M
mark_
Hi all,
Your help would be appreciated. We are mainly domestic sparx so I havn't much experience with cable sizing for motors.
On site, we need to supply a motor control panel which operates the sewage pump. There are in fact two pumps but I think they switch between periodically to prolong the life span and offer back up incase one goes down.
Anyhow, wiring diagram shows a 230v single phase supply, each pump is shown with a FLC (running i think) of 9.9 amps or 1.5kw. Each pump has an overload set between 7.5 and 11 amps. Ive spoken to the pump supplier who has asked for a D40 mcb as the protective device.
My question is do I size the cable for the D40 mcb as normal (which seems unlikely) or for the 11a maximum that the over load provides. If the latter is the case I would presume that the MCB would only be offering short circuit protection so we would need to be sure the circuit would provide the required short circuit current to trip the mcb in 0.4sec. According to BS7671 thats 800amps (am I wrong) so I may need an RCD to help here.
Hopefully I have explained the situation enough for someone to respond.
Lastly the cable length is max 60m
Many thanks
Your help would be appreciated. We are mainly domestic sparx so I havn't much experience with cable sizing for motors.
On site, we need to supply a motor control panel which operates the sewage pump. There are in fact two pumps but I think they switch between periodically to prolong the life span and offer back up incase one goes down.
Anyhow, wiring diagram shows a 230v single phase supply, each pump is shown with a FLC (running i think) of 9.9 amps or 1.5kw. Each pump has an overload set between 7.5 and 11 amps. Ive spoken to the pump supplier who has asked for a D40 mcb as the protective device.
My question is do I size the cable for the D40 mcb as normal (which seems unlikely) or for the 11a maximum that the over load provides. If the latter is the case I would presume that the MCB would only be offering short circuit protection so we would need to be sure the circuit would provide the required short circuit current to trip the mcb in 0.4sec. According to BS7671 thats 800amps (am I wrong) so I may need an RCD to help here.
Hopefully I have explained the situation enough for someone to respond.
Lastly the cable length is max 60m
Many thanks