24VDC Control panel layout questions.

I have a few questions about 24vdc power distribution in control systems.
I am concerned about noise and voltage dips during "power up" of instrumentation (Panelview Monitor, Honeywell Temp Controller, Controllogix CPU....etc).

I presently have:
1 power supply for analog devices
1 power supply for digital I/O

Instrumentation power? I was thinking analog power but...

I believe the Digital I/O PS will be the noisy line (break of switch contacts, coils spikes...etc) and the Analog may suffer from voltage dips caused by "power up" load from instrumentation.....without using an oversize power supply.
I assume, I have answered my own analysis...and I should add another power supply for the instrumentation?

What do others use as an approach to 24VDC supply power distribution?
Do you use this many power supplies...less or more?

Two power supplies is a good approach.

Make sure you put surge protection across any inductive loads.

Mickey said:

Two power supplies is a good approach.

Make sure you put surge protection across any inductive loads.

Click to expand...

In previous jobs, I put the Instrumentation and Analog on same supply.
I try to get all my I/O switching devices with built-in spike/surge protection, that option isn't too hard to find. I also have about 15 coils (which are internally protected) in the I/O and 6 "snap action" thermal switches to handle. I sort of consider this the "noisy" 24 vdc power. It is still used to power up about 10 flow switches and an electronic pressure switch.

In this upcoming job....
I am going to have a Dewpoint Meter, Honeywell Limit Controller, (2) Controllogix Power supplies, (4) 1734 Point IO Power Supples on Ethernet/IP, plus a Panelview 600+.
That is why I was thinking about a 3rd power supply for inistrumentation.

I normally use a 2450VAC/24VDC switch mode for the PLC, inputs, outputs, driving relays with flywheel diodes fitted, instrumentation - just one supply. The negative is not grounded and the 24VDC is allowed to float.
My AC control voltage is 24VAC through an isolation transformer - once again the 24VAC is allowed to float - the neutral is not grounded. I do not use 240VAC control circuits at all - rather use isolation transformers for safety.
I do not see the need for a 3rd power supply to be honest - I have never had a problem with the above.

NetNathan said:

I have a few questions about 24vdc power distribution in control systems.
I am concerned about noise and voltage dips during "power up" of instrumentation (Panelview Monitor, Honeywell Temp Controller, Controllogix CPU....etc).

I presently have:
1 power supply for analog devices
1 power supply for digital I/O

Instrumentation power? I was thinking analog power but...

I believe the Digital I/O PS will be the noisy line (break of switch contacts, coils spikes...etc) and the Analog may suffer from voltage dips caused by "power up" load from instrumentation.....without using an oversize power supply.
I assume, I have answered my own analysis...and I should add another power supply for the instrumentation?

What do others use as an approach to 24VDC supply power distribution?
Do you use this many power supplies...less or more?

Click to expand...

I try to have a separate power supply for I/O and HMI/PLC stuff. I like PULS power supplies. They are over engineered and will run above their current rating in most cases for inrush and power up things like HMI. Be aware that the Panelview Plus (>=700) can draw 7 amps on inrush!

We had two of them and some ethernet switch hardware all powered from a 5 amp supply, I am not sure how it worked initially, but several years later, when we had it shut down for the first time, it blew our fuse on teh supply output several times until I finally found that nothing was wrong and disconnected one PV+ and let the other one boot first.

It is recommended to use a separate ungrounded supply for each Panelview.

Also PULS is offering some new power supplies with multiple outputs and short circuit protection and separation built in. These might be suitable in place of multiple supplies in some instances.

Thanks for the tips...

OkiePC said:

I like PULS power supplies

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I'll second that! We've been using them for about 7 years now, very reliable.

I've seen the new PULS PISA range. I think that's what your referring to Okie? They are classed as more of a protection module. You have a standard PSU feeding whatever, but also feeding to the input on the PISA. You can then have up to 4 seperate protected outputs from it. I think they go up to 4 x 10A? Less than 2" wide DIN rail mount.

I think they'd be ideal in this situation.

G.

I have looked at PULS. They look pretty functional and well protected.
I have been using Phoenix Contact "Quint" units for a few years now with no problems.
I really like Phoenix, They are a little pricey, But it is good stuff and a wide selection of options.

I was actually going to name Phoenix Contact as well, but thought PULS would do you. We've used Phoenix Contact as well for our PLC supplies, also very good. Haven't used the "Quints" though.

G.

It would not surprise me if PULS is making those for Phoenix. They were the original maker of the good Sola units and A/B rebrands some PULS too.

Yes, a rep. came out here and showed us a brochure for the PISA modules, they are very slick.

Geospark said:

I'll second that! We've been using them for about 7 years now, very reliable.

I've seen the new PULS PISA range. I think that's what your referring to Okie? They are classed as more of a protection module. You have a standard PSU feeding whatever, but also feeding to the input on the PISA. You can then have up to 4 seperate protected outputs from it. I think they go up to 4 x 10A? Less than 2" wide DIN rail mount.

I think they'd be ideal in this situation.

G.

Click to expand...

Interesting on the PSIA. It connects to the output of the DC Power Supply and it only divides the power supply output. It does no filtering?? Nice idea, but with no filtering makes it sort of a wash.

Some models will sequence the outputs at power-up - would be handy for Okie's problem in post #5.
Paul

NetNathan,

Have a read of the attached PDFs on the PISA, if you haven't read them already. I'm really starting to like these units. No they are not filtered supply units, per se, but more an overcurrent and short circuit protection unit. It would replace, say, a 4 x MCB distribution setup after your normal PSU. But with a lot of nice features and smaller footprint. It would prevent the loads on its outputs from pulling down the main PSU by maintaining a min 21VDC at its supply input by limiting the current on its 4 outputs. You place your heavy, noisy loads on its outputs to segregate them from the sensitive loads on the main PSU. It has active current limiting which enables the maximum rated current of the output to be available at inrush, solving the high startup inrush of displays, etc and the need to time delay the outputs.

So you could put the 2 x ControlLogix on the main PSU and the "Dewpoint Meter, Honeywell Limit Controller, (4) 1734 Point IO Power Supples, plus a Panelview 600+" all on the PISA's 4 outputs.
Depending on the current ratings of the above, there are many models you could use, such as a 4x10A, 2x6A+2x12A, etc.

Pleasa Usa PISA!

JarJar.

Geospark said:

NetNathan,

Have a read of the attached PDFs on the PISA, if you haven't read them already. I'm really starting to like these units. No they are not filtered supply units, per se, but more an overcurrent and short circuit protection unit. It would replace, say, a 4 x MCB distribution setup after your normal PSU. But with a lot of nice features and smaller footprint. It would prevent the loads on its outputs from pulling down the main PSU by maintaining a min 21VDC at its supply input by limiting the current on its 4 outputs. You place your heavy, noisy loads on its outputs to segregate them from the sensitive loads on the main PSU. It has active current limiting which enables the maximum rated current of the output to be available at inrush, solving the high startup inrush of displays, etc and the need to time delay the outputs.

So you could put the 2 x ControlLogix on the main PSU and the "Dewpoint Meter, Honeywell Limit Controller, (4) 1734 Point IO Power Supples, plus a Panelview 600+" all on the PISA's 4 outputs.
Depending on the current ratings of the above, there are many models you could use, such as a 4x10A, 2x6A+2x12A, etc.

Pleasa Usa PISA!

JarJar.

Click to expand...

I read up on it quite a bit, I know it current limits to maintain voltage and I may use one but I sill have to put in circuit protection (CB or fuse) for UL. The distributed outputs may work well (especially how you described) and probably using 1 for the Panleview alone.

I still think they should have added some isolation between outputs.

..

NetNathan, sorry I didn't see your reply, I haven't been receiving all my email notifications from the forum.

NetNathan said:

...I know it current limits to maintain voltage and I may use one but I sill have to put in circuit protection (CB or fuse) for UL...

Click to expand...

Just to be clear...

The PISA unit is not a power supply unit, it's a protection module. It replaces circuit breakers, standard fuses, or electronic fuses, that you would normally have on your PSU's distributed outputs. Overcurrent and short circuit protection is its primary function.

PULS PISA said:

Approvals: UL 508, UL 2367, UL 60950-1, IEC/EN 60950-1, NEC Class 2

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The PISA is a fully certified overcurrent and short circuit module. UL should have no issues with you using it after the main PSU as a substitute for circuit breakers.

Its secondary features are the input voltage monitoring and output active current limiting to protect the main PSU's other sensitive loads. If one of its outputs draws too much current it is tripped immediately, allowing its other outputs to remain active, and the other loads directly off the PSU. Same for a sustained short. It's like having separate circuit breakers or fuses on each output, but with the added bonus of protection against faults back to the main PSU.

PULS PISA said:

If necessary, the wires to these loads can be protected using standard miniature circuit breakers or lead fuses.

Click to expand...

If you have to seperate out any of the PISA outputs to more than one device, then I would use fused terminals in the panel before the field wiring. You would normally fit a circuit breaker or fuse local to the output devices out in the field, such as Panelviews, or other instrumentation. This is for discrimination, isolation, and protection of the cable run.

NetNathan said:

I still think they should have added some isolation between outputs.

Click to expand...

Do you mean noise filtering or do you mean make/break isolation?

Filtering:
Noise immunity between the outputs or to the outside world is not mentioned specifically, but it is a certified advanced electronic fuse unit. I'm sure they would have incorporated good noise/EMC suppression and or tracking isolation. You would have to ask this from your distributor.

Isolation:
There is an ON/OFF input for enabling and disabling the PISA module. Whether you can isolate each output individually or not, I'm not sure from the literature? I would imagine you can, but again you would have to ask. As the PISA is acting as the circuit breaker, as I mentioned above, a fused terminals would suffice directly after the outputs, and before the field wiring. There is also a reset input for a controlled reset or a manual button on the module.

NetNathan said:

I believe the Digital I/O PS will be the noisy line (break of switch contacts, coils spikes...etc) and the Analog may suffer from voltage dips caused by "power up" load from instrumentation..... without using an oversize power supply.

Click to expand...

For your setup, I would use one PSU, large enough to carry the total load of the installation, no more. Place the sensitive loads such as, Analog, PLCs, safety circuits, directly off this PSU, through their normal circuit breakers or fuses.
Supply the PISA directly from the PSU and place the Digital I/O, instrumentation, panelview and POINT I/O on the PISA's outputs.
No inrush current or faults on the PISA's outputs will affect the Analog or PLCs' supply.

I don't think you need to put the panelview on it's own PSU, the PISA should handle it ok. It is what it is designed for. The PISA saves you needing more than one PSU, but if you feel the total load is too great for one PSU, then consider a second for load sharing.

The PISA also saves you using an oversized PSU. Because it limits the overload current on its outputs, it never overloads the main PSU beyond its normal rated capacity. Normally, you would have to select an oversized current rating on the PSU, beyond the installations' maximum capacity, to allow for any potential overcurrent.

NetNathan, I have not used these units, but knowing how good PULS are, I would recommend it. It would appear to suit your needs, or something similar to it.
I will definitely try one if the need arises.

But what do they cost?
This may have a bearing on your choice.

G.