Is my stc1000 on its last legs?

[soupdragon]

Hi all.

Over the last few weeks my beer fridge hasn't been maintaining it's 12⁰c target. In the past the compressor has stuck and I've needed to give it a "kick" to get it going again, usually it then behaves for a good 12 months before it happens again. More recently, the compressor hasn't been sticking but even though the controller is in cool mode the fridge isn't running.
The only way now to get it going again is to unplug the controller (just turning it off doesn't work) for 5 mins or so. When I switch it back on the fridge kicks in after the 5 min delay and runs fine until the next time. This is the 2nd time in two weeks I've had to unplug the controller so is it just one of those things or is it showing signs of a more permanent failure?

Cheers Tom

 

[JockyBrewer]

Certainly sounds like an issue with the relay sticking. I've had other things go on them, but not that before.

The STC-1000 unit is not expensive to replace, as long as you're happy with a little wiring.

 

[soupdragon]

I've not opened up the box but I believe the connections are all proper contact block thingies. It almost 8 years old and has never been switched off since it was first set up

Cheers Tom

 

[soupdragon]

Are the relays a part of the actual stc unit?

Cheers Tom

 

[JockyBrewer]

Are the relays a part of the actual stc unit?

Cheers Tom

Yes. There's two relays, one for cooling, one for heating. They're usually 10 amps each which is fine for a fridge or small heater, but not for a 2.4kw element you'd normally have in a brew kettle. That's when people wire them up to an additional external relays that can handle more current.

Obviously I don't know how yours is wired up, but that's what I'd expect.

 

[soupdragon]

I only use the cooling side as it's my dispensing fridge

Cheers Tom

 

[soupdragon]

Certainly sounds like an issue with the relay sticking. I've had other things go on them, but not that before.

The STC-1000 unit is not expensive to replace, as long as you're happy with a little wiring.

Any recommendations for a particular brand(?) or seller of the unit. There's tons of them on eBay from £6 or £7 but would like one that's not going to fail after a couple of months

Cheers Tom

 

[jof]

I use on my massive whole house storage heater. (at least I did until I moved to a heat pump last year but it's still there as a backup)

Like JockyBrewer says, the stc1000 10a output relay drives a much bigger set of contactors to switch up to 9kw of power.

Sorry, no brand recommendation as mine is a cheap generic one

 

[soupdragon]

The reports I read about failures was many years ago. Hopefully they've upped their game

Cheers Tom

 

[soupdragon]

New unit ordered so for now I've plugged the fridge directly into a socket. Can't be doing with warm beer

Cheers Tom

 

[RoomWithABrew]

Make sure you set the cycling interval to something like 10 minutes to reduce stress on compressor. Can't your fridge thermostat be set / adjusted to keep a steady temperature? That's what they are meant to do. You aren't controlling a dynamic situation after all.

 

[soupdragon]

Is the cycle interval the compressor delay? If so, the old one was set to 5 mins although the time between reaching 12⁰ and naturally climbing to 12.5⁰ when it kicks in again is a lot longer than 10 mins.
I've set the fridges thermostat to it's minimum (warmest) setting and it started to cycle around 11.8-12⁰ but now it's been on for a few hours it's down to 10.5⁰ ish. Don't know how low it'll go on that setting as it really is an old fridge but we'll see how it goes. New unit won't be here for a week/10 days so it should get the chance to bottom out by then

Cheers Tom

 

[RoomWithABrew]

Is the cycle interval the compressor delay? If so, the old one was set to 5 mins although the time between reaching 12⁰ and naturally climbing to 12.5⁰ when it kicks in again is a lot longer than 10 mins.
I've set the fridges thermostat to it's minimum (warmest) setting and it started to cycle around 11.8-12⁰ but now it's been on for a few hours it's down to 10.5⁰ ish. Don't know how low it'll go on that setting as it really is an old fridge but we'll see how it goes. New unit won't be here for a week/10 days so it should get the chance to bottom out by then

Cheers Tom

Yes cycle interval is the delay that you set.
If you slowly adjust the thermostat you might find the right setting over the next few days, another option whilst you wait for the next STC could be a straightforward time switch with the little click in actuators around the outside. With that you could manually play with some times of it being off and get some control closer to your ideal.
Do keep the old STC as the sensor could be reused if needed. My ferment fridge I got for free as it would only keep chilling to freezing so must have a broken thermostat but using an STC and then Brewpiless it works perfectly.

 

[Sorcerers Apprentice]

Is it easy for you to bypass the stc ? I'm not sure of your setup. There's a starting relay on fridge compressors, which can go dicky . It could be causing the issue rather than the stc . Next time you have a problem with the fridge compressor, try plugging powering the fridge directly, this could mean disconnecting the stc and wiring a short across the stc relay contacts . That or you could test that the contacts are closing on the stc with a multimeter set to ac voltage and check the terminal which is connected to the compressor for power .

 

[Sorcerers Apprentice]

Usually if the starting relay is acting up ,
The compressor will feel very hot to touch, be careful not to burn your hand , there's an overload as part of the starting relay , which will operate if the compressor gets too hot , and won't let the fridge compressor operate until it cools down , hence possibly causing the 5 minute delay that you've described.
I forgot to add that its a serviceable part and easily enough replaced . There's lots of videos on you tube describing how to do it , which will save me a lot of typing

 

[soupdragon]

Next time you have a problem with the fridge compressor, try plugging powering the fridge directly

That's exactly what I've done, whenever it's plugged directly into the mains the fridge runs without issue

Cheers Tom

 

[soupdragon]

possibly causing the 5 minute delay that you've described.

The 5 min delay is a built in setting of the stc1000 unit

Cheers Tom

 

[soupdragon]

I've set the fridges thermostat to it's minimum (warmest) setting and it started to cycle around 11.8-12⁰ but now it's been on for a few hours it's down to 10.5⁰ ish. Don't know how low it'll go on that setting as it really is an old fridge but we'll see how it goes.

It's down to 9.4⁰ now. I can put up with beer that's a bit colder than usual for now. It's only for a week or so

Cheers Tom

 

[Sorcerers Apprentice]

Hopefully the new stc resolves the issue, if it doesn't then you know where to look next . What made me consider the starting relay was that the fridge had been responding to the stimulation of a size 11 boot previously

 

[soupdragon]

The size 11 does work well to un stick the compressor High tech solutions, you can't beat them

Cheers Tom