Two outbuildings side by side with a party wall.
Each is supplied as a TT by its own sub main from the main building via 4 core SWA. Each has its own CU each with 30 mA RCD and earth rod. The CUs are fitted almost back to back on each side of the party wall. The rods are internal through the floor at the opposite ends of the party wall.
Each earth rod has an impedance of about 190 ohms which calculates as allowing a maximum of 6 volts on the CPC before the RCD will trip on 30 mA.
Question. Is there any good reason to NOT link the two CPCs by a link between consumer unit earth bars (and hence the earth rods are linked) to obtain effectively an even lower maximum fault voltage on the CPC's and also to provide a back up if one rod should for any reason fail.
Each is supplied as a TT by its own sub main from the main building via 4 core SWA. Each has its own CU each with 30 mA RCD and earth rod. The CUs are fitted almost back to back on each side of the party wall. The rods are internal through the floor at the opposite ends of the party wall.
Each earth rod has an impedance of about 190 ohms which calculates as allowing a maximum of 6 volts on the CPC before the RCD will trip on 30 mA.
Question. Is there any good reason to NOT link the two CPCs by a link between consumer unit earth bars (and hence the earth rods are linked) to obtain effectively an even lower maximum fault voltage on the CPC's and also to provide a back up if one rod should for any reason fail.