About SMB350

Troubleshooting Questions

Questions & Answers

Does the SMB350 come with its own CTs?
  • The SMB350 is sold with the CTs included. The SMB350 cannot be used otherwise, since it is neither direct connect nor a regular 5A output CT can be used.

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What are dedicated CTs?
  • Dedicated CTs are the CTs specifically provided for use with the SMB350 and some other meter models from DAE. These are not available from anywhere else other than DAE and is proprietary to DAE. They are called dedicated CTs because they are dedicated for use with DAE branded meters.

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Why do you use dedicated CTs?
  • The SMB350 meter is designed for submetering. Submeters are adjunct to the main utility meter, and as such their CTs often need to be installed in electrical panels which are already cramped, especially in residential and commercial electrical panels. Thus the CT used by the SMB350 would need to share space with other already previously installed CTs.
  • Regular 5A output CTs are large and bulky and often cannot fit into the panel. Dedicated CTs on the other hand are small enough to fit even in such cramped spaces. Not having to install a new panel just for the CTs eliminates or reduces the cost of the labor and materials which would otherwise be needed.
  • Another reason for using dedicated CTs is because they are much more accurate than regular 5A output CTs. The smaller the CT, the more precise the construction. Solid core dedicated CTs have an accuracy better than 0.5% and split core dedicated CTs have an accuracy of 1%.

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Can I make use of my own CTs?
  • The short answer is no. The longer answer is yes but not directly.
  • The SMB350 uses dedicated CTs and cannot directly accept regular 5A output CTs. The CT input of the SMB350 can only accept milli-amps which matches our dedicated CTs. Connecting a regular 5A output CT directly will thus damage the Polaris. If a regular 5A output CT is to be connected, it needs to first be connected through a dedicated 5A CT.

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Can the SMB350 measure amperages greater than 600A?
  • Since the SMB350 uses dedicated CTs, the selection of dedicated CTs that can be used is necessarily limited. The selection of dedicated CTs is only up to 600 A. To measure amperages greater than 600A, regular 5A output CTs must be used in conjunction with the Polaris model using dedicated 5A CTs.

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How can different types of CTs be used on a single SMB350?
  • Different types of CTs may be used on a single SMB350 under certain conditions and with certain limitations, please see the product manual section on “Product Information” for a detailed explanation.

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Can a single SMB350 be used to monitor two different subpanels?
  • It is possible if the two subpanels have the same power source.
  • If the two subpanels do not share the same power source, then two SMB350s must be used.

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Can a single CT be used to monitor multiple circuits?
  • It is possible to do so if the different circuits share the same phase and power source. The L wire for each circuit must go through the CT in the same direction, and the current rating of the CT in must be higher than the total amperage for all the circuits to be measured.

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Can the wires for both the measured voltage and CT secondary be placed within the same conduit?
  • Yes they can be placed together in the same conduit.

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Can the wires for both the measured voltage and the communication be placed within the same conduit?
  • No, it is not recommended as the communication is sensitive to noise and interference. They should each be placed in their own conduits separately.

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How to connect to a host computer that doesn’t have an RS485 communication port?
  • If the host computer only has an Ethernet port, then use an RS485 to Ethernet converter.

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Why is there unstable or no communication between the RS485 interface of the Polaris to the host computer?
  • Make sure that the network does not form a tree or star topology and that there are no loops.
  • Check that the converter has its parameters set up properly.
  • Make sure that the baud rate set for SMB350s and the host computer are the same.
  • Make sure that each of the SMB350 on the same bus has its own unique device address.
  • Make sure that the polarities for the RS485 wiring are correct for all the SMB350. All positive terminals must be connected together, and all negative terminals must be connected together.
  • Make sure that the total length of any single RS485 bus segment is less than 1000 meters (3000 feet), a segment is defined to be one without any intervening repeaters.
  • Make sure that there are no more than 32 devices on a single RS485 bus segment.

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What will happen if the polarities are reversed for each of the following: auxiliary power, CT and communication?
  • The auxiliary power requires AC power which doesn’t have a polarity.
  • The auxiliary power is available in models for either 120 or 240 VAC. If 120VAC is applied to a 220VAC model, the SMB350 will not be damaged, but it won’t work either. But if 220VAC is applied to a 120VAC model, then the unit will be damaged.
  • The SMB350 only considers the absolute value of the current and disregards the direction; thus, the current and energy values can only be positive. However, we still recommended that the current transformers be connected with the correct wiring orientation.
  • The communication cable is polarity sensitive. RS485 requires that all positive terminals are connected together, and all negative terminals are connected together, reversing any one on any single device will cause the entire RS485 bus to collapse and all communication will fail. If the polarity to any one device is inconsistent with the rest, simply reverse the polarities and the communication should be restored.

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Why aren’t the LCD or indicators lighting up?
  • Make sure that the auxiliary power terminal wiring is connected properly.
  • Check that the fuse and circuit breaker are neither blown nor tripped, respectively.
  • Make sure that power is being supplied from the power source to the auxiliary power.
  • Check that the power source voltage is within the rated power supply.
  • Check to make sure that the enclosure or terminals are not damaged.

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Why is the voltage reading correctly, but the amperage shows zero?
  • Check that the CT wiring to the terminal have the correct polarity.
  • Make sure that the measured circuit corresponds to its phase.
  • Make sure that the power is on for the load circuit being measured.
  • Check the fuse or circuit breaker.
  • Make sure that only the L wire passes through the CT, if the N wire is also passing through then remove it from the CT.
  • The CT may be damaged or defective, do a cross cehck by swapping it with another CT. If defective or damaged, replace the CT.

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Why doesn’t the kWh reading match the actual consumption?
  • For models using a regular 5A output CT. Check that the CT ratio set matches the main CT used. (e.g. 500A:5A, then the CT ratio should be 100)
  • Make sure that there is continuous power to the auxiliary voltage input 24 hours a day.
  • Check the CT wiring direction on load and polarity on meters if parallel 2 or 3 CTs for any phase. When parallel 2 or 3 CTs, the wiring direction and polarity must be the same.

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Why does a channel show a very poor or erroneous power factor value?
  • Check the CT and voltage wirings and make sure that each CT input is matched to its corresponding voltage.
  • Make sure that the measured circuit corresponds to its phase.
  • Use a separate instrument to independently verify that the PF is indeed awry. If so then check the circuit and load to determine what is causing the PF to go askew.

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