Building Automation Knowledge Base

Issue Why not enter more than one reference host in a host or NPR configuration? Environment I/NET site Cause Why not enter more than one reference host in a host or NPR configuration Resolution Because if someone brings in an NPR to a site which has been used before, it will contain all of the IP addresses and links from the previous site. If any host or NPR on site refers to it as a reference host, those addresses may get spread to all of the hosts/NPRs on site. More than one reference host will make it tricky to get rid of the erroneous addresses. Besides that, the system doesn't need more than one.

Issue Calculate conversion coefficients for a PWM output Environment I/NET Resident I/O Editor PWM output Cause The key fact to remember is that the counts (in the built in calculator) are no longer counts but "ticks" or .01 seconds. The second key fact is that the A/D converter has NOTHING to do with this process. It only applies to voltage or current outputs, not pulsed outputs. Resolution If your minimum pulse is a tenth of a second you would enter counts low as 10. Full pulse is 5.2 seconds, 520 for counts high.

Issue How do I calculate conversion coefficients for a PI input? Environment I/NET site Cause How do I calculate conversion coefficients for a PI input? Resolution B will always equal 0. M will be the power factor assigned by the power company (or the manufacturer of the meter such as Veris.) So if you're told that each pulse is .305 KWh, your M is .305. Veris' 6000 series are configurable from .005 to 1 KWh per pulse. The exception to this would be a dual contact meter. In that case, they may alternate between contacts for each pulse. Therefore, you would double the power factor for your M since you're only reading half of the pulses.

Issue How can I clear the memory of an MR? Environment MR Cause If an MR with a database is given a new address using the dip switches, the DDC, I/STAT parameters and points remain in its memory. Resolution The only way truly clear the memory is to use an I/STAT or M/STAT: Enter the service mode Re-enter the address or communication speed. Changing these parameters can work but be careful not to leave the speed at anything other than 9600. Refer to the I/STAT instructions in TCON 126 or TCON 130 for instructions on service mode operations.

Issue How can I clear the memory of an ASC? Environment I/NET site Cause How can I clear the memory of an ASC Resolution Turn on dipswitches 6-12 and cycle power. Turn them back off and cycle power again. According to the instructions, this should do it but a few times, I've had to do this twice in a row.

Issue What does the disable light on a controller mean? Environment I/NET site Cause The disable light indicates an error in the controller. Resolution If the disable light is on, the controller is totally inoperable and cannot be fixed.  You must ship it for repair.

Issue What does the test light on an MR mean? Environment I/NET site Cause What does the test light on an MR mean? Resolution If it's on solid, the controller is ok. Flashing constantly - database problem, clear memory and start over. Other flashing patterns mean that various devices on the board have failed and it will need factory repair.

Issue What are termination resistors used for? Environment I/NET Site Cause What are termination resistors used for? Resolution As the signal travels down the cable, it sees a characteristic impedance (AC resistance). The closer it gets to the end of the wire, the higher the impedance goes until it gets to the end where it reaches infinity. Ohms law..so the voltage signal goes up and causes a reflected signal back up the wire at a lower energy level. This can be seen by the controllers as noise and if the timing is right, can disrupt communication. The timing and reflected signal level are functions of the cable length. Using termination resistor presents the signal with a consistent impedance and clamps the reflection. (They're also referred to as clamping resistors.)

Issue How do I install termination resistors? Environment I/NET site Cause How do I install termination resistors? Resolution They must be installed at each end of the lan. Keep in mind that if you have a stub (tee) near what you think is the end of the lan which is very long, the stub (or what you thought was the stub) is really the end. Anyway, the resistor is installed between the signal wires. In other words, one end goes into terminal one of the controller/tap/NPR along with the positive signal wire and the other end goes in terminal 2 with the negative wire. If you have a controller lan separated by a repeater or FOIs, it should be treated as 2 lan segments and each of them terminated at the repeater or FOI as well.

Issue What value resistors should be used as termination resistors? Environment I/NET site Cause What value resistors should be used as termination resistors? Resolution On a controller LAN, use 100 to 120 ohm resistors. If a repeater is installed, or controllers are being installed on a subLAN, use 620 ohm resistors.

Issue Thermistor temperature readings are 10-20°F below actual temperature Environment I/NET Site Cause Thermistor temperature readings are 10-20°F below actual temperature Resolution One of the universal inputs on this controller is using a 4-20ma sensor whose resistor input configuration has a 10K ohm in the B-slot instead of a 249 ohm in the A-slot.

Issue Can analog outputs be expanded on a 7718? Environment I/NET site Cause Can the analog outputs be expanded on a 7718 Resolution No. This is due to the address limitation of 3100-7 being already assigned to the baseboard.

Issue On a 7756 does 24vac need to be wired to TB4 Environment I/NET Site Cause On a 7756 does 24vac need to be wired to TB4 Resolution If the triacs on the lower board are going to be used then it needs 24vac wired to TB4.

Issue Why won't the output relays on a 7780 energize? Environment 7780 Output Relays Cause If the fuse in F2 has blown, the output relays will not energize. Resolution Verify that fuse F2 is not open.

Issue How can I verify that the onboard battery of a PCU is good? Environment I/NET site Cause How can I verify that the onboard battery of a PCU is good? Resolution Remove power from PCU. Voltmeter reading should be above 2.0vdc.

Issue What is the maximum number of lighting circuit relays that can be used on a 7780 controller? Environment 7780 Cause Configuration question Resolution 64 relays.

Issue When using the optional expansion enclosure within the 7780, is there a longer length matrix cable available than the standard 6-foot cable? Environment I/NET Site Cause When using the optional expansion enclosure within the 7780, is there a longer length matrix cable available than the standard 6-foot cable Resolution There is no alternative to the 72-inch matrix card ribbon cable (part# 606105-0041) that we supply. Since these signals are low voltage levels and there is no shielding within a ribbon cable, the 6-foot distance cannot be exceeded.

Issue Can the memory within an MR55 or MR88 be completely cleared by changing its dipswitch address? Environment MR55 MR88 Cause Changing just the dip switches is not sufficient to clear the memory. Resolution The address must be changed from the I/Stat or M/Stat.

Issue What is the maximum cable distance between the I/stat and the controller? Environment I/NET site Cause What is the maximum cable distance between the I/stat and the controller? Resolution 100 feet when using specified wiring type.

Issue When starting I/NET from filemaster PC, why do I receive an error message that states "cannot equalize with filemaster?" Environment I/NET Site Cause When starting I/NET from filemaster PC, why do I receive an error message that states "cannot equalize with filemaster?" Resolution Verify that the PC name of the filemaster has not changed. You can do this within the Configuration profile by deselecting/reselecting the filemaster checkbox. If the PC name change is discovered: Shut down I/NET, I/O Server, Equalsrv, and Equalcli. Go into Windows Explorer and delete all *.hfg files. Reboot PC Start I/NET