stc-1000 questions

[raouliii]

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.

 

[thatjonguy]

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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[jekeane]

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?

 

[mattd2]

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.

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

NOOOO!! AND NOO!!
...you're running a risk of burning your place down!
...

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]

You guys are chopping up extension cords to wire your whole set up?....So I don't need to buy a roll of wire, just hack up a 12ga cord?...

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]

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.

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.

 

[acafro]

I'll toss in a few more cents.

The internal relay of the STC1000 that I own is rated at 15A/125VAC.

[

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]

Maybe I should look inside mine... the paperwork and stickers say 10 amps. It would be nice to have one rated to 15......

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.

 

[acafro]

I have a 750 watt space heater that draws 12.5 amps that I would much rather use if my STC-1000 would handle up to 15 Amps...

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[user 163849]

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.

 

[Brumateur]

I have a 750 watt space heater that draws 12.5 amps that I would much rather use if my STC-1000 would handle up to 15 Amps...

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]

I have a 750 watt space heater that draws 12.5 amps that I would much rather use if my STC-1000 would handle up to 15 Amps...

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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

 

[Lopsy]

Well I personally feel that a 4awg/3 is the only thing capable of handling that kind of power!

Keep it cool boys. Use a 14awg and be done with it. No more discussion necessary.

 

[day_trippr]

fwiw, the typical "computer power cable" is rated for 10A...

Cheers!

 

[acafro]

You puzzled me. To draw 12.5 Amp to get 750Watt you should run it at 60Volt. What kind of application do you have?

Its a space heater... it a 750 watt space heater and according to manufacturer specifications it draws 12.5 amps.

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[acafro]

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

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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[jleiii]

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...

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.

 

[mattd2]

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!

 

[acafro]

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).
.

It very well could be a 750 / 1500 that would certainly make more sense..


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[jleiii]

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!

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.