120VAC to Low voltage clearance

After searching around the net I find there is SO MUCH controversy about this, I’m uncertain what to believe. I’ve learned the difference between clearance and creepage. Here’s a snapshot of my pcbs layout. I have 6.6mm clearance between the 120VAC pin on a relay and the closest 5 volt trace. From what I’m reading that should be plenty, but a confirmation of this from someone who’s more familiar with it would be nice. Does someone have a recommendation on a reliable chart/source for this information?
Thanks,

Screen Shot 2015-02-13 at 11.45.48 AM.png

What is it you are worried about ?

If its safety then there are a whole lot of other considerations.

Example what is the ip rating of the enclosure , (can anyone accidentally touch or poke).

Humidity , condensation could cause unwanted circuit behaviour due to bridging, conformal coating helps here.

In the event of a short are all the operator controls sufficiently isolated or insulated.

I have always assumed clearance and creepage to be effectively the same on pcb's.

http://www.smps.us/pcbtracespacing.html

There is a calculator there designed to comply with Underwriter Labs requirments.

There is no easy answer. You need to look at the safety standards, international standards IEC 60065 and IEC 60950 which are published in the USA as UL standards. You might be able to find pdf copies online. There are lots of factors to be taken into account such as class I vs. class II insulation.

Russell.

Sounds like a chicken project!

There are really inexpensive opto isolated relay modules on ebay. That would give the best isolation. I have a couple of examples, and one in use. They seem fine in an IP65 box inside the coop. (well, no longer IP65 as cables are entering and exiting, but that what it started as...)

-fab

Thanks. I have used solid state relays on smaller projects like coffee pots, but this is for a water pump, so it needs to be heavier. The solid star ones will handle heavier loads but only with adequate heat sinks.

Imagine an ant gets into the device and walks over the board. Can it bridge between high and low voltage parts of the circuit? If so you've potentially(!) put lives at risk at the whim of an insect... (*)

It pays to be really careful with mains, a nominal 120Vac can have kilovolt spikes superimposed on it if a nearby fluorescent light fitting or fridge motor is defective, so insulation needs to be rated at kV levels, not 100's of volts. Look at the typical specs for an opto isolator, they are in the multi kV range for a reason.

In the early days of electric power before regulations were tightened up there would have been a lot of fires and electrocution accidents - leave these banished to history!

(*) earwigs are even larger...

MarkT: It pays to be really careful with mains, a nominal 120Vac can have kilovolt spikes superimposed on it if a nearby fluorescent light fitting or fridge motor is defective, so insulation needs to be rated at kV levels, not 100's of volts. Look at the typical specs for an opto isolator,

Yes, we used to do insulation tests at 4 kV for every product leaving the factory in the UK (240 V mains)

Russell.

This relay has a clearance of about 9mm from the coil pins to the 120VAC pins, so if I maintain that, I shouldn't have anything to worry about. I will also coat the Mains Pins with this conformal coating for added protection. I really don't even need the Mains voltage on the PCB, as with this relay I'll be connecting the 120VAC in/out to the top terminals.

SouthernAtHeart: to worry about. I will also coat the Mains Pins [url=http://www.amazon.com/MG-Chemicals-Acrylic-Lacquer-

That's probably not a good idea just use shrouded terminals for the top connections