STC 1000 Problem

[Dark-Farmer]

I have made 2 STC 1000 units is the past. The other day I received another one I order off ebay and have a bit of a problem.

It has 3 wires for the heating and cooling leads. I'm a little confused as the other 2 i have only have 2 wires.

Anyone else have any experience with this?
I'm thinking perhaps it could be an extra lead for perhaps an indication light?

 

[rprego]

"NC" is commonly "not connected". So I'd say just wire it like the other two you've done and leave the nc ones disconnected.

 

[Dark-Farmer]

Seems strange that a chinese product would add an additional wire spot (ie add costs) when they didn't have to if there isn't a purpose.

 

[Bigdaddyale]

NC might stand for normally closed

 

[raysmithtx]

First the disclaimer, I am not an electrician.

The diagram shows it's switching a Common wire (which should be the Black wire) so there will be no wires going to terminal 3 or terminal 6. The NC stands for Normally Closed in this instance. From there just wire it like your other 2 wire controller.

Here's a little more info:
From the wall the Power and Common wires are run to terminals 7 and 8. The Black wire will be the hot wire and the white wire will be the neutral wire.

Note which terminal you attach the hot wire (black) to. You can then jumper that power terminal (7 or 8) to terminals 2 and 5.

You then splice the other wire (the white wire) coming from the wall to white wire on the heat device and black wire on the cooling device. So you have a power wire going to one side of the heat and cool and the other side is switched though the STC.

The other wire on the cord to the heating and cooling device goes to terminals 1 (cooling) and 4 (heating).

I bought a box for my controller and installed a couple of wall outlets and wired the STC directly to them so I could just plug the heating and cooling device into the outlet and all the wiring is hidden and safer. I used a standard 2 outlet box from Lowes for mine.

 

[Dark-Farmer]

Thanks for the detailed response Ray.
I fully understand the wiring. Like I said I have successfully made 2 STC's for ferm chambers in the past.

This time it had that extra NC lead and it was throwing me off a bit.

I ordered a waterproof electronics project box off ebay for mine

 

[doug293cz]

First the disclaimer, I am not an electrician.

The diagram shows it's switching a Common wire so there will be no wires going to terminal 3 or terminal 6. The NC stands for Normally Closed in this instance. From there just wire it like your other 2 wire controller.

Here's a little more info:
From the wall the Power and Common wires are run to terminals 7 and 8. The Black wire will be the hot wire and the white wire will be the neutral wire.

Note which terminal you attach the neutral wire (white) to. You can then jumper that power terminal (7 or 8) to terminals 2 and 5.

You then splice the other wire (the Black wire) coming from the wall to black wire on the heat device and black wire on the cooling device. So you have a power wire going to one side of the heat and cool and the other side is switched though the STC.

The other wire on the cord to the heating and cooling device goes to terminals 1 (cooling) and 4 (heating).

I bought a box for my controller and installed a couple of wall outlets and wired the STC directly to them so I could just plug the heating and cooling device into the outlet and all the wiring is hidden and safer. I used a standard 2 outlet box from Lowes for mine.

The RED sentence reads to me that you are saying connect the NEUTRAL from the incoming power to the COM terminals of the output relays: terminals 2 and 5. This is an incorrect way of wiring (even though it will work), since it ends up switching the NEUTRAL wires not the HOT wires. Code (NEC) requires switching the HOT wires to the load. Therefore, the incoming HOT (black) wire needs to connect to either terminal 7 or 8, and also to terminals 2 and 5. The only NEUTRAL connection (incoming white wire) on the STC is to either terminal 7 or 8 (whichever didn't get the black wire.) There should be no neutral connection to any of terminals 1 thru 6.

If OP still has questions about how to wire, please ask. Include in the request for more information whether you want to wire to an outlet or pigtails.

Brew on

 

[raysmithtx]

The RED sentence reads to me that you are saying connect the NEUTRAL from the incoming power to the COM terminals of the output relays: terminals 2 and 5. This is an incorrect way of wiring (even though it will work), since it ends up switching the NEUTRAL wires not the HOT wires. Code (NEC) requires switching the HOT wires to the load. Therefore, the incoming HOT (black) wire needs to connect to either terminal 7 or 8, and also to terminals 2 and 5. The only NEUTRAL connection (incoming white wire) on the STC is to either terminal 7 or 8 (whichever didn't get the black wire.) There should be no neutral connection to any of terminals 1 thru 6.

If OP still has questions about how to wire, please ask. Include in the request for more information whether you want to wire to an outlet or pigtails.

Brew on

I obviously wasn't very clear. That's what being in a hurry does for you. I have corrected my original post.

 

[Dark-Farmer]

You know it came with a piece of paper that i guess where the instructions/manual.
You would think it would tell you this .... all it had to say was NC means "normally closed" and it wall would have made sense

 

[doug293cz]

You know it came with a piece of paper that i guess where the instructions/manual.
You would think it would tell you this .... all it had to say was NC means "normally closed" and it wall would have made sense

To be fair to the manufacturer, the STC-1000 is not a consumer device. It is a component meant to be built into higher level devices by system integrators. It is not marketed to novices. Assuming that the system integrators are familiar with standard component nomenclature is not an unreasonable assumption. Also, there are very clear schematics of what the terminals are, that would be obvious to anyone trained in electric/electronic devices.

This is where sites like HBT come in to help. We have experts that loiter around here, who are willing to help novices out, educating them, answering their questions, and helping them fix their mistakes. This thread is an example of that.

Brew on

 

[MaryB]

You could add an indicator bulb to the NC side and when that light is off that side is working.

 

[doug293cz]

You could add an indicator bulb to the NC side and when that light is off that side is working.

No, an "Operating" indicator light has to be added on the NO (normally open) side of the relay, in parallel with the load. The STC-1000 has built-in display panel indicators indicating when the cooling relay and heating relays are closed (both are NO.) However, added external indicator lights can tell you if power is actually being provided to the load.

Edit: Misread where you said light "off" means side is working, so what you say will work. But I find "Light Off = On" and "Light On = Off" to be counter intuitive and confusing.

Brew on