Hi ouberlord,
If you want to monitor Hardware Health on Dell servers you need use SAM. The NPM is able monitor only switches, routers or hub class hardware. Server Hardware Health is monitored by SAM 5.0 or higher. You should use SAM 5.5 for the best result.
When you do install SAM then you need to run discovery on the server nodes. Please take in consideration that for SNMP and WMI node types only HP, Dell and IBM can be monitored at the present time. For ESX nodes the manufacturer is not important the VMware should be able provide necessary information's for any hardware. The discovery is necessary only for existing (already added) nodes. Newly added nodes will pickup the hardware health automatically.
Regards
Dalibor