Hot water control
AssigneeFluidmaster, Inc.
InventorTom R. Vandermeyden
Life of this patent
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Abstract
A system is described for use with a hot water supply for hotels, apartment buildings and similar multi-unit structures, which controls the temperature T.sub.1 of water at the outlet of a water tank to make it close to a desired temperature DTEMP that is low during times of low demand to save energy and which is high at times of high demand to assure adequate hot water at all times. The desired temperature at the tank outlet, DTEMP, is adjusted according to the sensed demand for hot water during an immediately preceding period of given duration, such as 45 minutes. The circuitry is used in parallel with an existing Aquastat on a commercial tank type water heater.
Claims11
In a hot water heating system which includes a water tank having an inlet for receiving cold water and an outlet for delivering hot water, and a heater which can be turned to on and off states to heat and not heat water in said tank, the improvement comprising:
- a first circuit which includes a sensor that senses the water tank temperature, said first circuit constructed to generate a signal representing said tank temperature T.sub.1 ;
- a second circuit which senses the state of said heater and generates a signal representing the state of said heater;
- a third circuit having a portion settable to a minimum tank water temperature T.sub.min, a memory circuit portion coupled to said second circuit and storing a quantity substantially representing the proportion of time during an immediately preceding period of time that said heater was on, and a portion that generates a signal representing a desired temperature DTEMP substantially equal to said minimum temperature T.sub.min plus a quantity multiplied by the proportion of time during said preceding period that said water heater was on;
- a fourth circuit which compares said signal representing said tank temperature T.sub.1 to said signal representing DTEMP, and which urges said heater to an on state when DTEMP is above T.sub.1.
In a hot water heating system which includes a water tank having an inlet for receiving cold water and an outlet for delivering hot water, a heater which can be turned to one and off states to heat and not heat water in said tank, and an Aquastat which is coupled to said tank and which has a settable temperature and that urges said heater on and not on when the tank water temperature is respectively substantially below and at the set temperature, the improvement comprising:
- a control circuit having means for setting a maximum temperature T.sub.max and a minimum temperature T.sub.min, said control circuit being responsive to the percent of time said heater has been on during an immediately preceding time period for generating a signal representing a desired temperature DTEMP between said temperatures T.sub.max and T.sub.min which lies progressively closer to T.sub.max and T.sub.min as the percent of time said heater was on during said period is respectively greater and smaller, said control circuit including means for sensing the temperature T.sub.1 of water at said water tank and for urging said heater on and not on when DTEMP is respectively less than and not less than T.sub.1 ;
- said control circuit and Aquastat being connected in parallel to said heater, so each individually turns on said heater, and so only when both are off is the heater turned off.
A method for controlling a water tank heater of a hot water heating system comprising:
- setting maximum and minimum tank water temperatures;
- establishing a desired water tank temperature DTEMP between said maximum and minimum temperatures;
- sensing tank water temperature T.sub.1 ;
- establishing said heater in an on state when said tank water temperature T.sub.1 is less than DTEMP and establishing said heater in an off state when said tank water temperature T.sub.1 is substantially as high as DTEMP;
- said step of establishing a desired temperature DTEMP includes sensing the proportion of time the heater was on during an immediately preceding period whose beginning and ending times repeatedly advance, and increasing and decreasing DTEMP as said proportion of time respectively increases and decreases.
Dependencies are inferred from the claim text.