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Ok I am finding more info on this. The meter is made by GE, model# VW63S. Line K is attached to 2 single-pole single-throw switches "Y" and "Z". "Y" and "Z" open and close as the disk rotates. As the meter rotates in one direction, Y closes then Z closes, then Y opens, then Z opens. When it...

For a KWH meter: What does KWC pulse value of 10 mean? What does RVA pulse value of 4.8 mean? How can the above values be used to calcualte KW?

We have an old KWH meter that has been isnatlled more than 12 years ago. I was told that it's not easy to access the meter to look at it. But I was tasked to figure out if the exisiting calculations are correct for KW values. The meter measures KWH. Every so many KWH it create a pulse which is...

I have a PLC that talks Modbus. I am going to use Modscan software running on my laptop (master), to pull data form the PLC (for initial testing purposes). The PLC have 3 terminal blocks for communications (+,- and shield). In order for me to connect from my laptop comports (comm1, RJ485 to USB)...

Sorry, I meant to say DDC (Direct Digital Control)....

What about RS485, can I use Hyperterminal to anlayze the data, or should I use a different analyzer. Some one was telling me to use "HDD serial monitor". Say the PLC is talking Modbus RTU (using RS485), and I just want to make sure that I can comminicate with the device and maybe pull one...

I would vote for a DCC system, it's cheaper and it does the job. You won't be compromising on the quality if you choose the right BMS integrator. HVAC sytems don't normally require high processing speed, which is usually provided by PLC's. In addition to that, DCC BMS systems are easier to...

If I Have a computer running Hyperterminal, and it's connected to the controller using serial commport-1. How can I use hyperterminal to test and trouble-shoot the serial communication. Can some one point me to a manual or a tutorial on how to use Hyperterminal to test serial communications...

We are installing VAV controllers in the ceiling plenum of a building. The controllers require 24V and each one is 10 VA rated. How big of a 24V transformer can we install in the ceiling plenum to provide power to the controllers? What are the limitations by the NEC code? If the controllers, as...

Bernoulli: "Pressure Energy" + "Kenetic Energy per unit volume" + "potential Energy per unit volume" = constant P/? + V2/2 + gh = Const Where V2 is "V square".

Thanks guys!

What is the formula that connects differential Pressure (inwc) and water Flow (GPM) in a pipe. Thanks

When wiring input sensors as inputs to digital controllers, I sometimes see that a "IIM board" being used. My understanding is that they are used for electrical isolation between field devices and the controller. My question is , when is it a must, and when is it an option? Or is it an extra...

Thanks for the feedback. Another idea that came to mind, is to reset VAV temp setpoints when the KW peak is approached. Since peak KW will cost much more $$.

I have a large commerical office building with a fully auomated systems. The HVAC (BAS) system is controlled by DCS controllers. It has multiple AHU units, VAV units, Chillers, etc. I am trying to come up with sequences to save energy. We are already using economizer mode (free fresh air), when...

I am not sure if this is the right place to post this questions? But any way.. I have a large commerical office building with a fully auomated systems. The HVAC (BAS) system is controlled by DCS controllers. It has multiple AHU units, VAV units, Chillers, etc. I am trying to come up with...

I know the answer might be very involved, but I cann't help but asking why ? Why is a bigger resistor is unable to absorb (dissipate) all the induced enegry by the signal? Thanks

Thank you for the valuable feedback. It is starting to make sense to me. I have a question however: If the purpose of using the resistor is to absorb the signal energy on the transmission line, what happens if someone install a resistor (at the end of the line) with higher value that the...

Recently I installed a "RS485" connection between our controller and a third party controller. It was specified that one must connect terminating resistor on each end of the RS485 loop (because it's a long run). It says that resistor is designed to match the electrical impedance characteristic...

I am a mechanical engineer, and I work in the building automation industry. I often come across many engineering disciplines. I have been, for the most part, on the software side (programming of controllers and IT) for quite a while now. I would like to learn more about the hardware (field...