Heat Sink for Triac

[WillEert]

I am installing a system using the Midnight Classic 150 charge controller. I intend to dump the excess electricity from my existing PV system into a hot water tank - diverting the electricity on the AC side, using the Midnight Solar sourced triac to control the AC. The Triac needs a heat sink to operate however I am having a difficult time sourcing one. I would like a passive sink as we are off grid and I do not want to operate a fan if I don't have to.Teledyne states that for my system parameters I need .3C/Watt dissipation. Any sources out there? Also this device gets hot and appears to have exposed wiring. I am thinking it should be put in a cage of some kind to prevent contact and allow for heat transfer. Is anybody running a triac in their system? A picture of an installed device would be much appreciated. Thanks

Will

[boB]

The key to a good heat sink is a large surface area and good heat conduction of
the material of course.  Also, the contact between that SSR (triac) and the heat
sink is good to have.  Using some of that silicone thermal grease helps there.

A lot of times, just a semi-large piece of aluminum can work well out in the air.
A fan can also help.

I haven't bought an off the shelf heat sink for a long time but I'm sure that Googling
will give you some results.  Also, try the Google images search results for visuals.

boB

[philb]

I have also robbed the heat sink and 12 volt fan from an unusable computer CPU. It works great on my SSR;s. So far, the fan has not been needed.

[WillEert]

I guess I am just nervous about these relays. They say that they operate at 100 - 115C which seems pretty hot to me. I am sure that someone has used one in the same application as I am going to do - which is divert excess AC KW into a HWT using the Aux 2 opportunity Hi function. I will be sending about 5KW through the triac, about 21A per phase. Any ideas on a suitable size of sheet or where I could search for this information?

Also I do not find in the Classic manual if the Aux 2 signal is Ac or Dc. I am guessing it would be Dc but this does affect the type of relay that could be used.

Thanks

Will

[Vic]

Hi Will..

Have you tried to use a Heat sink selector?

Here is a random one:

http://www.aavid.com/product-group/extrusions/search

You are correct that cooler is better,  and 100 C or more is HOT for semiconductors.  Perhaps a thermostatically controlled fan could help,  and not make noise,  waste power,  or circulate dust when not really needed.  FWIW,   Vic

[WillEert]

Thanks for all the help. i think I have found a suitable SSR and heat sink package at Crydom. this comes with covers, a sink and the relay. they also offer lugs that screw onto the terminals to upsize for the size of wire I need. Thanks again. Will