We have seen in the previous § that if a system has 2 boilers, it is not of much use them both being condensing boilers. Let’s study some heating lay-outs with one condensing boiler and one standard boiler.
– Connection example of a single return condensing boiler coupled with a standard or low-temperature boiler
Connection of a single return condensing boiler and a standard boiler
- The condensing boiler above (and those after) is supposed to be able to operate at zero flow.
- The motorised 2 way valves installed above on the heating returns are of the “all or nothing” type and will be piloted by the boiler cascade control, subject for example to outside temperature.
- Note, above, the 2 balancing valves necessary for the sharing of the flow between the 2 boilers (with different hydraulic resistances).
The balancing valves required to split the flow between the different boilers and the motor of the 2WV (all or nothing) necessary for a cascade control are drawn in red below.