How to Choose a Hydraulic Separator for Your Boiler Room

The hydraulic separator — one of the most underrated components in any boiler room. It is invisible during operation, yet it determines whether a multi-circuit system runs stably. Let us break down the principle and provide a clear selection algorithm. **Why You Need a Hydraulic Separator** In a modern boiler room there is almost always more than one pump: one on the boiler, separate ones for radiators, underfloor heating, and the domestic hot water cylinder. When they all work on a shared network, they compete for flow. The boiler may receive insufficient coolant and overheat, while remote circuits remain underheated. The hydraulic separator creates a low-resistance zone where the boiler flow and consumer flows meet without interfering with each other. The boiler receives a stable flow rate regardless of how many circuits are open. In simple terms — it hydraulically decouples the primary (boiler) circuit from the secondary circuits. **What This Means in Practice** - Stable flow through the boiler — no thermal shock or short-cycling. - Protection of [circulation pump](/catalog/nasosy) impellers from hydraulic conflicts. - If the unit has top/bottom connections, it simultaneously removes air and sludge, combining the functions of a [separator](/catalog/separatory). **Sizing by Capacity — the Key Criterion** The hydraulic separator must be sized by the maximum total coolant flow rate, not by guesswork. Approximate ranges for ΔT=20 °C: - **ГС-25 (1")** — boiler rooms up to approximately 50 kW - **ГС-26 (1¼")** — up to ~90 kW - **ГС-27 (1½")** — up to ~130 kW - **[ГС-28 (2")](/catalog/hidravlichni-rozdilnyky/gidrostrilka-gs-28-v-izolyacziyi)** — up to ~170 kW - **Flanged ГС-30 and the ГС-31…34 series** — for boiler rooms from 200 kW and industrial applications **Material and Design** Termojet standard: steel in removable XPE thermal insulation, which reduces heat losses and condensation. For higher capacities — flanged models with a base frame. **When a Hydraulic Separator Is NOT Needed** - A single boiler with a single circuit at identical flow rates. - Systems with a [heat pump](https://tjheatpump.com.ua/) and a buffer tank — the buffer itself typically performs the decoupling function. **Common Mistakes** 1. Sizing by pipe diameter rather than flow rate. 2. No automatic air vent and no drain valve for sludge removal. 3. Installation without thermal insulation — unnecessary heat losses. 4. Using a separator where a thermo-hydraulic distributor (combining separator and manifold) would suffice. **Summary** A correctly sized hydraulic separator is relatively inexpensive but saves the boiler and pumps from premature wear. The [Termojet ГС](/catalog/hidravlichni-rozdilnyky) range covers models from 1" to industrial flanged versions — with thermal insulation and ready to install.