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There is only one screw connection per channel, with all channels sharing a common. Very frustrating because i always need interface relays to solve the problem. The units are Siemens SM321 (6ES7 321-1BH02-0AA0) and definately have a common ground. I just wanted to know what implications of...

It's not a space issue, the electromechanical relays i've used are 15mm (width), but they're £5.50 each so if i could not use them, it's a win/win situation (space and money)!

Hi Mathew, The PLC card inputs are optically isolated so i haven't got any circuit protection between field and PLC card. As mentioned the circuit diagram for the PLC card seems to illustrate that every +24V input must have a common 0V. I did request clean contacts, but that was not...

Hi, I'm in a situation where i have 45 machines, each with their own 24VDC power supply. I'm taking a +24VDC output from a limit switch and a start button on the machine and feeding them into a digital input card for a siemens PLC. The PLC card uses one common 0V for each +24VDC input to it...

Thank you for the replies everyone, but can i remind you that BS/IEC are standards from the United Kingdom, so that was what i was looking for. Thanks again.

Any ideas? Our wiring technician is begging me to let him use a colour other than blue for control wire, but until i find out blue he shall use!

Hi, I'm trying to work out cable colours for a control panel. The colours for AC wiring seems quite well documented, but does anyone know any details for 24VDC wiring? I've been searching and i'm having trouble trying to find any convention. I think i read that there is a BS for machine colour...

Is there some sort of table that let's you know if a BS has IEC equivalent? If there is, which one do you work to?! I feel i'm digressing from the topic, but another issue i've just encountered is wire colours. Does the wiring regs state correct wire colour for all voltages? I'm trying to find...

ScottyUK, Firstly, thanks for the reply. You mention that BS EN 60947 is the most relevant standard for equipment. If in future i wanted to find the correct standard to follow for my particular application, how can i find out? I was about to order a copy of BS 7671 and i assumed that as it was...

Hey, I just called the British standards enquiries line to ask them about that area. They said that british standards are a guide, but when following a regulation they are required by law. So my new task is identifying regulations to follow. So as you said there are the wiring regulations...

My question is how do you know that a standard exists for a given application? How do you define the correct standards to use and how do find out if you're required by law to follow them? *** This is the most important question *** I've only just joined the company and it's a very small one...

Hi SendoUK. I have to admit i was told that the supply was 415VAC by someone else, i've not been able to confirm it myself (yet). The panel is a control panel containing a Siemens PLC and whatever additional parts are required for controlling the motor(s). As far as i can see it will connect...

I meant "I'm not sure about the source of the 415VAC" and would you say i need additional information to select a CB. A colleague mentioned a MPCB, would that be the type of CB to use?

Wow, thank you for all of the replies. I'm sure about the source of the 415VAC 3phase supply to the motor. All my panel will do is switch it on and off using a digital output on a siemens PLC (via a contactor). The CB is there for the installers to wire in/out to and all the information i have...

Thanks for another useful post! Believe it or not the power factor looks the most familiar! Is it usually referred to in percentage then? I remember someone saying to me that usually a PF of 0.8 is used, so i assume that's 80% of real power? Cheers!

Thank you for your reply. I agree with you, it concerns me that i don't know which codes to follow, but i'm very willing to learn and i don't think that my degree course is going to let me know either.. I'm starting to wonder who's responsibility it is to inform students which codes to follow...

Hey dpc, I looked at the NEC website earlier today and it seems very good, but i can't find anything like it for the uk unfortunately.. I understand that codes could influence things, but surely things like "FLA", "power factor" and "efficiency (losses)" apply to all countries? To be honest...

jraef, I understand where you are coming from, but i need to learn how to do this regardless. I am a trainee, so that's why i need help. The company has an electrical engineer contractor that they employ, but he is away for 2 weeks and if i don't find the correct way of selecting a CB they are...

Hi, I am a trainee control systems engineer and i'm currently designing a panel and i would like to know how to select the correct circuit breaker for my project. I spoke with a colleague in work and was horrified to find out that they guess the correct size and expect me to do the same. The...