[Den Socling]

You could use a single relay output to start/stop a boiler circulating pump from a water temperature input. A second relay output could open/close vents with a wetbulb input.

I prefer to set a three-way modulating valve to send some hot water to the kiln, as needed and the balance back to the boiler.

5000BFt can be worth enough that you shouldn't risk ruining it by trying to control with junk.

[Jason_WI]

Do you want to risk 5000 bf with a cheap controller? Maybe 500 bf but you are takling some serious risk.

With the cost of one ruined load you could purchase a pretty decent controller.

Proportional control is $$$$$

A on/off controller is cheaper but you will want a dead band to prevent oscillation.

Check Watlow and Omron for process controllers.

Then again there ways to build your own controller.....


Jason

[oakiemac]

I agree that proportional control is generally better, but an on/off controller (just a temperature switch with adjustable deadband and setpoint) would work for this application. I bet you could get everything you need a heating/airconditioning shop. The real question is what are you using for a heat source? Hot water? Electric heat? Steam? Once this is determined then you can set up a control plan. If you need help, let me know I have 15 years process instrumentation experience.

[Den Socling]

Jason,

I can put in a voltage or current output for $33 more than a relay. We don't even add that cost when somebody wants proportional control. Three wire, mod valves can run from less than $100 to hundreds depending on size and MTBF. It's not big bucks compared to the value of a kiln charge.

And, as I've told you at another forum, it isn't worth the hassle to try to build your own. The learning process would kill some small guys. Go to somebody with lots of experience. And don't buy cheap crap from somebody that claims cheap control. I don't want to advertise here but, I guarantee you that you can't buy decent control with less money than ... well, go to members and look at my webpage.

Den

[BBTom]

Solidwoods,

I don't have anything to sell, I just have a small hot water kiln that works.  Control is within 1 degree dry bulb, and 1 percent humidity.  No it doesn't have a chart recorder, Yes I did have to implement some small power relays.  I have under $350 in my controller,  including valves and relays.  I realize that I have $10,000 worth of lumber in my kiln at times, but see no reason to let someone scare me into spending more money than necessary.  The unit I am using is purchased from Kiln-direct.com, and cost $240.  BTW the manufacturer of this unit is Pola, They have been building climatic controllers for over 25 years.

Now don't get me wrong, If you feel you need to spend 2500 to 5000 for your kiln controller, then you will probably get a real good turnkey package that will do a fantastic job.  I spent a few years of my life in process control, so it isn't scary for me like it is for many.  

[Den Socling]

BB Tom,

Somebody gave you an effective snowjob. You don't have 1 degree on drybulb or 1% on RH. If it looks that way, you are seeing process rounded averages. Unless you have one extraordinary kiln.

Den

[Jeff]

Hi Guys, just wanted to stop by and see whatcha all are talking about. Hmmm interesting.  

[Den Socling]

Oh! Hi Jeff. ;D

[Den Socling]

Let me add this. Our minimum order is $10,000.00 () and still I'll sell to you only if I like you!  :D  But then, if you want some good advice, that's free. But not for a day or two. I'm tired and will be out of town tomorrow.

[biziedizie]

  Den I've been reading what you say here and on other forums and your answers are always consistant.
  I as a person that really has no ideas about kilns would be looking your way when it comes down to the crunch of building a kiln.
  I've read up about vaccum kilns and I agree with everything that you say about them even though I have alot to learn about things.
  You have a way of explaining things and I hope you go far with your honesty.
  If you ever need a dealer out my way let me know as I would be interested.

   Steve

[BBTom]

Den,

I know that you have a great deal of expertise in kilns and controllers.  Your controllers are well know and respected by many in the industry. I, in no way mean to cast any dispersions at you or your products. I apologize and retract anything I said that sounded that way.
I do feel that some of the gentlemen asking about small kiln controllers cannot afford to spend more than 5000 for their entire kiln.  Again, I say these are small kilns, 1000-5000 BDFT.  They do not have the capital for major investment, just want to dry some lumber, and are looking for control that they can afford.  Rather than sending them packing because they cannot afford top of the line controls,  I believe they should be enlightened as to what low cost options are available. I also know that when it comes to the top of the line kiln controllers, that yours are more affordable than most, unfortunately these guys cannot afford them.

Tom

[Jeff]

 

[Den Socling]

Thanks Tom. no offense taken.

We try very,very hard to make good controllers affordable for everyone. And the same goes for vac kilns. It's hard to make "good" and "cheap".

Had a lot more written but deleted it. Sounded like a sales pitch.

Point is this, I'm here to help if I know an answer.

[Larry]

Here's simple.



Out of FWW "Wood and How to Dry It" a collection of short articles available from Taunton press.  There is a short article on how to build a kiln using steam, hot water, or electric.  The schematic is for electric heat but the author describes how to change it for steam or hot water.  The article is old but does have a lot of ideas.  The author was a kiln operator and later a well respected Professor at the University of Massachusetts.  Don't see why it wouldn't work with a conservative schedule and a regular check of the sample boards but I have never tried it.

Mark,
University of Massachusetts also did some research on hybrid solar kilns.  Never have been able to track down the final result but that might be someplace to make some inquires.

[Den Socling]

Larry,

The box in the block diagram that is labeled "remote bulb thermostat" is actually the kiln controller. Now days, you don't use bulbs but RTD's (a few guys still use thermocouples) and you can get really cheap with a thermister. So, that's the input to an electronic device. The question is, do you want to use two $300 loop controllers with keypad, display and control algorithm built in, or, do you do want to go really cheap with a PLC that needs enclosed, a power supply, a display, probably RTD "adapters" and programmed.

I'm going to gather information for people who want to go the mini-PLC route. There's a bunch of different brands. We will check them out, buy one and see what's involved in making a minimal kiln controller.

Den

[Larry]

Den,
That sounds like a great idea to me.  I don't have a good understanding of conventional kilns and sure don't want to spend a bunch of time and money making something that may or may not work.  If you could come up with a package controller with kiln chamber plans in the neighborhood of 3 to 5 mbf there might be a market.

I run an Ebac LD800 and solar kiln right now.  Looking to buy a Nyle L200 this winter or next spring. An alternative would be nice to look at.

[woodhaven]

Den,
I have a moisture meter that uses pins to insert into the wood. If I were to build a digital system using thermisters how would I insert them into the wood for a reading? Drill a little hole and slid it in or what.

[Den Socling]

Richard,

When I'm experimenting with really thick stock, I sometimes put RTD's in the core and the shell. Just drill oversize or the wood will shrink and you will have a heck of a time getting them out.

I do this with vac kilns to study heat transfer. In a conventional kiln, the temperature of the wood is less important because you need to be concerned mostly with the conditions on the surface of the wood. But knowing wood temperature could have some value even in a conventional or DH kiln. As long as water is evaporating rapidly, there is an obvious cooling effect. When the wood is nearly dry, it's temperature rises rapidly.

Den

[Frank_Pender]

Mark, I am sorry that it has taken me so long to get back here.   I have been extremely busy trying to pretty the place up for a class I am involved with sawing a drying through Oregon State University, on Sept. 4.  

     The heat exchanger is a unit that is approcimately 32" square and has a 24" fan helping to circulate the air.  I use an additional 5 24" box type fans to keep the air moving in a 24' refer trailer.  Part of my initial theory was to generate the moisture in the air, inside the trailer, and have a dehumidifier that could not remove it as fast as the moisture was being extracted from the lumber.  It works very well.  the hot steam helps then in the drying process, just like the big boys toys.  I DO NOT release or as the pros say, exhaust the steam at any time what so ever.   I will open the kil only 4 times in a 30 day run.  That is for the purpose of testing the moisture content of the specific boards at each test.   I use a Delhorst pin meter.  It works great.

[solidwoods]

This is an interesting subject, I asked about it at woodweb 5ish years ago and ideas and info flew prety well .  We could have a whole round table discussion about what business model uses boilers (non pressure), up to 10000bf kiln, and less than 10 souls to earn an income,  but the real point is can a simple prorortional or non proportional system be put togather with off the shelf components (no data recording)?  Simple digital control (or manual control if just as accurate) ,quality sensors, relays, venting sys, fans etc.  Really if you put fusing, sensors, relays, venting apparatus, and fans separate , all that's left is the controller (quality schematic design/materials yes).  Controller reliability is what will make the difference.  How long will it work with proper use? A sensor can fail any time it feels like it.
I'm using a Taylor 165000btu boiler.
Any suggestions for the wetbulb system components, sensors, solinoid-valves?
A simple controller like Kiln Direct sell should be fine for me.
I wouldnt mind making the controller, but without a parts list and some spoon feeding it would be cheaper/less labor to buy a simple pre-made controller.
JIM