control panel building

[mconner]

AC Supply Routing

Hey All, Great thread, I'm getting a lot of good ideas, also seeing a lot of non-standard practices in our assemblies. How is that for tactfull?
Now I have a question, we are building a small panel for a customer and they insist on having the AC supply (120) come into the box at the bottom. We have always routed through the top, but I never asked why. What is the reasoning (argument) I can use for continuing to route the AC through the top of the box?
Thanks in advance,
M.C

 

[darrenj]

Hey All, Great thread, I'm getting a lot of good ideas, also seeing a lot of non-standard practices in our assemblies. How is that for tactfull?
Now I have a question, we are building a small panel for a customer and they insist on having the AC supply (120) come into the box at the bottom. We have always routed through the top, but I never asked why. What is the reasoning (argument) I can use for continuing to route the AC through the top of the box?
Thanks in advance,
M.C

dont quite know what you mean.. I can think of one reson for bring the ac in at the top and that would be to seperate it from the DC side but when you say you bring it in at the top of the box do you mean you knock the hole at the top?

 

[mconner]

Hey Darren,
I'm sorry when I mean top, I mean upper left. On this particular panel all DC componets etc are in the upper section and feed in/out through the right, while all AC componets are in the lower section and feed in/out through the left. That help any?
Thanks,
M.C

 

[darrenj]

the only thin i can think of would be interferance..you always try and keep the ac signals away from the dc/analog signals..perhaps this is why they do this..

 

[mconner]

Cool Thanks for the fast reply. So far this panel design appears to follow the rules, no AC lines are ducted with DC. If I hear no greater arguments, I will smile and say "the customer knows best".
Thanks again,
M.C
Ps Where are you at Darren your clock shows 8 hrs difference, Dubai, Eastern Europe?

 

[JohnW]

Now I have a question, we are building a small panel for a customer and they insist on having the AC supply (120) come into the box at the bottom. We have always routed through the top, but I never asked why. What is the reasoning (argument) I can use for continuing to route the AC through the top of the box?

It depends on the instllation, most boxes we use have a gland plate at the bottom, if you need to feed in from the top it means that you ave to drill through the box top and not through a removalble gland plate. If you turn a standard glanded box upside down you will probably invalidate its IP (NEMA) protection rating.

For EMC purposes keep power and signal cables at least 300mm apart, if you look in the photos i've posted earlier you can see I havn't done that with the VSD compartment, sometimes it isn't possible, so I also ensure that in VSD boxes all signal cables are shielded. I don't concern myself too much about running LV such as 415 and signal cables 24Vdc separately but all our wires are "tri-rated" with 600/1000V insulation. The thing to avoid is long straight runs of power and signal cable together. I once had a panel from a machine manufacturer where a 24vdc signal cable was run for a distance of about 2m with a power cable for a 90kW VSD and this was inducing a 300v spike on the 24dc line when it started. Also had a case of where a poorly screened VSD power cable run too close to a properly screened analog signal cable faulted a PLC every time it started.

This is the best info i've found on EMC http://www2.schneider.co.uk/seweb2/internet/literature.nsf/0/D5A4F51322D48DAA80257052003D86D8?opendocument

 

[JohnW]

JohnW, nice looking panel. I exclusively use the ABB ACS550 drives in our plant, love them

Thanks for that, we install about 50 ACS 550s a year,here is the full MCC picture, it is for a small rural sewage treatment plant. There are 2 VSDs and one DOL starter, incoming and a control section. It is a form 4a panel where the supply cables are in seperate cableways from the starter sections, the centre section is the cableway,

 

[Atlascycle]

As a general rule 50mm(2") but sometimes I just don't have the space. See attached photo. In this case we had to fit it in the compartmment we had so that the MCC would fit in the building ( see the other photo) The compartment has a 180 cubic metre/hour vent fan.

John what kind of overload Relay is that in the picture? I canot find anything like that in my IEC contactor section of my Square D digest.

 

[JohnW]

The overload is a Telemecanique LRD fitted to a LAD7 din-rail terminal base adaptor. This allows for separate mounting of the overload when we have short compartments.

 

[Atlascycle]

The overload is a Telemecanique LRD fitted to a LAD7 din-rail terminal base adaptor. This allows for separate mounting of the overload when we have short compartments.

Thank you, I like using the Tele starters but my panel are pretty tight and connecting the overloads to the contactor eats up a lot of height.

 

[Tom Jenkins]

What difference does it make? In my experience the routing of conduit for field connections comes down to what is the most convenient for the owner or for the electrician.

Many engineers specify, for new construction, that the conduit be embedded in the concrete floor. I'm not sure of the reason, but it does make for a clean looking installation. In these cases the entry for all field connections is going to be the bottom of the panel.

On the other hand it is usually less expensive and simpler for the electrician to run the conduit exposed and overhead. In these cases the panel entry is from the top.

Over the years I've never observed any difference in performance or reliability between the two methods.

 

[rsdoran]

Tom, in many plants the buildings have large open spaces and high ceilings for cranes etc. The open space may need to handle forklift, semi-truck/trailer, and other traffic. Many of the steel plants here run their conduit in the floor (underground) for that reason. In many (most) of these plants it would not be cheaper and sometimes not possible to run overhead...usually have a crane and these days have the automatic forklift systems.

As was mentioned earlier, routing to the bottom of the box may eliminate issues with water.

 

[Atlascycle]

http://www.plctalk.net/qanda/showthread.php?p=132983#post132983

Questions on Ferrule Crimpers.

Don't want to send this thread off on a tangent.

 

[rsdoran]

I think its applicable to the subject.

I am providing the same answer in the other thread.

I have a ratcheting type front entry 10-26ga Panduit model CT1002, I like it but have not used the others so can nor offer a comparison. The ratchet part is what I like, you can use it to hold the ferrule, insert the wire then crimp and it doesnt take much pressure.
http://www.panduit.com/products/Ope...uals/101942.pdf

 

[kittydog42]

my method

When I lay out a panel, I place all of the components on the backpanel so they are in their approximate locations and appear square. Then I pencil all the mounting holes. I then run the a square across the backpanel and square the marks. I use a center punch on all of the final marks. I drill all the holes and then tap them using a Bosch electric tapper, which really is a fine piece of equipment. I make all of my holes either 6-32 or 10-32, unless 8-32 happens to be perfect, in which case I use that (basically only transformers).

On my doors, I use a 7/8" hole saw for 22mm switches (1/2" conduit knockout), and 5/8" hole saw for pilot lights. I use a reciprocating saw for cutting out holes for the HMI. We send our panels out to be painted so it is important not to be careless with the saws. I don't like punches unless the holes get messed up and a punch is the only salvation. This is because running the punches is pretty slow compared to the hole saws.

I always drill for my disconnect handle after the backpanel is fitted. I measure the center point of the shaft and then mark it out on the front. I have built a lot of panels over the last 10 years and this is how my routine has evolved.