HIgh current terminal blocks

[analogkid2digitalman]

Had to replace my water heater timer (again, due to chinesium relays) and went to a different make (DTWH40).
What concerns me is the new unit has terminal blocks as opposed to screw terminals. Unit is rated for 40A resistive load up to 277VAC.
My application is around 30A, was a bit hesitant to install it this weekend after seeing the terminal block connections, need to insert 10AWG stranded copper into them.

My question is- any suggestions regarding high current terminal blocks? Are they safe, should I prep the wires by splaying the individual strands flat before insertion?

Thanks

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[ScottyUK]

Biggest problem usually isn't the terminal, but the copper traces. It's hard to judge the scale as big terminals are scaled versions of little ones, but I have used plenty equipment with terminals at that current level and have had no problems. If you're not happy with the idea is there any room to fit a chassis-mount relay or a small contactor to handle the large currents?

 

[xnuke]

This product is UL recognized, so it should be safe when installed per manufacturer instructions. I wouldn't be concerned with the terminal blocks. They appear to be cage-style blocks, so there is no need to splay the wires.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[analogkid2digitalman]

The solder fill on the backside of the PWA where the terminal blocks mate to the traces seems to be more than adequate.
I have had experience with such blocks up to 10A ratings, was a bit concerned using such flora at 30A. Indeed they are scaled up to proportions I have never used before.

I have had half a mind to retrofit the previous failed unit for firing a pair of SSR's in lieu of the chinesium relays which is common to all the previous failed units.

Not surprised that the first Intermatic timer lasted for 12 years, the second for 2 years, the third for a year (warranteed), and the fourth just over a year.

The Tork unit does have a holographic UL label, FWIW.

Will proceed with the install.

Thanks ScottyUK and xnuke

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[ScottyUK]

I come across big terminals on VSDs and some power supplies as an end user and I was curious just how high a current PCB terminals can handle these days: 125A for those made by Phoenix. I found that surprising - I didn't realise they went quite that high. It must need a very heavy copper foil, and either dual sided or a multi-layer PCB. Apologies for the length of the following link - hope it works!

https://www.phoenixcontact.com/onli..._X1eO63WM-nZ6HIORSq_X_fhP_sEOX5Lmd3uN1lVleo!/

 

[mcgyvr]

I use the 125A (Phoenix/TE/Sauro) ones all the time on my products.. No problems at all.
Yes I have large traces on both sides of the board but heating in that area is very..very minimal compared to everywhere else.. Plenty of copper/mass in the actual wires to keep that area cool.

For some reason many companies HATE screw terminals like that.. Some of our customers will not use them at all.. For no good reason though other than they just never have accepted them.. (Old guy mentality.. we've always done it that way so why change)

And no need to do anything but strip the wires, insert and torque down.

 

[ScottyUK]

I hate the spring-loaded type made by Wago and a few others: they're great for one-time-ever installations but no good for ones where the connection needs to be split and reconnected to allow calibrations and the like. Maybe not so bad for solid-core cable but we don't see that stuff much. Does that qualify as 'old guy mentality'?

 

[FreddyNurk]

ScottyUK, somewhat unsurprisingly, the springcage terminals have options (that no one wants to pay for) that will allow for test plugs, links and other accessories. Integrated banana sockets for hooking up the secondary test kit along with integral shorting / disconnect links, all of which have no copper anywhere near fingers are a good thing to me, but they're always more expensive than the standard screw type.

A lot of the issues often stem from expecting the terminals to be exactly like the screw type, when they're not. Admittedly, I do not like the push-in tool-less "TopJob" Spring terminals either, but I'm all for the other spring type.

Whether it makes it an 'old guy' argument is debatable, I've met a few 'old guys' who love the spring terminals as well.

 

[racookpe1978]

Today's installers and factory-floor (Chinese ?) are all to often poorly trained, not-hand tool capable of much more than "strip the wire, and stick the wire in here" . Reqiring a torqued precise screwed-in connection is - at the end - less reliable than an oversized spring-and-push plugin. And the plug-in connection will be faster for one-time installation. (After all, why should a manufacturer in China care about repair time later in the US? He has already sold the unit. And, if you break it trying to get the wire back out, YOU have to buy the new one. From him! )

 

[ScottyUK]

I love the old RSF series made by Weidmuller for the CEGB: these have a powerful spring closing a conventional screw-type cage clamp terminal. When used with a lipped blade type lug these have a fantastic grip of the cable even if the screw works loose or falls out and are very reliable. The newer type are a creation of the devil. I'm with racookpe on the reasons!

 

[jraef]

Re: "splaying" the wire leads, yes, that's fine, done all the time if the termination is designed for that. Just do NOT "trim" the strands to make them fit into a block that will not accommodate that size wire. I bring that up because you said that the unit is rated for 40A, but are implying the terminals will only hold #10, and you cannot run 40A through #10 wire in most field wiring situations (as opposed to inside of a factory assembled and listed unit).

Further clicking resulted in seeing that this Tork timer uses terminals rated for up to #8 wire. So use that, not #10. If your heater says it is rated 30A, you can use that to size the wire, but the wire must be sized for 125% of that current rating, so you will need #8.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[analogkid2digitalman]

Finally got to replacing the timer this weekend. I was incorrect on my ampere requirement, jraef you got me thinking (and a bit nervous).

SO I current clamped it out, running 18.7A at 240VAC.
Dual 4500W element heaters, only one element can be on at a time. Breaker is rated at 25A, so 10AWG should suffice.

Went to flush this 2yr old water heater to no avail. It would not drain even with the water inlet feed on, snaked a zip tie into the drain valve and a shotgun like spray of chunks of sediments sprayed out for about 2 seconds and then clogged right up again. After a few reps myself and the surrounding area were covered top to bottom in chunks. I have a few ideas in mind to overcome this....

The old heater lasted 15 years before rusting out with about 7 flushes over that span. Each time it was flushed just a handful of Calgon-like crystal sediments came out. The quantity and quality of the sediments produced by the new heater are a totally different animal, large planar flakes and side-by-side rice grain chunks. Granted, I do live in a hard water town.

Thanks for your inputs, was totally unaware that such style of contact blocks hold up in the 100A range, pretty amazing.

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[OperaHouse]

You can get 40 years out of a water heater if you replace the sacrificial anode about every 3 years in severe water conditions. Most of the sediment is from that. The rest is from scaling popping off the heating element due to high density heating. If heaters were fed with 120V there would be almost no scale buildup.

 

[mcgyvr]

Just flushed mine last year after replacing one of the elements..
A 5 gallon bucket was half filled with sand/silt/scale,etc...
Then hot water looked like cola for an hour or so after..
It was gross

 

[ScottyUK]

I sometimes wonder about arranging an acid clean / pickle for my boiler at home, but the prospect of leaks elsewhere in the system doesn't appeal much, and it works reasonably well other than moderate kettling noises at times. Efficiency is crap by modern standards, but it's got an old-fashioned cast-iron HX and will outlast all the modern efficient stuff, plus I can buy a whole lot of extra gas for the cost of a new boiler.

 

[sbkenn]

Many of you probably know ... never solder prior to inserting into a crimp, screw or screw-clamp terminal. Solder cold-flows, so the connection will get loose surprisingly quickly, resulting in a hot spot. Solder prior to crimp, then re-solder if you must.