40A SSR Heat

[Goocher]

I am finished with my new electric set up and ready for a wet test. My set up is a simple 1 element (5500w), 1 PID design with a 40A SSR. I have everything mounted inside a 12x12x6 enclosure. I have one concern though... the heat sink for the SSR is mounted inside the CP (completely sealed). Do I need to add a fan to circulate air or will it cool it sufficiently as is?

 

[kdigman]

You should really get some air circulation going on in the box, otherwise you will be heating up the other components inside the enclosure.

The heat sink will move heat off of the SSR, but where will it go if it is trapped in the enclosure? That is one reason most guys will cut a hole and mount the heat sink outside the enclosure.

Other option would be to cut a hole and run a fan like your PC has.

My vote would be to just mount the heat sink on the outside.

Just my .02

 

[schmagy]

Yes. Failure mode for a solid state relay is closed, or ON. Common failure root cause is excessive heat. De-rating of relays is required at even modest temperature.

For example, page three of this 40 amp relay data sheet indicates that it can only pass slightly more than 20 amps at roughly 150 degrees F.

http://www.automationdirect.com/static/specs/ssclass6relays.pdf

You will almost certainly need to mount your heatshink external to the box or ventilate it with a fan.... unless you want to liquid cool it.

 

[Goocher]

Ok, thanks for the answers. Glad I didn't just "give it a go". Will I need two fans, intake and exhaust? Or will 1 fan suffice?

 

[l3asturd]

One is fine. Just make sure your exhaust hole is offset, or not directly behind the fan. Force the air to circulate before exhausting.

 

[thargrav]

Ok, thanks for the answers. Glad I didn't just "give it a go". Will I need two fans, intake and exhaust? Or will 1 fan suffice?

Mount one fan blowing in & across the heat sink. Also the heat sink fins need to be parallel to the airflow.

The air exhaust can be one or more holes anywhere in the cabinet as long as the total area of the holes is at least 50% greater than the total area of the fan. If you make the exhaust holes the same size or smaller then the fan has to do double duty, pushing air in & pushing air out and you won't get as much airflow.

If it were mine the inlet would be in one of the sides and the exhaust would be a series of 1/2" holes drilled across the bottom. But it's not mine and I don't know where your SSR is mounted.

 

[stevehaun]

I have two 40 amp SSRs in my control panel that I run simultaneously. My system is 35 gallon and has two 4500 watt elements in the BK. My heat sinks are quite large and my control panel is approx 16" X 20" X 8" and metal. My SSRs do not get hot and I do not have any ventilation in my panel. I was going to add a fan but I opened my panel and touched the SSRs at the end of a batch and they were barely warm to the touch. Granted, your enclosure is smaller than mine but you may want to boil some water and see if things get hot before you bother with a fan. I have not had any SSR failures over the past 4 seasons that I have used the system. A metal enclosure will dissipate heat better than a plastic one. Obviously, YMMV.

 

[thargrav]

What brand and part numbers are your SSRs and heat sinks?

 

[Goocher]

What brand and part numbers are your SSRs and heat sinks?

Bought it off ebay here is a picture.

 

[ScottSingleton]

Goocher; I have those exact SSR's and heat sinks. I've been struggling with trying to figure out how to get the sink outside the enclosure myself.

There just isn't enough surface area around the SSR mounting point to affix it to an enclosure.

I broke down and am just putting in a muffin fan.

 

[aubiecat]

I just built a controller with the SSR, heat sink and computer fan inside the case. I did several hours of test brewing and auto tune last night. The exhaust from the fan stayed very cool the whole time.

 

[aubiecat]

Goocher; I have those exact SSR's and heat sinks. I've been struggling with trying to figure out how to get the sink outside the enclosure myself.

There just isn't enough surface area around the SSR mounting point to affix it to an enclosure.

I broke down and am just putting in a muffin fan.

You could always add a 1/16" thick aluminum plate to the heat sink that is 1/4"-1/2" larger than the size of the SSR. That would give you plenty of mounting space without losing heat conductivity to the aluminum heat sink.

 

[thargrav]

Bought it off ebay here is a picture.

View attachment 54426

OK, that's one of the cheap Chinese SSR's - China does make good ones.

 

[Goocher]

OK, that's one of the cheap Chinese SSR's - China does make good ones.

Ok... So you're saying its cheap AND good? Or just cheap?

 

[thargrav]

Cheap and decent. Mager brand model MGR-1 D4840 out of China is a better part.

http://www.dhgate.com/mgr-1-d4840-ssr-40da-dc-ac-40a-ssr/p-ff808081353c09d2013560b0ea9b6f98.html

I know because I bought and tested both in a brew pot controller I'm designing. The one you have runs hotter than the Mager part.

 

[Goocher]

Cheap and decent. Mager brand model MGR-1 D4840 out of China is a better part.

http://www.dhgate.com/mgr-1-d4840-ssr-40da-dc-ac-40a-ssr/p-ff808081353c09d2013560b0ea9b6f98.html

I know because I bought and tested both in a brew pot controller I'm designing. The one you have runs hotter than the Mager part.

Good to know. I had installed a fan, but regretting it... So this morning I bought a 40A external heat sink from Auber. It will cover the hole of my little fan and give me a watertight box again.