SSR

[Arbe0]

Doing a 120v 20 amp Controller with a PID for my Brew in a bag.
Aurber says the SSR I have will be good without a heat sink for the 20 amp, just sand off the paint I guess in the controller box and screw it on to where I want it with of course thermal past. I just need to know what kind of sand paper to use to sand off the paint. I am assuming that it needs to be pretty scratch free, or will the thermal past take care of the scratches?

 

[doug293cz]

The thermal paste will take care of small scratches. Normal sanding procedure is to start with coarse grit and then use progressively finer grit to make scratches finer. Finishing at 200 grit should be fine. The thickness of the original paint will determine how coarse you need to start.

Brew on

 

[Arbe0]

thank you Doug, nice fast answer.

 

[Brumateur]

Aurber says the SSR I have will be good without a heat sink for the 20 amp,

What SSR is it? Regular SS are good only for up to 5 Amp without a heatsink, If you going to use your controller box as heatsink - it should be big enough to dissipate heat generated by 20Amp (around 25Watt)

 

[Bobby_M]

I would only chance it if the box is aluminum. Heat sinks are the cheapest part of any build so it's not where I'd cut any corners.

 

[mabrungard]

I’m with Bobby, don’t skrimp on a heat sink. Blowing a SSR in the middle of a brew will ruin your day.

 

[Bobby_M]

I’m with Bobby, don’t skrimp on a heat sink. Blowing a SSR in the middle of a brew will ruin your day.

For that matter, SSRs are the most likely part to fail so buy two.

 

[Arbe0]

in an email to Auber the information back was that I wouildn't need a heat sink for this build as 120V 20 amp is what will be used,

this is the box: Multi-purpose Enclosure with all Pre-cut 10x8x6 [B252015-PCO] - $49.98 : Auber Instruments, Inc., Temperature control solutions for home and industry

 

[Bobby_M]

"Need" is relative. I am simply suggesting that the total lifespan of the SSR may be impacted by running a little hotter and using a heat sink may mitigate that. You could probably run a 240v/30a SSR in the same box without a heat sink for some period of time without smoking it also. It's 12 bucks.

 

[tdiowa]

I have several heat sinks sitting around, pm me and I will send you one. It will cost you a beer.

It is my semi informed opinion that if you are using a SSR in a enclosed box everything in the box will be hot. Including the SSR, PID and wiring. I would hate to see any wiring come in contact with the SSR and short out. Of course I always over engineer but that is me.

 

[augiedoggy]

Ive used many of these and never had an issue.
https://www.ebay.com/itm/Aluminum-H...581898?hash=item1a1fad030a:g:vP4AAOSwAHBaQyZZ
Realistically a lot of the professionally designed machinery I work on does not use a heat sink at all but rather mount the ssr directly to the metal enclosure but that said I agree its worth having it for piece of mind.

 

[Vale71]

in an email to Auber the information back was that I wouildn't need a heat sink for this build as 120V 20 amp is what will be used,

this is the box: Multi-purpose Enclosure with all Pre-cut 10x8x6 [B252015-PCO] - $49.98 : Auber Instruments, Inc., Temperature control solutions for home and industry

Fromt the page you linked:

"The external mounted heat sink eliminates the venting requirement of the enclosure for internally mounted heat sink"

So it's either external heat sink or internal+ventilation but you can't skimp on both. Personally I think a passive heat sink is better than mounting fans that:

1- need a power source
2- could fail without you noticing

 

[RufusBrewer]

I am a believer in over building when it comes to keeping semiconductors cool and operating well within spec. The cost of buying over spec SSR and heat sink is not much. By the time you figure out you are running out of safe operating area, too many bad things can happen.

 

[augiedoggy]

I am a believer in over building when it comes to keeping semiconductors cool and operating well within spec. The cost of buying over spec SSR and heat sink is not much. By the time you figure out you are running out of safe operating area, too many bad things can happen.

This is also why I always use 2 pole contactors in conjunction with ssrs to kill all the power going to the elements when they are turned off.