Why are AC adapters (wall warts) designed to block adjacent AC outlets?

Question

The AC adapters for a lot of equipment seem to be specifically designed to block the AC outlets around it (this is in the US).

Is this a safety feature to minimize the power to that outlet or just lack of common courtesy?

Clarification: I am NOT asking how to "fix" the problem, but why it exists in the first place. Most of the fixes comprise of adding more wires to a problem which I don't understand why it exists in the first place.

NB! Question is not - What is an AC adapter? There sure is bad/lazy design out there but some adapters seem to be

"specifically designed to block the AC outlets around it"

. Why would that be? Since

"There is no need to limit the current from the output, as most such devices handle low power levels, if compared to an iron or a room heater."

Please see the attached picture of the AC adapter with "ears" to prevent the use of nearby outlets:

Answer 1

The kind of adapter you are referring to is called a wall wart. To quote the article referenced :

One of the major advantages to a wall wart has to do with preventing overheating to both the power source and the device that is receiving the power. Because the wart proper is removed from the equipment that receives the electrical current, it is possible to maintain a proper temperature at both ends of the device. Many models of the wall wart are manufactured with built in thermostats that shut down the unit if a malfunction takes place and the wart begins to overheat.

The wall wart hence has to accommodate for all the components needed to the switching and matching and also accommodate for the transformers size which is required to handle and do the switching. The larger the size of the transformer, the larger and heavier the adapter thus blocking up the surrounding area making it difficult to put in other outlets.

Here are two examples of inbuilt transformers for linear and switching power supplies.

That said its pretty bad design and there are a lot of complaints about how the system was initially designed.

Answer 2

It's not as if engineers sat around and designed them to block adjacent plug points. They are large because of the physical size of the components that they need.

With newer technology, and lower power devices, some AC adapters no longer do that, but for larger devices that is likely to be an issue for years to come.

One solution is to use a cable extension between the AC outlet and the adaptor.

Answer 3

Another solution (along the lines of @JohnGB's answer but with no supplemental cables needed) is to use a newer type of power strip that can accommodate large AC adaptors without blocking other outlets. One novel design is the Quirky PowerPivot that bends not only to accommodate large power "bricks" but also to fit in your space neatly:

Answer 4

IMO they are not designed, just engineered. With due respect for engineering, which is a must. Design seems to be considered optional.
There is no need to limit the current from the output, as most such devices handle low power levels, if compared to an iron or a room heater.

Since some time ago I see bricks without a transformer, the component that made the old ones heavy and bulky. Modern power supplies are smaller, lighter and colder.
But yes, even the smallest, like my cellphone charger, will interfere with the adjacent connections in a power stripe.

Answer 5

Firstly, this hindrance is not true of all adapters. Transformer-based adapters take up space because they contain a large transformer. Switching supplies can be fit into a much smaller space. For instance look at the current crop of cell phone chargers.

Secondly, even transformer adapters are small enough that they can be plugged into a two-socket outlet along side with another appliance or another such adapter. Where they become a hindrance is power bars. This is due to the arguably bad design of a power bar, which stacks the outlets vertically, without space in between, failing to anticipate that users have numerous adapters.

The fix is to design a power bar whose outlets are on a 90 degree angle and have surrounding space.

Look at this power bar. It has an outlet with extra space around it which accommodates one wall-wart, and the outlets are at 90 degrees:

The transformer-based wall-wart shown is more than a decade old, yet compact. Two of them could fit into two-socket outlet, and this is by deliberate design. In other words, the engineers took steps to ensure quite the opposite of what you're suggesting, by placing the prongs close to the edge of the box.

Of course, you cannot place N of these warts into a conventional N socket power bar. This is simply not possible due to the size of the transformer.

Also shown in the picture is a modern cell phone power adapter, which is not much larger than a passive plug. Its power handling is about the same as that of the other adapter.

Now here is one more shot, which contrasts two transformer-based adapters. The large one is late 1980's Yamaha unit. It has to be that way because it's robust. This thing runs quite hot, and still works after 25 years of use.

The small wall-wart is also transformer-based (I believe) rather than switching, and shows you that these things can get down to size. However, it is only rated for 200 mA at 9V. A switching supply in that size can deliver a lot more current.

Large as it is, the Yamaha one can still be plugged into a two-socket wall outlet, while that outlet accommodates another appliance. Again, it's designed for minimum hindrance, while providing the necessary space for the transformer and ventilation around it. Note how the tiny wart, and the big one, both have just about exactly the same clearance between the prongs and the closest edge.

Here are two of these power supplies easily plugged into the same outlet, with half an inch of clearance in between!

So basically, your premise that engineers deliberately design adapters to hinder other devices from being plugged in is wrong; you just have to think about your adapters when you're shopping for a power bar.

Answer 6

There is a cost involved in designing things in ways that changes basic engineering. Printed circuit boards for a long time (and probably still) were easiest to layout and cheapest to purchase if rectangular. Components are laid out on PCB's according to engineering needs. For example, the placement of heat sinks for optimal cooling. Plastic housings can be purchased in bulk with little customization. So I think most companies rightly did not invest their money in redefining the adapter. Of course, laptops changed that because you need to carry the adapter with you.

Answer 7

Wall warts sometimes block adjacent AC outlets, not because they were designed this way, but because it's easier and cheaper to make a product with an external power supply. Usually the wall-warts are provided by Chinese manufacturers as a turn-key solution for other companies, at ultra-low cost.

It is not always feasible to do an internal power supply, because it takes a lot of time & money to develop. There are also size considerations, because the main components of a power supply usually involve physically large capacitors and a transformer, so it could add bulk to a product.

Take for example, the AppleTV. Apple did care enough about this design consideration to spend its time & money creating an internal power supply. Roku, on the other hand, being a much smaller company, has an external power supply. However, at least Roku has enough consideration to make their wall-wart expand horizontally, so to not block another vertical outlet.

There is a 3rd option, which is to do a "line-lump", where the power supply is separated from the plug, so it also solves the problem of blocking outlets. A neat example of line-lump is Apple's power supply for its MacBooks. The design gives the user the option of either have a wall-wart or a line-lump. Even in wall-wart mode, it does not block the other outlets.

Answer 8

So far as I can tell it's some AU/NZ regulatory requirement.

My reasoning is thus the official raspberry-pi wall-wart has an annoying flange that is only present on the type I plug it's not on the type A or type G

Also when a supply comes with interchangable live pins it's only the type I that has the ears.

perhaps there is some regulation that requires some minimum spacing between the bodies of these devices ans so flages or ears are added to enforce this.