Can STC-1000 source 10A long term?

[Homer]

Can STC-1000 really source 10A (heat and cool) long term? I'm thinking of using it to control a small air conditioning unit for my ferm chamber. The ac units says that it will draw a little over 5A. Do you think I will be okay using only the stc-1000's built in relay's, or should I just have the stc-1000 control a pair of external 15A relays to be safe?

Thanks

 

[FuzzeWuzze]

If it just uses a bit over 5A you will be fine. You wont be sourcing 10A long term...more like 5.5A probably.

 

[HumulusHead]

They say the relays inside that guy are 15 A

Though don't base a decision off of me. I'm just a civil engineer, not one them fancy electrical engineers


Sent from myPhone

 

[Falcon3]

Keep in mind that when the compressor on the AC starts, it will draw considerably more than the rated running amps- depending on the size of your unit.

 

[Homer]

Keep in mind that when the compressor on the AC starts, it will draw considerably more than the rated running amps- depending on the size of your unit.

That's what I'm worried about, and why I was wondering if anyone has done this long term. I'm just worried that it will work fine for a while, but the internal relays are getting so beat up from the short durations of high current, that they will eventually smoke.

 

[danath34]

If the AC unit can be plugged into a standard 110V wall socket, you're A-OK. The internal relays are supposedly actually rated for 15A, and most wall sockets are rated for 15A as well. So if you can plug it into the wall, you can run it with the STC.

However, I certainly encourage more research and caution when wiring anything, because, I am also not one of them fancy electrical engineers.

You can prolong the life of the internal relays by setting a wider temperature range, or by using the compressor delay function the STC has. If your chamber is well insulated, it shouldn't be switching on and off too often. I set mine to turn on at 2 degrees above the setpoint. (that means if I set it for 17C, it turns on at 19C and turns off again when it reaches 17, so keep in mind the setpoint is the temp the cooler turns OFF). It probably turns on for 10-15 minutes and is off for probably 45 mins or more. Though I've never actually timed the cycles so this are completely wild guesses.

As for long term, I've had mine running for 6 weeks straight and so far so good. I'm running a 2A fridge, but again, I don't think you'll have a problem as long as whatever you run with it can be plugged into the wall.

 

[Stealthcruiser]

He said "the size of your unit".............

 

[snowman_fs]

The major source of contact damage to a relay occurs when dielectric breakdown occurs across the air gap which causes sparks. Normally only as the contacts are closing or opening and they are within 0.00004" for 120v.

I have been doing the exact thing for the past 2 months with no electrical issues. I wired in an STC-1000 to replace the analog dial on the AC unit. To my surprise, my cheap Danby AC unit has a built-in start-up delay of 2 minutes where just the fan runs prior to the compressor turning on. Therefore the STC-1000's relay is already firmly closed prior to the compressor trying to turn on; avoiding the sparking of STC-1000 contacts. It will still disconnect under running load, (5.5A) but that is much better than the start-up spike.

The issue I had was freezing temps within the chamber. I had the temperature probe in a thermowell through my stopper. I came home after a weekend away and discovered my AC unit had the chamber temp at -2C. Due to the internal heating of the fermentation the carboy temp was still at 16.8 degrees C. I have now daisy chained two STC-1000's together to limit the low level of the air within the chamber to 3C. I actually think this would be a novel way of cold crashing the previous batch if the timing could be mastered. Let the AC run the chamber temps down low during the initial stages of a new batch while the older batch crashes.

In hind sight my recommendations would be:
1. Not installing the STC-1000 into the AC unit like I did; I can't see the temperature display while the chamber is closed.
2. Use two controllers from the beginning. Especially if you store additional beers/ciders in the chamber or wish to hold other products at serving temps within the same unit. Either way two controllers allow you to protecting from too low an air temp while initial fermentation takes off or by driving serving temp air from the serving chamber to the fermentation chamber as needed.
3. Ensure the fan is in always run mode to improve the energy transfer and equilibrium within the chamber.
4. Plan on a drip pan below your AC unit. Mine collects 1/2 a gallon every week or so. I even covered all seams on the chamber and clamp the door closed to prevent moisture ingress. But the cold side of the refrigeration circuit has some un-insulated lines on the hot side of the AC that will frost up while running and then drip while idling.

 

[day_trippr]

They say the relays inside that guy are 15 A
Though don't base a decision off of me. I'm just a civil engineer, not one them fancy electrical engineers

I'll be gentle

You cannot freely substitute component performance ratings for assembly performance. A 15A relay connected with a board trace rated for 10A - and/or connected to a terminal block rated for 10A - serve as classic examples.

It would serve no beneficial purpose for the manufacturer to significantly understate product performance as that would limit the scope of the potential market, so I'd be inclined to respect the product ratings and not potentially test the response time of the local fire brigade

Cheers!

 

[HumulusHead]

I'll be gentle



You cannot freely substitute component performance ratings for assembly performance. A 15A relay connected with a board trace rated for 10A - and/or connected to a terminal block rated for 10A - serve as classic examples.



It would serve no beneficial purpose for the manufacturer to significantly understate product performance as that would limit the scope of the potential market, so I'd be inclined to respect the product ratings and not potentially test the response time of the local fire brigade



Cheers!

The weakest link methodology

Makes sense!

I could probably relate it to civil engineering, but it would be terribly unimpressive haha


Sent from myPhone

 

[PlinyTheMiddleAged]

The weakest link methodology

I could probably relate it to civil engineering, but it would be terribly unimpressive

Sent from myPhone

I think you just did! "Weakest link" is from the olden days of bridge building where chains were used in their construction. The strength of the bridge was determined by the strength of the weakest link - at least that's what I was taught way back when (which was after chains were used in building bridges). I am not vouching for the accuracy of the above "fact" but I am vouching for the fact of that is what I was taught.

 

[HumulusHead]

I think you just did! "Weakest link" is from the olden days of bridge building where chains were used in their construction. The strength of the bridge was determined by the strength of the weakest link - at least that's what I was taught way back when (which was after chains were used in building bridges). I am not vouching for the accuracy of the above "fact" but I am vouching for the fact of that is what I was taught.

Well now I was just accidentally unimpressive. Dammit!

I vouch for none of my knowledge.
I learned most of it here!


Sent from myPhone

 

[day_trippr]

The weakest link methodology
Makes sense!
I could probably relate it to civil engineering, but it would be terribly unimpressive haha

I actually stopped to think how I could include a bridge-building analogy, but to be honest, civil engineering was strictly a must-pass graduation requisite for an EE and aside from a minor fascination with slumping concrete I never gave it its due...

Cheers!