20

Power supply units are often large relative to the outlet and block access to adjacent outlets in a power bar.

A simple solution is to use 1/2 ft or 1 ft (15cm, 30cm) power extension cords to keep all outlets in a power bar available.

Yet my hunch tells me that doing so increases the fire risk.

Could someone with actual knowledge in the matter pitch in with an opinion?

Does unblocking power bar outlets through short extension cords increase fire risk?

I am not considering an exotic setup (daisy chaining, forking, etc..), nor will the wattage be high (laptop and paraphernalia, at most a stereo amplifier in one slot). The question is whether this increases the risk of fire. The idea is that there are now many more places where rust, or just a poor contact, will happen. And rust/poor contacts cause heat that can spiral to something sinister.

multiple short extension cords

Update

I marked Isherwood's answer right, but thanks to Harper's and Owain's answers I see now that there is an abundance of options to avoid even a small increase in risk. One key keyword is "metal". Search, for example, for "metal power strip" to see ones where right angle plugs will not occlude adjacent outlets. Some have a larger inter-outlet spacing. The challenge is find one not painted yellow.

  • Goodwill, Salvation Army, Habitat for Humanity store, flea markets etc. are your friend when searching for metal power strips. The best use plain old COTS duplex receptacles, and not only can you easily replace them, you can swap them out prophylactically with the $3 commercial grade outlets. They also use readily available power cords and switch knockout holes, switches and breakers readily available in the Mouser catalog. – Harper - Reinstate Monica Jul 21 at 13:44
20

Yes, but negligibly.

Any connection increases fire risk by increasing the chance of heat buildup due to resistance, sparks due to arcing, etc. The question is how much, and the answer is not much.

Since you already probably have dozens of such connections in your home (including such high-current things as a microwave and kitchen range), and since most of these are low-current devices, I see no reason to be concerned.

One caveat would be the potential for heat buildup around the transformers. They're normally held captive by wall outlets or power bars and not likely to end up in a heap on the carpet. In combination, many transformers without good cooling airflow could overheat. Don't let that situation arise.

Make sure all hardware is in good working order and be happy.

16

In fact, there are UL-listed power strips that provide an octopus of short cords-on-sockets. (by the way it was hell to find a genuine UL-listed unit of good provenance from Stanley; most of the Amazon listings are cheap Cheese junk off the Amazon marketplace.)

enter image description here

It depends

If it's blocky because it's a wall-wart style transformer, then normal loads simply won't allow it to get warm enough. Wire/adapter/bad connection heat is a function of appliance power squared, so a 1000 watt air conditioner makes 10,000 times the wiring heat as a 10-watt power block. That's how it's possible to sell the total junk often seen on BigClive etc.

However, if it's blocky for some other reason, like an in-cord GFCI for a heavy draw appliance like an air conditioner or hair dryer, that's a no-go. Don't even connect such a load to a power strip in the first place - it should only go either a) direct into the receptacle, or b) straight from the receptacle to the appliance via a 1-socket heavy 12 AWG appliance-grade extension cord.

Quick test question: Which draws more power: a 75 pound, 10,000 BTU wall air conditioner? Or a common hair dryer?

The air conditioner is typically 800 to 1200 watts. The hair dryer, like most cheap resistive-heat appliances, is almost always 1500W or more. Both are too large for power strips. Point being, a "high power" appliance isn't necessarily obvious. A good measure, though, is they make a fair bit of heat.

  • You misspelled trick :) – Mazura Jul 18 at 20:46
  • I use grounding adapters as stand-offs; the contacts are continuous solid chunks of metal, not some questionable and cheap short cord from some other country. - I've set them on fire before... what the OP really needs is a power strip with "good provenance" +1. – Mazura Jul 18 at 20:56
  • Many products that aren't UL Listed are ETL Certified, which many retailers and Authorities Having Jurisdiction regard as an acceptable alternative. Of course there are many products that have no meaningful certification whatsoever, but the lack of a UL listing hardly implies that something is junk. – supercat Jul 19 at 15:39
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    @user207421 Because we are talking about two different power/heat locations. One is the (intended) power drawn by the appliance, where voltage is substantially constant and so current is proportional to power. The other is the power loss in (bad) wiring, where voltage drop is proportional to current. How is this not obvious given the context and example given? Apply Watt's Law to the appliance to get current, then Ohm's Law to the cheapie power strip to get voltage drop, then Watt's Law again for cheapie power loss/heat. – Harper - Reinstate Monica Jul 21 at 12:52
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    @user207421: From the point of view of a small resistance inside the plug, the appliance is basically a constant-current source so the I^2 * R formula applies. But for the appliance itself, the wall socket is a constant voltage source so its current draw is linearly proportional to power. Of course I^2 R applies there, too, but power isn't linear with resistance of a heating element plugged into a constant-voltage source, only current is. Harper's answer and comments are correct. (But it's easy to get mixed up.) – Peter Cordes Jul 21 at 14:49
7

The problems of 'greedy' power supplies can be resolved by using power bars which have proper individual sockets for each position. They also tend to have better quality contacts than the cheap multi-way strips.

olson multiway socket strip

from

https://olsondirect.co.uk/oldsite/13a_standard_flat.htm

They also do USA standard ones, eg

https://olsondirect.co.uk/oldsite/usa_15amp.htm

  • You don't really need something as over-engineered as those devices. The issue is that the strips you can buy from general retail outlets are designed to the minimum legal size, to minimize cost. A smaller box = less plastic = more profit! – alephzero Jul 19 at 12:08
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    Also, the UK doesn't really have this problem as much as in NA since the unwieldy BS1363 is already such a hog for space that you don't really end up with congestion problems with class-2 warts since they generally fit fine within the mammoth footprint of the BS1363. This isn't the case in NA with its demure, tightly packed NEMA sockets. – J... Jul 19 at 16:12
  • @Tetsujin Nope, lived both places long time. UK plug is actually huge. NEMA plug is actually small. Your second sentence is a non-sequitur. – J... Jul 21 at 11:40
  • @Tetsujin It sounds like you want to have a debate about which plug is superior. Seems to be a hangup with Brits. That wasn't the point of my comment - I was merely observing that the BS1363 is significantly larger than a NEMA plug and, consequently, does not have congestion problems on power strips with class-2 power supplies. Not every mention of the BS1363 has to end in an epic fight about which plug is better. – J... Jul 21 at 16:29
  • @J... - if you're going to open with terms such as 'unwieldy', 'hog for space', 'mammoth ' & in comparison, 'demure' then expect some bite back. Otherwise don't lead with emotive terminology. To then claim after that it is some "hangup for Brits" just makes you seem arrogant. I'm going to clear the rest of the comments now, because you obviously have your own hangup about Brit plugs, which I don't want to upset you further on... – Tetsujin Jul 21 at 16:41
1

An alternative solution for your photograph is to use a single larger+higher capacity PSU and connect the low power devices directly. A lab power supply would be ideal and can be set to a variety of voltages, but generally only one, maybe two voltages, so don't connect 5V and 12V things to the same line. https://www.priggen.com/media/image/product/930/md/peaktech-6075-regulated-laboratory-power-supply-2-x-0-30v-dc-0-5a-5v-3a-fixed.jpg


They're expensive, so a DIY solution is to convert an ATX PSU from a computer to a bench power supply. Example: From https://blog.adafruit.com/2012/12/04/converting-atx-power-supply-to-lab-bench-power-supply-f-a-q/ and an index of projects at https://www.instructables.com/id/Encyclopedia-of-ATX-to-Bench-Power-Supply-Conversi/


You could simply replace multiple USB chargers with a single USB power supply, like this 10 port charger:

https://cdlnz.com/content/images/thumbs/1262466_Y-2190__y2190_550.jpg
capable of 9 devices at a time plus a QC port to charge a laptop at 60W, or something smaller like :

https://cdlnz.com/content/images/thumbs/1239623_PTA7724__pta7724_550.jpg
capable of 4 devices at a time.

  • 4
    This doesn't really answer the question as stated, but does address the unstated underlying cause. – Criggie Jul 19 at 4:36
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    Assuming (with all inherent dangers) that the picture in the OP is the OP's current setup, very few of those bricks are for plugging in USB chargers, thus the multi-port USB setups won't help. The bench power supply is a lovely idea, but all those bricks probably have proprietary connectors on the ends and taking the time to snip the wires, put on spade connectors, label the wiring so ensure you know the correct brick output voltage, then connect a stack of spade connectors to your bench supply is... a challenge most people won't tackle. – FreeMan Jul 19 at 14:02
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    I had this problem in my entertainment shelf at home. I looked at all the power bricks and realized that most of them were for 5vdc (USB power). A multi-usb-charger cleaned up the plugs quite nicely. – JPhi1618 Jul 19 at 20:40
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    @FreeMan Wouldn't it be nice if governments insisted that the amount of garbage generated by these disposable and mediocre adapters is intolerable, and that manufacturers must choose among very few connector types with predetermined voltages? The CE appears to have set its sight on this problem. Why they don't actually act is a mystery. Imagine a future where all these adapters with flimsy cables, which are nearly designed to be disposable within a short term, are not allowed to be sold, or are otherwise prohibitively taxed to the maker. But I digress. – Calaf Jul 19 at 22:35
1

As other answers state, the extensions shouldn't add any significant fire risk.

For that to be true, however, each extension cord should be rated for (at least) the maximum current allowed by the upstream breaker! (or the power strip's breaker, if it has one).

A standard, lower-price extension cord may be #16AWG, which is rated for 10A. Your wall outlet is likely rated for 15A (in the USA, at least).

If you went with the 10A cords, and an end device draws 15A, the cord could melt and catch fire without the breaker being tripped. This may happen because of an electrical fault, or because you plugged in a higher-power device.

So, ideally, you should check your breaker. If it is 15A, go with #14AWG extension cords. If it is 20A, choose #12AWG cords. Short #12AWG cords may be hard to find, and expensive :)

0

The use of short extension cords is an acceptable solution, but not a particularly good one.

To avoid any increase, however small, in fire risk, replace the power strip instead of augmenting it.

There are power strips on the market that solve this problem by providing more space between outlets, which is often necessary for the rather narrow NEMA 5-15R connector.

While shopping for an improvement, there are a few more questions to ask to make this a long(er)-term solution:

  • How many power adapters can fit side-by-side?
  • What is the surge suppression rating? The values on the market range from 300 to 4500 Joules.
  • Does the power strip dissipate energy just between L and N, or also between L and G, and between N and G ("Mode 1" or "Mode 2")?
  • Did the power strip pass UL 1449, or another reputable certification?
  • Is the casing made of plastic or metal?
  • Is the power strip made by a reputable manufacturer?

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