What happens if the Power Meter loses the connection? (Fail-Safe)

1. Site with 1 power meter

When a power meter disconnects, the load manager cannot monitor the building load. The load manager will immediately reduce the charging limit to 0 A (Safety Current) to avoid overload.

Manual override of "Safety Current"

As a HARMON-E user with admin permissions you can set up a static limit for the charging cluster in the Advanced Configuration of the power meter. The limit is called Safety Current.

The static limit will be enforced whenever the connection to the power meter gets lost.

1. Add your preferred maximum charge current as "Safety Current"
2. Save your settings

2. Site with more than 1 power meter

The Safety Limit is the limit the cluster/sub-cluster it is in will be reduced to. If there are multiple power meters, the behaviour of the load manager will be different.

The logic behind the safety current

When a power meter does not respond, the Charging Limit is calculate as follows:

Charging Limit - (Charging Limit - Safety Limit)

If there are multiple power meters in the same cluster, it is calculated as follows

Charging Limit - (Charging Limit - Safety Limit PM1) - (Charging Limit - Safety Limit PM2)

Example

Site - Charging Limit = 100A
PM1 - Safety Limit = 50A

If PM1 does not respond, Charging Limit is set to 50A (= 100A - (100A - 50A))

Site - Charging Limit = 100A
PM1 - Safety limit 0A

If PM1 does not respond, Charging Limit is set to 0A (= 100A - (100A - 0A))

Why it does not work as expected for 2+ meters

Site - Charging Limit = 100A

PM1 - Safety Limit = 50A

PM2 - Safety Limit = 25A

If PM1 does not respond, site limit is set to 100A - (100A - 50A) = 50A

If PM2 does not respond, site limit is set to 100A - (100A - 25A) = 25A

If PM1 and PM2 does not respond, the site limit is set to 100A - (100A - 50A) - (100A - 25A) = -25A (clamped to 0A)