WO1990012261A1

WO1990012261A1 - A system for supplying hot water

Info

Publication number: WO1990012261A1
Application number: PCT/US1989/001576
Authority: WO
Inventors: Davey Jenkins Chance
Original assignee: Voltage Regulated Systems Of South Carolina, Inc.
Priority date: 1989-04-13
Filing date: 1989-04-13
Publication date: 1990-10-18
Also published as: KR920700380A

Abstract

A system supplies hot water by using an electrical current (30, 38) or energy source. Temperature control is accomplished utilizing a digital processor (36). Energy is transferred to the water (32) in accordance with time-amplitude modulated cycles which permits the desired energy to be transferred with maximum power determined by an electric utility. This permits flexible control of peak utility loads related to such systems.

Description

SPECIFICATION

"A SYSTEM FOR SUPPLYING HOT WATER"

Background of the Invention

Field of the Invention:

The invention relates to energy transfer controllers, and more specifically, to energy transfer controllers for use in such systems to sequentially increase the energy transfer rate from an electric utility system to the hot water system in accordance with a predetermined time-amplitude modulated cycle to permit the utility system power loading to be controlled, thereby reducing the cost of energy usage.

Description of the Prior Art:

Systems utilizing energy transfer controllers are well known in the prior art. An on-off switch which enables the transfer of energy from an energy source to a load in response to initialization of the switch is a simple energy transfer controller. Simple energy transfer controllers have significant limitations because they do not provide means for modulating the rate of energy transfer. Additionally, in recent years, the electric utilities have become interested in limiting the peak utility power demand to reduce the cost of the energy utilized. A favorite technigue for limiting peak power demand is to control intermittent loads, such as hot water heaters, such that peak power demand is reduced even though the ratio of on-time to off-time may be increased. Such an energy utilization cycle permits the energy demand to be met while the peak power demand is reduced. The controller which is the subject of this patent application was specifically designed as a result of a program to provide hot water systems using improved energy transfer technigues which permit flexibility in managing the heating rate and the utility loading.

Specifically, _r the disclosed hot water system which comprises the preferred embodiment of the invention utilizes a controller which provides means for transferring energy from a source to the hot water system in accordance with a predetermined time-amplitude modulated cycle with the cycle determined by a digital processor. Auxiliary inputs are provided permitting the electric utility to randomly modify the energy transfer cycle to aid in management of the utility load. It will be appreciated by those skilled in the art that the controller and the flexible energy cycle implemented thereby may be useful in a variety of other applications.

Summary of the Invention

The invention was specifically developed to provide an improved hot water heater utilizing a controller permitting the energy transfer rate to be modified by both the customer and the utility to reduce cost of energy usage. It is with respect to such an application that the preferred embodiment of the invention is discussed in detail below. The details of the energy transfer cycle are determined by a combination of customer specified inputs and a second group of optional inputs, which may be supplied by the utility. The energy transfer cycle is determined by a programmed digital processor. This permits the selection of an energy transfer cycle which results in a lower energy utilization cost. Modifications of the energy transfer cycle can be accomplished through the use of additional input signals, modifying the operating program for the digital processor, or both. The preferred embodiment of the invention includes a digital processor programmed to control an on-off switch to time-amplitude modulate the transfer of energy from the electric utility buss to the upper and lower heating elements of a conventional electric hot water heater. The energy transfer rate is modulated in accordance with first and second time-magnitude modulated cycle, with the cycle used selected by the upper and lower thermostatically controlled switches of the hot water heater. The maximum energy transfer rate during the first cycle is normally selected by the customer with a priority override in response to a signal provided by the utility. The maximum energy transfer rate during the second cycle is set by the software subject to the priority limit determined by the utility to control utility load conditions to reduce energy cost. A typical energy transfer cycle is discussed below.

In response to the utility priority signal and signals from the thermostatically controlled switches initiating the first energy transfer cycle, the controller transfers energy to the lower element, beginning at a first selected low value (for example 10%) and seguentially increasing in timed intervals to a higher upper limit (80% for example) . During low or moderate periods of hot water usage, this cycle is sufficient to supply all of the demands for hot water without utilizing the upper heating element, while operating the lower element a reduced power level. Assuming, as is typically the case, that for a high percentage of the time the demand for hot water is supplied without exceeding the energy capacity of the lower heating element, this energy transfer cycle substantially reduces peak power demand associated with the hot water system. Additionally, in typical hot water systems there is a considerable distance between the heating element and the temperature sensing element. During a typical heating cycle, a considerable temperature difference develops between the heating element and the sensor, resulting in overheating of the water. Such overheating increases energy utilization cost by increasing losses and utility loading.

Should the hot water heater be unable to supply the demand for hot water using this first time-amplitude modulated energy transfer cycle, the upper thermostatically controlled switch will close generating a signal which initiates the second energy transfer cycle, turning off the lower heating element and turning on the upper heating element. In the preferred embodiment of the invention, energy transfer during the second cycle is essentially the same as the first energy transfer cycle described above except that energy transfer rate reaches 100% of the capacity of the water heater in a very short time unless limited by the utility to control utility priority signal. More specifically, priority inputs are provided for priority signals permitting the electric utility to set maximum energy transfer rates for either of the above described energy transfer cycles. This provides the utility a means of reducing utility power demand to aid in the management of total energy usage cost and for other purposes.

As previously described, the first and second time-magnitude modulation cycles are determined by the digital processor (preferably programmed controlled) . This, in conjunction with the capability of utilizing additional input signals and the capability to generate additional output signals, permits the time-amplitude modulated cycle to be modified and the functions of the controller to be modified without significantly modifying either the water heater or the controller.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a functional block diagram illustrating a hot water system in accordance with the invention. Figure 2 is a functional block diagram of the preferred embodiment of the controller.

Figure 3 is a chart illustrating a typical time-amplitude modulated energy transfer cycle.

Figure 4 is a diagram illustrating a first energy transfer method.

Figure 5 is a second diagram illustrating a second energy transfer method.

Figure 6 is a functional block diagram illustrating the program utilized by the digital processor.

Figure 7 is a detailed schematic diagram of the controller.

DETAILED DESCRIPTION

Figure 1 is a functional diagram of the preferred embodiment of the invention. In its broadest concept, the system utilizes a controller to transfer energy between a conventional utility buss, comprising lines 30 and 38, and a load which is illustrated as a conventional two element hot water heater 32, through an on-off switch such as thyristor 34. Operating power is provided to the programmable processor 36 by the utility buss comprising lines 38 and 30. Operating programs are supplied to the programmable digital processor 36 using a program input 37.

In the developmental embodiment, the programs were stored in an external read-only memory. However, the preferred embodiment of the invention utilizes a microprocessor which includes an internal read-only non-volatile memory, as illustrated in Figure 7. This configuration of the system has not been tested at the time this patent application was prepared. Auxiliary inputs 40 provide means for receiving input signals which modify the energy transfer cycle 1. One example of such a modification is an input permitting the electric utility to set maximum limits on the rate of energy transfer to control peak electric utility load conditions using priority signals previously described. The hot water heater can be completely disabled using this technique by setting the maximum power transfer rate to zero. This permits the electric utility to set energy transfer limits to reduce the energy usage cost and for other purposes. Other modifications could be implemented.

A typical hot water system includes a water storage tank which is cylindrical ancC designed to stand upright. That is, the major axis of the cylindrical tank is vertical. In most installations two heating elements are used, one in the top portion of the tank and the second in the bottom portion of the tank. Each element is designed to operate at the full power rating of the water heater with two thermostatically controlled switches connected, such that turning on the upper heating element turns off the lower heating element. Controlling the utility load associated with,the hot water heater requires that the utility have means for controlling the rate of energy transfer. Typical prior art hot water systems can not be controlled by the utility to set the maximum energy transfer rate at a desired value. Additionally, overheating frequently occurs, as previously explained, resulting in additional energy utilization cost.

Conventional hot water heaters, such as hot water heater 32, include two thermostatically controlled switches, 42 and 44, respectively controlling energy transfer to the upper and lower heating elements 46 and 48 as described above. The temperature of water at the top of the water heater is normally higher than the temperature of the water at the bottom. Since the thermostatically controlled switches are set to operate at substantially the same temperature , most of the energy to heat the water is supplied by the lower heating element 48.

The controller operates to time-magnitude modulate the energy transfer rate to the lower heating and upper heating elements in accordance with a first and second time-amplitude modulated cycles. These cycles are designed to supply the required energy while maintaining utility loading due the hot water heater below a level determined by the utility and to reduce hot water overheating.

If the lower heating element 46 is sufficient to provide the required energy in accordance with the first time-amplitude modulated cycle, the upper thermostatically controlled switch 44 never closes, resulting in the upper heating element 48 being inoperative. The user selected upper limit of energy transfer rate limit during the first cycle is set to less than maximum, for example 80% of the hot water heater capacity, resulting in lower energy transfer rate. Should the lower heating element 46 be insufficient to maintain the temperature in the upper part of the water heater 32 at the desired temperature, the upper thermostat 44 will close, turning off the lower heating element 46 and turning on the upper heating element 44, which is operated in accordance with the second time-amplitude modulated cycle described above.

Signals indicating the status of the upper and lower thermostatically controlled switches 42 and 44 are coupled to the digital processor 36 by lines 50 and 52. In response to these signals the digital processor generates a control signal which is coupled to the thyristor 34 by a line 54 to time-magnitude modulate the energy transfer rate to the heating elements as subsequently described in detail. Figure 2 is a functional block diagram of the embodiment of the invention actually implemented. In the embodiment of the invention constructed and tested the programed digital processor 36 is a conventional 8048 microprocessor chip using external memory for storing programs. A conventional AC to DC converter 60 coupled to the 240 volt AC power buss produces a DC output which supplies operating power to the microcomputer 36. As will be subsequently explained, the thyristor 34 is turned on and off at the zero crossing of the AC line voltage to time-magnitude modulate the energy transfer rate while reducing electrical noise associated with current switching transients. To assure that this is accomplished, an interrupt generator 62 is coupled to the AC buss and generates a 60 cycle interrupt signal, which is coupled to the microprocessor 36 by a line 64. This provides the synchronization for the control of the thyristor 34. , As a further aid in controlling the peak power, energy transfer between the AC buss and the hot water heater is started at a relatively low rate and ramped upward in accordance with a predetermined time related function. During the first energy transfer cycle the ramp increases at a rate which frequently permits the desired water temperature conditions to be acheived before the upper limit of the cycle is reached, reducing the peak power demand associated with the hot water heater. Since energy is added to the water at a controlled rate beginning at a relatively low value and increases in increments, the temperature differential between the water in first regions near the heating element and second regions near the temperature sensor are reduced. This reduces the temperature overshoot common to typical hot water heaters thereby reducing overheating of the water and the energy losses associated therewith.

Additionally, a maximum energy transfer rate is placed on the lower heater element to limit peak power as previously discussed. Means is provided permitting the user to select the ^U-L beginning, and maximum energy transfer rates, permitting the

0 time-amplitude modulating function to be adapted to the

03 specific application. User specified signals determining the

04 beginning and maximum energy transfer levels for the lower

05 heating element 46 are provided to the programed digital

06 processor 36 by selector switches respectively illustrated at

07 reference numerals 64 and 66. The lower of the user specified

08 maximum energy transfer rate or the utility specified maximum

09 energy transfer rate controls the maximum energy transfer rate

10 and the utility loading due to the hot water heater. 11

12 in some utility systems, the utility provides signals to

13 customers who limit their peak power usage. Various electric

14 utilities have implemented such systems with respect to hot

15 water heating systems. Inputs, previously described,

16 permitting the utility to set the maximum energy transfer rate

17 at the desired value are coupled to the microprocessor 36

18 through external signal interface 69. 19

20 A common concern with digital controllers, such as the

21 microprocessor 36, is the possibility that the microprocessor

22 will hang up (i.e. stop) due to processing errors. To prevent

23 this condition, the digital processor 36 includes circuitry for

24 generating a pulsed reset signal having a predetermined

25 repetition rate, provided the microprocessor 36 is operating

26 properly. This reset signal is coupled to the input of a

27 watchdog timer and reset circuit 68. This circuit also counts

28 cycles of the AC line. If the time interval between adjacent

29 pulses of the reset signal exceed a time interval corresponding

30 to a predetermined number of cycles of the AC line, it is

31 assumed that the microprocessor 36 has ceased normal operation

32 and the watchdog timer and reset circuitry 68 generates and

33 couples a reset signal to the microprocessor 36 via a

34 conventional bus 70. This reset signal starts the

35 microprocessor 36 at the beginning of its processing cycle 36 permitting the controller to recover and resume normal 37 operation. Due to the design of typical hot water systems, signals from the thermostatically controlled switches controlling the current flow to the heater elements, 46 and 48, operate at full AC line .voltage. Special precautions are necessary to protect and isolate the circuits of the controller from these high voltages. Additionally, it is necessary to carefully consider electrical isolation of the microprocessor 36 from transients which may be generated on the AC line as a result of the switching of the thyristor 34, as well as from other sources. An acceptable technique providing such isolation is the use of conventional optical couplers.

In the preferred embodiment of the invention first, second and third optical couplers, 74, 76 and 78 respectively, provide electrical isolation between the microprocessor 36 and the thyristor 34, the heating elements 46 and 48, the upper thermostatically controlled switch 44 and the lower thermostatically controlled switch 42.

Figure 3 is a diagram illustrating the time-magnitude modulated first energy transfer cycle utilized to transfer energy between the AC buss and the lower heating element 46. In the embodiment of the invention implemented, it was elected to increase the energy transfer in increments of 10% of maximum, resulting, in ten steps, illustrated in Figure 3. The time interval corresponding to each of the step time-amplitude modulation cycle is selected by an interval switch 61. In a typical application, the time interval associated with each step is selected to be greater than ten seconds. A similar cycle is used to transfer energy to the upper heating element except that the time interval of each step is reduced and the maximum energy transfer rate is set to 100% or by the utility system priority signals for purposes of utility system load control. wnen the temperature of the hot water decreases sufficiently for the upper heating element 48 to turn on, the lower heating element 46 is turned off. This condition indicates heavy hot water usage requiring an energy input rate exceeding the capacity of the first energy transfer cycle to maintain the water temperature at the desired value. The second energy transfer cycle is designed to meet this need.

During the second energy transfer cycle the lower and upper limits for the energy transfer rate are set by the software with the maximum energy transfer rate set at 100%, unless limited by the utility for purposes of utility system management. This prevents the time-amplitude modulated cycle from significantly limiting the maximum hot water output of the hot water heater unless such a limit is necessary to assure the desired utility system operating conditions are maintained.

Figure 4 illustrates a control method for implementing the first and second energy transfer cycles. In this figure the switching on and off of the thyristor 34 is illustrated with respect to the waveform of the AC line for energy transfer rates, ranging in 10% increments from 10% to 100 %. For example, to transfer energy at 10% of the maximum rate, the thyristor is turned on at the positive going zero crossing of the AC line voltage and turned off at the next positive going zero crossing to reduce electrical noise. The off interval of the thyristor is equal to nine cycles of the AC line voltage as illustrated at reference numeral 100. The off interval of the switch is sequentially decreased as the on interval is increased by one cycle of the AC line to generate sequential increases in energy transfer rate in 10% increments, as illustrated at reference numerals ranging from 100A to 1001. Finally the thyristor is maintained continuously to achieve a maximum energy transfer rate as illustrated at reference numeral 1001. During the first energy transfer cycle, energy is transferred to the lower heating element. The beginning energy transfer rate, the maximum energy transfer rate, and the time interval for each increment of the time-amplitude modulated energy transfer cycle are respectively determined by manually operated switches, 64, 66 and 61. During the second energy transfer cycle these parameters are determined by the software and are typically 50% beginning, 100% maximum, 10 second intervals. This assures that the maximum rate at which energy is transferred is not substantially restricted unless such a limit is required to control utility load conditions.

In some installations the pulsating current resulting from the on-off cycling of the switch may be sufficient to generate objectionable flicker in the AC energy source. Should this occur, other energy transfer cycles are possible which increase the frequency of the on-of cycling and thus reduce the objectionable flicker. Such a control cycle is illustrated in figure 5.

For example, for the 10% energy transfer rate, the switching cycle is identical to the one discussed previously with reference to figure 4. However, this portion of the energy transfer cycle will be relatively short, making any flicker resulting from the low switching rate unobjectionable. Alternatively, the lower limit could be set above 10% to entirely eliminate this portion of the energy transfer cycle.

To achieve a 20% energy transfer rate, the switching technique illustrated at reference numeral 101A is used, in which the off interval of the switch is four cycles and the on interval one. This doubles the switching rate, increasing the flicker rate and thus reducing its seriousness.

An energy transfer cycle for achieving substantially a 30% energy transfer rate is illustrated at reference numeral 101B. In this cycle the on-time of the switch is limited to two cycles of the AC line and the off-time to one cycle. Similarly, a 40% transfer rate is achieved, as illustrated at reference numeral 101C, by an off time interval equal to three cycles with on time intervals equal to two. Energy transfer rates between 50% and 100% are illustrated at reference numerals 101D through 1011.

Figure 6 is a block diagram illustrating the signal inputs and the software utilized by the microprocessor 36 to produce the control signals. As previously explained, the preferred embodiment of the system operates in two different control modes depending on whether the upper or lower heating elements of the hot water heater is being utilized. The thermostatic switches for the upper and lower heating elements produce signals which indicate which heater element is to be used. These mode signals have been arbitrarily designated mode 1 and mode 2 and are coupled as inputs to the microprocessor 36 which is controlled by the software illustrated at reference numeral 122.

Data signals specifying the upper and lower energy transfer limits are produced by manually operated switches illustrated at Reference Numeral 124. Auxiliary inputs permitting the function performed by the software to be modified to include functions not specifically incorporated in the developmental model are provided by an auxiliary input signal generator 126. Such modifications could include utility generated signals for setting the maximum energy transfer rate to a selected value other than zero. Alternatively, the electric utility may supply signals to totally disable the hot water heater by setting all of the energy transfer limits to zero, as illustrated at reference numeral 128.

Provisions for setting the time intervals associated with the first energy transfer cycle are provided by interval switches 130. in response to these and the other input signals illustrated, -the microprocessor 36, as controlled by the software illustrated at Reference Numeral 122 produces all the signals necessary to operate the system.

For example, an interval timer 132, which is part of the microprocessor, is initialized to produce a timing signal which is coupled to a SYNC generator 134 to produce the SYNC signal for the system. Additionally, the interval timer 132 and the SYNC generator 134 are synchronized to the 60 cycle AC line. The microprocessor, 36 as controlled, by the software 122 produces a power demand signal which is coupled to the input of an output signal generator 136. In response, the output signal generator 136 produces a control signal to turn on and off the switch 138 as well as reset the watch dog timer 140. Additionally, the output signal generator 136 produces auxiliary output signals available on buss 142 to implement other functions which may be required by the specific application.

Figure 7 is a detailed schematic block diagram of the controller using the internal program memory version of the 8048 microprocessor. This diagram includes complete component identification information; therefore, no detailed description of this drawing is believed to be necessary. This is believed to be the best embodiment of the invention; however, the experimental model and the one for which the programs listed in detail below are for, is the external memory version of the 8048 microprocessor.

PROGRAM LISTING FOR 8048 MICROPROCESSOR

TITLE 'VOLTAGE REGULATED HEATING CONTROL March 14, 1989' ********************************

* and Dave J. Chance, Concord, N.C. *

* *

* Energy Efficient Proportional Control for Electric * Water Heaters ( or other electric heating elements ) * *

This software written for the INTEL 8048/8049 series * microcomputer or equivalents. It is written to * assemble with AVOCET's 8048 Cross Assembler. * *

****************************************

SBTTL 'COPYRIGHT NOTICE 1/27/89

ORG 380H

DB Copyright (c) 1988, 1989, Voltage Regulated Systems,' DB Inc., Georgetown, South Carolina, and ' DB Davey J. Chance, Concord, North Carolina. ' DB ALL RIGHTS RESERVED. No part of this publication' DB may be reproduced, transmitted, transcribed, or' DB translated into any language in any form or by any' DB means, electronic, mechanical, manual, or otherwise,' DB without written permission of DB VOLTAGE REGULATED SYSTEMS, Inc., DB Georgetown, South Carolina.'

;***********************************************************

REV. 1.00 djc ORIGINAL PROGRAM ENTRY BEGAN 11/8/88

Rev. 1.01 djc revised program flow/int structure 12/29/88

Rev. 1.02 djc debug changes 1/13/89

Rev. 1.03 djc init data memory 1/14/89

Rev. 1.10 djc restructured due to sensor overlap 1/18/89

Rev. l.ll djc modified "Main3" to check "Lflag" 1/19/89

Rev. 1.12 djc hardware debug changes 1/25/89

Rev. 1.13 djc more debug changes 1/26/89

Rev. 1.14 djc more debug changes 1/27/89

Rev. 1.15 djc add limits to swl & sw2 settings 1/27/89

REV. 2.00 DJC First PRODUCTION VERSION 1/27/89 ;REV. 2, 10 DJC moved 'watchdog' to main 3/14/89 »^•

SBTTL ' EQUATES 1/26/89 '

OVERFLO EQU 256 Counter overflo's on 256th cnt TIME EQU OVERFLO-105 14MS = 105 with 3.58mhz clock 14ms = 175 with 6.00mhz clock 14MS = 234 with δ.OOmhz clock (.014 * (Clock/(5 * 3 * 32))) TOFF EQU 01000000B data to turn off triac drive TTON EQU 10111111B data to turn on triac drive SW1 EQU 11101111B data to select SW1, steptime SWIOFF EQU 00010000B data to deselect SW1 SW2 EQU 11011111B select SW2, min/max duty cycle SW20FF EQU 00100000B data to deselect dip switch 2 LOMASK EQU 11110000B data to mask off lower nibble HIMASK EQU 00001111B data to mask off upper nibble DOGON EQU 10000000B watchdog timer on data (bit 7) DOGOFF EQU 01111111B watchdog timer off data DOGRATE EQU 15 watchdog timer update rate

.25sec, (15/60hz) STPRAT EQU 150 60 HZ / 150 = 2.5 SECONDS UPRATE EQU 4 4 * 2.5 sec = 10 sec/step UPMIN EQU 5 50% min for upper element UPMAX EQU 10 100% max for upper element

TEN EQU ((NOT 10)+1) AND 0FFH ;two's complement of 10

SBTTL ' DATA STORAGE EQUATES 1/27/89 '

RA EQU 32 ; BEGINNING OF DATA MEMORY

STEPCLK EQU RAM ; 2.5 sec. step clock generator STIMER EQU RAM + 1 ;Step Timer hi byte (swl = counts) DUTYCYC EQU RAM + 2 ;Step duty cycle CYCLE EQU RAM + 3 ;cycle counter UFLAG EQU RAM + 4 upper sensor activity flag LFLAG EQU RAM + 5 lower sensor activity flag TRIAC EQU RAM + 6 data to turn on/off triac MINDU EQU RAM + 7 start duty cycle (min) MAXDU EQU RAM + 8 finish duty cycle (max) AFLAG EQU RAM + 9 Activity Flag

00H =not active

01H =cycle 1 after heat request

55H =heat cycle active

0FFH =heat requested detected

SACC EQU RAM + 30 ;save ace here during int service

********************************************************

*

REGISTER ASSIGNMENTS * *

R0 general purpose pointer *

Rl general purpose pointer *

R2 watchdog timer loop counter *

R3 *

R4 temporary data storage *

R5 SW1, step time in 2.5sec increments (true) *

R6 SW2, duty cycle limits (true) *

R7 accumulator save area during certain routines

********************************************************

SBTTL INTERRUPTS & RESTART VECTOR 1/27/89

ORG 000H

DIS I

JMP INIT

ORG 003H ;60hz interrupt service routine INTERUPT: 18

JMP EI60HZ

ORG 007H ;14 ms interrupt service routine

TIMER14 : •

MOV R7,A

STOP TCNT

MOV A,#TIME

MOV T,A

MOV A,#TOFF

ORL P2,#TOFF

MOV A,R7

RETR

EI60HZ:

SEL RBI

MOV §R0,A

STRT T

MOV RO,IAFLAG

MOV A,@R0

CPL A

JZ EI01

MOV Rl,#TRIAC

MOV A,§R1

JB6 EI02

EI01:

ANL P2,#TTON

CALL C25

WAITO:

JNI ,. WAITO

MOV RO,#AFLAG

MOV A,@R0

DEC A

JNZ WTOA

MOV A,#55H

MOV @R0,A

WTOA: JTO UPSET

JT1 LOSET WAIT1:

CLR A

MOV @R0,A

MOV R0,#UFLAG

MOV R1,#LFLAG

MOV @R0,A

MOV §R1,A

JMP EXIT60 UPSET:

MOV Rl,#LFLAG

MOV A,@R1

JNZ WAIT1

MOV R1,#UFLAG

MOV A,#0FFH

MOV §R1,A

MOV . A,@R0

CPL A

JNZ EXIT60

MOV A,#01H

MOV @R0,A

JMP EXIT60 LOSET:

MOV R1,#UFLAG

MOV A,@R1

JNZ WAIT1

MOV R1,#LFLAG

MOV A,#0FFH

MOV @R1,A

MOV A,@R0

CPL A

JNZ EXIT60

MOV A,#01H

MOV @R0,A

JMP EXIT60 20

EI02:

ORL P2,#TOFF

CALL C25

WAIT2:

JNI WAIT2

MOV R0,#AFLAG

JTO EI03

JT1 EI03

CLR A

MOV @R0,A

MOV R0,#UFLAG

MOV R1,#LFLAG

MOV §R0,A

MOV §R1,A

JMP EXIT60

EI03:

MOV A,@R0

JNZ EXIT60

CPL A

MOV §R0,A

EXIT60:

MOV RO,#SACC

MOV A,§R0

RETR

SBTTL ' INITIAL] 1/27/89

INIT:

CLR A

MOV R0,#02

MOV Rl,#62

MOV §R0,A

DEC Rl

INIT2:

INC RO

MOV @R0,A

DJNZ R1,INIT2 SEL RBI

MOV RO, #SACC

MOV R2,#DOGRATE

SEL RBO

MOV R1,#STEPCLK

MOV A,#STPRAT

MOV @R1,A

CLR A

MOV Rl,#CYCLE

MOV @R1,A

MOV A,#SW1

OUTL P2,A

IN A,PI

CPL A

JNZ INIT3

INC A INIT3:

MOV R5,A

CALL TIMER14

MOV R0,#MINDU

MOV R1,#MAXDU

ORL P2,#SW10FF

ANL P2,#SW2

IN A,PI

CPL A

MOV R6,A

ANL A,#HIMASK

JNZ I3AA

INC A

JMP I3AB I3AA:

MOV R4,A

MOV A,#TEN

ADD A,R4

JZ INIT3D

JC INIT3D

MOV A,R4 22 I3AB:

MOV @R0,A

MOV RO,#DUTYCYC

MOV §R0,A

MOV A,R6

SWAP A

ANL A,#HIMASK

MOV R4,A

MOV RO,#MINDU

MOV A,§R0

CPL A

INC A

ADD A,R4

JZ 13AC

JC 13AC

MOV A,@R0

JMP 13AD I3AC:

MOV A,#TEN

ADD A,R4

JC INIT3C

MOV A,R4 I3AD:

MOV §R1,A

MOV A,#DOGOFF

OUTL P2,A

EN I

EN TCNTI

JMP MAIN INIT3C:

MOV A,#10

JMP 13AD INIT3D:

MOV A,#10

MOV @R0,A

MOV RO,#DUTYCYC

MOV §R0,A JMP I3AD

SBTTL ' MAIN PROG 1/27/89 '

ORG 100H MAIN:

JF1 WDOG

JMP MAINO WDOG:

CLR Fl

ORL P2,#DOGON MAINO:

MOV R0,#AFLAG

MOV A,@R0

JNZ MAIN3 MAIN1:

MOV RO,#TRIAC

MOV §R0, #TOFF

CLR A

MOV R0,#CYCLE

MOV @R0,A MAIN2:

MOV A,#STPRAT

MOV R1,#STEPCLK

MOV @R1,A

CLR A

MOV R1,#STIMER

MOV §R1,A

JMP MAIN MAIN3:

CPL A

JZ MAIN2

MOV A,@R0

DEC A

JZ MAIN4

MOV R1,#LFLAG

MOV A,@R1 JZ MAIN3B

ORL P2,#SW20FF

ANL P2,#SW1

IN A,PI

CPL A

JNZ MN3

INC A MN3;

CPL A

INC A

ADD A,R5

JNZ MAIN3A

ORL P2,#SW10FF

ANL P2,#SW2

IN A,PI

INC A

ADD A,R6

JZ MAIN3B MAIN3A:

ORL P2,#SW20FF

ANL P2,#SW1

IN A,PI

CPL A

JNZ M3A

INC A M3 :

MOV R5,A

MOV R0,#MINDU

MOV R1,#MAXDU

ORL P2,#SW10FF

ANL P2,#SW2

IN A,PI

CPL A

MOV R6,A

ANL A,#HIMASK

JNZ M3AA

INC A JMP M3AB

M3AA:

MOV R4,A

MOV A, #TEN

ADD A,R4

JZ MAIN3D

JC MAIN3D

MOV A,R4

M3AB:

MOV @R0,A

MOV R0,#DUTYCYC

MOV @R0,A

MOV A,R6

SWAP A

ANL A,#HIMASK

MOV R4,A

MOV RO,#MINDU

MOV A,@R0

CPL A

INC A

ADD A,R4

JZ M3AC

JC M3AC

MOV A,§R0

JMP M3AD

M3AC:

MOV A,#TEN

ADD A,R4

JC MAIN3C

MOV A,R4

M3AD:

MOV @R1,A

MAIN3B:

CALL HEAT

JMP MAIN

MAIN3C:

MOV A,#10 JMP M3AD

MAIN3D:

MOV A,#10

MOV §R0,A

MOV RO,#DUTYCYC

MOV §R0,A

MOV §R1,A

JMP ^" MAIN3B

MAIN4:

MOV R0,#LFLAG

MOV R1,#UFLAG

MOV A,@R0

JNZ MNSIX

MOV A,gRl

JZ MAIN1

MAIN5:

MOV R5,#UPRATE

MOV A,#UPMIN

MOV R1,#MINDU

MOV @R1,A

MOV R1,#DUTYCYC

MOV @R1,A

MOV A,#UPMAX

MOV R1,#MAXDU

MOV §R1,A

CALL HEAT

JMP MAIN

MNSIX:

JMP MAIN6 ;go 1

ORG 200H

MAIN6:

ORL P2,#SW20FF

ANL P2,#SW1

IN A,PI

CPL A

JNZ M6A INC A M6A:

MOV R5,A

MOV RO,#MINDU

MOV R1,#MAXDU

ORL P2,#SW10FF

ANL P2,#SW2

IN A,PI

CPL A

MOV R6,A

ANL A,#HIMASK

JNZ M6AA

INC A

JMP M6AB M6AA:

MOV R4,A

MOV A,#TEN

ADD A,R4

JZ MAIN6B

JC MAIN6B

MOV A,R4 M6AB:

MOV @R0,A

MOV RO,#DUTYCYC

MOV @R0,A

MOV A,R6

SWAP A

ANL A,#HIMASK

MOV R4,A

MOV RO,#MINDU

MOV A,@R0

CPL A

INC A

ADD A,R4

JZ M6AC

JC M6AC

MOV A,@R0 JMP M6AD M6 C:

MOV A,#TEN

ADD A,R4

JC MAIN6C

MOV A,R4 M6AD:

MOV §R1,A M6AE:

CALL HEAT

JMP MAIN MAIN6B:

MOV A,#10

MOV §R0,A

MOV RO,#DUTYCYC

MOV §R0,A

MOV @R1,A

JMP M6AE MAIN6C:

MOV A,#10

JMP M6AD

SBTTL ' SUBROUTIN] 1/27/89 '

ORG 300H HEAT:

MOV R0,#CYCLE

MOV R1,#STIMER

MOV A,R5

CPL A

INC A

ADD A,@R1

JZ HEAT5

JC HEAT5 HEAT1:

MOV R1,#DUTYCYC

MOV A,§R1 CPL A

INC A

ADD A,§R0

JZ HEAT3

JC HEAT3 HEAT2:

MOV R1,#TRIAC

MOV @R1,#TTON

RET HEAT3:

MOV A, #TEN

ADD A,@R0

JNZ HEAT4

MOV @R0,A

JMP HEAT2 HEAT4:

MOV R1,#TRIAC

MOV @R1,#T0FF

RET HEAT5:

MOV A,#TEN

ADD A,@R0

JZ HT5A

JC HT5A

JMP HEAT1 HT5A:

MOV R1,#MAXDU

MOV A,@R1

MOV R1,#DUTYCYC

CPL A

INC A

ADD A,§R1

JZ HEAT6

JC HEAT6

INC §R1 HEAT6:

MOV Rl,#STIMER CLR A

MOV §R1 ,A

MOV §R0 ,A

JMP HEAT2

C25 :

ANL P2 , #DOGOFF

DJNZ R2 , C25A

MOV R2 , #DOGRATE

CLR Fl

CPL Fl C25A:

MOV RO , # CYCLE

INC @R0

MOV R1 , #STEPCLK

MOV A, §R1

DEC A

MOV §R1 ,A

JNZ C25B

MOV ^" A, #STPRAT

MOV . §R1 ,A

MOV R1 , #STIMER

INC §R1 C25B: RET

END

As illustrated in Figure 7, the system and the controller can be implemented using standard commercially available components. However, many changes can be made, all of which are within the capability of those skilled in the art. As specifically discussed above, additional inputs can be provided to the processor to modify the control sequence. All portions of the system can be implemented using components other than those illustrated. The control technique can be used in other applications, for example in resistance heating systems for structures. Real time clocks could be included, permitting time-of-day control techniques to be implemented. Energy sources other than an electrical utility may also be used.

Claims

1) A hot water system including means for controlling the energy transfer between the energy source and the water system such that the peak rate of energy transfer is time-amplitude modulated in accordance with a selected energy transfer cycle, comprising in combination:

a) first means for producing a first signal indicating a transfer of energy between said source and said hot water system is required to meet the current demand for hot water;

b) second means responsive to said first signal for initiating energy transfer between said energy source and said hot water system in accordance with a first time-amplitude modulated cycle;

c) third means for producing a second signal indicating that the current energy transfer requirements of said system exceed the capability of said first transfer energy cycle;

d) fourth means responsive to said second signal for initiating a second energy transfer cycle, said second energy transfer cycle having a capability of transferring energy at a higher rate than said first cycle.

2. A hot water system in accordance with claim 1 further including means for accepting a signal specifying the maximum desired energy transfer rate from said energy source to said load and for modifying at said first and second time-amplitude modulated cycles to maintain the energy transfer rate below said maximum desired energy transfer rate.

3. A hot water system in accordance with claim 2 wherein energy source is a public electric utility.

4. A hot water system in accordance with claim 3 wherein said signal specifying the maximum desired energy transfer rate reduces said energy transfer rate to zero.

5. A system for controlling the transfer of energy between an energy source and a load in accordance with a selected energy transfer cycle, comprising in combination:

a) first means for producing a first signal indicating a transfer of energy between said source and said load is required to meet current demand for energy by said load; b) second means responsive to said first signal for transferring energy from said source to said load in accordance with a first time-amplitude modulated cycle; c) third means for producing a second signal indicating that the current energy requirements exceed the capability of said first energy transfer cycle; and d) fourth means responsive to said second signal for initiating a second energy transfer cycle having an energy transfer capability exceeding the capacity of said first energy transfer cycle.

6. A system for controlling the transfer of energy in accordance with claim 5 further including means responsive to priority signals to limit the energy transfer capability of said first and second energy transfer cycles to permit management of system load conditions.

7. A system for controlling the transfer of energy in accordance with claim 6 wherein said system further includes a programmed digital processor responsive to a stored program to implement at least one of said energy transfer cycles.

8. A system for controlling the transfer of energy in accordance with claim 7 wherein said second energy transfer cycle is implemented by said digital processor.