Controls

4-20mA to 2-10V resistor, 4-20mA BMS input, 500 ohm resistor 4-20mA, convert current signal to voltage HVAC

If a field sensor outputs 4–20mA but the BMS controller only has a voltage input, can you convert it using a resistor?

Yes, provided the transmitter and input arrangement are suitable.

Using Ohm's law:

V = I × R

With a 500Ω resistor:

I have found that using the Set feature in Niagara does not always write to BACnet priority 10.

By doing this you can still use Set in Niagara/ Tridium graphics

A simple workaround I use is to create a link within the Bacnet Setpoint block so the Out value feeds back into In10.

How to do it

1. Add a Bacnet block.

BACnet MSTP and BACnet IP are both widely used communication protocols in commercial HVAC and Building Management Systems (BMS), but they serve different applications and have different performance characteristics.

BACnet MSTP

Operates over RS-485 (twisted pair).

All devices share a single communication trunk in a token-passing loop.

Lower bandwidth, typically 9.6–76.8 kbps.

Very stable when installed correctly but sensitive to cable quality, grounding, and addressing issues.

Regular BMS maintenance keeps HVAC systems efficient, compliant, and energy-smart. Learn how Australian facilities can reduce costs and extend equipment life.

As buildings become smarter, the Building Management System (BMS) is the heart of every modern facility. Yet many sites in Australia still run outdated or poorly maintained systems.

Routine BMS servicing helps identify hidden inefficiencies, sensor drift, and faulty control logic that drive up power bills.

Whether you’re running Niagara N4, Reliable Controls, or Optergy, scheduling quarterly or bi-monthly maintenance ensures chillers, AHUs, and CO₂ systems operate in sync.

Investing in BMS optimisation often returns 10–20% energy savings within months.

#BMS #HVACAustralia #EnergyEfficiency #FacilityManagement #NiagaraN4 #ReliableControls #BuildingAutomation