Hi, I fitted down lights in my bathroom replacing old rose & decided to add a Fan (Vents 100 mtpk) it is pir with timer . My query is it only has two pole connections not marked L or N. I have assumed that because it has over run timer it must have a live & a switched live. It works ok ie(pir )until the light is switched on which switches the fan off,have changed live & switched live in fan around but made no difference.Any help please