... and installed in the building of low-voltage main power distribution cabinet usually. 2.Installation guideSPD-20R is used in ... of LPZ1, LPZ2 and LPZn, such as before the residential distribution box, computer center, the information, electronic, and control equipment or ... the nearest socket box. 3.Specification data ModelSPD-20RPoles1P,2P,1P+N,3P,3P ...