Make note of patchiness for set_manual_preset_runtime

Closes #147

README.md

@@ -164,7 +164,7 @@ This integration provides the following services:
 | `bhyve.stop_watering`             | `entity_id` - zone(s) entity to stop watering. This should be a reference to a zone switch entity                                                           | Stop watering a zone                                             |
 | `bhyve.enable_rain_delay`         | `entity_id` - device to enable a rain delay. This can reference either a zone or rain delay switch <br/> `hours` - number of hours to enable a rain delay   | Enable a rain delay for a device for a specified number of hours |
 | `bhyve.disable_rain_delay`        | `entity_id` - device to enable a rain delay. This can reference either a zone or rain delay switch                                                          | Cancel a rain delay on a given device                            |
-| `bhyve.set_manual_preset_runtime` | `entity_id` - zone(s) entity to set the preset runtime. This should be a reference to a zone switch entity <br/> `minutes` - number of minutes to water for | Set the default time a switch is activated for when enabled      |
+| `bhyve.set_manual_preset_runtime` | `entity_id` - zone(s) entity to set the preset runtime. This should be a reference to a zone switch entity <br/> `minutes` - number of minutes to water for | Set the default time a switch is activated for when enabled. Support for this service appears to be patchy, and it has been difficult to identify under which conditions it works      |
 | `bhyve.set_smart_watering_soil_moisture` | `entity_id` - zone(s) entity to set the moisture level for. This should be a reference to a zone switch entity <br/> `percentage` - soil moisture level between 0 - 100 | Set Smart Watering soil moisture level for a zone     |
 
 ## Python Script