@B.Will I ended up just guessing and choosing the switch closest to the breaker box and luckily it was the right one! Only downside was I had to install it upside down as that was the only way it fit...

@B.Will Awesome thanks so much ! I will give this a go!

Hi there, I am wondering if the HS220 will work in a 3 way swich if I only use that one switch with the HS220 installed to adjust the lights and not use the other switch at all? Thanks