Today we have a review of a product we use in several of the STH lab racks. Specifically, the Schneider Electric APC AP7921B switched 1U PDU is designed to provide key functionality in our power infrastructure. Since we have used them for years and had three that were about to be deployed, we snapped a few photos and screenshots to do a short review of them. These PDUs cost significantly more than some other units specifically because they are remotely switched. In this review, we are going to show you the units.
Schneider Electric APC AP7921B Hardware Overview
The AP7921B is a 1U horizontal switch. With PDUs the form factors matter a lot. Our racks all have zero U PDUs that are mounted in the rear of each rack. This type of PDU is often meant to augment those zero U PDUs or other PDUs and that is how STH uses them.
The input is via a C19/ C20 connection and is designed for 200V-240V input at up to 20A (16A after being derated by 20% for North America safety standards.) This is quite different from some of the larger PDUs where there is a fixed power input line such as a NEMA L21-30P.
Instead of fixed power input, included in the package is an APC locking C19 to C20 cable (2.5m long.) One generally uses this cable to connect to another PDU. It also features a locking mechanism to prevent accidental removal. The key reason there is one can imagine a technician working in a rack and bumping a cable that causes the PDU and downstream devices to lose power.
The main power ports are located on the front of the chassis. These are eight C13 ports that are designed for standard servers.
Each port is switched which means that the ports can be independently power cycled. One can also use features such as power cycling based on timers. This is perhaps the headline feature of this PDU.
Just as an example, here are two PDUs we use running pre-production servers in lab racks. Pre-production servers sometimes have firmware bugs that require hard resets. Hard resets are more challenging since one is rarely near the servers. As one can see here, we are color-coding cables from each PDU to each servers’ redundant power supplies to make tracing cables very easy in this rack.
Other features are metering and management. One can see that this PDU also features a load meter on the front of the chassis via a simple LCD screen showing Amps being used. It is not the higher-quality interactive displays that we see on some of APC’s higher-end PDUs.
Other key features are that we have both a serial port as well as an Ethernet port. This PDU has a management interface that we will show later in this section.
On the other side of the PDU, we have a label and a grounding point. Some of these horizontal PDUs have ports on both sides to increase density. Since this is a short PDU and has a limited number of ports, it does not have rear ports.
One item we thought that was fun on this unit is that there is a “DANGER” sticker in English on the PDU. APC provides a complete set of stickers in other languages to replace this label or augment this label. In many jurisdictions having properly labeled electrical gear in certain languages is important so this is one of those nice touches, but also one that may not be used if you have only a US data center.
Included in the kit we have rackmount ears and also a cable tie-down bar. We have the bar installed in the picture with the colored power cables above on the bottom unit. In more permanent solutions than our lab racks, one can secure cables to this cable management bar.
One item we normally do with hardware, even expensive servers is to open the unit to show the inside. Since we needed this to function, and we could not install this in a data center with a broken seal, we had a challenge.
What we found was that there is a YouTube teardown of the discontinued/ previous APC AP7921 model which is likely worth looking at if you want to see what is inside.
We know this is not the best solution, but in this case, we only had access to the unit because it needed to be deployed.
Next, we are going to take a look at the management aspect of the PDU before getting to our final words.