I am not aware of any limit, simply follow accepted good design to as to overloading the circuit.

If each load does in fact use half an a amp, then presuming use of a 32 amp circuit, then limit the loads to about 90% of the circuit capacity.

There is no 'maximum' number of connection units on a circuit in BS 7671, although do remember that we should select so that the design current doesn't cause unwanted operation of the protective device, and select the cable size  accordingly, i.e. we often see this written as.:

I_z ≥ I_n ≥ I_b

(I_z is the cable current-carrying capacity under the specific conditions of installation and use, I_n is the nominal rating of the circuit's overcurrent protective device, and I_b is the design current, for the circuit, which can include diversity in the general case  ... although for fixed loads constantly on then perhaps no diversity). You might also need to take into account unwanted operation of RCDs if the circuit requires an RCD.

You said that the loads are sensors - whether you need to account for 'interleaved' circuits depends on the application. If the system stops working when one sensor goes down, then two circuits won't help ... although it really depends on what they are doing and whether a safety assessment is necessary for anything. This is generally outside the scope of BS 7671, except for:

• considering an adequate number of circuits to minimize inconvenience in a fault; and
• any special requirements if the circuits are circuits of 'safety services'

Finally, from a practical perspective, is there an 'inrush' current that might operate the circuit protective devices (fuse, breaker or perhaps RCD if there's a residual inrush current).

The problem of having 60 odd  half amp loads on the 32A circuit is probably inrush, and they are SMPS based, total earth leakage. regs wise no limit, but more info needed to avoid designimng in a problem - would you want FCU at all ?

Mike.