Method and device for feeding the various rooms of premises with ventilation air

This method consists in supplying the various rooms of the premises with air under stable low pressure using a relatively high-pressure fan, in feeding the fan, on the one hand, using fresh air, and, on the other hand, using recycled air, that is to say air that has been displaced by the fan and not let into the premises, and in regulating the respective proportions of fresh air and recycled air so that the proportion of fresh air increases and the proportion of recycled air decreases when the ventilation requirements increase, and so that the proportion of fresh air decreases and the proportion of recycled air increases when the ventilation requirements decrease, so that the delivery rate of the fan is kept almost constant. Application to systems for controlled mechanical ventilation of premises.

The subject of the present invention is a method and a device for feeding 
the various rooms of presses with ventilation air. 
BACKGROUND OF THE INVENTION 
It is known that the various rooms of premises, such as an apartment, have 
variable ventilation requirements, depending on their occupation by 
persons and depending on the conditions of their use. 
These requirements change with cycles which are not predictable and which 
may be very different from one apartment to another, or even from one room 
to another in the same apartment, or, for one and the same room, vary 
during the length of occupation of the apartment. 
There are various techniques for ventilating premises. 
The first technique consists in carrying out mechanical extraction at fixed 
flow rate in the technically designed rooms, with passive air inlets in 
the main rooms. 
A second technique consists in carrying out mechanical extraction in the 
technically designed rooms, slaved to a requirement in the technically 
designed rooms, with passive air inlets which may or may not be slaved in 
the main rooms. 
A third technique consists in carrying out double-flow ventilation, 
consisting in single mechanical extraction in the technically designed 
rooms and single blowing into the main rooms, the extraction and blowing 
being carried out with equal flow rates. 
The first and third solutions concern ventilation systems with fixed flow 
rates which are of little relevance to the requirement for variable flow 
rates which currently exists. 
The second solution has the advantage of slaving the ventilation to a 
requirement expressed in the technically designed rooms, insofar as the 
extraction is slaved, and in the main rooms insofar as the air inlets are 
slaved. 
However, the main defect of this latter technique is that it only varies 
the cross section of the air inlets and does not vary the actual flow rate 
into the rooms where they are installed. In fact, the flow rate passing 
through the main rooms is the same as that which is extracted mechanically 
from the technically designed rooms. The total flow rate extracted is 
distributed in proportion to the open areas on the outside of each room. 
The flow rate passing through these rooms therefore results from the 
relative opening cross section of the air inlets, but also from possible 
leaks from the apartment which are distributed randomly and upset correct 
operation of the whole. 
It should be noted that apartments are frequently encountered in which the 
parasitic leaks are equivalent to the maximum opening cross section of the 
air inlets. These leaks are highly problematic for the lowest flow rates 
because the air distribution of the extracted flow rate is no longer 
provided as a function of the air inlet cross sections but as a function 
of the air inlet cross sections plus the leaks. 
Similarly, if a window is open in a room, for example, essentially all the 
extracted flow rate comes from this room, and the other rooms, even if 
they have higher ventilation requirements, are little ventilated or poorly 
ventilated. 
It should also be borne in mind that it is not possible to define a mean 
value of the leaks from apartments over a large number of apartments, 
which prevents consideration of a stable pressure on either side of the 
air inlet. Moreover, it is this pressure which generates the flow rate 
through the passage cross section. 
Furthermore, the technique of natural air inlets does not allow very 
effective measures to be taken against outside noise, because of the head 
loss to which acoustic absorption devices in general lead. 
Finally, it is impossible to interpose an efficient filter, intended to 
capture dust or the like, between the outside and the inside of the house, 
because such a filter requires an operating pressure which is incompatible 
with the normal values in natural passage. 
SUMMARY OF THE INVENTION 
The object of the invention is to provide a device which ensures stability 
of the pressure of the air let into the various rooms of premises, 
independently of the random leaks of these premises, whatever the flow 
rate required in each of the main rooms, and whatever the outside 
conditions such as wind or temperature. 
A further object of the invention is to make it possible to filter the air 
let into the premises and, optionally, preheat it. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For this purpose, the method to which it relates consists in supplying the 
various rooms of the premises with air under stable low pressure using a 
relatively high-pressure fan, in feeding the fan, on the one hand, using 
fresh air, and, on the other hand, using recycled air, that is to say air 
that has been displaced by the fan and not let into the premises, and in 
regulating the respective proportions of fresh air and recycled air so 
that the proportion of fresh air increases and the proportion of recycled 
air decreases when the ventilation requirements increase, and so that the 
proportion of fresh air decreases and the proportion of recycled air 
increases when the ventilation requirements decrease, so that the delivery 
rate of the fan remains relatively constant. 
The stable low pressure is obtained by variable internal recycling on a fan 
working at substantially fixed flow rate and pressure (this pressure lying 
between 80 and 180 Pa), the fixed low pressure for distribution into the 
rooms of the premises lying between 5 and 40 Pa. 
According to one embodiment, this method consists in varying, 
simultaneously and in the opposite sense, the valve cross sections 
arranged on an intake opening for fresh air to the fan and on a pipe for 
recycling the air. 
Advantageously, this method consists in regulating the proportions of fresh 
air and recycled air by monitoring the difference in the pressures 
prevailing respectively upstream of the fan in a region subjected to the 
influences of the recycled air and of the fresh air, and downstream of the 
fan in a region located upstream of the pipes for feeding the various 
rooms of the premises with air. 
The cross sections of the valves arranged on the intake opening for fresh 
air to the fan and on the air recycling pipe vary simultaneously and in 
the opposite sense in order to increase or decrease the flow rate of fresh 
air and to decrease or increase the flow rate of recycled air while 
maintaining a fixed total flow rate. 
According to one possibility, the difference in the pressures upstream of 
the fan and upstream of the pipes for feeding the various rooms is defined 
with respect to a reference pressure. The proportions chosen are fixed and 
not variable. 
This reference pressure is obtained by mixing the pressures, respectively, 
of the fresh air outside the premises and of the air inside the premises. 
According to one possibility, the reference pressure is obtained by mixing 
from 0.5 to 0.15 times the pressure of the fresh air and from 0.5 to 0.85 
times the pressure of the air inside the premises. The proportions chosen 
are fixed and not variable. 
The pressure difference may be read periodically, given that it is not 
necessary to adjust the pressures continuously for use in ventilation, the 
variations in requirements of the main rooms being always fairly slow. 
In addition, it is possible to alter the setting only when several 
successive measurements give the same information, in order to avoid false 
measurements which can result from external influences such as gusts of 
wind, slamming doors or the like. 
According to another feature, this method consists in arranging head-loss 
elements upstream and downstream of the fan in order to obtain balanced 
pressures at the fan and to lower the pressure of the air supplied to the 
pipes for feeding the rooms of the premises, with respect to the pressure 
supplied by the fan. 
This makes it possible, although using a fan operating at a relatively high 
pressure, to provide a low-pressure supply to the rooms of the premises to 
be ventilated, which increases comfort by, in particular, limiting noise. 
Thus, it is possible to create two compartments on either side of the fan, 
in which the pressure will be at an intermediate value, for example 30%, 
50% or 70% of the total pressure of the fan. 
A device for implementing this method comprises an enclosure having a fresh 
air inlet pipe communicating with the outside and equipped with a valve, 
and air outlet ducts connected to the pipes for feeding the premises with 
air, this enclosure being equipped with a fan, and with a recycling pipe 
which, returning a portion of the air from the region including the outlet 
ducts to the region including the fresh air inlet, is fitted with a 
regulating valve whose cross section is actuated in synchronism and in the 
opposite sense to the fresh air inlet valve, while keeping the flow rate 
supplied to the fan constant. 
In addition, two chambers are made upstream and downstream of the fan, the 
one arranged upstream being bounded by a filter and the one arranged 
downstream being bounded by a cross section reduction generating 
substantially the same head loss as the filter. 
Advantageously, in order to balance the pressures upstream and downstream 
of the fan, the cross section reducer element placed downstream of the 
filter has a cross section equal to the equivalent cross section of the 
filter when clean, less half the equivalent cross section variation of the 
filter during clogging. 
According to one possibility, the filter is a winding filter, the 
replenishment movement of which is triggered by the exceeding of a defined 
difference between the relative pressures (P.sub.i -P.sub.2) and (P.sub.3 
-P.sub.i) prevailing immediately upstream and downstream of the fan. 
According to one embodiment of this device, the valves located on the fresh 
air inlet and in the recycling pipe consist of a single valve in the form 
of a three-way mixer valve.

FIG. 1 represents a device comprising a main enclosure 2, in one wall of 
which an opening 3 is made which is equipped with an air inlet valve 4. 
The outside air is at the pressure Pe, and the opening 3 and the valve 4 
define a passage SO. 
In another wall of the enclosure 2, ducts 5 for connection to the pipes for 
feeding air to premises emerge. These ducts corresponding to an overall 
cross section S3 distributed, in this case, in four cross sections S3.1, 
S3.2, S3.3 and S3.4. 
Inside the main enclosure 2 there is a smaller enclosure 6, whose end face 
located on the side of the inlet opening 3 is closed by a filter 7 
corresponding to a passage cross section S1, and whose other end is 
equipped with an opening 8 of reduced cross section, corresponding to a 
passage cross section S2. A fan 9 is mounted in the middle of this 
enclosure 6 which it divides into two compartments. 
This is a relatively high-pressure fan, from 100 to 200 Pa, the 
pressure/flow rate operating curve of which does not require a large 
plateau because the flow rate of the fan is kept substantially constant. 
Between the enclosure 6 and the enclosure 2, a pipe 12 is made for 
recycling the air leaving the enclosure 6 back to its inlet. A recycling 
valve 13 providing a passage cross section S4 is mounted on this recycling 
pipe 12. 
In operation, there will be a pressure P2 in the enclosure 6 upstream of 
the fan 9, P3 in the enclosure 6 downstream of the fan 9, P4 in the 
enclosure 2 on the side of the pipes for feeding air to the premises, and 
P1 on the side of the air inlet 3. A pressure Pi prevails inside the 
premises. 
Using a device 14 which is not described in detail here, the difference 
between the pressures P4 and P1 is measured with comparison to a reference 
pressure which is defined on the basis of the pressures Pe and Pi. For 
example: 
EQU -P ref=A Pe+B Pi 
where A lies between 0.5 and 0.15, 
and B lies between 0.5 and 0.85. 
The device 14 acts on the valves 4 and 13 so as to close one when it opens 
the other, in a constant proportion in order to increase or decrease the 
flow rate of fresh air and to decrease or increase the flow rate of 
recycled air, while maintaining a fixed total flow rate. 
The ventilation requirement of the premises is expressed by the cross 
section S3. When S3 varies, S0 is to vary so that the air leaving the 
enclosure to enter the rooms of the premises is replaced by outside air. 
If S3 increases, this results in a fall in P4 and a slight fall in P1, due 
to a slight increase in the pressure reduction. An imbalance between P1 
and P4 is produced and detected by the device 14. 
The valve 4 is then opened to increase S0 by a preset quantity 
corresponding to an increment step, and the valve 13 is closed by the same 
step. If the imbalance remains on the following reading, the valve 4 is 
opened by a further step and the valve 13 is closed by a further step. 
When the equilibrium defined between the pressures P1 and P4 is again 
achieved, the valves remain in the state in which they are. 
If the ventilation requirement falls in the rooms, S3 decreases and this 
results in an increase in P4 and a slight increase in P1 due to a slight 
fall in the pressure reduction. An imbalance is then produced between the 
pressures P1 and P4 in the opposite sense to the preceding case. This 
imbalance, detected by the device 14, leads to opening of the valve 13, 
increase in S4 and closure of the valve 4, decrease in S0. 
The combined use of the interior pressure and the exterior pressure for 
obtaining the reference pressure for measuring the imbalance between P1 
and P4 makes it possible to weight the pressure variations due, for 
example, to the wind, or to the switching on of auxiliary ventilation such 
as a cooker hood. The weighting referred to above makes it possible to 
minimize these external phenomena. 
Another advantage of the invention is that it uses a fan 9 with high 
operating pressure, which makes it possible to combine with the device an 
efficient filter 7 for the air entering the apartment. It is, in 
particular, possible to filter out any pollen and trap a large proportion 
of the dust normally present in the air in urban or industrial areas. 
The filtering device is placed upstream of the fan in order to protect the 
mechanical or air-treatment members. 
The efficiency of the filtering is enhanced by the recycling principle. In 
fact, since the valve 13 is generally at least partly open, a proportion 
of the air which is blown in passes over the filter several times, so that 
it is already purified during its first passage. 
When an apartment is little occupied, the ventilation requirement 
decreases, and the internal recycling of the air increases. In 
consequence, the air blown into the apartment when it is unoccupied is 
very clean and the filter clogs up slowly. 
This method and this device also have the advantage of allowing good 
insulation of the premises with regard to outside noise. It is, in fact, 
possible to interpose a baffle between the fresh air intake which may be 
placed on a front which is exposed to little noise and the blowing in 
enclosure. 
It is possible to have efficient acoustic absorption because of the 
localized treatment of the air, which is no longer distributed over each 
air inlet, and of the presence of the fan which makes it possible to 
combat the head loss inherent in an acoustic absorption device. 
It is also possible to treat the air thermally inside the premises, in 
particular by heating the recycling air, or by passing it over a cold body 
without having to resort to excessively complex systems. 
FIG. 2 shows a variant of the device in FIG. 1, in which the valves 4 and 
13 have been combined into a single pivoting valve 16 which opens the 
cross section S0 of the inlet 3 when it decreases the cross section S4 of 
the pipe 12, and vice versa. 
The cross section S2 of the opening 8 makes it possible to maintain the 
operating position of the fan 9 as the filter clogs up. S2 is chosen with 
respect to the head loss of the filter and its predicted change over time. 
When the filter is clean, it is S2 which constitutes the main head loss. 
The more the filter 7 clogs up, and the more its equivalent cross section 
S1 decreases, its head loss increasing progressively to outweigh S2. 
This change is detected by means 14' (not described) for monitoring the 
pressures P2 and P3, which means make it possible to generate either a 
signal for warning of a clogged filter, or replenishment of the filter if 
the enclosure is equipped with a filter with automatic replenishing 
system. 
As indicated above, the cross section S2 may be chosen to be equal to the 
equivalent cross section of the filter halfway through its lifetime. 
The relatively high operating point of the fan and the presence of the 
head-loss elements S1 and S2 make it possible to have pressures P2 and P3 
which are not negligible and close to each other in absolute value. P2 is 
a reduced pressure with respect to the reference pressure, while P3 is an 
overpressure. 
FIG. 3 represents a device according to the invention in the case of 
implementing a filter 17 with automatic winding. The device comprises, in 
this case, an all-or-nothing distributor 18 capable of sending either the 
pressure P2 or the pressure P3 into two bags 19 and 20. The two bags 19 
and 20 bear, on the one hand, on a fixed wall and, on the other hand, on a 
mobile wall, 22 and 23 respectively, the walls 22 and 23 acting via two 
connecting rods, 24 and 25, respectively, on a disk which drives, via a 
freewheel mechanism 26, a cable 27 for winding the filter. 
The two bags are also subjected to the action of springs, 28 and 29 
respectively, which tend to oppose their inflation. When the pressure sent 
into the bag 19 is P2, the spring 28 exerts a force which tends to deflate 
this bag. If, on the other hand, it is the pressure P3 which is sent into 
this bag, the force exerted by the spring 28 is more than compensated for 
by the force developed by the pressure difference between the ambient 
pressure P2 and the internal pressure P3. 
Inflation of the bag 19 leads to displacement of the connecting rod 24 
upwards, which, via the freewheel 26, drives the cable 27 and consequently 
the filter 17. Similarly, when a pressure P2 is sent into the bag 20, the 
pressure difference between the interior and exterior allows deflation of 
the bag, while pressure equilibrium in and around the bag inflates it by 
the action of the spring 29. 
The distributor 18 controlled by a deformable-wall capsule makes it 
possible to change the pressure sent into the bags 19 and 20 alternately 
from P2 to P3. The resulting movement of the mobile plates 22 and 23 is 
transmitted by the connecting rods 24 and 25 to the freewheel 26 which 
drives the filter 17. 
Given that this movement is controlled by the pressures P2 and P3, it is 
necessary to replace the filter only when it is dirty. 
As explained above, the invention provides a great improvement to the state 
of the art, by providing a device of simple design which makes it possible 
to stabilize the pressure of feeding air to the rooms of premises while 
providing other functions such as filtering this air, acoustic damping 
and, optionally, thermal treatment of the air.