Installing a CRO on condensing unit and its nameplate ratings

[bhellmer]

I am an engineer with a client in the frozen food business. A manufacturer of their freezer boxes is modifying condensing units from Copeland by adding a Compressor Rack Optimizer (CRO) which throttle the refrigerant flow through the suction line to limit compressor loading.

The Copeland nameplate lists the minimum circuit ampacity as 36.0 and maximum fuse size as 60, but the freezer box manufacturer is wiring the boxes with 30 ampere cords and connectors. The freezer box manufacturer states that we only need to provide a 30 amp branch circuit for each truck.

I am trying to comply with NEC Article 440 and obey Copeland's nameplate. NEC Article 440 does not reference the use of CROs.

Must I comply with the condensing unit nameplate, or may I disregard the nameplate and trust that the CRO will prevent an electrical overload?

 

[greenspark1]

Sounds like the CROs will trip the 30A breakers that are being installed with the 30A cords. I am not familiar with these devices and if they are an intermittent type load or considered continuous.

 

[GoldDigger]

Well, if the CRO is specifically designed to limit the operation of the compressor(s) so that they will never draw FLA because they will never see full load, then a 30A breaker may well hold if they can still start successfully. And I expect that the CRO will also make sure that the compressors are unloaded when starting.

Tapatalk!

 

[kwired]

I am an engineer with a client in the frozen food business. A manufacturer of their freezer boxes is modifying condensing units from Copeland by adding a Compressor Rack Optimizer (CRO) which throttle the refrigerant flow through the suction line to limit compressor loading.

The Copeland nameplate lists the minimum circuit ampacity as 36.0 and maximum fuse size as 60, but the freezer box manufacturer is wiring the boxes with 30 ampere cords and connectors. The freezer box manufacturer states that we only need to provide a 30 amp branch circuit for each truck.

I am trying to comply with NEC Article 440 and obey Copeland's nameplate. NEC Article 440 does not reference the use of CROs.

Must I comply with the condensing unit nameplate, or may I disregard the nameplate and trust that the CRO will prevent an electrical overload?

Well, if the CRO is specifically designed to limit the operation of the compressor(s) so that they will never draw FLA because they will never see full load, then a 30A breaker may well hold if they can still start successfully. And I expect that the CRO will also make sure that the compressors are unloaded when starting.

Tapatalk!

I would also say that it is supposed to be a optimizing method, not some add on to essentially make it a different sized unit. If it is set to never go above a certain level, just maybe a smaller compressor should have been used in the first place. OP says nameplate says 36 MCA, therefore a 36 amp or more conductor must be used. If it says max overcurrent protection of 60 then there is no violation installing a 30 amp device if it will start on one.

I also find many compressors never draw anywhere near full rating when new, but over time they may start to draw more, this is more then just wear on the compressor itself, as the demand from the refrigerant may increase the load if the condenser or evaporator isn't operating efficiently, plus a freezer that is near set point should draw less than one that is well above freezing with or without this optimizer.