Low effectiveness Cause: wheel not rotating (motor or belt failure), or condensate/fouling blocking the matrix.Fix: verify rotation and speed; wash the wheel with low-pressure water and a mild detergent; confirm belt tension. Frost or ice buildup (cold climates) Cause: exhaust-side temperature dropping below freezing.Fix: enable purge sector, reduce speed, or add preheat. See frost protection […]
Heat Exchanger Selection by Climate: Cold, Temperate, Hot-Humid
Cold climates (heating-dominated) Long, sub-zero winters make frost the enemy. Rotary wheels need purge sectors and occasional defrost; plate exchangers need bypass or preheat. Frost protection strategies are mandatory. Sensible-only recovery is usually enough because winter air is dry. Temperate climates Mild seasons with both heating and cooling loads favor balanced, all-season recovery. Plate and […]
AHU Heat Recovery Selection Calculation: A Step-by-Step Method
Step 1 - Known airflow Start with the supply/exhaust airflow Q (m3/h). For balanced AHUs, Q_supply approx Q_exhaust. Step 2 - Temperature difference Find the outdoor design temperature T_out and the exhaust (room return) temperature T_exp. The available temperature lift is DeltaT = T_exp - T_out. Step 3 - Effectiveness Choose an effectiveness epsilon (typical […]
Heat Exchanger Selection by Application: Hospital, Data Center, Food Plant
One device, many jobs Air-to-air heat recovery is applied across very different buildings, and the "best" exchanger depends on what each building values most: air purity, uptime, moisture control, or simply first cost. Below are three common sectors and the logic that drives their choice. Hospitals Air quality is non-negotiable. Fresh-air volumes are huge and […]
Heat Recovery Payback Calculation
Before buying a recovery unit, a quick payback calculation shows whether it makes sense. You only need a few field numbers and the local energy price. The Core Formula Annual energy saved (kWh) = 1.2 x airflow (m3/h) x eta x dT (C) x hours/year / 1000 Where 1.2 is the approximate volumetric heat capacity […]
Frost Protection in Heat Recovery Systems
In cold climates, exhaust air can be warm and humid while intake is far below freezing. When that exhaust cools below its dew point inside the core, frost forms. Left unchecked, ice blocks the airflow entirely. Why Frost Happens Frost appears when exhaust outlet temperature drops near 0 C and the core surface is below […]
Heat Exchanger Cleaning and Maintenance Guide
Heat recovery equipment only delivers its rated savings if it stays clean. Dust, grease, and moisture film raise pressure drop and lower effectiveness. A simple maintenance plan protects the investment. General Inspection Schedule Environment Inspect Clean Clean office air Every 6 months Annually Dusty / industrial Quarterly When dP +15-20 % Greasy (kitchen, booth) Monthly […]
Selecting a Heat Exchanger for HVAC Retrofit
Retrofitting heat recovery into an existing building is different from designing new. Space, duct layout, and control integration usually drive the choice more than peak efficiency. Step 1: Audit the Air Streams Confirm there is a dedicated exhaust and a matching supply. Measure airflow (m³/h or CFM) and temperature profiles. Note operating hours — recovery […]
Heat Exchanger Pressure Drop and Fan Energy
A heat exchanger only saves energy if the recovered heat exceeds the extra electricity needed to push air through it. That trade-off is governed by pressure drop. What Drives Pressure Drop? Face velocity (higher speed = steeper rise) Core depth and plate count Surface corrugation and coating thickness Dust or fiber loading on fins Reading […]
Heat Recovery Efficiency Metrics Explained
When comparing heat recovery products, efficiency numbers can be confusing. Manufacturers may quote temperature effectiveness, sensible recovery efficiency, or total energy recovery. Understanding these metrics helps you make fair comparisons and avoid under- or over-sizing equipment. Temperature Effectiveness (Sensible) Sensible effectiveness is the most common metric for air-to-air heat exchangers. It compares the actual temperature […]