Networking a 5100MP???

We have a ceiling mounted 5100MP projector that we would like to be able to connect to our network for management purposes. In the on-screen setup for networking I can set the IP, gateway and DNS server but the only values in the Subnet Mask setup are 0 and 255. We use a 255.255.252.0 mask. Is there any way to change the Subnet Mask settings? If I select DHCP for the settings how do I determine what IP it is using?