INFO Maintaing PID Longevity

First of all, Auberins makes good products and have great service from my experience. What I am about to say is probly true for most PIDs that a homebrewer would use.

After several successful runs with my SYL-(SSR output) PID unit on a heat exchanger I decided to use the unit in COOLING mode with simple ON/OFF configuration for a freezer thermostat. It was a BIG and OLD freezer. The unit died after a week or so of running just fine. (Note I had the PID powered with the same power supply as my SSR, and thus my freezer)

Anyway I emailed the guy and he was really nice about it, I'll just quote below.

BEGIN QUOTE
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I am sorry to hear that. Is it possible that your refrigerator is generating spikes? Are you using the SSR to switch it on and off? One of our OEM customers that specializes in freezers puts a snubber on the power input to protect the controller.
We sell about 1500 of SYL-2342 and 2352 controllers each year. Most of them are for heating applications. The return rate is less than 1%. We noticed that the failure rate for inductive load, or the system that involves a pump in the same power line (e.g. espresso machine) has slight higher failure rate. One of the solution is put a ferrite bead on the input.
...
END QUOTE

Anyway he offered to fix mine for free, which is great. Again very good product and service -- I will probly buy a third PID from Auberins. I figure with all the PIDs I have seen on people's rigs they may want the info to ensure that their unit lives past the 90 day warranty (although he fixed mine past that time).

MY QUESTION for someone more knowledgeable than me: what's a good cheep snubber that I can get to protect my units in the future? (I am aware that I could just run two power lines but I dont want to, I'd rather use a snubber)

Im not an EE, so hopefully someone more knowlegable will speak up. Ill try to get the ball rolling. I hope my explanation is correct...never dealt with this problem but maybe what I do know will help

The problem is that when your pump first turns on it pulls a high inductive load from the coils inside the pump. This effect is visable, such as the lights dimming for a second. V=L di/dt

Basically you need something to eleminate that spike from entering the PID. You can use a "snubber" RC (resistor capacitor) to filter out the high frequency component "spike/noise". The capacitor will store energy and resist that change in voltage i = C dV/dt.

Its like having a dam. When the rain comes the water surges down the river but the damn is able to take that energy and store most of it as potential energy in the form of height, only letting a certain amount of fluid thru. The amount let thru is determined by the height of the damn and the restriction of the pipe or in an electrical circuit the value of the capacitor and resistor.

To lower some of the problems mrburnsbud mentioned use only Zero Crossing SSRs ,.
The supply voltage to the load will always start close to 0 and rise to 120 V (240V) lowering the di/dt effect.
If you use a non zero crossing SSR the voltage to the load during turn on can be between any voltage from 0-120 V (240 V).
Also during the turn off of an inductive load a very large voltage is produced which can destroy your SSR.
You can use a snubber or MOV on your PID input and SSR output.

I use SSR output protection, green disks are MOV's (Metal Oxide Varistors).


My supplier http://www.jameco.com/

Cheers,
ClaudiusB

Good info to know! Thanks!

I am an engineer so yea I understood what happened but with beer I guess I turn off my brain and hope for the best.

Can anyone tell me a good supplier for RC snubbers or MOVs? Thanks for the pics and info you have been very helpful.

David

i'm in the process of researching parts of my build. i use a lot of omega stuff in my lab at work, and planned on using these SSR's:

SINGLE-PHASE SSR Vdc & Vac Input/ Vac Output. DIN Rail or Panel Mount

they've got a lot of "extras" over the auber SSR's. not that they're all necessary, but it's a pretty marginal increase in price over the standard auber SSR/heatsink combo.

p.d.

Can anyone tell me a good supplier for RC snubbers or MOVs?

Click to expand...

My MOV supplier http://www.jameco.com/

i use a lot of omega stuff in my lab at work

Click to expand...

I get all my thermocouples from Omega, the dual elements are great.



Cheers,
ClaudiusB