Hot water heater controller

Apparatus for use with a hot water heating system which includes a tank means having an outlet, a supply water inlet, and a recirculating inlet, and which includes heater means for heating water in said tank means, a pipeline with a supply portion extending between said outlet and each of a plurality of water consumption stations and with a return portion extending from the last of said stations to said recirculating inlet, and a recirculating pump for pumping water along said pipeline comprising:

• a first sensor means for sensing the hot water temperature T.sub.1 substantially at said outlet;
• second sensor means for sensing the hot water temperature T.sub.3 at a location substantially along said recirculating portion of said pipeline;
• processor and control means for determining a desired hot water temperature DTEMP at said outlet, said control means including means for determining an unadjusted desired temperature D.sub.u TEMP and for respectively increasing and decreasing D.sub.u TEMP to obtain DTEMP according to whether T.sub.3 is respectively less than and greater than a predetermined value T.sub.3min ;
• said control means being coupled to said heater to operate said heater when T.sub.1 is less then DTEMP to bring T.sub.1 close to DTEMP.

A method for controlling a hot water heating system which includes a tank means having an outlet, a supply water inlet and a recirculating inlet, and which includes heater means for heating water in said tank means, a pipeline with a supply portion extending between said outlet and each of a plurality of water consumption stations and with a return portion extending from the last of such stations to said recirculating inlet, and a recirculating pump for pumping water along said pipeline, comprising:

• measuring the temperature T.sub.1 at said outlet;
• measuring the temperature T.sub.3 at a predetermined location along said return portion of said pipeline;
• determining whether T.sub.3 is greater or less than a predetermined desired temperature T.sub.3 min;
• determining a desired hot water temperature DTEMP at said outlet, including determining an unadjusted desired temperatue D.sub.u TEMP and respectively increasing and decreasing D.sub.u TEMP to obtain DTEMP according to whether T.sub.3 is respectively less than and greater than T.sub.3 min;
• operating said heater when T.sub.1 is less than DTEMP to bring T.sub.1 close to DTEMP.

In a hot water heating system for a structure with numerous water consumption stations including a last station, which includes walls forming a boiler room, a water tank located in said boiler room and having an outlet, a supply water inlet and a recirculating inlet, and which also includes a heater in said room for heating water in said tank, a pipeline with a supply portion extending from said outlet and out of said room and past said stations and with a return portion extending from the last of said stations into said room to said recirculating inlet, and a recirculating pump for pumping water along said pipeline to flow some of it back to said recirculating inlet, the improvement comprising:

• a first temperature sensor for sensing the temperature T.sub.1 of water substantially at said outlet and generating an electrical signal representing T.sub.1 ;
• a second temperature sensor for sensing the temperature T.sub.3 of water substantially along said return portion of said pipeline and generating an electrical signal representing T.sub.3 ;
• control cicuitry connected to said sensors and said heater, said control circuitry constructed to operate said heater to increase T.sub.1 when T.sub.3 decreases below a predetermined level;
• said return portion of said pipeline extending into said boiler room at a location spaced a plurality of meters from said recirculating inlet;
• said temperature sensor located along said return portion of said pipeline which is closer to said location than to said recirculating inlet, whereby the sensing of T.sub.3 is made at a pipeline position that is far from the tank and upstream of most of the part of the return portion of the pipeline that would be cooled by air in said room.