VRF Over Capacity

[Husky250]

All,

I have experienced some recent issues with Inverter compressors over amperage alarms. In reviewing data from the system it seems the Indoor units are really over sized for the space. I say this as all Indoor units seem to reach setpoint very rapidly. This causes the Inverter compressor to cycle frequently. In cases with no remotes and central controllers, I see this more often. Its easy to give all Indoor units the same mode and setpoint. When there is no load and all Indoor units are oversized all Indoor units reach setpoint at the same time.

Increasing the amount of refrigerant into the piping and suddenly stopping and starting the compressors I feel could cause liquid refrigerant flooding.

Is it possible to cause problems from gross coil over sizing? Have you guys ever seen this before?

Thanks in advance.

[defender1be]

maybe that the outdoor unit is also over sized, then the compressor is on low load even if the indoor unit are not over sized. combine this with over sized indoor unit en you have a load below minimum load for the compressor. a solution could be to replace the outdoor unit, most VRF allow 130% power for indoor units on the outdoor unit.

[Husky250]

maybe that the outdoor unit is also over sized, then the compressor is on low load even if the indoor unit are not over sized. combine this with over sized indoor unit en you have a load below minimum load for the compressor. a solution could be to replace the outdoor unit, most VRF allow 130% power for indoor units on the outdoor unit.

I never thought the outdoor unit could be oversized as well. Good point!

I seen this when turning all Indoor units on . System is running fine, then more capacity is needed. Between second stage compressor coming on and hot gas energized, several Indoor units meet setpoint. This results in two compressors running and usually only one Indoor unit only running. In my opinion, its very strange to see only only one Indoor unit operating alone.

At one site, I have been told the outdoor unit (10 Indoor units connected) cycles 5 - 6 times an hour. I find this very strange. All thermistors and transducers reading correct. This is very odd, I notice no load in the spaces.

[back2space]

I never thought the outdoor unit could be oversized as well. Good point!

I seen this when turning all Indoor units on . System is running fine, then more capacity is needed. Between second stage compressor coming on and hot gas energized, several Indoor units meet setpoint. This results in two compressors running and usually only one Indoor unit only running. In my opinion, its very strange to see only only one Indoor unit operating alone.

At one site, I have been told the outdoor unit (10 Indoor units connected) cycles 5 - 6 times an hour. I find this very strange. All thermistors and transducers reading correct. This is very odd, I notice no load in the spaces.

Have you tried setting all indoor units to low fan speed to lower the airflow so they should take longer to reach set point so if they are oversized then running them in low may mean they are running at closer to the actual required output for the heatload of the room etc.

Also means less noise from the units!