This post is the conclusion to the Thermostat series. In the last post we looked at a few different Thermostat types and chose a Bi-Metal style for our Wood Shop installation.

I’ll get into the specifics of each part shortly, but let’s take a quick look at the parts for this project.

Parts

Sometimes I’m in the hardware store looking for a particular piece for a project and feel like I’m wearing a blindfold. I’m sure that what I need is here… sigh… somewhere…… I just can’t see it.

Some days I will walk away with nothing, because they just “don’t have” what I need. Other times I will pick up a few parts and see what I can do. I enjoy experimenting with new pieces of hardware because the more I learn about each piece the more the blindfold begins to fall away.

Looking at row upon row of hardware pieces is both bewildering and inspiring. With experience, you can start making connections between which pieces work together.

This can turn into a real treasure hunt when you begin combining things from different isles throughout the store. Perhaps a quick trip to the plumbing department will turn up a piece can contribute to an electrical project.(foreshadowing)

Enclosure

This 3-Hole box will be the focus of our build instructions. It has a hole on each end, and one in the bottom.

At the end of the post, I’ll show you a 5-Hole box alternative that might work better for your shop.

Enclosure Ratings and Standards

While we are on the subject of enclosures, let’s take a second to look at the standards available that we can use to rate our project.

Electronics enclosures are rated by a couple of different standards organizations.

For a bit of standard related humor, check out this clever and all too true XKCD web comic.

The National Electrical Manufacturers Association (NEMA) is the most common in the US. I feel that their numbering system is less that ideal. An alternative European setup by IEC is called the IP rating system.

The nice thing about IP ratings is the two digit number system. The first number is determined by solid object protection and ingress, the second is for protection from liquids. This make it easy to spec out a rating for your application based on where it will be used.

This webpage has a great deal more information on the subject and includes a handy cross reference.

Cable

Good circuit design means ensuring all parts of your device are properly specified. We don’t want any weak links. The thermostat we are using can switch up to 22 Amps, so we will match our wire size to that.

The particular cable type we will use is called “12-3 Service Cord”. This is a good choice for a liquid fuel heater because the Seoprene jacket is solvent resistant and flame retardant.

Cable Connectors

To connect this round cable to our box, we will use a cable connector. We previewed three different connector styles in the Switched Outlet project, but those were for flat Romex cables and will not work for the round service cord.

The cable connectors I chose is a three-piece construction. Be sure to pick a connector that will fit the diameter of your cable. If you look closely, the text on the top of the plastic bag lists the cable diameter range as 0.260″ to 0.375″.

From left to right, you can see the Box Fitting, the Rubber Gripper and the Compression Nut.

Thermostat

Here is the King Thermostat we selected in the last post.

Plug

Choosing to use 12-3 service cord also affects our choice of input and output plugs. Be sure the terminals will accept 12 AWG wire.

Let’s get started

I gathered the parts listed above and did a preliminary fit, this is when I first noticed a problem. Here you can see how the Thermostat Switch Bracket interferes with the large mounting flanges in our box.

No worries though, a quick trip to the shop and a little Dremel action took care of that problem.

 

With the box “edited”, we can get back to work. I decided to buck the trend here and read the manufacturer’s instructions. You know, that piece of paper that usually goes straight to the trash along with the packing material. It included this handy schematic diagram.

Schematic

We can see from the image above that we will be switching the HOT wire. This single pole Thermostat works well for 120VAC applications. For 240VAC, where there are two hot wires, we would need a double pole Thermostat.

The Thermostat has two wires coming from its switch. A RED wire and a BLACK wire. Per the instructions we are to connect the LINE, that is the voltage coming from the wall, to the RED wire. The LOAD, which is our heater, is connected to the Black thermostat wire.

The White neutral will pass straight through with no connection to the Thermostat.

The Green ground conductor will pass through as well, after being tied to the Thermostat case.

Step by Step

First cut two pieces of service cord, also referred to as cable, about 12″ long. Feel free to use longer lengths if you prefer.

Removing the Cable Jacket

First, we will prepare one of each cable to go into the box. Strip 4-5″ of jacket off each cable.

Does this next picture worry you? I know most people would think it is OK.

No matter how careful I try to be, I always nick the insulation of the wires when I try to remove the cable jacket this way. This is a problem because any damage to the insulation could lead to DANGER down the road.

So I’ve switched to a head-on approach for getting the cable jacket off. Start your side cutters at the end of the cable, with the point in the gap between two of the wires.

Snip your way down the cable then turn the side cutters 90 degrees and cut along the perimeter of the cable.

This method removes the cable jacket without cutting into the wire insulation.

After the cable jacket is gone, strip about 3/4″ off each wire in the cable. This is about the right amount for wire nut connections.

Attaching the Plugs

Now prepare the other end for the plug. Again begin by stripping 1″ of cable jacket off the plug end.

The female plug has a strip gauge on the inside, so use that to expose the correct length of bare copper on each wire, for both cables.

Although the other end of the cable is still un-terminated, it is good to get into the habit of sliding the hood on first.

Attach the Black wire to the Gold colored screw, the White wire to the silver screw and the Green wire to the Green screw.

Cable Connectors

Once both plugs are assembled, it is time to put the cables into the box.

First, spin the box fitting into the box.

Then slide the compression nut on the cable.

Only after the nut is on the cable, install the rubber gripper. Position it about 1.5″ beyond the stripped jacket.

Slide the prepared cable into the box and hand tighten the compression nut.

Double check to be sure that the jacket is protecting the wires all the way into the box. If not, loosen the nut and pull a bit more cable in. Tighten the compression nut once you have the cable properly positioned.

Wire Nut Connections

For connecting the wires in the box, we will use wire nuts.

Yellow wire nuts are rated for one to three 12 AWG wires. This will work well for the Red, Black and White wires.

Connect the BLACK wire from the MALE plug to the Thermostat’s RED, LINE wire.

Connect the BLACK wire from the FEMALE receptacle to the Thermostat’s BLACK, LOAD wire.

Then connect the White neutral wires from each plug’s cord together with the final Yellow wire nut.

The last wire nut is not like the others. It is bigger and it is RED. Here’s why:

Choosing parts based on their maximum capacity is like holding your foot to the floorboards while driving down the interstate. Besides being illegal, it is hard on your vehicle to run at 100% for a long time. This is why I try to give my parts a little breathing room when considering them for a task. Maximum values are typically determined by tests in ideal conditions. Gunning your car down a hot desert highway would be even less advisable, so remember to keep ambient conditions in mind when selecting parts.

This bigger wire nut can easily manage the two 12AWG wires from the cables along with the 14 AWG pigtail.

Connect the pigtail wire to the screw on the inside of the Thermostat cover and the connections are DONE!

Close it Up

Man, that sure look like a lot of stuff to fit into such a little box. The key to getting it to fit easily is to tuck the wire nuts into the corners of the box.The middle area must be kept clear to allow room for the Thermostat switch.

Two screws hold the Thermostat to the box. Then you can snap on the cover.

Enclosure Rating Example

If we install our Thermostat into the 3-Hole box without plugging the unused hole, you could accidentally slip your finger into this hole and be exposed to 120VAC. Our box would get a NEMA 1 rating and an IP 21 rating at best.

Just by installing the plug, we’ve sealed the enclosure from debris and stray fingers. Our box is now in the NEMA 4 and IP 44 range, pending certification of course.

 

5-Hole Box

Here is an alternative Thermostat mounting method using that 5-Hole box.

All the wiring is the same, with the exception that we will put both cable connectors in at one end of the box. This prevents unnecessary bend strain on the cable.

With a bit of 1/2″ pipe, you can mount this box to a floor flange as shown below.

The right angle connector was the hardest to find in the plumbing isle. It is called a “Street” connector, so if you are looking for one, find a helpful associate and ask for it. If you can’t find a helpful sale associate, you’re shopping in the wrong stores .

All that is left now is to go out to the shop and plug it into the heater!

If you have questions about any of the products or procedures in this project, let me know. You can get in touch with me through the Contact page, or by leaving a comment below.

I’m open to ideas for future projects here at The Lumber Lab. Please leave a comment below if you have a suggestion.

If you want to pick up a few of the parts I’ve listed here in this post, visit Lumber Lab aStore.

Thanks,

David

If you’re looking for a mid-week boost, check out #woodchat on Twitter. I’m there as often as I can be tweeting as @DavidJUlschmid!

 

It has been a couple of months since my initial Status Update. A lot has changed since then, but I couldn’t be happier with the path that starting The Lumber Lab has set me upon. Let me catch you up with some recent happenings.

Family

This time of year we are all busy catching up with family. For me, this quality family time has delayed the final post to wrap up the thermostat series. See this post about my shop, and this one about thermostat types if you need to catch up.

In the middle of this project, I realized there is a lot I want to cover about enclosure types, so stay tuned for some great information.

Now, if you will bear with me, I’d like to share a story about family life.

It recently struck me that I am at a peculiar age. I’m now old enough to truly appreciate how much I don’t know. I’ve been reading more than ever and learning a ton, but at the same time, I see others, some older and some younger, that have accomplished so much. We’ve all heard the phrase “He/She has forgotten more about _______ than you will ever know!”. This came very close to home last weekend.

I always stay at my grandparent’s house during my annual deer hunting trip. The food can’t be beat, and it is a great chance to get into conversation with my grandparents, one on one. This year we talked long into the night while sipping on homemade Brandy slushes (a family holiday tradition).

Makers

Among other things, she told me a great story about making clothes from flour sacs during the depression. This struck a cord with me, because until then, I considered the “Maker” crowd to be affluent youth, those not afraid to throw money away on an idea.

This is just not true. It is necessity that is the mother of invention and this forced my grandparents to be “Makers”. Perhaps it was even easier in their time because their parents were “Makers” too. They didn’t have much and didn’t let anything go to waste.

In this day and age, even in the midst of a “Great Recession”, most people still have enough.

An example of this came in the Eco Home magazine I get for FREE from Hanley Wood. Check them out here. They featured a new insulation material made from discarded blue jeans. Jeans in my grandparents day were worn until they’ve fell apart. Then the frayed and worn material would get sown into a quilt.

Learning from the past is a priceless and quick way to gather knowledge. The lessons seem especially important when they come from family stories. These stories connect you to the past and can partially explain you, to yourself. Think about it.

The Take Away

What I learned from the Flour Sac story is that we can take what industry gives us and make what we need. And it is OK to be creative with how you use materials. Why be ashamed that your clothes are made from scraps, they get the job done better than the NEW clothes that are sold with HOLES in them already!

Wood and Electronics

So, does industry still supply us with reusable materials, as the Flour Sac story would imply? That depends.

I think the concept is still very true in the electronics world.

The electronics industry can sell a unit for less than the cost of the discrete parts.

Some of the best sources are toys. For a good example, look at game system controllers. They are a wealth of buttons, sensors, transmitters and receivers, batteries and ergonomically designed enclosures.

Sadly, I cannot say that this reuse concept works as well in the woodworking world.

Offshore factories can build furniture and ship it half way around the world for less than the cost of the plywood it would take to build it. And for the most part, the material they use isn’t worth recycling.

Good Wood

Antiques on the other hand, can be great sources of very good wood. I’ve been working on this antique restoration project for quite some time now and it is nearing completion.

I’ve never worked with nicer Oak and I know that my work has given this piece another hundred years of life.

Learning Arduino

In my post about Embedded Development Environments, I mentioned that when I decided to take the leap, I would jump on the Arduino platform. I finally took that big first step and I couldn’t be happier.

I picked up the Arduino Cookbook first. Sorta like putting the cart before the horse. I got through 100 pages of the book and then pulled the trigger on buying the Arduino Uno development board.

I did a post on the electronic suppliers Jameco and Mouser, but I ultimately did not purchase from either of them.

I absolutely knew that I wanted to move beyond the development board and get some electronics circuits embedded into some projects. For that I would need a programmer.

The website with the best documentation for Arduino programmers is Adafruit.com. Adafruit also has an amazing selection of Arduinos and Adruino compatible products. Their blog is amazing.

I bought the Adafuit kit to put together a parallel programmer, so I can burn Arduino bootloaders.

And I got their ISP serial programmer, so I can reprogram my future projects. (Back to putting the cart before the horse).

Open Source Hardware

Limor Fried is the founder of Adafruit. I first saw her talking about Open Source Hardware in 2010.

This is an inspiring video about the Open Hardware movement, but there are a couple “strong” words in it.

 

Legacy

One of the last slides she shows says “What we make will outlast us”. Isn’t this why we woodwork? To build something that will outlive us? You can do the same by contributing knowledge to the open source movement.

Open Source Woodworking?

In a way, woodworking has become “open source” thanks to the contribution of SketchUp from Google.

This great FREE software is in use by many woodworkers. SketchUp lets you easily make and view 3D designs.

Even if you don’t want to create in SketchUp, Popular Woodworking magazine has built up an impressive SketchUp Library. It is a great source of free woodworking project designs.

Invest in YOUR Capacity

I created The Lumber Lab because I want to contribute to the empowerment of everyday people to create value for themselves and others. If we look in the right places, the raw materials and the information is out there. Some of my  best pieces of lumber have come from pallets.

There are problem solvers all around us who have recognized that others have the same needs and questions. They are putting forth the effort to document a solution for the benefit of all. I hope to add to this collection of priceless free information.

I’m happiest when I’m learning so I never hesitate to invest in something that will expand my horizon. I’m a big fan of this Oliver Wendell Holmes quote.

The mind, once expanded to the dimensions of larger ideas, never returns to its original size.

Find books, new or old. Subscribe to websites and magazines, and take the time to thoroughly walk through the information.

Intellectual capacity is something you can never have enough of. And unlike a bigger shop, you cannot be taxed on having a bigger brain. Although, too much reading may leave your brain feeling taxed. Nothing a good night with a Brandy slush can’t cure.

Thanks, Grandma Bonnie.

David

As I mentioned in my last post, I’m lucky enough to have a large heated wood shop to work in during the brutal midwestern winters.

In this post, I keep my promise to let you know how I control the loose cannon in my shop, which is my “vintage” tube-style heater. Just imagine this heater, but much older and very dirty.

Let’s start this discussion off right, with a reference to Pop Culture.

Perhaps you’ve heard a certain heriess mutter the words…

“That’s Hot…”

It is a wonder to me how words so simple were used to fan the flames of fame.

Today we’re going to look at a few neat ways that thermostats detect when things get “Hot…”.

First we need to convert “That’s Hot…” back to its original meaning. No fashion opinions here. We just want to detect the fact that the temperature has risen. For that we need devices that change in response to a change in temperature, or, in engineering lingo, Delta T.

Delta T (ΔT)

As a woodworker, we learn about wood movement and how the dimensions of a piece of lumber are affected by humidity. Here is a link to a great webpage explaining wood movement.

Electronics also change in response to humidity, but not as dramatically as they do to changes in temperature.

Just as we choose species and cuts of wood for specific project pieces based on our knowledge of lumber, temperature sensitive component engineers choose materials based on their knowledge of that specific materials response to Delta T. These devices often pair one material that does not change much in response to temperature with another that changes dramatically. Since they are constructed with two different metal alloys, these materials are referred to as “Bi Metal Clad” materials.

Thermostat Types

The iconic “The Round” thermostat by Honeywell is a good place to start a discussion of thermostats.

Jammed within this classy and smooth case is not one, but TWO bi metal coils. One to display ambient temperature. The other Bi Metal coil is where the magic happens within this beauty (I seem to have lost it, calling a thermostat “beauty”). The other coil is fitted with a mercury bulb switch on the end. As the coil shrinks and expands, the mercury travels around within the bulb like the fluid in a levels vial.

Contacts within the bulb are closed by the conductive mercury when the bulb is at the correct angle. This triggers additional electronics to control the heat source. The temperature is set on this thermostat by rotating the Bi Metal coil.

Here is an image showing the movement vector of a Bi Metal coil.

The mercury vial would be attached to point A in this illustration.

This webpage shows many other Bi Metal designs that create motion in different vectors.

Pros / Cons

This thermostat technology is limited to stationary applications. Perfect for home installation, but today we are looking for a thermostat that can be installed onto a mobile heater.

Digital Thermostats

Mercury is a hazardous material, so why keep it around?

Digital thermostats like this one use a Thermistor to sense temperature. A Thermistor (wiki link) is a small electronic device that changes resistance based on ambient temperature.

To understand how a Thermistor works, we need to dig deep down into electronics theory, all the way down to the structure of an atom. Too deep for ya, ya me too. So here is a campfire story to sum it up.

Atoms are constructed of three parts.

The first two parts protons (positively charged) and neutrons (neutral charge), sit in the atoms nucleus. Think of this like a campfire on the 4th of July. If your family is like mine, the parents sit around the fire most of the time and chat. These parents are the nucleus.

Running around this nucleus of parents are their kids. These are the negatively charged electrons. The kids are bonded (or attracted to, because opposite poles attract) to their parents at different levels, depending upon how close it is to supper time. Mostly, these electrons are just spinning around, waiting for something with some energy to excite them.

All of the sudden, BANG! Energy is introduced into the atom structure in the form of a fireworks display.

The kids are much more drawn to the sight of explosions and off they go. These electrons have just jumped from the atom’s valance band to the conduction band.

Back to our Thermistor example, when the atoms of a Thermistor get excited by a source of heat, conduction between the atoms goes up, causing the resistance of the device to go down. A device with these properties is said to be a NTC or Negative Temperature Coefficient device, which is just a fancy way of saying resistance goes down when temperature goes up.

Digital thermostats are outfitted with a microcontroller that is used to monitor the Thermistors.

Pros / Cons

Digital thermostats are great. This technology can very accurately measure temperature, but this precision comes at a cost and that makes them a bit too expensive for my shop budget. After all, Im not after a specific temperature. Im just looking for not cold.

Line Level

Another drawback of the last two thermostats is that they dont switch line voltage like we need to. So Ill kill any suspense now and tell you that I use this next thermostat style. It requires NO additional circuitry. In fact it doesnt use any electricity at all. Pretty neat, huh. Lets take a look.

Bi Metal Thermostat

This thermostat uses a clever mechanical adaptation of the Bi Metal expansion coefficient that almost directly controls our heat source.

Like the coil in “The Round” thermostat, this unit uses a movement vector to open and close a circuit.

The front view of the Bi Metal Clad plate can be seen in the picture below.

The plate has a set screw in the middle. The tip of the set screw is positioned directly over a high voltage / high current switch.

When the ambient temperature rises, the plate flexes downward. When it is flexed enough, the heater is switched OFF.

Temperature switch point is adjusted by rotating the dial, which has a cam profile on the underside. As you move the dial towards a lower set point, you push that end of the cantilevered clad plate toward the switch.

One thing to note is that although this is a simple device, just like the more complex options above, it needs to be wired according to the manufacturer’s instructions. Red to line, or source voltage, and Black to load, or the heater.

Here is a link to the manufacturers website.

Knowledge is Power

So much of both woodworking and engineering is rooted in knowing the characteristics and properties of the materials and using that knowledge to make things happen.

In the next post, I’ll show you how to wire this device in line with a heater.

Id like to know what heaters and thermostats you are using in your shops. Leave a comment below.

David

As the temperature drops in my neck of the woods, I begin thinking about how to keep my shop warm for the winter.

This post will introduce you all to my shop environment. I’ll cover the basics construction, which I used make my decisions about how to warm my shop. I hope this will help you design a way to keep yourself warm.

The Shop

I am lucky enough to have a separate building as my woodworking shop. It is just 20 yards or so out my back door. It is pole barn construction and is sheathed and roofed with “wavy” tin. The shop has a 30 x 60 footprint, 20×30 of which has a poured floor, so that is where my shop space is.

After a couple of winters of working in an ice box, I decided that my passion for woodworking was being snuffed out by the extreme cold of an uninsulated space. It can get down to 40 below around here and my cast iron tools soak up all that frigid air, making them painful to the touch.

First thing to do was to put up a wall along the edge of the poured floor. I took this opportunity to add a few outlets along the wall for 230 VAC service. This was a wonderful addition to the shop, but a topic for another post. The was insulated with fiberglass rolls and sheeted with plywood.

The next step was to make a ceiling. Yep, this shop was as basic as they come when I started working in it. Just open rafters. With significant help from my father-in-law, we put rigid insulation and steel on the bottoms of the rafters, giving us a 12′ ceiling height.

Now the 6 sided box that is my shop had two insulated sides. Two of the remaining sides were purely wall surface, with no doors or windows. The final wall surface is a big sliding door and the entry door. I installed 2″ (because it was $5.00 cheaper per sheet than 1 1/2″, go figure) rigid insulation on the walls, and 1″ foil faced in the sliding door.

I covered the walls with plywood for the first 8′ then OBS for the final 4′.

Alright, now 5 out of 6 surfaces are insulated. Just the floor remains as a poured surface. Now we can talk about putting a heater in, without going broke trying to maintain a reasonable temperature.

The 20 x 30 x 12 space is 7200 cubic feet. Based on this number, and my desire to keep the shop temperature in the 50-60 degree range, it was recommended to me that I needed around 30,000 BTUs (or 30K BTU, look at the Very Big and Very Small numbers page to learn about metric prefixes) of heat.

I mulled over the options:

Forced Air

I had a 50K BTU high-efficiency forced air furnace available to me. We salvaged it from a house that was being torn down to make way for a children’s hospital.

Pros: Heater was essentially free. House heat is natural gas, so fuel supply was close by.

Cons: More BTUs than required, would it run efficiently? No natural gas line to the shop. Filter cost would add up quickly.

Electric Heat

My shop has a dedicated service line for power, so I have 120 Amp capacity.

Pros: Energy supply already in place. Easy to install.

Cons: Not the cheapest source of heat in my area.

Propane

I also had access to a few different models of propane heaters. My father-in-law, being the avid outdoorsman that he is, was willing to set me up an “Ice Fishing” heater.

Pros: Again heater were almost free, but under rated, so I would need to run more than one.

Cons: Would require the purchase of a tank (or two if I ran multiple heaters).

Decisions, decisions…

In the end, I chose to buy a 30K BTU “blue flame” heater.

I also bought a 110 gallon tank from my local propane delivery service shop. The up front cost for this setup was much higher than a simple electric unit would have been, but I think I will make up the cost in energy savings over the course of a few years.

This heater will keep my shop at 50 degrees even during the depths of winter. For extra heat, I fire up a tube style heater.

Fire in a WOOD shop!

I’ve written a few posts about how you can control your tools, but for a heater application, you want the heater to control itself.

When we turn control over to the unit, we have to make sure the unit can keep itself operating safely.

The blue flame heater has sufficient safety features built-in. It has a thermostat to control the flame and a thermocouple to make sure the pilot light is burning. Should the pilot light extinguish, the flow of gas would be cut off.

The secondary heat source, the tube style heater, is a loose cannon. As soon as you plug it in, it atomizes the fuel, kicks on the fan and starts sparking. If the igniter falls down on the job, a stead spray of fuel will start collecting in the tube. Can you say time bomb?

This could spell disaster in a wood shop. I absolutely NEVER EVER let this heater run when I’m not in the shop. During the next post, I’ll show you how I control this beast.

Can you see your breath?

How about you? Is you shop heated? What kind of heater do you use? I’d love to hear about your situations and hear your questions about how to stay warm.

 

David

 

P.S. Check out the following posts to catch up with the valuable shop tips I’ve shared here so far.

Switched Outlet with Fuse

Router Table Switched Outlet