Comparison of 1734-EP24 and 1734-FPD: Isolating Power to Field Section without Cutting Inputs

Question:

Hello, I am looking to isolate the power to the field section (cutting power to outputs but not inputs) - is this feature available with the FPD, or does the EP24DC also offer this capability? It appears that the power supplied to the EP24DC will be distributed to both the system and field, so cutting power to one will result in a fault in the entire IO-node. Considering the number of IO cards, would replacing the EP24 still be necessary? I am concerned about potential costs exceeding the budget. Best regards, Jon

Top Replies

Utilize the Output Power Isolation feature of the FPD to effectively manage power distribution. The EP24DC serves to disconnect power from modules located to the left while supplying power to modules on the right. It is important to note that the EP24DC should not be used to trail a safety relay, as this can disrupt module communication power to subsequent modules, ultimately causing a rack fault. Make sure to carefully consider the power distribution plan to avoid any complications within the system.

Field power distribution (FPD) supplies power to specific sections of the rack. In a setup like AENT-IB4-IB4-OB4-OB4-FPD-IB4-IB4-OB4-OB4, the first two output cards receive power from the 24VDC on the AENT, while the second two output cards are powered by the 24VDC on the FPD. The input common for the first two input cards is connected to the AENT, and the input common for the second two input cards is connected to the FPD. On the other hand, the EP24DC not only supplies field power but also provides backplane power. In addition to the above, the EP24DC supplies 5V power to cards on the right to enable them to function properly. Using an FPD is essential for isolating I/O field power in sections, while an EP24DC is necessary when the AENT cannot power all required cards. It is important to consider the maximum bus power available on your AENT (Note: AENTR can supply more bus power than AENT). Check the bus power requirements for each I/O module to determine when an EP24DC is needed. A general rule of thumb is that around 8-10 cards can be powered by an AENTR before requiring an EP24DC. Cutting power to an FPD only affects field power, while cutting power to an EP24DC turns off cards completely, resulting in an I/O fault. It is important to carefully calculate power requirements to avoid any issues in your setup.

Thank you for your guidance. I plan to utilize the IAB tool on the AB website to size the nodes based on power and determine the FPD. AB has cautioned about potential data cap limits with multiple analog cards and advised against excessive use of the AENTR to prevent one node from dominating traffic.

The Field Power Distributor (FPD) only supplies field power, while the EP24DC supplies field power and backplane power. In a rack configuration like AENT-IB4-IB4-OB4-OB4-FPD-IB4-IB4-OB4-OB4, the first two output cards receive power from the 24VDC on the AENT, and the second two output cards are powered by the 24VDC on the FPD. The input common for the first two input cards is connected to the AENT, while the input common for the second two input cards is connected to the FPD. It is important to use an FPD to isolate I/O field power in sections, and an EP24DC when the AENT cannot power all the cards. The EP24DC also provides 5V power to the cards on the right. Check the maximum bus power available on your AENT and compare it to the bus power requirements of your I/O modules to determine when you need an EP24DC. Typically, around 8-10 cards can be powered by an AENTR before requiring an EP24DC. Keep in mind that cutting power to an FPD only affects field power, while cutting power to an EP24DC turns off the connected cards completely, resulting in an I/O fault. It's crucial to plan power distribution effectively to avoid any issues with your system.

Hey Jon, You're right about the power distribution on the EP24DC - it'll indeed go to both the system and field. Isolating power to the field section isn't readily available with the FPD or EP24DC. As for replacing the EP24, that really depends on the specific needs and configuration of your IO-node. If you need to maintain separate power controls for the output and input, then a replacement might be necessary. Just remember to analyze whether the functionality gained justifies the cost within your budget. Hope this helps! Regards

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Frequently Asked Questions (FAQ)

FAQ: 1. Question: Can the 1734-EP24 isolate power to the field section without cutting inputs?

Answer: Answer: No, cutting power to the field section on the 1734-EP24 will result in a fault in the entire IO-node as the power is distributed to both the system and field.

FAQ: 2. Question: Does the 1734-FPD offer the feature to isolate power to the field section while keeping inputs intact?

Answer: Answer: The capability to isolate power to the field section without cutting inputs is not available with the 1734-FPD.

FAQ: 3. Question: If cutting power to one section causes a fault in the entire IO-node with the 1734-EP24, would replacing it be necessary?

Answer: Answer: Replacing the 1734-EP24 might be necessary if isolating power to the field section is crucial and cannot be achieved without causing faults in the IO-node.

FAQ: 4. Question: Are there concerns about potential costs exceeding the budget when considering replacing the 1734-EP24?

Answer: Answer: It is important to evaluate the costs associated with replacing the 1734-EP24 if the feature to isolate power to the field section is a critical requirement, especially if it leads to additional expenses beyond the budget.

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