stc-1000 questions
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hopdropper
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Just built mine, and used 16GA throughout. According to the label on my chest freezer, it only draws 5 amps, so I figure 16GA ought to cover it. Haven't actually tested it with a full load yet though. Might just add a 10 amp inline fuse just as a precaution. And for what it's worth, check out this link. This guy has an AWESOME and easy-to-decipher diagram showing you how to wire up the entire project, including some LED bling.
http://loudmouthbrewer.wordpress.com/2013/12/10/diy-stc-1000-2-stage-temperature-controller-wiring-diagram-with-indicator-lights/
http://loudmouthbrewer.wordpress.com/2013/12/10/diy-stc-1000-2-stage-temperature-controller-wiring-diagram-with-indicator-lights/
NOOOO!! AND NOO!!
IMO 16 gauge wire is generally FAR to small to run a refrigerator compressor! 16ga is only good for 12-13 amps. In all seriousness if you run 16ga to a refrigerator that draws over the amperage a 16ga wire can handle you're running a risk of burning your place down!
And I highly recommend AGAINST permanently using extension cords for anything! There is a reason it is against fire code!
For a refrigerator you are going to want a 14ga wire and a 110v 15 amp circuit and the least!
I just built a fermentation chamber and I actually wired a 25 foot plug using 14/2 with a ground using outside wire. The STC-1000 can only handle a 10amp draw on it so a 15 amp circuit would be fine as long as what is drawing on the controller is less than 10amps.
But If your refrigerator draws less than 10 amps then go for it. Otherwise don't let your wiring job become your weakest link!
I really feel you are far better off over sizing the wire and not needing the capacity then trying to skimp on the wire and need the extra capacity.
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hopdropper
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acafro, forgive me for being thick...i'm not an electrician (nor do i play one on TV), but if the STC-1000 is, in fact, only rated to 10 amps, and a 16GA extension cord to 13 amps, wouldn't the OP be perfectly fine building his controller with wire from a 16GA extension cord??? Cause it seems to me that the STC-1000 would be the weakest link (and fail first, 3 amps worth of draw before his extension-cord-build would give out)...
By using your reasoning you should not be using a STC-1000 that is rated only for 10A on a 15A circuit. What is your reasoning for saying the you can not use cable with a lower ampacity, but you it is ok to use other electrical componants with lower current ratings. By the way from what I have read the relays are in fact rated for 15A @ 120V.
I am not running a 15 amp system, I am running a 10 amp system on a 15 amp circuit. The circuit is the wiring going from the outlet to the breaker panel and that particular system, is on a 15 amps breaker, thus it is a 15 amp circuit (as is most of the circuits in my house other than 220 volt circuits). Now for the record I am not an electrician and my terminology could be off, but the licensed electrician who helped my with this system seems to feel it is an appropriate set up. The 15 amp circuit merely means that circuit that the fermentation chamber is plugged into can handle up to 15 amps
The system I have set up does not draw more than 10 amps on the controller. So yes, the STC-1000 is appropriate for this particular application.
as far as the STC-100 rating go, here is a picture of the wiring diagram that came with the STC-1000.
10A/220VAC to me indicates the STC-1000 can only handle 10 amps up to 220 Volts AC. Though I could be mistaken...
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the STC-1000 is only rated for 10 amps and yes it may be the weakest link depending on how it is wired, if the wiring between the heater / Air conditioning and the STC-100 is too small then that could be the weakest link, and if the controller does not fail and draws too much on the extension cord then that may become the weakest link. Why even chance it and use wiring that comes close to max capacity?
Just because the STC-1000 is rated for 10 amps doesn't mean it will shut itself down. There is no fuse or circuit breaker in the STC-1000 to shut itself down, so if the system draws above 10 amps you are chancing a dangerous situation.
also extension cords are not designed to be used as permanent wiring, that is why there are fire codes against using them in such manner
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Thanks for the really entertaining thread everyone! I've enjoyed reading it.
I am currently using a stc-1000 for a ferm chamer myself, but its not a fridge or freezer.
I fear saying so, but I am an electrician.
First off to cover the extension cord topic. Have you ever looked at the wires in an extension cord to a vacuum, or even for the fridge or freezer you are using? The wire size that is supplied by a manufacturer for a device is rated for the amperage the thing will use. When I turn on my vacuum at home if I feel the cord I can physically tell the cord is warm, but it is not burning up or ready to cause a fire. This is simply because by design there is no way for the average user to overload the wire.
If the nameplate on your device (fridge) says it draws 8 amps then 16 awg wire is safe to use. Its safe because you have purposed the wiring to only that device. The unfortunate part about it is simply the temptation of having power supplied at the receptacle. I would recommend not plugging anything else into it. Leave it as a single purpose plug.
If I were to be wiring this myself the way you did I probably would have used 14 (15 amp) or 12 (20 amp) awg wire to the receptacle, whatever the breaker supplying the power is rated at. I would do this simply for the fact that I would then know that I could plug anything into the plug and it would be protected.
Second is your wiring of the box you created, and addressing the fan not running.
There are 9 terminals on the stc-1000. Three for the power input, 4 for the heat and cool contacts, and two for the thermostat. The power terminals simply do what you think they would do. You hook up the three wires from the cord and it will turn on. You don't need to have anything else hooked up and the thing will still turn on.
The heat and cool are simply contacts. They open, or close when the stc-1000 tells them to do so and that is all they do. Which is of course governed by the thermostat.
The way things look from your picture. The stc-1000 is turning off and on the power to the plug in the same box. So the fridge will turn on when the stc tells it to, but turns completely off when the temperature setting is met. The stc contact has broken and stopped supplying power to the fridge at all. That is why the fan does not run all the time.
There are other ways to wire the stc into a fridge replacing the fridges thermostat with the one supplied with the stc. That involves drilling into the fridge though and I don't blame a guy for shying away. I'm not going to write about how to do that as it is well documented on the net, (including videos) if one were to simply google it.
Sorry for the lengthy post, but I hope I was descriptive in enough to help, and stop the wire guage bickering.
I am currently using a stc-1000 for a ferm chamer myself, but its not a fridge or freezer.
I fear saying so, but I am an electrician.
First off to cover the extension cord topic. Have you ever looked at the wires in an extension cord to a vacuum, or even for the fridge or freezer you are using? The wire size that is supplied by a manufacturer for a device is rated for the amperage the thing will use. When I turn on my vacuum at home if I feel the cord I can physically tell the cord is warm, but it is not burning up or ready to cause a fire. This is simply because by design there is no way for the average user to overload the wire.
If the nameplate on your device (fridge) says it draws 8 amps then 16 awg wire is safe to use. Its safe because you have purposed the wiring to only that device. The unfortunate part about it is simply the temptation of having power supplied at the receptacle. I would recommend not plugging anything else into it. Leave it as a single purpose plug.
If I were to be wiring this myself the way you did I probably would have used 14 (15 amp) or 12 (20 amp) awg wire to the receptacle, whatever the breaker supplying the power is rated at. I would do this simply for the fact that I would then know that I could plug anything into the plug and it would be protected.
Second is your wiring of the box you created, and addressing the fan not running.
There are 9 terminals on the stc-1000. Three for the power input, 4 for the heat and cool contacts, and two for the thermostat. The power terminals simply do what you think they would do. You hook up the three wires from the cord and it will turn on. You don't need to have anything else hooked up and the thing will still turn on.
The heat and cool are simply contacts. They open, or close when the stc-1000 tells them to do so and that is all they do. Which is of course governed by the thermostat.
The way things look from your picture. The stc-1000 is turning off and on the power to the plug in the same box. So the fridge will turn on when the stc tells it to, but turns completely off when the temperature setting is met. The stc contact has broken and stopped supplying power to the fridge at all. That is why the fan does not run all the time.
There are other ways to wire the stc into a fridge replacing the fridges thermostat with the one supplied with the stc. That involves drilling into the fridge though and I don't blame a guy for shying away. I'm not going to write about how to do that as it is well documented on the net, (including videos) if one were to simply google it.
Sorry for the lengthy post, but I hope I was descriptive in enough to help, and stop the wire guage bickering.
Firstly sorry, you are right that all the documentation states 10A limit - it is only those that have opened up that have found that the relays are actually also rated for 15A @ 120V.
Your reasoning does not make sense - the cable can handle the expected current, the STC-1000 can handle the expected current. Why would you need to use cable that can handle more current than the breaker can handle for appliance cord. As someone said above if that was the case no appliances would be wired with anything less than 14 AWG.
Why are you distiguishing between two componants both rated below the CB rating and so could potentially (but not likely) be overloaded. You are basically saying that for some reason you trust the STC-1000 to stay together even though the rating says it should, but you don't give the same level of trust to the cable... personally I would trust the cable more
A fair as I am aware most warnigns about contious use of extention cords are due to the fact their is not control over the general publics use of them - i.e. people can easily plug loads over the rated current, if not used continously you would notice your cable is stating to burn/melt/etc. when you put it away.
Firstly sorry, you are right that all the documentation states 10A limit - it is only those that have opened up that have found that the relays are actually also rated for 15A @ 120V.
Your reasoning does not make sense - the cable can handle the expected current, the STC-1000 can handle the expected current. Why would you need to use cable that can handle more current than the breaker can handle for appliance cord. As someone said above if that was the case no appliances would be wired with anything less than 14 AWG.
Why are you distiguishing between two componants both rated below the CB rating and so could potentially (but not likely) be overloaded. You are basically saying that for some reason you trust the STC-1000 to stay together even though the rating says it should, but you don't give the same level of trust to the cable... personally I would trust the cable more
A fair as I am aware most warnigns about contious use of extention cords are due to the fact their is not control over the general publics use of them - i.e. people can easily plug loads over the rated current, if not used continously you would notice your cable is stating to burn/melt/etc. when you put it away.
The system is plugged into a 15 amps circuit, why would I not use 14 GA wire? If you would like to use wire that is smaller than go ahead, I simply do not feel comfortable using wiring that cannot support the total use of the circuit it is plugged into.
I also have other outlets and lights running in the same system that are not connected to the STC-1000, the potential is there to draw up to 15 amps from the system. But the heater and AC I have wired into the STC-1000 draw under 10 amps. I really fail to see why the concept is so difficult to understand nor do I see why it's an issue.
raouliii
Well-Known Member
I'll toss in a few more cents.
The internal relay of the STC1000 that I own is rated at 15A/125VAC.
The extension cord issue is a non-issue IMO. If an extension cord is hacked and used in a STC1000 build, it essentially is no longer an extension cord but a power cord for the device. Using 14 gauge as a power cord for an STC1000 build would result in the entire device being rated for 15amps. If the device is being built as a 10amp device, use 16 gauge, but it should probably be labeled as such.
I've built up a few of these devices and haven't seen the need to use 14 gauge wire on any of them. One used a scavenged 16gauge computer power supply cord. Another used both ends of a 16 gauge extension cord with the controller boxed in the center. Another is surface mounted to a cooler with 16 gauge wire inserting it into the thermostat circuit.
I believe the regulations associated with using an extension cord in a permanent installation is for a situation where one is used to extend a circuit to a permanent fixture or appliance instead of adding a circuit to the building or dwelling.
The internal relay of the STC1000 that I own is rated at 15A/125VAC.
The extension cord issue is a non-issue IMO. If an extension cord is hacked and used in a STC1000 build, it essentially is no longer an extension cord but a power cord for the device. Using 14 gauge as a power cord for an STC1000 build would result in the entire device being rated for 15amps. If the device is being built as a 10amp device, use 16 gauge, but it should probably be labeled as such.
I've built up a few of these devices and haven't seen the need to use 14 gauge wire on any of them. One used a scavenged 16gauge computer power supply cord. Another used both ends of a 16 gauge extension cord with the controller boxed in the center. Another is surface mounted to a cooler with 16 gauge wire inserting it into the thermostat circuit.
I believe the regulations associated with using an extension cord in a permanent installation is for a situation where one is used to extend a circuit to a permanent fixture or appliance instead of adding a circuit to the building or dwelling.
thatjonguy
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You guys are chopping up extension cords to wire your whole set up?
I am getting ready to build my first fermentation chamber and will be framing it out with 2x4s, plywood and R19 insulation.
So I don't need to buy a roll of wire, just hack up a 12ga cord?
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I am getting ready to build my first fermentation chamber and will be framing it out with 2x4s, plywood and R19 insulation.
So I don't need to buy a roll of wire, just hack up a 12ga cord?
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jekeane
Well-Known Member
You can but 12g and 14g wire by the foot at Home Depot for .39 and .29 cents respectively. You need 4 ft of wire max for your box. Thats less than 3.25 for good clean wire... Using an old power cord like a computer cable is fine for your power but is it really worth the hassle scavenging a extension cord for your box wiring?
Well what you are saying is the OP should not use cable that is adequate for his use because it is not adequate for your use. Your original post was basically
Sorry for taking you slightly out of context
If you have designed your system that the likely maximum current draw is close to 15A then I completely agree with you that you should use 14AWG cable (Don't quote me but 18AWG is actually rated for 16A in free air @ ambient temp 86°F - Facinerous care to confirm?)
14AWG for 15A circuits is only a derating requirement for building wiring as per the NEC, i.e. the wire inside the walls between the breaker and the wall socket(s)
raouliii
Well-Known Member
Sure. Why not? Now, I'm not sure what your "whole set up" will be but an extension cord can be sacrificed into use as a power cord. And it already has a handy molded plug attached. Individual conductors can be pulled from the sheathing to be used as jumpers if necessary. The entire load of your "whole set up" needs to be considered in sizing the cord.
thatjonguy
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The chamber need a power cord from the wall outlet when in use to a master switch on the exterior with a constant on outlet after the switch for a small fan. The two additional outlets controlled by a STC 1000 for heating and cooling. Heater is a small ceramic and cooling is a 5k but AC. Using the plug end to connect the master switch to the outlet.
Hence the choice of 12ga to be safe.
Maybe I should look inside mine... the paperwork and stickers say 10 amps. It would be nice to have one rated to 15...
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raouliii
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The paperwork on mine indicated 10A. Unless using a heater above 1000watts or a larger than normal refrigerator or freezer, 10amps is all the device capacity that is needed. Any additional loads, not running through the STC1000, need to be considered only for power cord sizing.
user 163849
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Once the extension cord is cut and wired to the STC-1000 it is no longer an extension cord. It is a perfectly acceptable power cord and as the STC-1000 is rated at 10 amps by the manufacturer a 16 gauge power cord is the "right"/minimum size wire to use. In this case minimum size is an advantage when it comes to fitting the wire to the small terminals on the STC-1000, and it is more than adequate for the current ratting of the device. You could use 16 gauge or any larger size wire that you choose (though 500 mcm might be a bit of overkill) but there is no valid reason to recommend that others not use 16 gauge wire on a 10 amp circuit but instead should use a wire size larger than what the load current demands.
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You puzzled me. To draw 12.5 Amp to get 750Watt you should run it at 60Volt. What kind of application do you have?
user 163849
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There is something seriously wrong if a 750 watt space heater is drawing 12.5 amps. Should be about half that at 120 volts.
Watts/volts=amps
fwiw, the typical "computer power cable" is rated for 10A...
Cheers!
Cheers!
Its a space heater... it a 750 watt space heater and according to manufacturer specifications it draws 12.5 amps.
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On the rating sticker, that appliance are required to have, it reads that the heater draws 12.5 amps. And it is a 750 watt heater I get the mathematics of it. I'm just telling you what the specifications are...
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If that's what's on the label, then it can't be a UL approved device. They would never allow that. W/V=A, in this case 750/120=6.25 amps. There'e more to this heater. Are you sure it's not 750/1500 watts? 1500 is 12.5 amps, and this is typical for virtually every space heater made in the last 50 years (I own a heater element mfg business - we deal with these devices all the time).
To those opening your controllers and reading the ratings of the parts - Stop! The ENTIRE device has a rating based on ALL the components in the system. That relay is connected via copper traces on a circuit board, and to the outside via the screw connectors. If it says 10 amps max, there is a reason, very likely the copper traces.
Power cord ratings (actually wire in general) are based on the type of wire, and how it's used. Interior household wiring is 14awg for 15a and 12awg for 20a. This is because the insulation will overheat if you exceed it, and it's rated that way. That same size copper conductor when used inside of a heating appliance is rated higher. If you were to look at the wire inside of that space heater it's very likely smaller gauge, probably 16awg, as it's rated differently, and insulated differently, but still quite capable of handling the current. It will be warm to the touch when at full rating, whereas your typical power cord is (should?) not.
Good point about not taking the relay rating as the actual rating!
For what it is worth 14AWG is rated for 20A and 12AWG is rated for 25A, but the NEC specifies in certain circumstances that the maximum CB allowed for 14AWG is 15A and 12AWG is 20A. And that is for insulated conductors in raceways, cable or earth.
As mentioned above it is alright if the cable gets warm to the touch - depending on its specs the temperature limit of the cable could be between 65°C-90°C. It should not be hot to the touch though!
It very well could be a 750 / 1500 that would certainly make more sense..
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Appliance wire we work with is rated at 200, 250, 450 and 550C. According to Belden, 200C wire, 16 awg, is rated to 35 amps (in free air, 86F ambient) which means it won't exceed 200C. A whole lot more than you'd think!
Stick with the 14awg/15a and 12awg/20a and you'll never have to worry.
