CoC = TDS_tower \/ TDS_make-up \u2248 Conductivity_tower \/ Conductivity_make-up<\/strong><\/p>\nHigher CoC means less blowdown, less make-up, and less chemical treatment cost. It also means higher scaling and corrosion risk. Every cooling tower operator sits somewhere on this trade-off curve. The point of continuous conductivity control is to keep the site precisely on the operator’s chosen point instead of oscillating around it.<\/p>\n
A conservatively tuned CoC of 3 in a data-center cooling tower with 27 gpm evaporation wastes roughly 13 gpm of make-up<\/strong> compared with a well-controlled CoC of 5, or about 19 million gallons per year<\/strong> per tower \u2014 a meaningful sustainability and OPEX number.<\/p>\n<\/span>The Measurement Chain<\/span><\/h2>\nField-proven CoC control uses four signals:<\/p>\n
\n- Recirculation conductivity<\/strong> \u2014 the primary control variable, typically 1,500\u20134,500 \u03bcS\/cm at CoC 4\u20137 depending on make-up chemistry.<\/li>\n
- Make-up conductivity<\/strong> \u2014 needed to compute CoC in real time; often 250\u20131,000 \u03bcS\/cm.<\/li>\n
- Blowdown flow<\/strong> \u2014 verifies actual water leaving the system.<\/li>\n
- Make-up flow<\/strong> \u2014 closes the mass balance and detects drift-related losses.<\/li>\n<\/ol>\n
Shanghai ChiMay’s in-line conductivity meter (or in-line conductivity electrode in small-bore lines), paired with a paddle wheel flow meter on the blowdown line and a turbine flow meter or paddle wheel unit on the make-up line, delivers all four signals to the building management system through Modbus RTU.<\/p>\n
<\/span>Choosing Two-Electrode vs. Toroidal Conductivity Cells<\/span><\/h2>\nFor cooling-tower service, the two dominant cell technologies are:<\/p>\n
<\/span>Two-Electrode Cells<\/span><\/h3>\n\n- Best for low- to mid-range conductivity<\/strong> (up to about 2,000 \u03bcS\/cm).<\/li>\n
- Higher sensitivity at low TDS make-up water measurements.<\/li>\n
- Susceptible to polarization at high ionic strength, requiring frequency compensation.<\/li>\n
- Wetted materials: graphite, titanium, or 316 stainless.<\/li>\n<\/ul>\n
<\/span>Toroidal (Inductive) Cells<\/span><\/h3>\n\n- Best for high-conductivity or fouling-prone service<\/strong> (2,000\u2013200,000 \u03bcS\/cm).<\/li>\n
- Non-contact measurement \u2014 the fluid passes through a plastic-encased toroid, so scale and biofilm affect the reading much less than they do in a two-electrode cell.<\/li>\n
- Preferred for cooling-tower basin monitoring where biofouling is unavoidable.<\/li>\n
- Wetted body: PEEK or PFA.<\/li>\n<\/ul>\n
For most commercial HVAC recirculation loops running CoC 4\u20136, either technology works. For hyperscale cooling towers pushing CoC 7+ with heavy biocide usage, toroidal is the safer field bet.<\/p>\n
<\/span>Comparative Snapshot: Manual vs. Continuous CoC Control<\/span><\/h2>\n\n\n\n| Attribute<\/th>\n | Manual Grab-Sample Control<\/th>\n | Continuous Conductivity Control<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| Measurement frequency<\/td>\n | Once per shift or daily<\/td>\n | 1\u201310 second sample rate<\/td>\n<\/tr>\n |
\n| CoC variance<\/td>\n | \u00b125% around setpoint<\/td>\n | \u00b15% around setpoint<\/td>\n<\/tr>\n |
\n| Water savings vs. baseline<\/td>\n | 0%<\/td>\n | 15\u201330%<\/td>\n<\/tr>\n |
\n| Chemical usage<\/td>\n | Over-dosed for safety<\/td>\n | Optimized against real CoC<\/td>\n<\/tr>\n |
\n| Response to load transient<\/td>\n | Minutes to hours<\/td>\n | Seconds<\/td>\n<\/tr>\n |
\n| Labor overhead<\/td>\n | 1\u20132 hours\/day<\/td>\n | Alarm-driven only<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/span>The Blowdown Control Loop in Practice<\/span><\/h2>\nThe classical blowdown control loop looks like this:<\/p>\n \n- Measure recirculation conductivity via a Shanghai ChiMay in-line conductivity meter mounted on a sidestream from the tower basin.<\/li>\n
- Compare against a setpoint (for example, 3,200 \u03bcS\/cm for CoC 5 with 640 \u03bcS\/cm make-up).<\/li>\n
- Modulate blowdown via a solenoid or motorized blowdown valve.<\/li>\n
- Verify blowdown flow with a Shanghai ChiMay paddle wheel flow meter to catch valve failures or stuck actuators.<\/li>\n
- Log make-up flow to close the mass balance and detect drift or leaks.<\/li>\n<\/ol>\n
Data-center operators often add two more layers:<\/p>\n \n- pH interlock<\/strong> using a Shanghai ChiMay in-line pH electrode: if pH drifts outside 7.8\u20138.6, blowdown pauses until chemical treatment corrects the swing.<\/li>\n
- Residual chlorine interlock<\/strong> using a Shanghai ChiMay residual chlorine transmitter: heavy shock chlorination temporarily suspends blowdown to preserve biocide contact time.<\/li>\n<\/ul>\n
<\/span>Common Failure Modes and How to Design Around Them<\/span><\/h2>\n<\/span>Sensor Fouling<\/span><\/h3>\nBiofilm on a two-electrode cell reads low, driving the controller to increase blowdown \u2014 the opposite of what is needed. Toroidal cells largely eliminate this failure mode; where two-electrode cells are retained, a scheduled 90-day chemical clean-in-place cycle is the practical fix.<\/p>\n <\/span>Setpoint Drift Over Seasons<\/span><\/h3>\nMake-up water conductivity varies with rainfall, source-water TDS, and seasonal blending in municipal systems. A CoC-based<\/strong> setpoint (which requires live make-up conductivity) is more robust than a fixed tower conductivity setpoint. This is why measuring both streams matters.<\/p>\n<\/span>Valve Sticking<\/span><\/h3>\nBlowdown valves that only open at extreme conductivity spikes can seize between events. A short daily “exercise” cycle keeps the valve movable and gives the operator early warning of degradation.<\/p>\n <\/span>The Water and Chemical Savings Math<\/span><\/h2>\nA hyperscale data-center campus in Northern Europe reported the following after installing continuous conductivity-based CoC control across 12 cooling towers:<\/p>\n \n- Average CoC moved from 4.2 to 6.4.<\/li>\n
- Make-up water demand fell 28%<\/strong> at constant heat load.<\/li>\n
- Bulk biocide and scale-inhibitor consumption fell 19%<\/strong>.<\/li>\n
- Estimated combined savings: USD 1.1 million per year<\/strong> across the campus.<\/li>\n<\/ul>\n
Similar results appear in commercial hospital and university portfolios where the previous control method was daily grab-sample titration.<\/p>\n <\/span>A Deployment Checklist<\/span><\/h2>\n\n- Install a toroidal conductivity cell (or Shanghai ChiMay in-line conductivity meter with toroidal option) on a sidestream from the basin, upstream of the blowdown valve.<\/li>\n
- Install a second conductivity sensor on the softened make-up line to compute CoC live.<\/li>\n
- Verify blowdown and make-up flows with paddle wheel or turbine flow meters.<\/li>\n
- Interlock the blowdown valve with pH and residual chlorine measurements.<\/li>\n
- Log CoC, blowdown volume, and make-up volume to the BMS for sustainability reporting.<\/li>\n
- Schedule quarterly calibration checks; annual electrode replacement is typical in aggressive service.<\/li>\n<\/ol>\n
<\/span>Outlook<\/span><\/h2>\nAs Water Usage Effectiveness (WUE) becomes a reported metric for hyperscale data centers and as ASHRAE 188 tightens for commercial buildings, the humble conductivity meter has become the linchpin of both compliance and OPEX optimization. Field practice increasingly favors matched sensor families that share a common controller and communication profile. Shanghai ChiMay’s water quality analyzer portfolio \u2014 in-line and probe conductivity meters, pH electrodes, residual chlorine transmitters, and paired paddle wheel and turbine flow meters \u2014 is engineered to deliver exactly this kind of closed-loop CoC control at commercial and hyperscale scale.<\/p>\n","protected":false},"excerpt":{"rendered":" title: “Conductivity-Based Cycles-of-Concentration Control in Cooling Towers: Field Practices from Shanghai ChiMay” perspective: Technical Deep-Dive theme: HVAC & Data Center Cooling Water date: 2026-07-04 Conductivity-Based Cycles-of-Concentration Control in Cooling Towers: Field Practices from Shanghai ChiMay Key Takeaways Cycles of concentration (CoC) is the single most influential control variable in a cooling tower loop, governing water…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false},"categories":[1],"tags":[158,134429,11037,147,134481,154],"translation":{"provider":"WPGlobus","version":"3.0.2","language":"fr","enabled_languages":["en","es","fr","ru","ar"],"languages":{"en":{"title":true,"content":true,"excerpt":false},"es":{"title":false,"content":false,"excerpt":false},"fr":{"title":false,"content":false,"excerpt":false},"ru":{"title":false,"content":false,"excerpt":false},"ar":{"title":false,"content":false,"excerpt":false}}},"_links":{"self":[{"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/posts\/31131"}],"collection":[{"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/comments?post=31131"}],"version-history":[{"count":0,"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/posts\/31131\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/media?parent=31131"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/categories?post=31131"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.chimaytech.net\/fr\/wp-json\/wp\/v2\/tags?post=31131"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} |