Using non-UL insulation

[Hedges]

A while back I bragged about creative use of heater hose as tough, large size insulation for electrical terminals:

Fire!! Never cover LiFePO4 with wood!!!

Where did you come up with the "plan" (not sure what to call it) for the 3D printer? It's just a 3D model saved in the correct format.

diysolarforum.com

It seemed like a good idea at the time.


More recently, I was wiring up transformers to make 277/480Y out of 120/208Y. Here, most connections are nicely done with set-screw terminal blocks in a box, and a 4-wire plus ground outlet. (for now, I'm using a plug-in cord for Sunny TriPower so things are easy to swap and move around.)



A few loose wires are capped with set-screw wire nuts, and some pairs are joined with split-bolts. Need to get all those inside a box, the one above may or may not fit them. The split bolts (one in background for example) I slipped inside my heater-hose insulation and secured with electrical tape. All good, right??



Well, a bit of smoke and smell of burning rubber appeared. Bad connection getting hot?
I switched things off, tugged to make sure all secure, turned back on and conducted my tests without problems.
Later it happened again.

Finally, a light bulb went off. Why don't I check voltage to the rubber insulation, make sure it really insulates?
328V between two rubber parts!



Good thing I didn't touch them with power on. Wonder how much current it could have delivered?
0.120A, when pulled to zero volts!


Yikes! That thing is a human-safety hazard.

How much power?
328V x 0.120A = 38.4W, no wonder it smoked almost immediately.
328V / 0.120A = 2667 ohms. Not much of an insulator, now is it? (Maybe they meant to do that. Avoid built-up of electric charge due to water flow? Bonding for some corrosion reason?

These were new heater hose, so never had a chance to absorb water or anything else.
I still think the recycled hose is good as robust covers over battery terminals, will prevent a high-current short. But not good to prevent discharge due to contact with a conductive material. My battery has corrugated PVC over the top.

Now I need to get more proper UL listed terminals for my experiment.
I'm just using these toroids temporarily as 120V to 277V (really only getting 260V) auto-transformer.
I'm in the market for several 10kVA 240/480 to 120/240 isolation transformers. I'll use three to convert 120V to 480V, and one more between middle of one 480V leg and one corner to establish Neutral.

 

[chrisski]

I was thinking today of using hose hose for insulation. Thanks for sharing.

 

[MattiFin]

Black rubber hose is often somewhat conductive and black fuel hose is often even specifies and required by standards to be conductive(to prevent static build-up)

Black color comes from added carbon and it also makes the hose more or less conductive.

 

[curiouscarbon]

thanks for sharing!

thanks for the nice photos and explanation!

 

[Mrman1234]

These are UL listed but very pricy at $25 a piece.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

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If it was my $ id opt for wirenuts wrapped in electrical tape.

 

[Hedges]

Here's what I got:

Marathon 1413300 Terminal Block, Barrier, 3POS, 14-2AWG: Amazon.com: Industrial & Scientific

Marathon 1413300 Terminal Block, Barrier, 3POS, 14-2AWG: Amazon.com: Industrial & Scientific

www.amazon.com

Three 2-wire terminals took care of the 8 awg I need to join.
I plan to stuff it in a plastic junction box, along with the set-screw wire nuts I put on single unused taps.
(These weren't big enough to join pairs.)

 

[Goboatingnow]

Wire nuts are the stuff of hell.

 

[Hedges]

Wire nuts are cheap and fast, but SMA recommends against them due to possible arcing causing damage to inverter.
Have you tried the set-screw nuts? I've used a bunch at home and bought more for work, in the lab.
Wish there were larger sizes. Quite economical compared to Polaris.
I've used split bolts for splicing wires in the 6 awg to 2 awg range. Wrapped in rubber tape and electrical tape.

 

[Goboatingnow]

Wire nuts are cheap and fast, but SMA recommends against them due to possible arcing causing damage to inverter.
Have you tried the set-screw nuts? I've used a bunch at home and bought more for work, in the lab.
Wish there were larger sizes. Quite economical compared to Polaris.
I've used split bolts for splicing wires in the 6 awg to 2 awg range. Wrapped in rubber tape and electrical tape.

My first EE job out of college , in a research centre , my boss said. Three things get you fired “joining wires with tape, chocolate blocks or wire nuts “ !! Stayed with me ever since.

 

[Shimmy]

Really the best way to splice anything over #10AWG are the insulated multi-port connectors. I do not see any professional electricians going for devices that are not inherently insulated anymore; they become too dangerous. The terminal blocks you show should have covers at a minimum, and be fixed mounted to something.

As for your transformer setup-- why so complicated? As long as you do not need galvanic isolation, a single wye-wye transformer would do the job.

 

[Hedges]

The block is flopping around for the moment, will mount inside a plastic box so no ground wire needed.



I would have put all inside metal box of first picture if there had been space. Everything I used was on hand at the moment, except that one connection block I later ordered.

The immediate project was hooking up to try out 3x SI-5048US wired 120/208Y and Sunny TriPower STP 30000TL-US-10; this one accepts 480 delta while other models require 277/480Y. Even this one can't accept corner grounded delta for sustained time (e.g. fault to ground), so I want midpoint defined.
I had these transformers on hand, from UPS I think. So I wired them up as auto-transformer Y-Y boosting 120 to 260V.

Later I will buy a suitable transformer, 30kVA or more. Mostly I see 120/208Y to 480 delta, few are Y for the high voltage side. Only a few $hundred used, but I'm only seeing eBay listings from the East half of the U.S. and shipping runs $400, about doubling my cost. So I've tried to find a local source, haven't bought anything yet. Googling with city names all I see are paid search results for sellers of new transformers who would ship to my city. I need to find surplus yards, which aren't posting their inventory.

 

[Hedges]

Since I have these transformers now wired as wye-wye ("N", not labeled at intersection of the three)



I also use it to boost current for a circuit breaker tester. A couple extra sockets let me plug in an adapter to configure it.
A 277V 2-pole breaker (used not terribly far over rating at 338V when "off" and transformer used normally) connects X1 to H2 and H3.



Applying voltage between H1 and N provides double step-down for 4.7 ratio.
Output is taken by paralleling X2 with X3. Double wires from N junction block provide return path for 80A continuous.
Feeding it not directly with 120V but rather through a resistance element, shorting (X2 || X3) to (N) multiplies current by 4.7 (e.g. 17A from a couple space heaters in series with H1 produces 80A on X2 + X3)

I plan to connect one space heater through a variac so I can dial in the exact current I want. Rotating it slowly I will be able to determine the slow-trip point for thermal/mechanical breakers, and the fast-trip of magnetic/hydraulic. That will cover the range for breakers like 60A CBI (Midnight) that I have coming to use with Sunny Island. With enough resistive heaters it should be able to briefly deliver 4x or 5x, like 400A. I'm low on electric radiator heaters need to hit the 500A or 625A fast-trip of a 100A or 125A thermal-magnetic QO breaker.

Everything is wired up with plugs and sockets (5-wire twist-loc 277/480 for 3-phase configuration and 4-wire 120/240V dryer cords to connect DUT circuit breaker tester) so I can safely handle while reconfiguring. Once I permanently install the TriPower it will be hardwired.

Those tests are for breakers I use at home including for PV system. I've had nuisance trips with Schneider multi-9 rated 63A operated around 40 to 50A (that's the model shown in photo) and Square-D QO2100 carrying less than 70A. Subsequent tests did confirm they tripped below rating even at mild indoor temperatures.

For work, I would like to also investigate inrush handling. I've only see specs for one brand regarding guaranteed no-trip for pulse of current above its fast-trip rating but lasting no more than 1/2 cycle. Capacitors on input of SMPS have precharge inrush that varies with where in the cycle they are connected. Transformers have inrush depending on both that and where in the cycle they were previously powered off. To do this I would need something like triac to complete circuit on primary, and a trigger pulse which can be timed with delay from zero crossing (a one-shot light dimmer.)

 

[Hedges]

<duplicate post>

 

[Mrman1234]

Wire nuts are the stuff of hell.

Yoy might like wago. They have some setup specifically for stranded wire.
Heres a very detailed video. I follow him as well.

 

[Bluedog225]

Thanks! I would have never guessed about the rubber hose. Was thinking of using it.

 

[Hedges]

I should have known better. Or at least have been smart enough to try ohm meter and Hypot first.

In a class through work on Arc Flash etc. (or maybe another source), someone described not having the proper electrical insulating blanket to put over exposed wires, but had some other rubber sheet (maybe for roofing)? He draped it over the live electrical stuff, later looked back and saw it smoking.

 

[Shimmy]

Yoy might like wago. They have some setup specifically for stranded wire.

Personally I think Wago's are great. Some of the early ones were not reversible which could pose challenges for residential. Much less likely to get messed up by someone that doesn't really know what they are doing-- tug and if it comes out it isn't good. Using wirenuts without the right knowledge and tools is dangerous. Wasn't aware of ones for stranded wire.

 

[Quattrohead]

I was horrified to see wires connected with wirenuts when I first came to the USA, now I rather like them. KISS !!!
And NO I do not tape them up, the electric does not dribble out of the open end !!!!

 

[Hedges]

The terminal blocks you show should have covers at a minimum, and be fixed mounted to something.

Just found covers for them: https://www.amazon.com/MARATHON-CC1413-POWER-BLOCK-PLASTIC/dp/B00DWI88GK

https://www.carltonbates.com/static/catalog/products/images/PDF/MARATHON_Power-Blocks.pdf

I think I'll order some other model blocks that accept multiple wires and have multiple poles. Good for connecting 3-phase stuff.

Marathon 1403402 Power Distribution Block 600V 175Acu 135A Al 1In 4Out 1403402: Amazon.com: Tools & Home Improvement

Marathon 1403402 Power Distribution Block 600V 175Acu 135A Al 1In 4Out 1403402: Amazon.com: Tools & Home Improvement

www.amazon.com

I've also ordered L21-20P plugs (120/208Y with neutral and ground). I got a lot of 277/480 cords with plugs, use on several devices I'm testing. The proper 120/208Y will be used for primary of step-up transformer and loads like my compressor. Can also branch to 2-wire 120V or 208V loads. Very convenient to just unplug and everything is cold while working on it.

https://www.amazon.com/Legrand-Seymour-L2120-P-Locking-Plug-Nema/dp/B008SCW0GE

 

[Goboatingnow]

I was horrified to see wires connected with wirenuts when I first came to the USA, now I rather like them. KISS !!!
And NO I do not tape them up, the electric does not dribble out of the open end !!!!

When I joined a very reputable blue skies research facility and was involved in some electrical research I was told three things will get you fired

Using insulating tape , wire nuts or shooting the boss