Pressure is used to circulate liquid in a heating or cooling system and is induced by means of pumps. The pressure in a system is positive in relation to atmospheric pressure.
Pressure is increased by means of pumps. The pressure in a system is positive in relation to atmospheric pressure. Pressure has numerous units of measurement, though those most commonly used are: Pa, kPA, bar and mVC.
The ratios of the units are:
Bar and kPa
1 bar = 100,000 Pa = 100 kPa.
Other units include lbf/in² = psi (pounds per square inch) and mm mercury column (mmHG). These units are specified as:
1 psi = 6895 Pa
1 mmHG = 133 Pa
The unit mVC (meter water column) is dependent on gravitational acceleration, or g, which varies according to the distance from the equator.
When using mVC, the approximate value 1 mVC = 10 kPa is often used, which equates to a gravitational acceleration value of 10 m/s².