HVAC Question

[balerjoe 0]

In our facility we utilize Allen Bradley PLC software. In specific RS5000 & RS 500. I noticed in the refrigeration industry they make there own logic & HMI platforms. We are considering utilizing our PLC to write the Logic for our air handlers (Positive air) for the facility (Milk Plant). Does anyone here or has anyone used Allen Bradley as a platform for there controls.

[iismaiil 0]

Normaly PLCs are not used for HVAC (including Air handler). DDC (Direct Digital Control) controllers are used for such applications instead of PLCs. DDC are the controllers designed for HVAC control (Its I/O configurations and its build-in functions are oriented for such application). If you need more information contact me on: iismaiil@hotmail.com Ismail Ismail 25 years in HVAC and BMS control.

[TimWilborne 108]

Got a Plc on mine at the house. Cut my bill by $25 a month

[balerjoe 0]

I'm looking at bid that was submitted from a Refrigeration Company. They will be using LON WORKs. From what I understand they are made by ABB. I've never seen the the ladder logic of Lon works compared to AB. We utilize AB here in our plant for all processes. Is there by chance that you could get a demo of Lon works to compare it to AB. I know now they make a translator so Lon Works will be read by AB. Therefore standardize all controls in this plant. Utilizing a Carlson HMI. I just wanted to know what the main diffrences were between LON Works & AB. thanks Joe

[Mahidhar 0]

All PLCs vendors now a days support their windows based tools for logic development as per IEC 61131-3. It does not matter which vendor it is, if they are supporting above IEC, u can go a head to select any vendor. In factory floor, if u are already using AB, if u are not familliar with automation platforms and programming languages,u can always ask ur suppliers to offer new applications with AB PLC's only.If u know how to develop application using one PLC then there should not be any problem to understand other PLC's what ever the vendor is.Infact these will increase ur skills in other vendor products. On the other answer, saying PLC's not used for HVAC is not fair comment, now a days there is no area one can say it is not being used,u can get thousands of references where PLC's are being used arround the world for HVAC's. Mahidhar

[Sleepy Wombat 27]

Lon works like Devicnet, DF1 etc is a protocol. A language by which their conterllers can communicate to other devices. Lon Works and BACnet are the general comm;s standards that the building automtion industry is flooded with. There are other;s out there but i am sure i could count them on a single hand, unlike industrial enviroements where we have a squillion to choose from. HVAC is easily controlled and achieved through the use of PLC's. The HVAC have basic controller with the required IO to achieve their very simple task. I see there to be no reason to not use an AB PLC, you would probably get a greater flexibilty out of the system. The reason why the refrig comp hasn;t offered a PLC is because 1. They get a good deal for the equipment 2. They do not have to program it 3. A PLC to most in that indusrty is in the too hard basket for them 4. The job would be cheaper to you.

[gravitar 3]

Do tell, I've been dying to find a legitimate use for a PLC at home :)

[TimWilborne 108]

Started off with a bet. A HVAC buddy told me I couldn't do it any better. I couldn't get my house to heat evenly. It's a single story and about 80 percent windows so in the morning the east side heated more than the west and in the evening the west side heated more than the east. Luckily the duct work was already divided to the East side and the West side. So put a damper to switch from morning to even off of a timer. Worked alright but eventually added thermocouples to both sides of the house to adjust the damper. The house heats very evenly now. This helped tremendously because you had to get the front of the house to about 80 degrees to get the back to 65 degrees in the morning. The added a few more thermocouples inside and outside of the house. If it's 64 degrees outside and your thermostat is on 68 degrees do you really need to turn on the heat? Wrote some code to take in to account the outside temperture and the inside temperture to determine if the heat should be on. Already had a timer on the hot water heater to turn it off but added it too so the day of the week could be accounted for and so you wouldn't have to reset it everytime the power goes out.

[David Nelson 3]

i am somewhat of a newbie to plc's and couldn't help but to put in my to cents. but i have been experminting with home automation with the use of two slc 5/04 processors and a panelview 600. each 5/04 is on a 7 slot rack all connected via DH+ i have been remodeling my home at the request of my wife and i thought what the perfect time to wire in some of the thoughts i had for a plc. some of which include: all lighting and celing fans, outside lighting water heater, hvac and fire/burglar alarms are all tied in and can be controlled from the panelview. at first my wife didnt like it but after showing her how to work it she loves it. some exaples of its use are: if a smoke alarm goes off in the house all lighting is immediately turned on and the PV tells you which room it is in. if my wife has to get up in the middle of the night to go to the kids rooms a quick push of the touch screen and the path to the desired room is lighted including the kitchen(for bottle making) a photo cell in the drive way turns on the outside lighting as well as living room lights when i tell the PV we are leaving and we return home . i have many ideas for this type use and will be glad to share how i did it if any one wants info, david

[gravitar 3]

Wow.. most people start out with a micrologix or fixed SLC. your first car must've been a Cadillac :)

[gravitar 3]

Sounds like a pretty interesting project! I've thought of two things that I believe would make a difference in the home heating bill: First, the system needs to know when nobody's home. The heat should turn off until a low setpoint is reached when the house is empty. It should do this automatically, because people would inevitably forget to call in to turn it on. It should be able to sense when you're headed back home.. say when you're like a mile away. that way the house would be warm (or getting warm!) when you get back. The ideal situation would be that the house would be the same temperature when you get back as when you left. Since the above would be pretty hard to implement, a good first-step would be for the homeowner to hit a button on their way out the door to turn it off, and be able to call in remotely to turn it back on when they're heading home. Second, the system has to have a predictive capability. You've already started to work on that with your system, it sounds like. But I think it should go a step further. Not only should the current outdoor temp. play into the decition to turn the heat on or not, you should know what the temperature is going to be an hour from now, two hours from now, etc. The controller needs to know the weather report for the day. Some days the temp. warms up quickly at daybreak.. other days are overcast and there isn't much of a warm-up in the morning. the controller needs to factor that into the decision.. If it's 64 degrees in the house and 58 outside now, do I turn on the heat to bring it to 68 or do I leave it off, knowing that it's going to be 68 outside in another hour or two? Ok here's another screwey idea I had.. Here where I live in the frozen wasteland called Detroit, it's about 10-20 degrees outside. And I'm still cycling a refrigeration compressor in my house to keep my food cold. Why?! Why don't I just circulate cold outside air through the fridge and freezer to keep the food cold? I'll bet I could use a 10W fan motor to keep my food cold all winter.

[jstolaruk 9]

Being from the same area, I've had the same thought. Just got to tie into the defrosting cycle.

[David Nelson 3]

actually my first car was a sunbird, i know my collection is quite vast but 7 years of ebay and trading stuf with friends and people giving me stuff it didnt take long to get all this stuff. my first plc was a microligix 1000. i just wished would have started to learn programming when i started collecting plc parts and i would probably be a little better at programming. i just started to learn the actual programming end of it about a year ago .

[TimWilborne 108]

Should work fine but I would try to find an air to air exchanger so you wouldn't have to worry about contaminents and should lessen the moisture freeze up problem. I pump water out of my well in a very similar fashion to cool the house. Works fine. Don't use my well pump though. Have a small pump to circulate the water to the exchanger and it runs back into the well.

[brucechase 1]

With all this talk, I want to know if anyone has put a VFD on the HVAC. I have toyed with that idea alot but never went so far as get one and try it. I would probably get an AD or other inexpensive one. This would eliminate the lights dimming when the motor starts and could supply a more even heating and cooling system by reducing the "shock' of the hard blowing of cold or hot air.

[balerjoe 0]

I think you'd be better off w/a soft start. I don't believe you can run a VFD on a recipricating compressor, a screw compressor it would work great.

[TimWilborne 108]

I think brucechase was talking about a VFD on the air handler which is a regular motor. And some are multi speed so there could be an advantage to doing this. I think mine has a cooling speed and two heating speeds