If the system has several differently orientated circuits, or on which it is useful to reduce heat at different times, each is fitted with a control valve which permits fine tuning of the outlet temperature subject to its own set-point line.
The boiler temperature is carried out subject to the greatest demand from the different circuits.
The system diagram below ensures the feed of 2 differently orientated circuits, which is why there are 2 exterior sensors.
Mark on the diagram above the numbers indicated in the description below.
– 2 radiator circuits n°1 (left) & n°2 (right).
– The controller ensures the regulating of circuit n°1 subject to exterior temperature measured on sensor n°3; it controls the circuit outlet temperature on the sensor n°4 by action on the 3WV (3 way valve) n°5.
– The controller ensures the regulating of circuit n°2 subject to exterior temperature measured on sensor n°6 (left); it controls the circuit outlet temperature on the sensor n°7 by action on the 3WV n°8.
– By action on the burner, the controller also regulates boiler production temperature on sensor n°9 subject to the requirements generated by the control of the 2 outlet temperatures.
For circuits with differing orientations or different heat reduction times, it can, in certain cases, be wise to fit a 3WV (3 way valve).
How, in the below system, is temperature variation effected on the circuit n°2 outlet?
Circuit n°2 temperature variation is carried out by action on the boiler burner, subject to exterior temperature measured by sensor n°6 and a weather dependant set-point line.
In the below system, the temperature of circuit n°2 is that regulated by the boiler. Is this temperature:
– Always inferior or equal to that of circuit n°1 ?
– Always equal to that of circuit n°1?
– Always superior or equal to that of circuit n°1?
The water outlet temperature of circuit n°2 is always superior or equal to that of circuit n°1 which can be reduced by its 3WV.
Circuit n°2 always has an outlet temperature higher or equal to that of circuit n°1. We can, for example, suppose that circuit n°2 feeds a north-facing facade, whereas circuit n°1 is south facing.
Another hypothesis, is that the 2 circuits have the same orientation, but circuit n°2 feeds living accommodation 24/7, whereas circuit n°1 feeds commercial properties or offices where the temperature is reduced during inoccupation.
The idea that the 2 circuits are of the same orientation and even reduced, but of different temperature regimes (radiator, under-floor heating) is not optimal, because the fitting of a basic mixing bypass down-stream of the 3WV would suffice (see 1st §).