Heating systems – Automatic control – Water
Reexamination Certificate
2001-06-25
2002-05-28
Joyce, Harold (Department: 3749)
Heating systems
Automatic control
Water
C236S100000
Reexamination Certificate
active
06394361
ABSTRACT:
The present invention relates to a device for balancing a liquid-based heat-transfer system for a heating system. Such a system is equipped with a boiler or the like for heating a fluid which is sent by way of pump means to heat emitters, such as radiators, by a network of liquid pipes. The device according to the invention also provides thermostatic regulation of a heat emitter.
The present invention also relates to liquid-based circuits using fan convectors. It is as suitable for heating circuits as for cold-water circuits used for the air-conditioning of rooms. The description that follows is essentially given with reference to heating circuits but it also applies to cooling technology using a cold-water circuit or a circuit of some other fluid.
In a heating system, in addition to the boiler, radiators and pipes, there are also regulating means whose function is to correctly distribute the heat-transfer fluid to the heat emitters and ensure that a sufficient flow is sent through each of them. The heating circuit is balanced in order for the system to run properly. This balancing operation involves regulating the various regulating means in such a way as to obtain flowrates which are worked out beforehand for base conditions selected to suit different parts of the system that are kept permanently on. Admittedly, a system will almost never be kept permanently on, but that in no way detracts from the value of balancing a circuit, because if the flowrates are caused to vary in the course of operation, this must be allowed for at the design stage and, if necessary, differential pressure regulators connected in series or in parallel must be provided. This however has to do with regulation rather than balancing of the system.
There are several balancing devices, also known as balancing means, which enable a heating system to be balanced. These means are designed to regulate the distribution of flows to the various branches of the distribution circuits.
First of all, unadjustable balancing means are known. These are apertures, that is to say fixed calibrated orifices whose diameter is determined for each of them from a knowledge of the desired relationship between flowrate and loss of head. The use of this type of means requires a complete and painstaking hydraulic calculation of all the circuits of the system in order to determine the precise characteristics of each aperture. If there is any mistake in the calculation, the only solution is to change the aperture. This solution, though seemingly relatively inexpensive, is therefore very rarely employed.
To avoid having to change the balancing means in the event of a computational error, there exist adjustable balancing means known as for example lockshield valves or thermostatic radiator valves. These means enable the flowrate through a circuit to be regulated and hence balanced on the basis of prior knowledge of the desired relationship between flowrate and loss of head. This requires a complete hydraulic calculation of the entire heating circuit. These adjustable balancing means enable the regulation to be corrected easily in the event of error.
These balancing devices are inexpensive and very widely used by installers. However, they are rarely adjusted as they should be, largely because the calculations are done insufficiently or not at all. Thus fitted with badly adjusted means, the system is therefore unbalanced.
Also known are adjustable balancing means equipped with a device for measuring the flow. These balancing means are generally equipped with a pressure takeoff designed to make a differential pressure measurement. This measurement can be used to determine the fluid flowrate through the balancing means. Using an electronic differential manometer with a microprocessor, measurements of differential pressure and of flowrate can be taken quickly and easily.
For the installer, this type of balancing means has a very appreciable advantage. The setting of the balancing means can be decided by calculation as with the adjustable balancing means described above, but the adjustment can also be carried out directly in situ based on a knowledge of the desired flowrate alone.
In practice, it is not enough, in most cases, to regulate each of the balancing means in succession in order to obtain the desired flowrates. This is because distribution networks are often prone to hydraulic interference. This phenomenon makes it necessary to carry out several adjustments on each of the balancing means, utilizing for example a method of successive approximations or carrying out a careful balancing procedure which can only be done properly if a work plan is prepared beforehand and carried out rigorously.
These adjustable balancing means with flowrate measuring device therefore enable the system to be balanced correctly provided the balancing procedure is adhered to rigorously. This method is reasonably complicated to carry out and installers would prefer a much simpler method.
Lastly, there are also flow regulators. Such a regulator, fitted at the head of a branch circuit, keeps the flowrate constant whatever pressure fluctuations are generated in the main circuit by the action of the terminal controls of the emitters served by the other branch circuits. Interference caused by the operation of the other branch circuits of the same system are thereby eliminated.
The use of these flow regulators as balancing means has however a major drawback. If the valves of the emitters served by the circuit equipped with a flow regulator decide to partly close themselves to a greater or lesser degree, thereby necessarily reducing the flowrate, the regulator will attempt to oppose this reduction by opening. The regulator therefore functions as an antagonist to hydraulic disturbances downstream of the regulator. The use of these flow regulators is therefore incompatible with, for example, the thermostatic radiator valves which are currently widely used.
Actually, this type of equipment has no direct relationship with the balancing of systems as defined above. The use of such a flow regulator can be regarded as a palliative to insufficient calculation by replacing a relatively simple static balancing means with a regulating unit containing moving parts, purely in order to avoid the initial regulating operation using one of the procedures indicated above. The use of these flow regulators is limited because, on the one hand, its field of application is restricted owing to incompatibility with thermostatic radiator valves, and on the other hand because it represents a greater investment cost than conventional solutions.
FIGS. 1 and 2
each show a circuit branched off from a heating system equipped with balancing means. In both of these figures, radiators
2
are supplied with heat-transfer fluid via pipes
4
.
FIG. 1
shows radiators
2
equipped with conventional valves while in
FIG. 2
the radiators
2
are equipped with integrated valves.
FIGS. 1 and 2
both show a main flow pipe
6
and a main return pipe
8
. The branch circuit is connected at a branch point
10
to the main flow pipe
6
and at a branch point
12
to the main return pipe
8
. Upstream of the branch point
10
supplying the branch circuit is a balancing valve
14
. Downstream of this branch point
10
there is generally an isolating valve
16
which plays no particular part in the balancing of the circuit. At the tail end of each branch circuit is another balancing valve
21
. The latter is adjustable and is used to adjust the loss of head of the branch circuit.
In
FIG. 1
, each radiator
2
is provided upstream of its supply with a thermostatic radiator valve
18
and upstream [sic] with a lockshield valve
20
. The thermostatic radiator valve
18
is for thermostatic regulation of the temperature of the room where the radiator
2
is installed, while the lockshield valve
20
is for balancing the system.
In
FIG. 2
, in the case of radiators
2
with integrated valves, a hydraulic module
22
supplies a radiator
2
and each radiator
2
is fitted with a thermostatic radiator va
Fridmann Pierre
Leger Jacky
Robin Jean Philippe
COMAP
Oliff & Berridg,e PLC
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