Help! I am baffled by electricity, but as we all know it’s a must. Please be kind! My question is, would plugging in a 100-400 watt personal heater into a powerstrip be okay? With, say a 3 foot cord? This powerstrip is hard wired into my RV solar inverter. I have no way of knowing what gauge the wiring is nor do I have the knowledge to mess with it. Thanks in advance. - Zannie
The wiring and the power strip can almost certainly handle a 400 watt load. Your typical cheapie power strip can probably handle somewhere around 1000 to 1200 watts continuous load.
The weak link in your system may be your solar charging system and your inverter. Some RV systems are pretty small, and are meant to handle about 100 watts or so. A 400 watt heater would be too much for that type of system. On the other hand, they do make solar charging systems that can handle 400 to 600 watts of load, though depending on the size of your batteries you may only have a certain number of hours at that kind of load before your batteries are depleted.
You need to know what size batteries you have and what the rating is on your inverter.
(I’m an electrical engineer, by the way)
Using a good quality extension cord (14 AWG or 12 AWG) with your heater should not be a problem, assuming you aren’t running 100’ or so.
Frankly, I’m surprised that your multiple outlet unit even operated the space heater. Most multiple outlets have a breaker (technically called “supplementary overcurrent protection”) rated at 7A or 10A. Some go a bit higher, but I would not use one rated over 10A, regardless of the product description or marketing palaver.
Your extension cord probably has a label on the back that says what it’s rated for, and your appliance probably has a label near where the cord attaches that says what it draws. Make sure that the draw of the appliance is less than or equal to the rating of the cord.
Please note that the question about the heater and the extension cord dates from 3 years ago. This thread was re-animated by LaymanZannie with a similar but not identical question about a much lower-draw heater connecting to a solar inverter. It would likely be helpful if responses were clear about whose question they were answering, though I’m not sure there’s much to add to engineer_comp_geek’s response.
I have a power strip rated for 15 A. I took it apart. As you can see, the hot contacts for the six receptacles are tied together using a stamped, elongated metal strip. There’s an identically-looking strip used for the neutral contacts. Each strip contains spring tabs for making electrical connections to the prongs of each plug. It looks like the spring tabs are made using a punch and die.
I don’t know what the strips are made of. They look like they’re brass, though I’m not sure if they’re solid brass or if they’re solid copper with some kind of plating (brass or nickel plating?).
In pics 7, 8, and 9 I insert a plug into the contacts. I’m not an ME, but I am skeptical the spring force can remain constant after many years of use based on this design. It just looks very sub-par in my book.
There is a UL sticker on the enclosure. I assume this means it complies with UL 1363, which also means each of the six receptacles must meet UL 498 requirements. According to UL 1363, if a 15 A load is plugged into one of the six receptacles, the temperature rise of the electrical contacts should not exceed 30 °C above ambient.
So yea, my power strip should be O.K. when the load current is 15 A. But something still bothers me about it. I have heard quite a few stories (albeit anecdotal) about power strips melting or catching fire. Regular 120 V / 15 A wall receptacles (NEMA 5-15R / UL 498) do not seem to have this reputation.
So let’s compare a power strip to a standard 15 A/120 VAC wall receptacle. Here is a folder showing how I took apart a brand new 15 A/120 VAC wall receptacle. Note the large size of the contacts and “real” looking springs. I also noticed the insertion force was significantly greater when compared to the power strip.
So power strips might meet spec when they’re new, but I suspect the contact force decreases over time due to a crappy & cheap design.
Just found my 15-20foot ext. cord female end melted, with 1500 watt heater plugged in via 15 amp power strip. Been using it for two winters, no troubles. Recipe for disaster.
Last 5 days been smelling an odor near the heater and cords near my bed, old 1800s house with no direct hot air heat into this bedroom. Had not investigated the odor, but this a.m. my clock was out, plugged into strip.
I tried to pick up the plug and it was stuck to the carpet, pulled a 2x3" piece of melted carpet up melted to the plug which was on top of the carpet.
The male plug on strip was partially melted.
The plugs on the ext cord were repkaced and were thise cheap feel, molded plastic type installed by my neighbor, a licensed electrician.
I never leave heater on if I go out, but over time, this combination of heater, ext cord, plug strip, creating heat, molded plastic plugs, amazing it did not catch fire.
I did plug in a second heater once this winter which tripped the circuit breaker within a few minutes. So, thought things were safe.
Rules. 1. ALWAYS plug heaters into outlets, never use extension cords. IF an ext.cord is needed, get a very heavy duty cord as short as possible. 3-10 ft max.
2. A device that creates heat, is on for many hours, draws heavy power is DIFFERENT than a vacuum or circular saw than draws heavy power for a short time.
3. Heated over time can deteriorate the plastic and fail months or years later.
4. just because it worked for a while, does not mean it is safe.
If you have a high-current device that will be continuously powered for more than a few minutes, and you need some kind of extension cord, here are your options:
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Standard/cheap power strip. I do not recommend this. See post #46.
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15 A or 20 A extension cord. This is probably a better than option #1, though I would still feel somewhat uneasy about it. I have never disassembled the receptacle end of an extension cord to see how it’s constructed. And I am guessing build quality might vary depending on manufacturer.
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Use a 20 A power strip constructed using standard wall receptacles. Like this one. With this type of power strip, at least I know the receptacles are good. Expensive, but the peace of mind is worth it.
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Extend the length of the device’s power cord. Cut off the plug of the device’s power cord, cut off the receptacle of a 20 A extension cord, and then splice them together using solder and heat shrink tubing. This is a good solution, IMO.
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Replace the device’s power cord with a 20 A extension cord. This is also a good solution.
This topic looks like it has had the hell discussed out of it, but I’ll throw in a bit more information:
Yes, you can run 120VAC on both 18 AWG and 16 AWG conductors as power circuits. In fact, fixture wire is often used for this purpose.
Per NEC, if you use 16 AWG conductors, the overcurrent protection (fuse or circuit breaker) may not be larger than 10 amps. If you use 18 AWG conductors, the overcurrent protection may not be larger than 7 amps. (Reference NEC Article 240 if you need to.)
I think you can confidently extrapolate from this that running more than 7 amps on an 18 AWG conductor or 10 amps on a 16 AWG conductor is a bad thing. Don’t do it.
Unfortunately, while the US has standardized plugs and receptacles for 15 amp and 20 amp circuits, we don’t have any common ones for 7 amp or 10 amp circuits. We end up with crappy 18 AWG and 16 AWG extension cords that SHOULD not be permitted to carry more than 7 or 10 amps, but you can plug them right into a 15 amp outlet. Go figure.
(Yes, I am a licensed electrical contractor.)
That’s a good solution if you know what you’re doing and do it properly. Most people who would try that solution wouldn’t. I can just picture someone trying to follow your advice, but using a 10 A cord, or doing the soldering sloppily, or not wrapping the conductors well enough, or any of a wide variety of other ways to screw it up.
Thanks Crafter Man for your analysis. There is a recurring suggestion that the problem must be that the space heater was plugged into a power strip that was not rated for the heater’s amps. Everyone seems to suggest that the power strip must be rated for less than 15 amps. Most of the cheapest power strips I saw on Amazon were rated for 15 amps although I only checked a dozen or so out of thousands. Here is a 15 amp power strip for $4 from Harbor Freight. It even says it has 14 gauge wire. https://www.harborfreight.com/4-Outlet-Power-Strip-62505.html
I don’t believe that most of these cheap power strips are capable of safely handling 15 amps indefinitely.
In theory, the OP’s heater is only drawing 12.5 amps. So, any 13 amp extension cord should be adequate or power strip should be fine, right? I couldn’t find any power strips or extension cords rated less than 13 amps although I’m guessing there are some out there.
Here is a 13 amp cord with 16 gauge wire. The rating says it should be okay to run the OP’s heater but there is no chance I’m trusting it with my life to do that for hours on end. https://www.homedepot.com/p/HDX-6-ft-16-2-SPT-2-Cube-Tap-Extension-Cord-Brown-HD-144-983/100672793
The description says it’s for “small” appliances like lights or clocks. Not everyone understands that a space heater isn’t “small” as they mean it. I mean, this heater is only about a foot tall! https://www.amazon.com/Tenergy-Adjustable-Thermostat-Recirculation-Protection/dp/B07582RCLZ/ref=sr_1_1?s=hi&ie=UTF8&qid=1523467222&sr=1-1&keywords=1500+watt+portable+heater
I’m guessing all the heater instructions say that they should not be plugged into an extension cord. That’s good advice.
OSHA has a letter to help clarifiy this, note the bolded section below (emphasis mine)
https://www.osha.gov/laws-regs/standardinterpretations/2002-11-18
Consider too that power strips have a lot of outlets on them. Who’s going to put in a power strip and then use only one outlet? So even if the power strip as a whole is enough to handle the heater, it probably won’t handle the heater plus everything else plugged into it.
My wife, for one. She sometimes uses a power strips as a short extension cord for a light when she cleans out her closet.
But, there are plenty of things you could plug into power strip without theoretically overloading it. In a bedroom, that might include two 9 watt bedside light bulbs (0.08 amps each), a cell phone charger (0.01 amps) and a digital clock (0.1 amps). This is everything I have plugged into my 15 amp bedroom power strip and it’s less than 0.5 amps. Would you suggest that I would be fine to add a 1500 watt heater to the load? I know I’m not doing it.
I agree, and I should have also stated, “…but make sure you’re experienced at this and you know what you’re doing.”
When it comes to power strips, I am not as concerned about the gauge of the wire as I am the spring terminals in each receptacle. As long as it’s 12 AWG or 14 AWG, I’m good with it.
As I stated in Post #46, each receptacle in a power strip (even a cheap one) is supposed to meet UL 1363 and UL 498 requirements, which means each receptacle should be able to handle 15 A continuously. (Of course, as noted by Chronos, if a 15 A appliance were connected to one receptacle, nothing else could be connected to the power strip.) But we also know there have been a number of cases where power strips have overheated, so something is obviously amiss with the whole situation. I don’t know where the problem lies. Perhaps the manufacturers are lying or not performing the tests correctly. Or perhaps each receptacle in a power strip can safely handle 15 A when it’s brand new, but the spring contacts will exhibit excessive contact resistance after just a few insertion cycles. Again, I don’t know. (As you can see in Post #46, the spring contacts in my power strip certainly looked cheap and low-performance. But that doesn’t necessarily mean anything.)
Suffice to say, the recommendations by OSHA and others should be followed: do not connect “high current” devices to a cheap power strip such as heaters, refrigerators, hair dryers, air conditioners, etc.
IMO someone should do an investigation on these cheap power strips. They should do some lab measurements to determine if the temperature and contact resistance of the spring terminals become excessive as a function of current, time, etc. Testing should be repeated after a number of mating/demating insertion cycles (e.g. 1 cycle, 10 cycles, 50 cycles, 100 cycles, etc.)
Agree, but I believe most (all?) power strips have a built-in, 15 A circuit breaker. (But given how cheap these things are, I wouldn’t put much faith in the breaker reliably tripping if there’s an over-current situation…)
Sorry for all the posting but this OSHA quote caught my eye:
(Emphasis added.)
Well if a cheap power strip is not designed for a 15 A load, why is each receptacle on the power strip rated for 15 A?? :smack:
If a 15 A power strip is not rated for 15 A, what’s it rated for?? 
Again, something is really messed up with these cheap power strips. You would think UL or some government agency would get to the bottom of it…
You have to pay to see UL 1363, but I wanted to point out that it is the circuit that is typically rated at 15 amps, you cannot plug more than 1500w of load to the entire circuit, including the second plug on a wall receptacle on a 15A run.
While I can understand the confusion the issue is that 1500w devices really should have their own dedicated run in the building wiring for typical US 15 Amp 125-Volt circuits.
Here is an excerpt from the October 2001 edition of UL 1363. Not sure if the latest edition is different: