Arduino, relays and building code

Question

I want to install several Arduino controlled relays which are use to turn on/off some lights, a fog machine and some door locks in a building. What do I need to do to insure that the power relays don't violate building code?

Do components need to be put in a box or can they be mounted to a 2x4? Are there requirements regarding the points were the bear wire is screwed into the relay?

I am assuming that if anyone as ever wired an Arduino into a garage door opener, these questions may have come up.

• Russell McMahon: NB: IANAL nor US regulations expert.There are a few standard certifications that will essentially guarantee that a part will meet US regulatory requirements. Usually more of the form "your building burned down and you have no insurance because ..." rather than prosecuting you for non compliance. Relays with UL rating bought via a reputable US supplier will usually quality. eg if Digikey sell it it is PROBABLY Kosher. Also if made by reputable manufacturers the same applies, as long as its genuine. eg (1 of many) Omron - they don't make no junk largely and even their junk is certified :-).

Answer 1

Disclaimer: IANAL nor US regulations expert.

There are a few standard certifications that will essentially guarantee that a part will meet US regulatory requirements. Usually more of the form "your building burned down and you have no insurance because ..." rather than prosecuting you for non compliance.

Relays with UL rating bought via a reputable US supplier will usually quality.
eg if Digikey sell it it is PROBABLY Kosher.
Also if made by reputable manufacturers the same applies, as long as its genuine. eg (1 of many) Omron - they don't make no junk largely and even their junk is certified :-).

HOWEVER if you are building something using such parts the whole unit will need to be certified. For small volume applications it may be easier and cheaper to buy comething COTS (commercial off the shelf) which has the relevant certifications. That said,be sure these are legitimate.

As a guide:

US standards a useful introduction

Extensive international standards summary

Wikipedia on UL

MET Labs strut their stuff comparison with UL.

Intertek test labs bow in

Useful - Understanding electrical certification

Possibly useful templates