Hot Water Heating Systems - Flow Temperatures vs. Outside Temperatures
Seasonal effects - outside temperature - and operating boiler temperatures in typical two-pipe forced hot water systems are indicated in the table below:
It is common to design a hot-water heating system for a temperature drop of 20 oC (36 oF ) in heating elements and radiators at what is considered as minimum outside design temperatures.
Maximum boiler flow temperature is often set to 80 oC (176 oF ) to avoid "burned dust" and accidentally injures on people when touching heaters. Outside design temperature depends on the actual location.
| Minimum Outside Design Temperature (oC) | Boiler Flow Temperature (oC) | ||||
|---|---|---|---|---|---|
| Outside Temperature (oC) | |||||
| -20 | -10 | 0 | 10 | 20 | |
| -20 | 80 | 66 | 51 | 37 | 37 |
| -10 | 80 | 58 | 37 | 37 | |
| 0 | 80 | 37 | 37 | ||
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