Terminal usage

Have a look at the Phoenix PT Twin terminal blocks, you can have 2 wires on one side and one on the other side. that way you would not have to have 2 terminals side by side to terminate 2 wires.


Or the PT Quattro have 2 connections on each side.
 
I can see leaving the bottom tier of a two tier terminal block open. This sounds like the first unit may have been installed in Europe. They normally run home runs from sensor to panel. The bottom terminal of the two tier terminal could be used to connect either power or 0V to a field device. I personally do not like multi tier terminals where all terminals are used for signals, makes troubleshooting that much harder.
 
assuming that we're talking about SINGLE TIER terminals – here is something just to muddy the waters ...

I have several customers who insist on their students being taught to consider the TWO-TERMINAL type connections as a "marshalling strip" – so as to separate things for their UNION workers ...

the ELECTRICAL union guys use ONE side of the strip ...

the I&E (Instrumentation and Electronics) union guys use the OTHER side of the strip ...

so ...

if an I&E union worker realizes that the reason his PLC input or output won't work is because of an obviously loose wire hanging next to the ELECTRICAL union's side of the terminal, then the I&E union guy cannot (read MUST NOT) simply reattach the wire and get on with his life ... instead he has to call in a work order request for the ELECTRICAL union folks – and then wait around until they come in and fix the connection on "their" side of the terminal ...

[you think that I'm making this up – don't you?]

back to the original question ...

personally I've always seen the "panel shop" vendor wire all of their connections to ONE side of the terminals ... the panel gets shipped to the job site that way ...

once the panel has been mounted at the job site – the "field wiring" vendor (often a completely different company) then connects the field wiring to the OTHER/EMPTY end of the terminals ...

specifically – that way the field wiring vendor should have no reason to "monkey around" with the "panel shop's" connections ...

at least that's the way I've always seen it done – but then again, I don't get around as much as most of you other guys ... personally I have NEVER seen two wires connected to one end of a terminal – and the other end left empty ... that falls squarely in the "new trick for an old dog" column of my personal clipboard ...

party on ...
 
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I just wanted to get some feedback here.

I started working with a new panel shop that thinks I’m using WAY to few terminals. I get out to the shop and find out that they are only using the top of the terminals – the bottom are completely empty.

The panel builder claims that our jobs are always empty on the bottom and that was a requested spec. I looked back and some other panels we sent there (from my predecessor) and he’s correct – all the panels are using only the top of the terminal block and the bottom is completely empty.

Personally, I’ve always been taught that terminals are just for connections outside the panel (or in this case for a door harness as well) I’ve always used the top/bottom of each terminal.

Is there any reason or have you heard of any company spec that says use one side only?

You've obviously confused several posters here with your description of the situation, but yes, it has long been standard practice to terminate panel wiring (from PLC IO points, pushbuttons or relay contacts, etc.) at the top of horizontal terminal boards or on the left side of vertically mounted terminal boards. This leaves the bottom side or the right hand side available for field wiring terminations.

It's not a hard and fast rule, but it is a well established de facto standard for a reason. the typical field electrician will expect to see this standard applied, just as they would expect fuses or circuit breakers to be fed on the top or left hand side with the loads connected to the bottom or right hand sides depending upon the mounting orientation.
 
Several consulting engineering spec’s that I’m familiar with say only one wire to a terminal. That eliminates the “our side” vs. “their side” mentality.”

Most times the field electricians end up taking off most of the wire duct covers anyway and run “their wires” however is easiest for them.
 
Have a look at the Phoenix PT Twin terminal blocks, you can have 2 wires on one side and one on the other side. that way you would not have to have 2 terminals side by side to terminate 2 wires.

Or the PT Quattro have 2 connections on each side.

+1 on the Phoenix Contact PT QUATTRO series of terminal blocks. They're wonderful for cramming lots more terminals into a given length of DIN rail than you'd think possible - especially when you needs lots of bussed points for 24V, 0V, ground, etc...

The PT -series blocks don't even need a screwdriver for assembly of most wires. You need to open the port on the block with a tool for fine conductors, but anything 18ga or larger should be stiff enough to push in.


-rpoet
 
Maybe I am not understanding this but it seems like they are using the same terminal strip for internal connection and the bottom level for field connections?

I guess that's ok but I would much rather see all the field wiring on a separate physical terminal strip if at all possible and if that needs to be 1 layer 2 layer or 3 layer terminal blocks.

Just saying it would be nice to have all the field connections on its own strip and not as a layer of a multi-level terminal strip.

Just 2 cents.
 
I'm lost but that's easy for for me.
A picture would help me anyways.


I use 2 tier and my bottom tier has jumpers for power dist to the field and the top tier are the signals going into the PLC.
 

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