ZA201000929B

ZA201000929B - Control system for an electrical load such as a geyser

Info

Publication number: ZA201000929B
Application number: ZA2010/00929A
Authority: ZA
Inventors: Marthinus Becker Carl; Parnell Claude
Original assignee: Marthinus Becker Carl
Priority date: 2008-11-07
Filing date: 2010-02-08
Publication date: 2011-06-29

Description

° 20 ls 4

Hill : 10700929

Background to the invention

This invention relates to a means of controlling electrical power consumption or electrical load.

In this specification, the terms “mains” or “mains electrical supply” refer to any electrical power derived from a source external to the electrical load being powered, a typical example being the general-purpose alternating current (AC) electric power normally supplied by electricity utilities, the terms including, in their scope, such commonly used synonymous terms as household power, household electricity, domestic power, wall power, line power, AC power, city power and grid power. The electrical load may be constituted by any electrical installation or appliance connected to the mains supply.

This invention provides a relatively inexpensive, easy to install system to control the electrical loads constituted by electrical appliances and installations, whether domestic, commercial or industrial, which consume large amounts of electricity, but

¢ T2010/0 0920 which can be switched off periodically without causing any real inconvenience.

Examples of such loads include water heaters, such as hot water geysers (domestic or otherwise), underfloor space heating, water pumps, swimming pool pumps, air conditioners and even area lighting.

In most countries electricity use for domestic purposes peaks twice a day. The first peak occurs in the morning from early- to mid-morning (typically from around 07:00 to 10:00), while in the afternoons electrical demand peaks between late afternoon to early evening (typically from around 18:00 to 21:00). It is during these so-called peak load periods that the greatest stress is placed on the electrical power supply grid and that power outages are most likely to occur and it is understandable that utilities are desirous of reducing electrical demand in these peak load periods.

Recent research has shown that the controllable electrical load of most households consists mainly of water heaters (hot water cylinders and geysers), pool pumps and underfloor heating. It has also been shown conclusively that the supply to these appliances can he interrupted to reduce the overall electrical load without inconveniencing the customer, particularly during peak load periods.

In the case of water heaters, the thermal capacity of the water in the water heater permits the interruption of power supply to these appliances for extended periods of time as long as a so-called “comfort” feed of an hour or two is applied intermittently to reheat the water in the water heater. As a result, many suppliers and distributors of electricity control the hot water load of individual customers. Most often this is achieved by installing radio frequency (RF) and power line communications (PLC) controllers or combination RF/PLC systems. Another common hot water load control technology is ripple control, in which so-called “ripple relays” allow the electricity supplier to disconnect geysers during high power demand periods.

The disadvantage of these control technologies and ripple controls in particular, lies in the communications infrastructure required to transfer the controlling signals.

This invention proposes, as an alternative, a simple locally installable control system that does not require expensive communications equipment.

Summary of the invention

According to this invention a control system for an electrical load connected to mains electrical power supply comprises: a control circuit including a programmable logic device and a real time clock; a switch adapted for connection to the mains supply in circuit on the mains supply between the control circuit and the electrical load; the programmable logic device being programmed: if mains power is switched OFF, to operate the switch to disconnect the mains supply from the load; and when mains power is thereafter switched ON again, to operate the switch to reconnect the mains supply to the load upon the passage of a predetermined period of time as determined by means of the real time clock and, in addition or in the alternative, to operate the switch to reconnect the mains supply to the load upon the occurrence of a pre-programmed event occurring in the operating environment of the control system.

The control system may conveniently be fitted with a user override switch by means of which an individual power user may override the control system, the programmable logic device being programmed to read the actuation of the override switch as a pre-programmed event and to operate the switch to reconnect the mains supply to the load.

In this embodiment of the invention, the programmable logic device may be programmed, on actuation of the override switch, to reconnect the mains supply to the load for a predetermined period of time and then to disconnect the mains supply from the load. In this way the user, by actuating the override switch, is able to switch an appliance that has been disconnected by the control system back on, even if only for a predetermined time.

. ® B2010/00500

This embodiment of the invention finds application as a pool pump control system and the invention therefore includes such a pool pump control system by means of which an electricity supply manager (such as an electricity supply utility or a building or estate manager) can load shed (in a controlled manner) a plurality of pool pumps in an area (each fitted with the control system of the invention), with the users in the area being given the option of reconnecting to mains if required, such as when pool maintenance is being carried out during such a controlled load shedding period.

The use of the control system of the invention to load shed an area will be referred to in this specification as “controlled load shedding”.

One or more further pre-programmed events may be included in the control circuit programming, the event or events being constituted by one or more changes in state in the operating environment of the control system, the system including one or more appropriate sensors interfaced with the control circuit and adapted to sense one or more changes in state in the operating environment and to convert the sensed change in state to a corresponding programmable logic device input.

In a preferred form of this embodiment of the invention, the system may conveniently include one or more passive infrared sensors configured as motion detectors adapted to sense human or animal motion (as a change in state in the operating environment of the control system) and to convert sensed motion into a programmable logic device input corresponding to a pre-programmed event adapted to trigger the programmable logic device to operate the switch to reconnect the mains supply.

This embodiment of the invention of the invention finds application in controlled load shedding of the load constituted by water heaters or geysers in an area. In such an application, the control system will be fitted to all the geysers in the area and programmable logic device in each is then programmed to switch off all the geysers in the area for controlled load shedding purposes and to permit a user motion signal derived from motion sensed by a motion detector, during predetermined times (normally non-peak load times) to switch the geyser back on for a predetermined time.

ot Co iss :

The programmable logic device is preferably programmed to use time and other sensed events in combination to control the application of mains power to the load.

Examples of such programming are given in the detailed description below.

The control system may combine the above and other parameters to provide a controlled load shedding mechanism by means of which an electricity supply manager can load shed an area by disconnecting specified electrical loads in the area remotely whilst nevertheless giving individual power users a degree of control over their individual electricity supply. To do this, the electricity supply manager simply switches the mains OFF, as is done in current load shedding practice (which is referred to in this specification as “general load shedding”). Instead of removing mains power for hours however, as is done in current practice, the electricity supply manager disconnects the mains for minutes instead of hours, knowing that a large component of the load (in the above mentioned example, all the geysers and pool pumps in the area) will be disconnected from the mains for a predetermined period by the control systems installed in the area. The controlled load shedding power

OFF period is limited only by the minimum disconnect time parameters determined by the electricity supply utility for the area.

The invention includes a method of controlling an electrical load substantially as described in this specification.

Brief description of the drawings

The invention will be further described with reference to the accompanying drawings in which:

Figure 1 is a block diagram of a pool pump control system according to the invention; and

Figure 2 is a block diagram of a geyser control system according to the invention.

Description of embodiments of the invention

This invention provides a relatively inexpensive, easy to install system to control the electrical loads constituted by electrical appliances and installations, whether domestic, commercial or industrial, which consume large amounts of electricity, but which can be switched off periodically without causing any real inconvenience.

The description that follows describes a pool pump (Figure 1) and a geyser (Figure 2) controller as examples of the invention. It will be appreciated that this is done purely for illustrative purposes and it is not intended to limit the invention to such applications.

Figure 1 illustrates a control system 10 for an electrical load constituted by a swimming pool pump 12 connected to a mains electrical power supply 14. The control system 10 comprises a control circuit 16, 18 and a switch consisting of a relay connected to the mains supply 14 in series with the pump 12. The relay 20 is located on the mains supply between the control circuit 16, 18 and the pump 12. The control circuit is made up of a transformer and a mains power supply unit 16 and a programmable logic device in the form of a programmable integrated circuit (IC) and its associated circuitry (the IC electronics is generally annotated 18). The IC electronics 18 includes a real-time clock (not shown).

In any situation in which the mains is switched OFF, the IC 18 is programmed (either when the mains is first dropped or when mains power comes back ON) to operate the relay 20 to disconnect the mains 14 from the pool pump 12. In this way, even when mains power 14 is switched back ON (after a short general load shedding period for instance), the IC electronics 18 is reconnected to the mains 14, but the pool pump 12 remains OFF, with the amount of time allowed between the IC 18 disconnecting and reconnecting the pool pump 12 determined by the electricity supply manager for the area. This OFF period will normally be calculated in hours and constitutes a controlled load shedding period. Switching the mains OFF, in effect switches the control system 10 to a controlled load shedding state in which it remains for the duration of the controlled load shedding period. The IC 18 is programmed to operate the relay 20 to reconnect the mains 14 to the pool pump 12 coy 8% automatically once the load shedding period Is over, as determined by means of the real time clock. The IC 18 in all or some of the pumps 12 in an area could be programmed with slightly different controlled load shedding periods thereby to reduce the system-wide startup load that might arise from a large number of pool pumps in an area switching ON simultaneously.

The control system 10 preferably includes a timer 22 that makes use of the real time clock and that provides the user with switches (such as jumper shunts, for instance), to set user- or installer selectable ON and OFF cycle times. The timer 22 allows the user to select, for example a 16, 12, 8 or 4 hour operating cycle per 16-hour period roughly coinciding with the daylight period in the area. The control system 10 is programmed such that user settings are subservient to the controlled load shedding functions of the control system 10.

The control system 10 is housed in a pair of housings 30, 32. The transformer and mains power supply unit 16 are housed in a first housing 30 together with the relay 20. The IC 18 electronics 18 are housed in a second housing 32. The first housing can be connected into the electrical system in close proximity to the pool pump 12 or in or near a switchboard controlling the mains supply 14 to the pool pump 12. The second housing 32 is adapted for location in close proximity to the pool pump 12 and includes one or more light emitting diodes (LEDs) 28 that are adapted to give an indication of the status of the control system 10. The second housing circuitry simply connects to the circuitry housed in the first housing 30.

The second housing 32 includes a control system override switch 24. At any point in time the user has the option of pressing the override switch 24, which will send an override signal to the IC electronics 118 which interprets the signal as a predetermined event and therefore operates the relay 20 to reconnect the mains 14 to the pool pump 12. This turns the pool pump 12 ON for a pre-programmed, relatively short period (for instance one hour) without reference to the controlled load shedding state of the control system 10.

It will be appreciated that the use of a programmable IC 18 permits of a large number of switching permutations whether time-based or whether switched by manual

0 o "2010700929 intervention of any one or more of an electricity supply utility, some other electricity supply manager or the user.

Figure 2 illustrates a control system 110 for controlling a geyser 112 (which substitutes for the electrical load constituted by the pool pump 12 of Figure 1). In

Figure 2, system components similar to those in Figure 1 are given similar numbering, but with a “100’s” prefix.

The control system 110 of Figure 2 controls an electrical load constituted by a geyser 112 connected to a mains electrical power supply 114. The control system 110 comprises a control circuit 116, 118 and a switch consisting of a relay 120 connected to the mains supply 114 in series with the thermostat of the geyser 112. The relay 120 is located on the mains supply between the control circuit 116, 118 and the geyser 112. The control circuit is made up of a transformer, a mains power supply unit 116 and a programmable IC and associated circuitry (generally annotated 118) with a real-time clock (not shown).

In any situation in which the mains 114 is switched OFF, the IC 118 is programmed (either when the mains is dropped or when mains power comes back ON) to operate the relay 120 to disconnect the mains 114 from the geyser 112. When mains power 114 is switched back ON (after a short general load shedding period for instance), the IC 118 electronics 118 is reconnected to the mains 114, but the geyser 112 remains OFF. The IC 118 is programmed to operate the relay 120 to reconnect the mains 114 to the geyser 112 after the passage of a predetermined period of time as determined by means of the real time clock. The amount of time allowed between disconnecting and reconnecting the geyser 112 is determined by the electricity supply manager. This OFF period of several hours constitutes the controlled load shedding period and in this state the control system 110 is in controlled load shedding state. The ICs 118 in all or some of the geysers 112 in an area could be programmed with slightly different controlled load shedding periods.

To permit the control system 110 to monitor changes in the state of the system operating environment, the system 110 is provided with one or more environment sensors interfaced with the control circuit 116, 118, the sensors being adapted to fray monitor and sense changes in state of one or more operating system environment parameters and to convert the sensed change in state to a corresponding programmable logic device input. In a relatively simple form of this embodiment of the invention, the control system 110 includes at least one passive infrared sensor (PIR) 126 configured as a motion detector that is adapted to sense human or animal motion (as a change in state in the operating environment of the control system 110) and to convert the sensed motion signal into a programmable logic device input signal.

The control system 110 is housed in a pair of housings 130, 132. The transformer and mains power supply unit 116 are housed in a first housing 130 together with the relay 20. The IC electronics 118 are housed in a second housing 132, which may conveniently also house the PIR 126. The first housing 130 can be connected into the electrical system in close proximity to the geyser 112 or in or near a switchboard controlling the mains supply 114 to the geyser 112. The second housing 132 is adapted for location, by ceiling- or wall mounting, in an area of frequent user activity and includes one or more light emitting diodes (LEDs) 128 that are adapted to give an indication of the status of the control system 110. The second housing circuitry simply connects to the circuitry housed in the first housing 130. The second housing 132 includes a control system override switch 124. At any point in time the user has the option of pressing the override switch 124, which will ensure the geyser 112 is turned ON for a predetermined (relatively short) period, depending on the then current controlled load shedding state of the control system 110.

The following is an example of IC programming in a control system 110:

Peak load state

The IC 118 switches the control system 110 to the peak load state during predetermined, pre-programmed peak load periods — typically two periods of.2 hours each — the first peak load period extends (for instance) from early morning to mid- morning and the second peak load period extends (for instance) from late afternoon to early evening and in the peak load state: ¢ switching OFF and ON is determined with reference to the real time clock

EE Co) . ® “010700999 o at the pre-programmed commencement of a peak load period, as determined with reference to the real time clock, the IC 118 operates the relay 120 to disconnect the mains 114 from the geyser 112 » at the pre-programmed end of a peak load period, as determined with reference to the real time clock, the IC 118 operates the relay 120 to reconnect the mains 114 to the geyser 112 e signals from the PIR 126 are not taken into account — the PIR 126 will not switch the geyser 112 ON even if motion is detected o signals from the override switch 124 are taken into account — the IC 118 is programmed, on receipt of an override switch 124 signal, to operate the relay 120 to reconnect the geyser 112 to the mains 114, thereby switching the geyser 112

ON — the IC 118 is programmed to operate the relay 120 to switch the geyser 112

OFF after a relatively short period — typically 1 hour

Controlled load shedding state

The IC 118 switches the control system 110 to the controlled load shedding state as a result of externally applied (not pre-programmed) load shedding signals constituted by (normally quite short) general load shedding periods and in the controlled load shedding state: e switching OFF Is determined by the electricity supply manager and switching ON is determined with reference to the real time clock and signals from the PIR 126 ¢ load switching OFF is determined by the electricity supply manager — the IC 118 is programmed to operate the relay 120 to disconnect the mains 114 from the geyser 112 and to switch the geyser 112 OFF when mains 114 is switched OFF by the electricity supply manager during general load shedding and to keep the geyser 112 disconnected when the mains 114 is switched back ON at the end of the general load shedding period eo the geyser 112 remains OFF for the duration of a pre-programmed, initial controlled load shedding period (typically 2 hours) in which signals from the PIR 126 are not taken into account — the PIR 126 will not switch the geyser 112 ON even if motion is detected o at the pre-programmed end of the initial controlled load shedding period, as determined with reference to the real time clock, the IC 118 switches the control system 110 to take into account signals from the PIR 126 — on receipt of a detected motion signal from the PIR 126, the IC 118 will operate the relay 120 to connect the mains 114 to the geyser 112 and to switch the geyser 112 ON e signals from the override switch 124 are taken into account — the IC 118 is programmed, on receipt of an override switch 124 signal, to operate the relay 120 to reconnect the geyser 112 to the mains 114, thereby switching the geyser 112

OFF after a relatively short period — typically 1 hour

Comfort state

Where the user is away from the premises monitored by the PIR 126 for an entire working day and there is no motion in the vicinity of the PIR 126, the possibility exists that the user will return from work to a geyser 112 full of cold water, which is a great inconvenience. The same applies at night when the user sleeps, with the possibility arising of the user waking up to cold water. To this end the IC 118 is programmed to switch the control system 110 to a comfort state to provide a comfort feed of mains power to reheat or maintain the geyser water temperature during periods of extended inactivity in the vicinity of the control system 110 (the PIR 126). The comfort state is applied after the end of the initial controlled load shedding period and in this state: e a comfort feed of mains power is applied if no motion is detected by the PIR 126 for an extended period, typically between 2 and 4 hours ¢ applied during comfort periods and serves to reheat the water in the geyser even if the user is not present (no motion detected by the PIR 126) — typically two periods of 1 to 2 hours each — time to occur any convenient time during the day but not during peak load or controlled load shedding periods e the first comfort period may extend from an estimated time just before the user arises, which is normally an hour before the first peak load period and the second comfort period may extend from an estimated time just before the user returns from work, which is normally an hour before the second peak load period e geyser loads in an area are randomly switched ON within a window period and then switched OFF — loads in the area are randomly switched ON which ensures not all geysers are turned ON simultaneously — provides a staggered startup load — if the comfort period is set the same for all units, the OFF time will likewise be staggered to avoid area-based power surges

Holiday state

Where the user is away from the premises monitored by the PIR 126 for more than a working day, such as when the user is on holiday, then, unlike present (un-controlled) usage, it makes sense to switch the geyser 112 off altogether and only to switch it on upon the user's return from holiday. To this end the IC 118 is programmed to switch the control system 110 to a holiday state during periods of greatly extended inactivity (more than 18 hours) in the vicinity of the control system 110 (the PIR 126). in the holiday state: e applied if no motion is detected by the PIR 126 for a greatly extended period — greater than 18 hours e the IC 118 is programmed to operate the relay 120 to disconnect the mains 114 from the geyser 112 and to keep the geyser 112 switched OFF; to not apply comfort reheating; and not to switch the geyser 112 back ON after any peak load period o the IC 118 switches the control system 110 to take into account signals from the

PIR 126 — on receipt of a detected motion signal from the PIR 126 (indicating the return of the user from extended absence, leave or holiday), the IC 118 operates the relay 120 to connect the mains 114 to the geyser 112 and to switch the geyser 112 ON o the IC 118 is programmed to keep the geyser 112 switched ON for an extended reheating period (typically 3 hours) to allow full reheating of the water in the geyser 112 o the IC 118 is programmed to return the control system 110 to the controlled load shedding state after the reheating period

Claims

14 CL Claims

1. A control system for an electrical load connected to mains electrical power supply, the control system comprising: a control circuit including a programmable logic device and a real time clock; a switch adapted for connection to the mains supply in circuit on the mains supply between the control circuit and the electrical load; the programmable logic device being programmed: if mains power is switched OFF, to operate the switch to disconnect the mains supply from the load; and when mains power is thereafter switched ON again, to operate the switch to reconnect the mains supply to the load upon the passage of a predetermined period of time as determined by means of the real time clock and, in addition or in the alternative, to operate the switch to reconnect the mains supply to the load upon the occurrence of a pre-programmed event occurring in the operating environment of the control system.

2. A control system according to claim 1 which is fitted with a user override switch by means of which an individual power user may override the control system, the programmable logic device being programmed to read the actuation of the override switch as a pre-programmed event and to operate the switch to reconnect the mains supply to the load.

3. A control system according to claim 2 in which the programmable logic device is programmed, on actuation of the override switch, to reconnect the mains supply to the load for a predetermined period of time and then to disconnect the mains supply from the load.

' 4, A control system according to any one of the preceding claims in which one or more additional pre-programmed events are included in the control circuit programming, the event or events being constituted by one or more changes in state in the operating environment of the control system, the system including one or more appropriate sensors interfaced with the control circuit and adapted to sense one or more changes in state in the operating environment and to convert the sensed change in state to a corresponding programmable logic device input.

5. A control system according to claim 4 which includes one or more passive infrared sensors configured as motion detectors adapted to sense human or animal motion (as a change in state in the operating environment of the control system) and to convert sensed motion into a programmable logic device input corresponding to a pre-programmed event adapted to trigger the programmable logic device to operate the switch to reconnect the mains supply.

6. A control system according to either of claims 4 or 5, adapted for controlled load shedding of the load constituted by a plurality of water heaters or geysers in an area, the control system being fitted to such geysers and the programmable logic device in each geyser being programmed to switch off all the geysers in the area for controlled load shedding purposes and to permit a user motion signal derived from motion sensed by a motion detector, during one or more predetermined times to switch the geyser back on for a predetermined time.

7. A method of controlling an electrical load by means of a control system according to any one of the preceding claims, the method including the steps of programming the control circuit programmable logic device: if mains power is switched OFF, to operate the switch to disconnect the mains supply from the load; and when mains power is thereafter switched ON again, to operate the switch to reconnect the mains supply to the load upon the passage of fi] a predetermined period of time as determined by means of the real time clock and, in addition or in the alternative, to operate the switch to reconnect the mains supply to the load upon the occurrence of a pre- programmed event occurring in the operating environment of the control system.

8. A method according to claim 7 in which the programmable logic device is programmed, on actuation of the override switch, to reconnect the mains supply to the load for a predetermined period of time and then to disconnect the mains supply from the load.

9. A control system substantially as described in this specification with reference to the accompanying drawings.

10. A method of controlling an electrical load substantially as described in this specification with reference to the accompanying drawings. Dated 5 February 2010 PFT Burgef Patenf & Trade Mark Attorneys Applicant's/Patent Attorneys