Can I daisy-chain 2 UPSs?

Q.

Is it possible to daisy-chain UPS systems together?

 

A.

APC does not recommend that you daisy-chain two or more UPSs together. Each unit should be plugged directly into a properly grounded wall outlet for optimum surge protection.

 

We do not recommend daisy-chaining UPS systems for the following reasons:

 

 

1. Daisy-chained UPSs do not provide any extra surge protection. A UPS is designed to remove any possibility of a surge reaching the output receptacles. In the event of a surge strong enough to damage equipment, the first UPS in the chain would sacrifice itself to protect the load. This would mean that power would be removed from the second UPS in the chain, forcing the unit into battery operation.

 

2. Whenever connecting a second UPS to another UPS, the chance of overloading the first one is greatly increased. The number of receptacles in a UPS is restricted by the power limitations of the UPS itself. Even if the number of receptacles was increased, the overall Watt capacity of the first UPS would remain unchanged. The capability of the second UPS would be inversely affected by that of the first unit. Therefore, the overall Watt capacity of the configuration is no greater than that of the first UPS in line.

 

3. In most cases, daisy-chaining UPSs does not allow for extra runtime. If you are using a UPS that outputs a step-approximated sine wave when running on battery, as soon as the first UPS goes to battery operation, the second one will also do so because it will see the step-approximated sine wave as distorted or bad power. Both UPSs will discharge together and will not provide any extra runtime to the load.

 

If you are looking for extra runtime, we recommend one of our Smart-UPS® XL products, which have the capability of adding extra external battery packs. If you require more runtime or VA capacity than you currently have, we recommend taking advantage of our Trade-UPS® program through which you could trade in your existing UPS for a unit with a higher VA capacity or one that has extended-run capability.



07/25/2008
 
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