> It's not very different from daisy chaining normal extension cords - safe if you know what you're doing
It’s not safe, and it’s expressly forbidden by the NEC, see 11.1.5 below:
> 11.1.5 Extension Cords
> 11.1.5.1
> Extension cords shall be plugged directly into an approved receptacle, power tap, or multiplug adapter and shall, except for approved multiplug extension cords, serve only one portable appliance.
Daisy chaining extension cords is unsafe and not recommended. Only use extension cords that you’ve inspected and are properly rated for the environment (don’t use indoor cords outside, don’t use an outdoor extension cord outdoors unless it’s GFCI protected) and power usage of the device you are powering.
Any time electricity has to flow through a splice or mechanical connection, the possibility of a loose connection causing an arc and subsequent fire exists.
It’s unlikely to happen to you specifically, but it does happen and avoiding electrical fires is a good thing if it can be avoided.
Daisy chaining power strips is also forbidden by the NEC:
> 11.1.4.2
> The relocatable power taps shall be directly connected to a permanently installed receptacle.
Yes, there is a risk of failure involved with anything electrical, but I don't see why anyone would consider chaining extension cords inherently dangerous enough to ban. It increases the number of connections, but that's a miniscule risk compared to the 5+ connections an extension cord might have on its own. The only significant risk I know is people disregarding the max amperage rating of everything in that chain.
For anecdotal experience, I've had both extension cords and wall plugs fail (nothing serious thankfully, but they did get a bit melted), but in those cases it had nothing to do with my extension cord chains, but rather an internal connection failure.
AFAIk, the rationale for extension chords is that they are sized to cause a controlled amount of voltage drop within their lenght. If you keep adding them, you will increase the drop, and many devices will react by increasing the current.
This is correct. For a 120v 12FLA load at a distance of 50’, you’re fine using a #14 cord. If you double that to 100’, you need to use #10 cord to account for the voltage drop. As voltage drop increases, the amount of current flowing through the cord increases, which can potentially heat up the insulation beyond its rated temperature.
It is probably one of those little process changes to minimize chance of catastrophic failure. Sure, the risk of the daisy chained system going poof is low, but not zero. Instead, you should try to re-work your plans so you do not need to daisy chain.
It’s not safe, and it’s expressly forbidden by the NEC, see 11.1.5 below:
> 11.1.5 Extension Cords
> 11.1.5.1
> Extension cords shall be plugged directly into an approved receptacle, power tap, or multiplug adapter and shall, except for approved multiplug extension cords, serve only one portable appliance.
Daisy chaining extension cords is unsafe and not recommended. Only use extension cords that you’ve inspected and are properly rated for the environment (don’t use indoor cords outside, don’t use an outdoor extension cord outdoors unless it’s GFCI protected) and power usage of the device you are powering.
Any time electricity has to flow through a splice or mechanical connection, the possibility of a loose connection causing an arc and subsequent fire exists.
It’s unlikely to happen to you specifically, but it does happen and avoiding electrical fires is a good thing if it can be avoided.
Daisy chaining power strips is also forbidden by the NEC:
> 11.1.4.2
> The relocatable power taps shall be directly connected to a permanently installed receptacle.