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 20oC (36 oF) in heating elements and radiators at what is considered as minimum outside design temperatures.
Maximum boiler flow temperature is often set to 80oC (176oF) 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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