EP0856136A1

EP0856136A1 - Ventilation system

Info

Publication number: EP0856136A1
Application number: EP96935013A
Authority: EP
Inventors: Howard Atkin; Chris Palmer
Original assignee: Advanced Design and Manufacture Ltd
Current assignee: Advanced Design and Manufacture Ltd
Priority date: 1995-10-21
Filing date: 1996-10-16
Publication date: 1998-08-05
Also published as: AU7311796A; GB9521632D0; WO1997015793A1

Abstract

The climate control system comprises a ventilator (1) controlled by control means (9), and a switch (30) connected to the ventilator system (31) in such a way that the ventilator system may work at either a high speed or a low speed. The ventilator will run at a low speed if the room to be ventilated is occupied, and at a high speed if the room to be ventilated is unoccupied.

Description

VENTILATION SYSTEM

This invention relates to a ventilation system and particularly, but not exclusively, to a ventilation system for use in controlling the humidity in a domestic environment, particularly in bedrooms. The invention also relates to a ventilation system combined with a filtration system and/or a de-humidifier, and to each of these systems separately.

Buildings of all types, even when adequately heated, commonly suffer from the effects of condensation and fungal growth, the source of which can be seriously detrimental to the health of the occupants .

Every day activities such as cooking, washing, drying clothes, bathing and even breathing, significantly increase the levels of humidity within a dwelling. Calculations suggest that in a four person household, up to ten litres of moisture per day may be produced. This amount may easily rise to a daily total of 18 litres.

The moist air becomes trapped within a building through the common use of modern insulation techniques, double glazing and draft stripping. Although this increases the thermal efficiency of the building, it allows little or no natural ventilation.

These conditions lead to the occurrence of condensation on colder surfaces which damages internal decorations, attacks the fabric of the building itself, and produces a generally unhealthy environment.

The occurrence of respiratory problems and asthma appears to be increasing over recent years . Asthma seems to be generated almost exclusively in temperature bands north and south of the equator where humidity levels are at a certain level. In addition, in these areas, buildings lack ventilation as people improve the sealing of windows, doors etc to conserve energy. It is believed that asthma is caused by raised humidity levels and has increased due to reduced natural ventilation in domestic houses as explained hereinabove.

In a typical bedroom, especially with the door and windows closed, the humidity level increases over night. A typical male might sweat about 1 litre of liquid per night, part of which is absorbed into the atmosphere, and part of which is absorbed by the bed sheets.

It is a well known medical phenomenon that dust mites consume shredded skin flakes. It is however believed that skin flakes are only digestible by the mites when they have on them a fungal growth such as aspergil. The fungus can attach itself to the skin flakes only in appropriate conditions of humidity. Once the mites can digest the skin flakes, they multiply at extraordinary rates and mite faeces are then deposited on bed sheets, pillow cases etc. It is believed that this is the material which enters the lungs and is a direct cause of asthma.

As mentioned hereinabove, it is believed that the humidity levels generally found in temperate zones coupled with the improved sealing of windows etc to conserve energy produces appropriate humidity levels for producing high rates of fungal growth on skin flakes. This theory is reinforced by the fact that the incident of asthma appears to be increasing in the more technically and economically sophisticated tropical and sub-tropical regions of the world where air conditioning units are installed. For example, asthma is now becoming a problem in Israel where it never was previously.

Known air conditioning units and "closed loop" cooling systems do not promote ventilation. In other words such known systems do not allow communication to and from the external atmosphere. This means that an air conditioning unit without ventilation could simulate a typical temperate zone environment thus allowing rapid reproduction of dust mites which in turn increases the incidence of asthma.

There is presently great interest in combatting asthma suffering without having to use drugs. There are known schemes such as a sophisticated vacuum cleaning systems which remove mites, or more particularly mites faeces from bed linen etc. However such systems provide only short term remedies, and are extremely expensive, typical costs being in the region of £2000 for a whole house operation.

According to a first aspect of the present invention there is provided a method of controlling the relative humidity in a room comprising the steps of: ventilating a room substantially continuously using a ventilator; controlling the rate of ventilation such that the rate of ventilation is lower when the room is occupied.

According to a second aspect of the present invention there is provided a climate control system for controlling the relative humidity in a room the system comprising: a ventilator; control means for controlling the ventilation rate of the ventilator whereby ventilation rate is lower when the room is occupied.

Any suitable ventilator may be used in the climate control system, but preferably the ventilator is a heat recovery ventilator .

Although the invention has been described in terms of a method and system for controlling relative humidity in a room, it is intended that the invention is equally applicable to any substantially confined area, for example, domestic rooms such as bedrooms, kitchens, bathrooms, and also to a whole house comprising a number of rooms. The invention provides a balanced ventilation system which provides continuous control of moisture levels and a supply of fresh filtered air to the room or area being ventilated.

Advantageously, the heat recovery ventilator is of the type described in UK patent publication number 2224111 the contents of which are incorporated herein by reference.

Advantageously, the system has a relatively low power requirement, for example, about 15 watts.

Conveniently the control system is operable at a plurality of different ventilation rates.

Preferably, the system is operable at two different ventilation rates .

Advantageously, the lower ventilation rate occurs when the room is occupied. When the system is used in a bedroom, the lower rate of operation will occur during the night when the occupants are asleep.

The ventilator will operate at the higher rate when the room is unoccupied. When the system is used in a bedroom the ventilator will operate at a higher rate during the day. This means that typically the ventilator will operate for perhaps two thirds of the day at a higher rate and perhaps one third of the day at a lower overnight rate.

Known systems operate in the opposite sense, namely the ventilator or air conditioning unit will run at a higher rate, during room occupancy than when the room is empty. However, this causes more noise at a time when it is least wanted, ie when the room is occupied.

The present invention operates in an opposite sense and has higher output operation during non-occupancy and lower output operation during room occupancy.

Typically, venting of the room is achieved throughout a 24 hour period whilst the windows of the room remain closed.

By means of the present invention therefore the relative humidity level of a room is lowered, the ventilation is improved and in addition the system is thermally efficient because heat is transferred from the spent air to the incoming fresh air.

Preferably, the control means comprises a trigger, for example, an infra-red sensor which may detect when the room is occupied. The control means thus causes the system to switch to a lower ventilation rate when the sensor senses that the room is occupied.

Alternatively, the control means comprises a timer which will cause a switch to trigger the system to operate at a lower rate say, for example, at 10pm when the occupants of the house will be retiring, and then will trigger the system to work at the faster rate, for example, at 7am the next morning when the occupants may be getting up.

The invention will now be further described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic representation of a ventilator used in the method of the first aspect of the present invention, and forming part of the climate control system of the second aspect of the present invention;

Figure 2 is a schematic representation of the ventilator of Figure 1 installed in the wall of a building;

Figure 3 is a schematic representation of a basic switch suitable for use in the control means of the present invention; and

Figure 4 is a schematic representation of a second embodiment of a switch suitable for use as the control means forming part of the present invention.

Referring to Figures 1 and 2 a ventilator of the type suitable for use in the climate control system of the present invention is designated generally by the reference numeral 1. The ventilator comprises a heat exchanger 2, a fan/motor unit 3. Supply air typically from outside the building enters the ventilator at 4. The supply air is drawn through the ventilator by means of the fan 3 and exits the ventilator at 5 where it enters the room in which it is installed. Stale air from the room enters the ventilator at 6 and is drawn through the ventilator 1 to exit at 7 into the outside air.

The ventilator 1 is installed in an external wall 8 of a room in which the climate is to be controlled. The ventilator 1 further comprises control means 9 for controlling the ventilator such that it operates at a higher rate when the room is not occupied.

The ventilator 1 serves to provide fresh pre-warmed air from outside continually to the room in which the climate is to be controlled whilst simultaneously extracting stale moist air from the room. Heat is transferred from the outgoing air via the heat exchanger to the fresh air supply maintaining internal temperatures and providing a fresh environment.

Referring to Figure 3 a switch suitable for use in the control means 9 is shown in more detail. The switch 30 is connected to the ventilator system 31 in such a way that the ventilator system may work at either a high speed or a low speed. The ventilator system 31 comprises a fan heat recovery unit 32, a de-humidifier 33 and a high efficiency filter fan 34. The switch comprises a live connection 35 and a neutral connection 36. Connection to point 37 will result in the ventilator system 31 operating at a low speed and connection to point 38 will result in the ventilator system operating at a high speed.

Referring to Figure 4 a more sophisticated switch suitable for use in the control means 9 is shown schematically. The switch system is designated generally by the reference numeral 40 and comprises three switches 41, 42, and 43.

The switch system 40 comprises a ten year clock which controls switch 41 and which may be programmed with switch on times for up to ten years. The switch system 40 would further include a back up memory. Such a control system can allow for weekend settings and can even account for leap years. It may be used alone or with switches 42, 43. The switch 41 has two main settings, one connected to point 44 which is the night time setting and the second connected to point 45 which is the day time setting.

Switch 42 is controlled by a humidity sensor (not shown) which senses room humidity levels. The switch has two settings and when connected to point 46 presents acceptable humidity and to point 47 represents high humidity, ie relative humidity above the set point. The switch 42 can be used alone with other switches 41, 43. It will inhibit operation of the ventilator during day time or occupied time if it senses that there is low or normal humidity, and will cause the ventilator system to switch to high speed only when high humidity is sensed.

The humidity sensor typically comprises a thin polymer film the electric resistance of which changes with humidity. An electronic circuit amplifies these minute changes so that at a given point, say 70% relative humidity, the humidity sensor will switch a relay.

In the present ventilation system, the relay opens the high speed circuit and at the same time closes the low speed circui t .

The set point can be tested from anything between 40% relative humidity to 90% relative humidity, for example.

Switch 43 is controlled by a second timer or passive infra red switch or air quality sensor. It can be used with other switches and sensors or on its own. The timer will allow variations in occupied or unoccupied running periods during day time running. The passive infra red sensor will switch to the low speed if the ventilator unit detects that people are in the room. The air quality sensor will cause the system to switch to high rates or low rates during the day time depending upon internal conditions.

Claims

C AIMS

1. A climate control system for controlling the relative humidity in a room, the system comprising: a ventilator; control means for controlling the ventilation rate of the ventilator whereby the ventilation rate is lower when the room is occupied.

2. A climate control system as claimed in claim 1 wherein the ventilator is a heat recovery ventilator.

3. A climate control system as claimed in claim 1 or claim 2 having a low power requirement.

4. A climate control system as claimed in any one of the preceding claims which system is operable at a plurality of different ventilation rates.

5. A climate control system as claimed in claim 4 having two different ventilation rates.

6. A climate control system as claimed in claim 5 adapted to operate at the lower ventilation rate when the room to be ventilated is occupied.

7. A climate control system as claimed in claim 5 or claim 6 wherein the higher ventilation rate operates when the room is empty .

8. A climate control system as claimed in any one of the preceding claims wherein the control means comprises a trigger for triggering the system to switch to a lower ventilation rate when the room is occupied.

9. A climate control system as claimed in any one of the claims 1 to 7 wherein the control means comprises a timer.

10. A method of controlling the relative humidity in a room comprising the steps of: ventilating a room substantially continuously using a ventilator; controlling the rate of ventilation such that the rate of ventilation is lower when the room is occupied.