noise on c-bus

Hi guys I am in the middle of commissioning a c-bus and multiroom audio /video system both stand alone that is the systems will not be linked . I am not sure yet if I have a problem but our standard way of doing c-bus is as follows. We create all connections for sw points join blue /orange and stripes and then attach an oscillator to send a tone over the net work go around with a probe checking that we have a complete network before walls are closed up, hopefully this prevents finding sw with no connection to system ( still has happened usually clumsy plasterers ). This was done however when we came back house now had power and we were ready to start fitting switches, dimmers were installed loads on but no power on packs. Because we wanted to start fitting sw we were going to double check our network to prevent fitting sw and then finding a problem however when we pressed the button on our tone probe there was a huge buzz and we found that we could only trace from one sw point to the next point and then move the oscillator because the buzz was overriding the tone.The only thing powered in the house was the heating system which we switched off and this got rid of the buzz and allowed us to discover that the plumber had managed to cut through a c-bus cable in the attic fixed the problem and thought we were happy. Came back next day electrician now had power on dimmers and started id and assigning. 5 of 8X1 amp,2 X 2 amp 2 8way 10 amp relay and a 5 X 4 amp. because client had changed mind about sw we could only fit the 14 sw we had and the rest cable left waiting . Following day we started to connect and check label on multiroom cable (we used a cable with 4 core speaker and i cat5e for our multiroomsystem) and found same problem with buzz . If you press the probe button in the middle of the room there is a loud buzz. No problem switched off heating buzz remained discover it was now being generated by c-bus . I had set max out on all dimmers to 80 % as we had left a whole house sw for painters to work . I know this is long winded but I have never had the probe react like this and wonder will this give me a problem with c-bus or my multiroomsystem . I have never needed to use noise suppression on a c- bus system should I be on this one and if so what type , where and how many. any advice thanks