# Rex C-100 not stopping (initially)



## Codehopper (4/10/16)

So I assembled a thermostat based on C-100 (I decided not to go after STC-1000 as I wasn't sure that it would sustain 2400W heating element).

The controller I've got from Aliexpress seems to be a bastardised version, it's missing quite a few functions described in the documentation available on the net. Not a big problem, since it still has functions required for controlling mash temperature.

I noticed a weird behaviour, though. First time after switching on, it doesn't stop after reaching the target temperature. Say, I set it to 63C -- it will go past that mark and continue heating. Then I switch it off and on again -- and since then it works all well. Until the next brew day.

Anything I can do that doesn't require replacement of the controller? I'm prepared to live with that bug, but if the fix is easy I'd appreciate if anyone enlightens me.


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## damoninja (4/10/16)

Codehopper said:


> I decided not to go after STC-1000 as I wasn't sure that it would sustain 2400W heating element


It will take 2400w no problems. I use it on my urn with a thermowell in the side. 

Does not get hot, cords do not get hot, points do not get hot.


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## Paul Smith (23/10/16)

Hey Codehopper, I was doing some testing on a system I am putting together at the moment and I have notice a similar problem, I have found the solid state relay to be the problem, the PID controller is switching but the SSR is staying engaged. I brought two of these and the first one played up right out of the box the second one that I have being using for my testing just faulted last night and now the SSR is staying engaged the hole time, 
Maybe I got a couple out of a bad batch of SSR,
Has anyone else had this problem or is it due to cheap SSR, They came in a kit off ebay..


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## Paul Smith (23/10/16)

I just found an article on the net about counterfeit SSR's, It looks like the ones I got are not genuine, they are the counterfeit ones getting around.
Watch out for counterfeit SSR's!
hope the link works.


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## mtb (23/10/16)

Is there a differential to set somewhere? Maybe it's allowing 10C difference from the target temp before kicking in. Just a thought - I have no knowledge of this particular model


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## takai (29/10/16)

Paul Smith said:


> Hey Codehopper, I was doing some testing on a system I am putting together at the moment and I have notice a similar problem, I have found the solid state relay to be the problem, the PID controller is switching but the SSR is staying engaged. I brought two of these and the first one played up right out of the box the second one that I have being using for my testing just faulted last night and now the SSR is staying engaged the hole time,
> Maybe I got a couple out of a bad batch of SSR,
> Has anyone else had this problem or is it due to cheap SSR, They came in a kit off ebay..


Is the SSR grounded? 

I have found in the past that if you have grounding issues the voltage differential across the TRIAC will latch it on, and not let it disengage.


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