question for Dan about heatsink grounding.

[Al in Raleigh]

Hi Dan,

I was just assembling a PC controller in the plastic enclosure. I was surprised to not see a bonding jumper from the grounding lug to the heatsinks. I researched the issue on this forum and found people that did in fact ground the heatsinks. From a design standpoint, is there a reason that you left the controller and heat sinks floating? Most of my experience is with industrial electronics, and we agonize over the bonding and grounding due to EMI noise. I just wanted to check with the design engineer before I grounded the heatsinks.

Many thanks,
Al

[-klb-]

I believe that the general consensus is that the cards themselves are indifferent to having the heat sinks grounded or ungrounded. Where grounding in plastic cases is recommended, is when any metal fasteners connect between the heat sinks, and the exterior of the case.. There is a slight risk that a triac failure could bond hot or channel output to the heat sink. If there are any metal fasteners connecting the heat sink to the outside of the case, then these fasteners could become hot in this failure mode. Grounding the heat sinks would cause the fuses to blow, and prevent having live AC exposed on the outside of the case.

- Kevin

[LightORamaDan]

-klb- wrote:

I believe that the general consensus is that the cards themselves are indifferent to having the heat sinks grounded or ungrounded. Where grounding in plastic cases is recommended, is when any metal fasteners connect between the heat sinks, and the exterior of the case.. There is a slight risk that a triac failure could bond hot or channel output to the heat sink. If there are any metal fasteners connecting the heat sink to the outside of the case, then these fasteners could become hot in this failure mode. Grounding the heat sinks would cause the fuses to blow, and prevent having live AC exposed on the outside of the case.

- Kevin

Agreed

Dan