Multiple STC-1000 Controllers

Hey Everybody,

I know that there are tons of STC-1000 wiring how-to threads out there, however I have a couple of specific questions around wiring up multiple, 2 in my case STC-1000s.

Below is a wiring diagram that I put together. I am not an EE, or even an electrician for that matter, so I will explain what I am trying to depict in the drawing:

I have a mini-fridge that I was using for serving, but I recently upgraded to a GE 5 CUFT chest freezer for serving, so moving forward I will be using the mini-fridge for fermenting. I plan to install 2 STC-1000s in a makeshift control panel. Each STC will be wired to 1-15 amp dual receptacle. A third 15 amp dual receptacle will be added and wired directly to the main feed for a "constant on". 1 of the STC-1000s and outlets will be used to power the mini-fridge (fermentation chamber) and the other will be used to power the chest freezer for serving. Each STC and receptacle will be wired identical as shown in the diagram. I plan on using the "constant on" receptacle to run 2-4" fans - 1 for the mini-fridge and 1 for the chest freezer.

The questions I have are below the diagram (I just realized as I was going to post this that the labels on the STC and the outlets in the diagram are flip-flopped, but I think it still gets the point across):



1. Can I run just one main line into the control panel (as shown in the diagram) and splice it to provide power to both STC-1000s? This essentially means that I could be running the mini-fridge and chest freezer at the same time through the control panel that is plugged into 1-15 amp outlet tied into a 15 amp breaker, that is responsible for the load of other lights and outlets in the house as well.

NOTE: The GE chest freezer is spec'd at 15 amps, I am assuming thats at the moment that the freezer turns on, probably does not run at 15 amps once up and running? GE just says 15 amps though.

2. Should I just play it safe and run 2 main lines in, one for each STC vs splicing one main between 2 STC-1000s? Even then, could I run the mini-fridge and chest freezer off of 1-15 amp dual receptacle that, as mentioned above, is tied into a 15 amp break? If both happened to turn on at the same instant could the sudden draw of power flip the breaker?

3. If I run 2 main lines, and the chest freezer requires ~15 amps, there is no need for me to put the inline fuse in place is there? Considering the circuit is 15 amps? Would the fuse blow before the circuit flips? If so the fuse could save some irritation of lights and other outlets going out if this setup happens to pull too much power.

4. Do I need to have a fan for the mini-fridge (about 4.5 CUFT)? If not, should I wire the main line into one of the outlets for my chest freezer receptacle (which would reduce my total receptacle count from 3 to 2)? As shown in the diagram I am wiring the heat up to one of the outlets but will probably not be using the heat, just the cool. Could I use the other as the "constant on" for a fan for the chest freezer?

5. Should I add ventilation to the control panel for the STC-1000s? I have read that they do not produce that much heat, however, here in the Texas hill country we can get consecutive days over 100 in the summer time, and I do plan to keep this setup outside on the back porch?

That is everything I can think of right now. My main concern is the power draw running the two appliances off of one 15 amp outlet that is tied to one 15 amp circuit.

I really appreciate any advice.

Thanks,

John

Does your freezer really pull that much juice? That's very surprising to me. I gave an older 5ish cf keezer that pulls 3 amps and a 7ish cf chamber that pulls less than 8. What you should really be concerned with is that those controllers are only rated for 10a and the mean it. I've burned them up Acer running just North of that after only 2 weeks off and on.

The 15 amps specified on the label may be the locked rotor rating of the freezer. It probably isn't that many amps in normal use - or even at starting.

Are you able to run both units on the same wall circuit now without tripping the breaker?

If yes, what you can do is use one 14 gauge power cord from the wall receptacle to your control box. Then use two 10 amp fuses in the control box to protect each controller circuit. You really do want a 10 amp fuse protecting each controller - the internal circuits aren't made to pass more than that.

Electrically, this is pretty much the same as if you built two stand alone controllers and plugged them both into the same duplex receptacle.


Yes, you can use the other half of a duplex receptacle for your always on fan circuit where you don't need it for the heat circuit. Since it won't run through the controller, that always on side doesn't need to be fused - but it does need to be wired with 14 gauge.


Ventilation of the enclosure can't hurt, given your high ambient temps on the porch.



Thinking about this a bit more, I would probably go with two separate control boxes so that I don't always have to keep the two units next to each other on the porch.

No need for two separate neutrals to each of the duplex outlets. Even if the tab is already broken, a short jumper is adequate.

OCBrewin said:

Does your freezer really pull that much juice? That's very surprising to me. I gave an older 5ish cf keezer that pulls 3 amps and a 7ish cf chamber that pulls less than 8. What you should really be concerned with is that those controllers are only rated for 10a and the mean it. I've burned them up Acer running just North of that after only 2 weeks off and on.

Click to expand...

I am not sure I have not tested it myself. That is just what GE is saying that they recommend? Thanks for the heads up on the 10A on the controller!

reynolds5520 said:

Are you able to run both units on the same wall circuit now without tripping the breaker?

Click to expand...

Actually I have not tried yet, the chest freezer is still sitting all brand new in its box. I should obviously give that a try and let it run for a couple of days.

reynolds5520 said:

If yes, what you can do is use one 14 gauge power cord from the wall receptacle to your control box. Then use two 10 amp fuses in the control box to protect each controller circuit. You really do want a 10 amp fuse protecting each controller - the internal circuits aren't made to pass more than that.

Electrically, this is pretty much the same as if you built two stand alone controllers and plugged them both into the same duplex receptacle.

Click to expand...

Once inside the box can I splice a lower gauge off of the main feed. Say I run 14 in for my main can I / should I use 12 or 10 to the controller and to the outlet?

OCBrewin mentioned the 10A max as well. I will definitely protect these controllers with a 10A inline fuse as mentioned. I updated my drawing below to show 14ga feed with 2-10A inline fuses just before the controllers.

reynolds5520 said:

Thinking about this a bit more, I would probably go with two separate control boxes so that I don't always have to keep the two units next to each other on the porch.

Click to expand...

Yeah I thought about that as well. I actually considered too, to just install the units directly into the door/lid of the unit, but opted against that. I think I am going to move forward with the single box. I do not anticipate moving them too far from one another, but if I do I will remember you told me so!

raouliii said:

No need for two separate neutrals to each of the duplex outlets. Even if the tab is already broken, a short jumper is adequate.

Click to expand...

Assuming the same goes for the ground? I removed the 2nd feed of neutral and ground to each outlet and updated my diagram.

I really appreciate the feedback guys.

I'm interested in this thread... I am building a 3-controller box right now. One will switch the chest freezer and the other two will control only heat for independent temp control of each of 3 vessels in my ferm chamber. (see signature line) I plan to post pix of the box once finished...

I am building a 3-controller box right now. One will switch the chest freezer

leokatero said:

I am building a 3-controller box right now. One will switch the chest freezer

Click to expand...

Is something missing? looks as though you were trying to quote me on this post...

jkmcd3 said:

Once inside the box can I splice a lower gauge off of the main feed. Say I run 14 in for my main can I / should I use 12 or 10 to the controller and to the outlet?

Click to expand...

Your logic is good in asking whether you can use a smaller wire. The next size smaller is 16 gauge (wire gauge numbers can be confusing - larger numbers are smaller wire) and capacity charts rate it to 13 amps.

So, you could use 16 gauge for all of the connections inside the box. Just make sure that you step down from the 14 gauge such that you fully split the loads. Don't share one 16 gauge neutral to all of the receptacles - run one to each. I hope I am making sense here - it would be easier to show on a drawing. In your drawing, the vertical lines representing the incoming power cord should all be 14 gauge. The horizontal lines that tap off of the vertical can be 16 gauge.

There isn't much difference in size though. If you can't find 16 gauge stranded type TFFN, THWN, or THHN, then just use 14 gauge. The 14 will be readily available.


On your drawing, it looks like you are ready to build this properly. To help someone that comes along after you and wants to use your drawing, there are a couple of things that would help with clarity.

1. In a U.S. standard 15 A 120V receptacle, the smaller of the two blades is the hot side, and you properly show the switched current running to the smaller blade of the receptacle. But, the small blade should be on the right side rather than the left.

2. You don't need to show ground and neutral wires to each half of a duplex receptacle since they are built in. But for clarity in the drawing, you could make a box around the two halves to show that it is one duplex receptacle and then show the internal connection tying the halves together. (A small modification of the bubble around the receptacles that you have there now, more like your original.) That way nobody will get confused.



edit: I just looked again at your drawing. The unswitched fans receptacle should be all 14 gauge - since it isn't on the fused 10 amp circuits.

Thanks Reynolds for all the help. I think I got it now. Here is the updated drawing:



Sorry to be short but I am out of town on business the rest of this week so this project is on hold until this weekend. But once finished I will post some pics.

In the mean time here is what I was able to get done before I left. Couple pics of all the parts and the case cut and mocked up:

Also, I decided to just run 14ga throughout the entire box (drawing does not show this, so I should update it). This shouldn't be an issue should it?

I just did not want the extra expense of buying 14 and 16ga.

John

The latest drawing looks good.


All 14 gauge is fine, won't hurt anything.


The wire in the pictures looks like it might be what is commonly called "primary wire". Perfect for low voltage applications like automotive work but not what you want here.

Look for type THHN wire. Stranded or solid are both OK but stranded will be more flexible for bending in the enclosure. Places like Home Depot sell it by the foot.

Man... this is crazy. You and I are building almost the exact same thing right now. I am running 3 temp controllers in mine though. It is a tight fit!

Don't worry about that 14 gauge. I am running 14 gauge THHN throughout my controller box and even after tinning the ends that insert into the controller they just BARELY fit. I would NOT go any bigger though.

A quick question to those in the know about wiring basics---Can I daisy chain all the grounds of each of the three outlets to each other and then to the ground that comes in on the supply wire? Likewise, can all three outlets have the Neutral daisy chained and back to a terminal block? I will of course be running each hot interdependently to each outlet, heat control and cool control.

Huaco said:

A quick question to those in the know about wiring basics---Can I daisy chain all the grounds of each of the three outlets to each other and then to the ground that comes in on the supply wire? Likewise, can all three outlets have the Neutral daisy chained and back to a terminal block? I will of course be running each hot interdependently to each outlet, heat control and cool control.

Click to expand...

Yes, with 14 gauge you can daisy chain all of the grounds and all of the neutrals back to the supply wire.

reynolds5520 said:

Yes, with 14 gauge you can daisy chain all of the grounds and all of the neutrals back to the supply wire.

Click to expand...

Great, thank you!
Glad my thoughts were confirmed...

Thanks reynolds for the heads up on the wiring. I took all that junk back and just got 14ga THHN by the foot. Actually saved me about 15 bucks so I was happy about that.

Well... I got it all wired up and... not working.

The always on outlet works but the two STCs are not coming on. One thing I have noticed is that people are splicing off of the main neutral feed and taking one to the outlet and then one to the STC. I did not do this. I ran a neutral from the STC to the outlet and then from the main to the outlet.

On another note I spliced the main hot 3 ways once in the box. One to the always on. One to a 10A fuse for STC1. One to a 10A fuse for STC 2. Once on the other side of the fuse I spliced the hot 3 times again for each of the STCs. One to pin 1, one to pin 5 and one to pin 7.

Anything you guys can think of that might not seem right? I broke both bridges on the STC outlets, so the neutral from the main and the neutral from the STC are never come in contact, if that helps troubleshoot.

Thanks guys,

John

jkmcd3 said:

I broke both bridges on the STC outlets, so the neutral from the main and the neutral from the STC are never come in contact, if that helps troubleshoot.

Click to expand...

If I read your description correctly, you have the neutral from the power cord connected to one half of the duplex receptacle, then the bridge between the halves removed, then the neutral for the controller connected to the other half of the duplex receptacle.

That is the problem, the neutral side on the control box (pin 2) and the neutral side of the duplex receptacle (both halves) each need to be connected to the neutral side of your incoming power cord.

You have no path back to neutral from the controller.

Your first drawing showed the neutral side correct. I guess the later drawings can be misinterpreted.

The fix is easy though, all you need is a piece of wire to replace that missing bridge on the neutral side.

reynolds5520 said:

If I read your description correctly, you have the neutral from the power cord connected to one half of the duplex receptacle, then the bridge between the halves removed, then the neutral for the controller connected to the other half of the duplex receptacle.

That is the problem, the neutral side on the control box (pin 2) and the neutral side of the duplex receptacle (both halves) each need to be connected to the neutral side of your incoming power cord.

You have no path back to neutral from the controller.

Click to expand...

Wow, thanks for the quick reply. You read that correctly!

reynolds5520 said:

Your first drawing showed the neutral side correct. I guess the later drawings can be misinterpreted.

The fix is easy though, all you need is a piece of wire to replace that missing bridge on the neutral side.

Click to expand...

So I could use just a small piece of wire and run it from one neutral post to the other, leaving what I currently have in place as well?

jkmcd3 said:

So I could use just a small piece of wire and run it from one neutral post to the other, leaving what I currently have in place as well?

Click to expand...

So this worked. Thanks for all the help guys. I will post some pics later tonight!!

John

So here it is all finished up. I tested it out with some lamps and it worked perfect. I got them both programmed as well:



The STC on the left controls the outlet on the left. The top outlet is cool and the bottom is heat. I will be plugging in a small 5 cubic foot chest freezer into the cool outlet and probably will not use the heat. So I have this one set up for 7 degrees Celsius, which is 44.6 degrees Fahrenheit for serving. +/- 0.5 degrees Celsius and the delay for the compressor I left at the default 3 minutes.

The STC on the right controls the outlet on the right. Same with the other: top is cool and bottom is heat. My mini fridge (fermentation chamber) will be plugged into the cool and a small ceramic heater will be plugged into the heat. This one is set up at 20.5 degrees Celsius (68.9F). +/- 0.5 degrees Celsius and the compressor delay is at 1 minute. Goal is to keep this between 68 and 70ish for fermenting ales. Obviously one plus of the temp controller is you can adjust it on the fly if you choose to cold crash or lager, which I pretty excited about.

The middle outlet is always on. will probably plug some small fans in here to help with circulation.

I have not plugged it in yet. I might get around to that tonight since I have an Amber Rye I need to keg and get chilled!

Thanks to all for the help! Next time I know not to cut the bridge on the neutral side of an outlet!

Thanks,

John

Here is the updated parts photo (showing the THHN wire and the plastic flex conduit) as well as a parts list (which keeps me organized when i go to buy everything I need). Hope this can help some of you if you are thinking of tackling a project similar to this.

One thing to note is that temp controllers from a typical Home Brew Supply Shop range from 60 to 80 bucks a piece (I would have needed 2) so not much savings, as you can see, but you do get additional benefits with the STCs:





Thanks,

John

You may want to seriously consider switching the Heat and Cold receptacles... Most refrigerators have a 90° plug on them and this will hinder the access to your lower receptacle to be used for heat.

Huaco said:

You may want to seriously consider switching the Heat and Cold receptacles... Most refrigerators have a 90° plug on them and this will hinder the access to your lower receptacle to be used for heat.

Click to expand...

You know what, now that you mention that I think my mini fridge does have a 90 degree plug.

It would be simple to switch them. I will check that out tonight and see what kind of plug my appliances have.

John