Cycles of Concentration from Conductivity

\text{COC} = \frac{\sigma_t}{\sigma_m}

Worked example: 2400 uS/cm tower over 400 uS/cm makeup → 6 cycles — press Try an example to run it live, then adjust anything.

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Cycles of Concentration from Conductivity explained

Nobody meters makeup and blowdown on a routine service call — they dip a conductivity probe in the makeup line and again in the basin, and divide. Dissolved salts carry current, they do not evaporate, and they concentrate in lockstep, so 2400 μS/cm in the tower against 400 μS/cm in the city water means the system is running at exactly 6 cycles. The same probe is what the blowdown controller uses: set a 2400 μS/cm setpoint and the solenoid opens whenever the basin drifts above it.

Two traps catch people. First, conductivity meters are temperature-compensated to 25 °C — a hot basin and a cold makeup tap read on different bases unless compensation is on, and a 10 °C error is worth roughly 20% on the reading. Second, if you dose an acid or a conductive inhibitor, that chemical shows up in the tower reading but not in the makeup, inflating the apparent cycles; that is precisely why many programs cross-check against a non-reactive tracer such as chloride.

Cycles of Concentration from Conductivity formula

\text{COC} = \frac{\sigma_t}{\sigma_m}

Where

$\text{COC}$ = Cycles of concentration
$\sigma_t$ = Tower water conductivity (μS/cm)
$\sigma_m$ = Makeup water conductivity (μS/cm)

Missing one of these? Work it out first, then come back

Cycles of concentration — Cycles of Concentration from Chloride, Boiler Cycles of Concentration
Tower water conductivity — Water Resistivity and Conductivity, TDS Estimated from Conductivity (TDS = k × EC)
Makeup water conductivity — Water Resistivity and Conductivity, TDS Estimated from Conductivity (TDS = k × EC)