Fans instead of heat sinks?

Hey guys, quick question that has probably been asked over and over, but I'm relatively new to the site, can I use 2 computer fans to cool my ssr's? I will eventually have 6 ssr's in my encloser, possibly 8. My system is based off of the electric brewery's control box, but have modified to my needs. Thanks for all your comments and suggestions, and for all the other good info you all respond to! Happy brewing, and cheers.

You won't need a fan if you have an external heat sink.

^^^ what he said. However if you don't have any sort of sink whatsoever then I don't think a fan would even cool them. There just isn't enough surface area on the bottom of the SSR to dissapate that much heat.


After re-reading your post it looks like you want to skip the sinks and just use fans? why is that? cost or space?

if it's cost, then the cost of replacing your SSRs when they fail will probably quickly surpass that of even the cheap aluminum sinks (which is what I use).

if it's space I would look into some sort of liquid cooled deal like you use on computer CPUs.

Heat sinks are much more efficient at dissipating heat and they're passive, so won't have to wire or power anything. The amount of heat produced will depends on the size of the SSRs and how much current you are drawing through them.

And what he said too....heat sinks are cheap, and you can't replace a heatsink with a fan. Heatsinks conduct heat very well, whereas air does not. You can use a fan to help move the hot air away from the heatsink, but you really can't use one in place of heatsink.

Somewhat off track, but I have a pair of SSRs to use in my build, and I'd like to keep everything contained in the enclosure. Will a fan or two moving the air around inside a 16x12x8 enclosure keep the SSRs cool enough or do I need to have the heatsinks outside of the enclosure?

Here's the wiring diagram for my build:
http://www.pjmuth.org/beerstuff/images/Auberin-wiring1-a11a-RM-SYL-2352-5500w.jpg

By all means, mount the heat sink outside the panel.
Use these for your heat sink: External Mount Heat Sink for 40A SSR

P-J said:

By all means, mount the heat sink outside the panel.
Use these for your heat sink: External Mount Heat Sink for 40A SSR

Click to expand...

+1

I replaced my fan with this one from Auber. It works great. Barely gets warm when running full blast.

You still need surface area for the moving air to strip the heat off of, like a radiator. If you run fans, you can use smaller sinks, but you would still want them. I have seen a few pictures of guys mounting the SSRs on a bit of square tube and then blowing air through the tube with PC fans. This idea is cost effective and has a relatively low footprint if space is an issue.

And of course applying a thermal compound between the SSR and heatsink helps out a good bit. No need to buy anything expensive though, and it's not absolutely necessary for this application.

P-J said:

By all means, mount the heat sink outside the panel.
Use these for your heat sink: External Mount Heat Sink for 40A SSR

Click to expand...

I ordered a pair of these today as there doesn't really appear to be a good way to mount the typical SSR heatsinks externally.

jtkratzer said:

I ordered a pair of these today as there doesn't really appear to be a good way to mount the typical SSR heatsinks externally.

Click to expand...

The Auber Instruments site for the item shows exactly how to mount it and set it up.

Just scroll down to "Mounting cutout"

nameless said:

And of course applying a thermal compound between the SSR and heatsink helps out a good bit. No need to buy anything expensive though, and it's not absolutely necessary for this application.

Click to expand...

I discovered that not applying thermal compond between a SSR and heat sink will kill a SSR.

The first one died and I mounted another. This time I felt the SSR temp and the heatsink temp and even though the heat sink was warm the SSR was noticibly warmer.

So I removed the SSR & added some compond and from touch, both seem to be the same temperature.

P-J said:

The Auber Instruments site for the item shows exactly how to mount it and set it up.

Just scroll down to "Mounting cutout"

Click to expand...

I meant these type:



It's why I ordered the Auber version.

Hey thanks guys, that's why I went right here. Not really a money or space issue, just knowledge I guess. I try to educate myself as much as I can before I jump into a project. Hope to post pics of my unit (s) soon. Thanks again

Wait, one more popped into my little brain, how come in the electric brewerys' control box, they have the two relays controlled from the pid mounted to the heat sink, but the 3 relays controlling the two tanks and main power are just mounted to the bottom?

Relays have contacts that open and close - they don't get hot unless something is wrong.

SSRs are solid state swirches and are never truely 100% on. And for every amp you draw through a SSR you dissipate about 1 Watt of heat. So, a 5500 Watt 240V AC element draws about 22 amps and you have about 22 Watts that have to go somewhere.

I made a modified heat sink/fan set up because I did not want to have the external heat sink, but on second thought now I wish I would have set it up with an external heat sink.

I used a 1"X4"X8" hollow aluminium bar that i mounted the 5 SSR's with heat compound, and i drilled a 3" hole in the center and mounted a 40mm fan. I've brewed 4 batches now without a problem and have run a few test runs, so it seems to be working.

Awesome info, thanks again, makes sense now, I think??? The reason we use ssr's is because the solid state relay will switch at a voltage the pid can give out right? (3-24v) that switches to 110 which powers the 110 v coil on the relay switch , relays themselves need more power to open/close, therefore are cooler because the are either on, or off, bad explanation on my part, but I think I understand, thanks again guys!!

Bsquared,

I think that's a great design. I assume it pulls air in from the outside and exhausts to the outside?

Thanks,

It blows air against the the back os the SSR mounting and comes out the side, the box is sealed so the air stays inside, but at the end of a brew session the box is warm, not hot. I think it gets in to the mid 90's but have not measured it yet.

I think the only thing you have left to do is to pull air in from the outside, but I understand sealed - nothing can get wet.