Three ways a reading goes wrong
It drifts or fails
Sensors age. A temperature sensor reading 2 to 3 °C low keeps a zone heating long after it's warm enough. A stuck reading never moves at all. This is one of the most common faults found in building tune-ups, and it wastes energy every day it goes unnoticed.
It's in the wrong place
A thermostat in direct sun, next to a door or above a printer measures its own corner, not the room. Sometimes a sensor is wired or labelled to the wrong zone in the BMS, so it controls a space it isn't in.
It's been tampered with
Security researchers have shown that a compromised refrigeration controller can switch off cooling while still showing staff a normal temperature. If the controller is the only source of truth, a manipulated controller can hide its own attack.
The fix: a second, independent reading
The answer isn't to replace every sensor. It's to add a small number of independent sensors, on a separate system and network, at the points that matter most, and compare them continuously with what the BMS reports.
- Where: cold rooms and freezer cases, server rooms, air handler supply air, and a sample of occupied rooms.
- How many: usually a handful per site, not hundreds.
- What it catches: drifting sensors, misplaced sensors, rules acting on bad data, and readings that don't add up because someone changed them.
The same comparison serves energy, comfort and security at once. That's why we use our own portable sensors in every assessment, and why monitoring keeps a few permanent ones in place.
Want a second opinion on your building?
Every Pasot assessment includes two weeks of independent readings compared against your BMS.