I have been making up a lot of little controller and devices of late to do different things.
Auto watering system for the aeronautics, made an auto switch for the Christmas lights that turned them on at dusk and off again 6 hours later, temp switch to control the cooling fan on the solar inverters, and significantly, the voltage controller for turning on the hot water heater when the solar is producing power.
All of these things I have been hooking up with some small extension leads I have been buying from our national hardware chain. It's cheaper to buy a 3M lead with the plugs on it than just the ends alone and having to stuff round wiring them up and buying cable at well. I cut the leads in half and then have my in and out leads and just wire them up. Been going though so many of the things I have been buying them 5 at a time and keeping a stock.
I built a box about a month or so back for the hot water controller setup.
The power goes in to a breaker which a watt meter with inductive pickup monitors. That goes through to the voltage monitor, to a larger mechanical relay, then to a PWM controller with readout, and onto an outlet socket. I didn't use the female end of the lead this time. Because the hot water heater has a 3.8 Kw element and I'm running it for the moment off a 2400W outlet, I avoided the overload by using the PWM which I can see on the meter and have verified with my multimeter to be outputting just under 1000W. I had it at 1500w but the Kettle in the kitchen is on the same circuit and I tripped the breaker a couple of times so backed it down. No worries since.
Takes longer for the water to heat up but no rush and leaves plenty of room on the circuit for other things as well.
The leads I have been using are rated to full outlet current of 2400W.
The other day I was out the back and moved the lead and it felt pretty warm but it was a cosy 38oc day so nothing felt cool anyway. Checked the current meter and saw the heater was on and then could hear my daughter in the shower so all good. It rained the other night and wife told me wind was blowing in the rain under the veranda and was my outlet on the ground OK? It was but I thought I'd unplug it any way just in case it got too damp and tripped the rcd.
I went to unplug the lead going to the box and found it had burned itself into the other plug I was running it into which was a home made one with 2.5MM wire and HD plugs.
I put the voltage relay into manual mode and saw the heater was pulling 980W. Went and got my clamp meter and confirmed that's what the thing was pulling. Wasn't over load it was under rating of the lead itself.
Pretty amazed these leads would heat up as much as they have when the most I have put on them is 1500W. This bit of lead is about 1.5M so certainly not getting hot through resistance cause by length. The leads are sold up to 25M on the same ( inferiour) spec wire and clearly rated to 2400W.
I would have thought that something sold by a large chain probably in the thousands a week would be better than that. I can warm these things up way too well just with a 100w load let along a 2400w as they are rated. The fact the things have burned obviously at 1500 is a concern.
My home made lead I did primarily for the welder is clearly fine but these other things.... Yikes.
I went and had a look at some other leads today and although many were marked heavy duty, they are still the same 1.0mm core.
There are some other really expensive ones with 1.5MM lead and still rated at 2400W. I think they might even struggle at the rated load.
Clearly these leads are fine for real light duty applications but can't even hold 2/3rds their rating without being stressed at only a 1.5M length. If I were running the things at 2000W i'd not be surprised at them warming up but 1000? That's bad! If I were running a 25M lead at 1500W and it got warm I'd think probably to be expected, but as short as I have and still getting hot??
I think the worst lead I have seen so far was on a Cup water heater element I bought last year. That was rated at 2000W and the leads would not have done as speaker wire in a crappy factory car sound system. I wouldn't even plug these things in because if that element was even good for 500W, the lead would be putting out more heat than the element would have. Couldn't change the lead as it was molded onto the element so in the bin it went with a suitable feedback to the seller.
The way things are here, it's illegal for me to make up my own leads not being a licenced sparky and not megga-ing them and tagging them to electrical cert.
Fact of the matter is what I have made up is good for twice the rated load of the outlet its plugged for but the legal leads would be an outright danger anywhere near their rating.
Can see myself buying some more 2 core+E round lead and the plugs and making up some leads far superior to anything I can buy off the shelf.