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Choose and Buy the Best DIN-Rail Fused PDU for Your Remote Sites

By Andrew Erickson

November 6, 2022


When it comes to choosing a PDU, there are a few things you'll need to keep in mind.

Fuses are fairly fundamental, but you might already have protection

There are two main types of PDUs when it comes to protection against power surges: unfused and fused. Fused PDUs offer protection against overcurrent and short circuits, while unfused PDUs do not.

As you know, fuses are usually a good idea. There may, however, be situations where you can avoid the trouble and small expense of choosing a fused PDU. Perhaps you already have circuit protection via a standard external fuse panel.

Also, don't forget that fuses can be the self-resetting PTC variety. This gives you good circuit protection (with excess current shunting to ground) without creating wasteful truck rolls to replace fuses after an incident.

What environmental conditions must your PDU survive once mounted on its DIN rail?

Next, consider the environment in which the PDU will be used. If you're looking for a PDU to use in an industrial setting, then you'll need to make sure it's rated for that environment.

Although it's not a 100% guarantee, most DIN-mounted devices will be installed in small cabinets. Many of those may not have climate control. That's an excellent use case for an "industrial temperature" PDU.

At DPS, we build our RTUs in both standard and industrial temperature ratings to suit these varying needs. For reference, industrial temperature ratings tend to run about 30 degrees warmer (to about 158 F) and about 40 degrees colder (to about -40 F). This varies slightly based on model, because components vary among our RTUs.

Don't forget that a DIN-mount box can be much more than just a PDU

Finally, consider the features you need. PDUs come with a variety of features, such as metering, remote monitoring, and environmental monitoring. Choose the PDU that has the right mix of features for your needs.

Because these are so important, let's pick them apart one at a time:

A metered PDU can track power consumption over time

Although it's not even considered for some, this is one of the most important features for many PDU users. If you need to track power consumption for billing, capacity planning, or just general information purposes, then you need a PDU with metering capabilities.

Power tracking is simply the combination of current monitoring (amps) and logging capability. If you log how much power is being consumed regularly enough, you can very accurately calculate how much power was consumed during that time period.

In my projects with clients like you, I've found that larger-amperage PDUs (20A per channel or higher) tend to see increased demand for power metering. That's due to the obvious fact that low-power PDUs won't consume enough power to matter in many cases. If you're just controlling network switches and other telecom gear, those usually don't even scratch the surface of even a 10-amps-per-channel PDU ratings. The cost of monitoring is sometimes higher than the benefit.

Consider also the possibility for a "just right" solution that involves only the total power flowing through a PDU instead of specific per-channel metering. As a PDU manufacturer, that means I only have to build a single current sensor into my PDU instead of one per channel (could be 8 or more). This can be a way to meter without breaking your purchasing budget on an expensive PDU.

Remote monitoring is a perfect "freebie" when you're installing a PDU

General remote monitoring is a great PDU feature to have, and it doesn't usually cost much extra. If you're installing a DIN-mounted box, why shouldn't it perform as many functions for you as possible?

Remote monitoring allows you to see what's going on with your PDUs without being in the same room (or even the same building).

There are two common ways that PDUs will talk to your central alarm master: network connectivity (Ethernet or cellular) and "dry contact" relay outputs. Protocol-based reporting via LAN is far more popular in today's world, as it allows for much more detailed PDU statistics to be collected and eliminates the need for another device. Relay outputs are useful for PDUs that will be used in locations without network connectivity or when using external programmable logic controllers (PLCs) for remote PDU control.

Since we're a semi-custom manufacturer, DPS PDUs offer both options for remote monitoring. We also build our PDUs with "future proofing" in mind.

For example, virtually all of our PDUs come with an Ethernet port. But we also offer cellular connectivity as an optional upgrade (via external modem).

So, if you're installing a PDU in a location that doesn't have network connectivity today, you can still get the PDU you need and seamlessly upgrade to standard ethernet monitoring later when (or if) LAN becomes available.

Don't make a short-sighted decision about remote monitoring today that will limit your options down the road.

Environmental monitoring helps you detect the largest (and most costly) remote site disasters

All of the above information about remote monitoring is true for more than just equipment alarms. Your PDU, whether rack-mounted or DIN-mounted, can also monitor environmental levels at your site like temperature and humidity.

This is another obvious opportunity to have your PDU, which must be out at your remote site anyway, perform another useful function.

Environmental monitoring can be as simple as an ambient temperature sensor directly on the circuit board of your PDU. That requires no additional space or wiring.

An ambient temperature sensor isn't as perfectly accurate as something mounted in a specific location, but it's plenty close enough (usually within about 5 degrees) to detect HVAC failures or excessive heat loads on hot summer afternoons.

The same is true for humidity sensors. We're not looking to predict the weather here. It's just good to have something that can spot some kind of site leak before it becomes a major problem that cuts off service to an area.

Call me to talk about your options for buying a fused PDU (DIN, rack, or otherwise)

At DPS, we make a lot of different PDUs for a lot of different purposes. Also, because our corporate heritage stretches back to building RTUs in the 1990s, we know a few things about remote monitoring and environmental monitoring.

Give me a call at 1-800-693-0351 or email me at sales@dpstele.com

We'll talk about what you're trying to accomplish and sketch out your ideal PDU together. Who knows? Maybe you'll even inspire our next semi-custom PDU design.

Andrew Erickson

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and opt...