Thermostat Controlled Plug Box

[Eric] has a problem with his new house, there was no heat in the attic space that had been converted into a loft. Facing no way to tap into the ductwork and wanting to use the space as a bedroom he did what most of us would, and just got a little space heater. Anyone who has lived with a space heater knows you have to be around to turn them on, and they usually dont have decent temperature control. These problems were quickly fixed by making a thermostat controlled plug box.

A quick trip to the hardware store resulted in a 2 gang metal junction box, faceplate with GFCI cutout, receptacle and a Honeywell baseboard heater thermostat. The thermostat is then wired to mains and its output connects to the receptacle.

He gives instructions on wiring which focuses on his parts, but you should follow the instructions to your specific thermostat, and error on the side of caution if working with mains current. The end story is a bedroom with a more constant temperature and doesn’t need a 3 hour burn to get there.

19 thoughts on “Thermostat Controlled Plug Box

  1. @Jesse: Give him a break… “To error is human,” after all. :P

    On a related note, a while back I needed a heavy-duty rheostat that could handle larger voltages/currents than the potentiometers available at Radio Shack, so I went to a home improvement store and purchased a dimmer switch. When I opened the thing up at home, though, I realized it was much more complicated than a simple rheostat. Apparently, modern dimmers use TRIACs to cut out part of the AC waveform, kind of like PWM. Wish someone would’ve told me…

  2. @Jesse: though the conventional idiom is to use “err”, it means the same thing. To “err on the side of caution” means, if you are going to make an error, it is better to be too cautious than insufficiently cautious, where the non-error condition is to be precisely cautious enough. So, Kevin is grammatically and semantically, if not idiomatically, correct.

  3. I have a feeling this does not meet code !

    I’m too lazy to pull up the relevant cite from my NEC code book here, but if I were doing the permit inspection on this, I’d fail it.

    A baseboard heater thermostat is designed to connect directly to the baseboard heater. Not an electrical outlet, where you plug in the heater. Cleary in violation of code. Code is bare minimum, contrary to popular opinion, inspectors are looking out for your safety.

    If the poster owns the property, any home inspector would fail it. If the poster rents it, I hope he got permission from the landlord. If it were me i’d be pissed !

    Wiring up electrical heaters (or components of same), in a way contrary to what the manufacturer intended, is a good way to put your butt in a sling with the insurance company when the house burns down.

  4. @Jason: Actually they’re not the same, because “err” is a verb and “error” isn’t. It’s not grammatically possible to “error” on the side of caution. Jesse was right.

  5. I think UhOh is talking about a different
    type of baseboard thermostat.

    The Honeywell CT410 is designed as a remote
    thermostat to control baseboard heating units,
    and is designed to be installed in a wall box
    just like it is in this hack.

    I’m not an inspector, but I’d expect this would
    pass an electrical code inspection.

    (BTW: I modified this thermostat to run a 100W
    light bulb in my oven to “bake” yogurt at 110F
    for 8 hours. I use it every week.)

  6. I’d say whether this meets NEC would be a gray area. If the control unit is being used in compliance with the manufacturer’s specifications, it meets code. Otherwise it does not.

    Insurance companies would most likely *not* pay if the house burns down and this hack is determined to be at fault. Insurance companies don’t make a profit paying claims, so they’ll use any excuse available.

    In the end, you have to ask yourself one question. If the insurance company refuses your claim, are you willing to take them to court over it?

  7. @krylenko: many technical fields have long since “verbified” the word “error”. Language evolves.

    On topic: I’ve been looking for something like this so I can automatically heat my hose bibs when freezing weather hits. I think soon I’ll be submitting a hack. :-)

  8. 2 reasons why this wouldn’t meet code.

    No connector for the cord going into the box.

    The ground is tied to the box cover.

    1 reason why it wouldn’t matter.

    inspector says NO, unplug it…..

  9. “no heat in the attic space that had been converted into a loft” Is enough information to know that no permit was obtained and the entire space is suspect as far as code goes. This hack would just be another item on the long list of problems. Top of the list would be electrical junctions in the wall, moisture/mold problems from poor ventilation, and structural modifications.

  10. If folks on here only did things that met the NEC then nobody could do ANYTHING using 110 AC. Forget about anything home built. Lets all just stay safe and only use things that are UL approved. Oh and if you have a good idea for something that plugs in don’t forget it only costs 10s of thousands or more to get it approved.

    Lawyers will be the death of innovation in this country.

  11. @tjb, you’re 100% right. When “Harry Homeowner” (or a plumber with a Sawz-All) is doing DIY work, look out ! Most attic floor joists = lower floor ceiling joists, are rated for 20lbs/sq ft live loads. I once inspected a property, where the homeowner not only notched the joists, but on top of that put a water bed over it ! I had learned several months later, it had collapsed, killing the owners child under the debris in the room below.

    @dbear, you want to burn down your house experimenting with questionable projects that insurance companies would love denying claims over. Have at it. No one stopping you.

    BUT, if you live in a row house, attached condo, etc. Expect to need a lawyer because those other folks will be suing you when the $hit hits the fan (not to mention the possibility of criminal prosecution). Again, if you live alone in a detached property, hey go for it. Your house, your money, your battle w/insurance company when they investigate and deny any claims.

  12. Sorry folks, but code has NOTHING to do with “bare minimum” (or indeed any likely consequence of a particular setup), and it has EVERYTHING to do with limiting liability in a “lets make sure nothing bad can ever possibly happen by legislating massive overkill” way – which, as we all know, is NOT something ANY amount of safeguarding can ever guarantee.

    Just to make it clear: whether this sort of thing fails or not depends on you respecting the basic laws of physics – and some caution and common sense – and not on respecting some arbitrary law called “code”.

    Whether you get in trouble for it or not is an entirely different issue…

  13. @Max

    If you really believe code is “overkill”, you and shoddy contractors should get along just fine.

    The type of contractor that cuts through load bearing engineered trusses to run plumbing. Or the type of contractor that see’s nothing wrong with multiple earth grounds where-ever it’s convenient. Or the type of contractor that installs new drain lines without a vent stack.

    Fact of the matter is, the NEC, and NFPA (and OSHA, and FAA) regs are “written-in-blood”. Someone had to die or be seriously injured because of something that happened that the regs address. Regs that are NOT arbitrary! They were put together in the same manner RFC’s are. Some very intelligent people (architects, engineers, master electricians, etc) have input into “code”.

    I’ve built many custom homes, and I always insist on “best practices”, not just “to code”. There’s a difference! Code is bare minimum.

    The lawyers will not have a case if everything is done ‘by-the-book’.

    Apologies to the OP, didn’t mean to “hijack” the thread.

  14. overall not a bad project. A few things, don’t use electrical tape to cover a connection for high current applications. Tape comes in varying qualities and with something high current like heating using the wrong kind can end badly. Use wire nuts.

    The thermostat choice wouldn’t be my first because the temperatures marked on the dial are probably calibrated to a specific model number of heater.

    A just as easy design would be to use a regular home thermostat with a 12VDC wall powered adapter to switch a 15A rated relay in the plug enclosure. It is the same thing every home heating system does.

  15. If there is something that troubles me more than anything else, it’s the lack of a connector on the box. A connector is designed to hold the cord in place (better than a knot) and keep it from rubbing against sharp metal on the box knockout. I did something similar but with a power supply, and I used a connector for the cord. And costs around 50 cents and would save a lot of trouble.

  16. Code issues aside, why not use a programmable thermostat so it will heat up before you arrived and turn off before you leave?

    It would be safer since it wouldn’t be running all day while you were gone and more efficient.

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