New to PLC's

Hi,

I am new to controls and I am looking to set up a control system for HVAC systems. The goal is to be able to monitor pressures, tempatures and to be able to control relays and contactors from a PC.

Can this be done on an ethernet network if not what is the best option?

What software is good for operating the network?

Thanks
Dan

Wow!!

Hi Dan and welcome...

You first say you are new to PLC's but you want to do what?

I have a HVAC system by Johnson Controls, I would not wish this on my worst enemy, it is controlling aprox 20 box car HVAC's and a hot water system, it is a very complex piece of ****.

What parts are you going to control? fan speed? compressors? or just temps and by pressure are you talking room pressure or condenser pressure. Do you have clean rooms?

What is your background? you may have better luck with a PC controlled if you know other programming.

Ethernet is a good option, I would look at Automation Direct for the PLCs and other hardware, they have good pricing and there stuff is good (not great but good)

I have wanted to do a HVAC system but I don't have the time, I hope you do.

So can you go into more detail? and we can help more...

a/c control

I did one several years ago using opto22 and pargon software.
mostrecently slc500 ab with panelview, slc works using thermalcouple and analog cards. can get pricey if not careful.

The ideal would be to see discharge and suction pressure, suction temp as well as amperage readings for condensor fans and evap fans. And a remotely operated pumpdown switch.

I have a strong background in computer networking which is why I feel like this should be easy.

Do they have plug and play controllers and sensors for tcp/ip networks...

Basically I want to set up a dedicated network to building controls using ethernet... every sensor has an IP and every control has an IP, and the computer software just reads the devices and there values through by communicating with them via IP.

Ideally I would like to be able to put tempature sensors, pressure sensors, amperage sensors, and switches and actuators on a computer network.

Then I would like to get a program through which I can Uniquely Identify Each device and program there relationships and track there data and control them (switches and actuators).

Possible?

I do this all of the time (PLC based HVAC). Typically we have one PLC per air handling unit, networked over Ethernet for monitoring and configuration.
It sounds like you have a grasp on your layout and what you want to accomplish.
The next step is to layout a controls system that will let you tie together all of the components, then start chosing a brand and family of PLC that will do what you want. There are a lot of options, but with some decent specs, most any distributor should be able to help you chose a PLC.

I just got the book that this site sells and I read the first two chapters and I realize PLC is not what I am looking for. I am looking for devices that are controlled directly by a computer through an ethernet network.


Do they have such?

If so what are some search terms I should look up to find out more information, and what programs would be recomended?

Thanks

This is what I was talking about needing more information.. you can do what you want with a PLC and a HMI (Human Machine Interface)

The PLC will be your real world contacts (input and outputs) the HMI can hold your code RSView can run a VBA application a close version to VB.

There are also more products out there such as Opto 22 http://www.opto22.com/ that I THINK can support something that I think you may be looking for.

What you need is a PLC that will run on CoDeSys, search here and mrplc.com (they have a section for it) but this I think is more of what you are looking for, I have seen this programming a few weeks ago, it was with a motion controller.... and this will be my next purchase as soon as I get the CLX down, I know in one of my engineering books I saw a PLC running with this software but I can't find it.

Hope this helps...
Mark

I am looking for devices that are controlled directly by a computer through an ethernet network. Do they have such?

Click to expand...

Perhaps you are looking for the old BACNET network and BACTALK software. This is a system designed to run on and work with the 24 VAC controls in HVAC systems. ethernet is an option now.

http://www.bacnetinternational.org/BMAProductCatalog/Alerton/Alertonall.htm

jimbo3123 said:

I do this all of the time (PLC based HVAC). Typically we have one PLC per air handling unit, networked over Ethernet for monitoring and configuration.
It sounds like you have a grasp on your layout and what you want to accomplish.
The next step is to layout a controls system that will let you tie together all of the components, then start chosing a brand and family of PLC that will do what you want. There are a lot of options, but with some decent specs, most any distributor should be able to help you chose a PLC.

Click to expand...

Huh, interesting. I looked into changing a Siemens Apogee to PLC control but I concluded the cost is just too much. How do you handle VAV with its flow sensing requirement with a PLC?

This may be what you are looking for? However I think these systems are fairly expensive.
http://www.alerton.com/

harryting said:

Huh, interesting. I looked into changing a Siemens Apogee to PLC control but I concluded the cost is just too much. How do you handle VAV with its flow sensing requirement with a PLC?

Click to expand...

I've only done VAV once, using a variable speed supply fan to maintain a set static pressure in the ductwork.

I don't work with many smaller, commerical type units. Most of the air handlers that I work with are larger industrial type.