We have a customer with a relatively new installation, unfortunately we are receving complaints of excessive noise which would appear to be emitting from the BSVQ boxes. As usual, when our engineer is on site everything appears to work normally. We have sought advice from Daikin, to no avail. The noise is not restricted to any one BSVQ box. Presumably this noise is caused when the system has been in heating for a long period of time and then changes over to cooling, this is only a guess as we have not been able to pin down when the noise might occur. The customer says that the period of the noise is long enough to interrupt speakers in meetings, estimated length of up to 3 or 4 minutes. Anyone else experienced this or have any ideas how we can cure it.