Lead Lag Control System for Water Heaters

Abstract

A control system is shown for a series of two or more water heaters arranged in parallel. A cold water supply line delivers cold water from a cold water source to a cold water inlet at each of the respective two or more water heaters arranged in parallel. A low pressure restriction is present at each cold water inlet of the water heaters which presents a low pressure restriction to the flow of cold water at each cold water inlet. A by-pass valve is also present at the cold water inlets for by-passing cold water from the cold water supply line around each of the low pressure restrictions. A hot water discharge line receives and discharges hot water from each of the water heaters. A controller is used to control when each of the by-pass valves will be open or closed based upon demand with only the by-pass valves being open which are needed to meet demand placed upon the system.

What is claimed is: 
     
         1 . A control system for two or more water heaters arranged in parallel, the control system comprising:
 a cold water supply line which delivers cold water from a cold water source to a cold water inlet at each of the respective two or more water heaters arranged in parallel;   a flow restricting element present at each cold water inlet of the water heaters, the flow restricting element presenting a low pressure restriction to the flow of cold water at each cold water inlet;   a by-pass valve for by-passing cold water from the cold water supply line around each of the flow restricting elements;   a hot water discharge line which receives and discharges hot water from each of the water heaters;   a controller which controls when each of the by-pass valves will be open or closed based upon a selection of a lead heater with only one bypass valve being open which are needed to meet low demand situations placed upon the system.   
     
     
         2 . A control system for two or more water heaters arranged in parallel, the control system comprising:
 a cold water supply line which delivers cold water from a cold water source to a cold water inlet at each of the respective two or more water heaters arranged in parallel;   a forward bias check valve present at each cold water inlet of the water heaters, the forward bias check valve presenting a low pressure restriction to the flow of cold water at each cold water inlet;   a by-pass valve for by-passing cold water from the cold water supply line around each of the check valves;   a hot water discharge line which receives and discharges hot water from each of the water heaters;   a controller which controls when each of the by-pass valves will be open or closed based upon selection of a lead heater with only one bypass valve being open which are needed to meet low demand situations placed upon the system.   
     
     
         3 . The control system of  claim 2 , wherein the controller is selected from the group consisting of lead lag timer, a lead lag controller and a device for emitting a control signal. 
     
     
         4 . The control system of  claim 2 , wherein the controller is manually set to determine which by-pass valves are open. 
     
     
         5 . The control system of  claim 2 , wherein the forward bias check valve has an open forward pressure on the order of 0.5 psi. 
     
     
         6 . The control system of  claim 2 , wherein the system uses manually operated valves instead of motorized valves. 
     
     
         7 . The control system of  claim 6 , wherein the system compensates for increased demand by an associated pressure drop in the system causing the check valves to open until demand is met. 
     
     
         8 . A control system for two or more water heaters arranged in parallel, the control system comprising:
 a cold water supply line which delivers cold water from a cold water source to a cold water inlet at each of the respective two or more water heaters arranged in parallel;   a forward bias check valve present at each cold water inlet of the water heaters, the forward bias check valve presenting a low pressure restriction to the flow of cold water at each cold water inlet, each of the forward bias check valves having an open forward pressure which does not exceed about 0.5 to 1.5 psi;   a motorized by-pass valve for by-passing cold water from the cold water supply line around each of the check valves;   a hot water discharge line which receives and discharges hot water from each of the water heaters;   a lead lag controller which controls when each of the motorized by-pass valves will be open or closed based upon selection of a lead heater with only the by-pass valves being open which are needed to meet demand situations placed upon the system.   
     
     
         9 . The control system of  claim 8 , wherein the lead lag controller comprises a programmable timer for determining when each of the by-pass valves will be open or closed. 
     
     
         10 . The control system of  claim 9 , wherein when demand is met by one bypass valve being open, only water from one water heater is being used. 
     
     
         11 . The control system of  claim 10 , wherein the control system compensates for increased demand by an associated pressure drop in the system causing the check valves to open until demand is met.