Control system methods for networked water heaters

1. A method for controlling a plurality of fluidly and operably connected water heaters in a network to meet a system demand, comprising steps of:

providing a value corresponding to relative remaining life of each said water heater, a value corresponding to a minimum output of each said water heater, a flow limiting valve for each said water heater and a pump for each said water heater;

obtaining a number of participating water heaters required to service said system demand by dividing said system demand by said value corresponding to minimum output;

obtaining an average heating load by dividing said system demand by said number of participating water heaters in said network;

selecting participating water heaters by identifying said number of participating water heaters having the longest relative remaining life; and

setting and activating each of said selected participating water heaters at said average heating load to provide a total load meeting said system demand.

2. The method for controlling a plurality of fluidly and operably connected water heaters in a network to meet a system demand of claim 1 , wherein said step of obtaining a number of participating water heaters comprises dividing said system demand by said value corresponding to minimum output.

3. The method for controlling a plurality of fluidly and operably connected water heaters in a network to meet a system demand of claim 1 , wherein said step of obtaining a number of participating water heaters comprises estimating the total cost of operating different quantities of water heaters of said plurality of water heaters where the heating load is substantially equally distributed over said different quantities of water heaters of said plurality of water heaters and selecting the number of participating water heaters that yields a lowest cost.

4. The method for controlling a plurality of fluidly and operably connected water heaters in a network to meet a system demand of claim 1 , wherein said value corresponding to relative remaining life comprises normalized factors of expended energy, thermal cycle count, blower speed, flow rate and outlet-inlet water temperature difference of a water heater.

5. The method for controlling a plurality of fluidly and operably connected water heaters in a network to meet a system demand of claim 1 , wherein each of said plurality of water heaters has a controller, wherein distribution of a heating load to each of said plurality of water heaters is determined by its controller.

6. The method for controlling a plurality of fluidly and operably connected water heaters in a network to meet a system demand of claim 1 , wherein each of said water heaters has a controller, wherein the heating load corresponds to a flow which is achieved by controlling concurrently said flow limiting valve of each water heater and said pump of each water heater.

7. A method for detecting a small flow in a plurality of fluidly and operably connected water heaters in a network, each of said plurality of water heaters has a flow limiting valve having a flow range of from zero to a non-zero value, a flow sensor having a minimum detectable flow, a value corresponding to a predetermined potential system demand, a value corresponding to the maximum output of a water heater in said network, comprising steps of:

obtaining a number of participating water heaters required to service said predetermined potential system demand by dividing said value corresponding to said predetermined potential system demand by said value corresponding to the maximum output of a water heater in said network;

obtaining an average flow limiting valve setting by dividing said predetermined potential system demand by said number of participating water heaters in said network;

selecting participating water heaters by identifying said number of participating water heaters having the longest relative remaining life; and

setting and activating said flow limiting valve of each of said selected participating water heaters at said average flow limiting valve setting.