How much heat sink?

[ed_denu]

Originally Posted by BottleFed70

For the record, I also used an old CPU heatsink and cooling fan after burning up my 1st SSR due to improper heat sinking. Works absolutely perfect and the SSR doesn't even get warm anymore.

I considered doing this awhile back, but I couldn't come up with an acceptable way of providing dc power to the computer fan. I first thought about building my own internal dc power supply using a transformer, bridge rectifier, etc. then I looked at a transformerless power circuit. Finally I considered adding a 120vac receptacle to the control panel and using a pre-made plug-in ac to dc adapter.

How did you accomplish this?

[CarWiz]

"CarWiz, In a standard light bulb , the filamint is in a vacuum isn't it?"
Nope.

The glass envelope of an incandescent bulb can't contain air because tungsten is flammable when hot and would burn up if there were oxygen present around it. One of Thomas Edison's main contributions to the development of such bulbs was learning how to extract all the air from the bulb. But a bulb that contains no gas won't work well because tungsten sublimes at high temperatures--its atoms evaporate directly from solid to gas. If there were no gas in the bulb, every tungsten atom that left the filament would fly unimpeded all the way to the glass wall of the bulb and then stick there forever. While there are some incandescent bulbs that operate with a vacuum inside, most common incandescent lamps contain a small amount of argon and nitrogen gases.

Argon and nitrogen are chemically inert, so that the tungsten filament can't burn in the argon and nitrogen, and each argon atom or nitrogen molecule is massive enough that when a tungsten atom that's trying to leave the filament hits it, that tungsten atom may rebound back onto the filament. The argon and nitrogen gases thus prolong the life of the filament. Unfortunately, these gases also convey heat away from the filament via convection. You can see evidence of this convection as a dark spot of tungsten atoms that accumulate at the top of the bulb. That black smudge consists of tungsten atoms that didn't return to the filament and were swept upward as the hot argon and nitrogen gases rose.

However, some premium light bulbs contain krypton gas rather than argon gas. Like argon, krypton is chemically inert. But a krypton atom is more massive than an argon atom, making it more effective at bouncing tungsten atoms back toward the filament after they sublime. Krypton gas is also a poorer conductor of heat than argon gas, so that it allows the filament to convert its power more efficiently into visible light. Unfortunately, krypton is a rare constituent of our atmosphere and very expensive. That's why it's only used in premium light bulbs, together with some nitrogen gas.

Incidentally, the filament in many incandescent bulbs is treated with a small amount of a phosphorus-based "getter" that reacts with any residual oxygen that may be in the bulb the first time the filament becomes hot. That's how the manufacturer ensures that there will be no oxygen in the bulb for the tungsten filament to react with.

[PhredAre]

CarWiz ,Thats interesting about the light bulbs, Did you say that the filament temp is approx, 2500 degrees? thats quite a bit warmer than 125 degrees C that is the max junc temp allowed on the SSR, could be that would have something to do with feeling it sooner on the light bulb.You wrote that gas is a good insulation,but if you are familiar with a large utility generator, a lot of them use hydrogen gas internally as a conductor of heat(BTUs) circulating that gas thru coolers supplied with cooling water. Fred

[peter61]

Thanks for all the input,heres my problem,I'm on my 3d ssr,the1st one I mounted right inside my controller box(no heat sink)the 2nd one I mounted to a piece of 1/2"aluminum(both ssr's were 40 amp I'm drawing 34)the 3d one I went to a 60 amp ssr,got some heat sink from a old pc but before I mounted the ssr I took apart one of the bad ones and used the bottom base plate for what I thought would be more sink but it still blew after a couple of minutes.I set the controller for 150 degrees,it hit that temp then shut off,I then set it for 300 degress and on the way up it blew.Any ideas?

[ed_denu]

If I understand your post, you took the bottom of one of the blown ssr's and added it to the bottom of the 60A ssr, then added a cpu heatsink? Are you using a thermal grease between the heatsink and ssr? If not you may not be getting good contact between them.

Most heatsinks are copper or aluminum so if you added an extra base that was steel you may actually have impeded the heat dissipatation process.

One other thing you might look at is the actual amp draw. If you have an ampmeter you might want to verify your draw.

Are you sure your wiring to the ssr is correct. Is it possibly you're shorting out the input contacts to the ssr somehow?

[peter61]

Ed,
What you say makes sense,I did take the steel piece from one ssr and put it under the new ssr,as far as wiring goes I followed the schematic I found here.When the ssr blows I still can set my controller and run my oven,it just won"t shut off when it reaches the set value.I am using the grease I found at Radio Shack(white paste like stuff)

[Kyrasis6]

If you're only drawing 34 amps and still blowing 60 amp SSRs with added cooling it sounds to me like you still have an electrical problem along with you're cooling.

How big is the is processor heat sink and fan you are using? If it is one of those that fits on the bios chip or something that is far too small. For a computer heat sink and fan you need one for probably a pentium 4 chip. The extra one I have here I have in mind is about 3" around and 2" tall with a fan on top and one on the bottom of the heat sink. But I also have some heat sinks in storage somewhere that where used for radio power amplifiers, I might just bolt one of those on there since they are pretty big.

For DC power for a cooling fan you should be able to go up to Radio Shack and get a small 120vac-12vdc or 5vdc transformer like what you find in the back of radio's and stuff, you should be able to wire that in no problem. Hell, cheaper yet you could take the power supply out of the computer you got the heat sink out of and just wire that to the AC, then connect you're fan to the original plugs.

[Kyrasis6]

Here are some links of what would probably be sufficient just to give you some ideas.... or overkill, lol.

AMD XP Heatsink

Thermotake P4 Heatsink

3.6 GHz Copper Core CPU Fan/Heatsink

And for the OVERKILL:

Thermaltake Golden Orb

Thermaltake Blue Orb

[peter61]

Thanks for the info,I'll be checking them out,I will try and post a picture of what I have now.I can't post my JPG pictures?Any idea why?

[Kyrasis6]

lol, I wasn't trying to sell you one, just trying to give you an idea of what would work. If this board is setup like mine (I also run vBulletin) there is a cap on how big a single image can be to upload it. Try cropping the image and reducing the size and uploading it.