Boilers and Their Components

The hydraulic system

It’s not possible to describe all the possible connections between generators and distribution channels, but  they depend on the following things:
- the type of generator (with or without condenser)
- temperature operating limits
- mode of production of ECS

A set of general rules apply to most installation. For example, you should interposition a bottle between the circuits of production and distribution, which facilitates all the settings and increases the accuracy of the water plan.

This type of arrangement:
- ensures a constant flow in generators and in the primary ECS balloons circuit
- ensures a better functioning of the control valve
- allows degassing at the output of generators
- allows sludge particles to settle in the heating circuits
- facilitates  flushing out  the production circuits

Design of the bottle

The rule is to choose a diameter of   a bottle smaller than 3 times the diameter of the largest pipe connected to it and minimize these connections so that there is turbulence and direct injections. To achieve efficient sludge hunting, it’s necessary that you install a gate valve with a large diameter (about 50 mm) at the bottom of the bottle.

When the number of circuits connecting the pipe to the bottle is inconsistent with the height of the boiler or the arrangement of connections does not adapt to the vertical arrangement of the bottle easily, you can install a "manifold" set.

In this case, degassing and settling is no longer possible, hence a collector and distributor with about twice the diameter of the water mains seems sufficient to avoid interference between the secondary circuits.

If you worry that there may be conditions for a reversed return (mixed operation), it’s preferable to have the bypass line at the other end of the connections to the primary collector and distributor. The secondary circuits which may be affected by a return are those located opposite to the bypass line. All circuits may be affected if the bypass line is connected to the primary circuit.

The expansion tank

The problems of water shortages experienced with heating systems  including a closed expansion vessel may be caused by improper sizing of the vessel (consider capacity and inflation pressure) or by overfilling the system.

Tank capacities suitable for the proper filling of the system are completely dependent on three variables, where it’s not possible to change one without taking into account the value of the other two.

Selection of the vase

There are two cases:

Case 1: a desk study calculated that the expansion system installer must have the following information: the capacity of the vessel, the inflation pressure of the vessel and the cold filling pressure.

Case 2: the installer has no calculations.

Many manufacturers have charts or tables for the selection of vases, generally based on the static height of the plant, the water volume and temperature. There is free software for Windows which allows you to make all these calculations.

Pumps

Pumps should be selected based on their characteristic curves as well as on those of the network. A flow control valve is installed whenever it’s necessary to adapt the characteristics of the pump to the mains. If the impeller is interchangeable, it’s advisable to select a pump that has an operating point thatis calculated as an intermediate gear diameter. If the pump has more adjustable speeds, it’s also advisable to select a pump that has an operating point  that is calculated at an intermediate speed. In the absence of valve flow measurements, it’s advisable to install both sides of the pump pressure taps in order to measure the total head.

It should be noted that some pumps have already taps. You can estimate the actual value of the flow in the circuit using the characteristic curves given by the manufacturer. Shutting down the valves on both sides of the pump is also required when replacing a pump or a wheel.

Pressure and flow sensors

Most generators, like low water capacity generators in particular, require a minimum flow and a sufficient static pressure in the exchangers to avoid evaporation. The risks of "water scarcity" are not to be neglected for the mini-boiler rooms located on the terrace or in the attic. It’s recommended to assemble these components in case the generators are not equipped with flow and pressure sensors from the very beginning.