Can I add a Lyric LKP500 Keypad to an L5100 or L5000?

No, the Lyric Security System is currently the only panel that a LKP500 Keypad can interface with.

The Lyric LKP500 is a wireless, alphanumeric, encrypted SIX Series keypad. The unit is the only wireless keypad currently compatible with the Lyric panel. The keypad is a bi-directional device and is able to display zone alpha descriptors and status. The keypad can also voice announce the systems status. Each Lyric system can have up to 8 keypads associated. The LKP500 can be wall mounted, with its backplate, or can be placed on a LKP500-DK desk stand. Included with the unit is its own, rechargeable backup battery, terminated power cable and dedicated power transformer.

The Honeywell L5100 and L5000 are both part of the Lynx Touch Wireless Panel family. These panels are all-in-one units that have the ability to communicate over WIFI, Cellular or ethernet. The L5000 and L5100 are the oldest all-in-one touchscreen panels Honeywell has released. The Lynx Touch panels are compatible with Honeywell 5800 series wireless sensors and the units do support devices that have a House ID. The House ID allows a device to communicate with the panel without having to occupy a zone. Two examples of devices that use the House ID are the 5800WAVE Wireless Siren and the 5828 or 5828V (Voice Annunciating) Wireless Keypad. The LKP500 has no House ID and is currently only supported on the Lyric. The LKP500 uses encrpyted, bi-directional transmission to communicate with the panel. The 5828 Voice Annunciating Wireless Keypad and the 5800WAVE Wireless Siren are not compatible with the Lyric at this time. In fact any device that requires a House ID for its communication is not currently compatible with the Lyric. Honeywell has said they want to expand this functionality to the Lyric with a firmware update but there is no date scheduled for its release at this time.