SMX 3000HV max load capacity

[BillP]

Hi,

does anybody know what is the max load capacity of APC SMX 3000HV when main power available?

Since the load, when mains are available, does not pass through inverter the allowable load should be a bit higher, isn't it?

When on batteries, 2700W is the max load but when on mains feed whats the max load and what is the corresponding time?

Thank you.

[BillP]

Hi Daniel - 

When online you will get an overload tone at 2700w, but the unit will still pass power. The limiting factor is the breakers (either input or output)

Thanks

Liam

[BillP]

Hi Liam,

thank you for the input. So let me get this straight: if we install a 40A breaker we can pass 40A through the UPS no problem as long as we are online? That's pretty handy for my scope at least. What I intend to do is to put an entire house on UPS and then lead all 3 output groups to a KNX 8 fold switch actuator, programmed with load shedding logic, then lead the channels to 8 circuit breakers. Through a voltage sensing unit I can make 2 load shedding programs so I needed to know how far I can go with the online mode. The only thing that concerns me is that when I opened the UPS I found power relay with 20 max rated amps. Maybe the UPS, when online does not pass this load through any of these relays?

[BillP]

Hi Daniel - 

The UPS itself has internal fuseable links as well as breakers on the outputs. The circuit feeding it should be sized appropriately - We would recommend no more than 30amps. If you are trying to pass 40 amps through it (or close to that) you are going to run into breakers tripping. We do not advise intentionally running the unit in overload mode.

Also - you mentioned an entire house. I can't see what region you are in, but if you are in North America, please note that this unit can not support 120v loads without a stepdown transformer.

Thanks

Liam

[BillP]

Thank you very much for your reply Liam. I live in Romania and my max load will be closer to 30A when online. I only mentioned 40A to see how far it can go. Besides, the info might be useful for other projects too.

So again, thank you, much appreciated.

[BillP]

Hi, Liam

I managed to implement to load shedding project I was talking about and it works quite well.

Still, during discussion with the client, some modifications are to be implemented. For that I need to know what is the overload time of the UPS when on batteries. As an example, if the house in on main feed and the instant power is 3000W and suddenly the mains are out, the UPS will switch to batteries but the load will be the same until the load shedding algorithm executes in the KNX system. The algorithm needs about 1-1.5 sec to execute. Do I have this allowance from the UPS side? Can it hold such overload for about 2 sec?

Thank you.  

[BillP]

Hi Daniel - 

Overload limits for this unit are:

Alarm over 105% load

Output shutdown if over 125% load for 4 Seconds, or over 150% for 1 Second, or over 200% for 250 mSeconds

Short circuit current limit is 39A

We would advise that your load should not exceed 80% (2160watts)  in normal operations so that you have enough headroom for in-rush.

Hope this helps!

Liam

[BillP]

Thank you!!

[BillP · Accepted solution]

Hi Liam,

I finalized the UPS setup with the following limits in KNX: on battery max current 11A and online 25A. Everything is working fine since then.

The client wants to repeat the setup in another house, this time though, we have a tri-phase power supply for which we intend to install 3 SMX3000HV units, one UPS for each phase. Is there any problem with this setup? One of my colleagues said that this setup is dangerous and should not be used, but I don't see why. Could you please clarify the matter?