A compact "in-line" tankless double element water heater includes a top connected to a manifold having a cold water inlet and a hot water outlet for connection to the cold, and hot water lines of a faucet. The compact water heater includes a body with a passageway through which cold water travels, from the top towards the bottom, where it is fed into four separate chambers, two each separated on opposed sides of the body and of a diaphragm. A first of the two chambers on each side has no outlet, and the pressure of cold water therein presses against a first side of the respective diaphragm, while the second of the two chambers on each side includes an outlet to a separate hot water chamber on each side, having a separate heating element therein. A second of the two chambers on each side also includes a plunger, biased by a spring against a second side of the diaphragm, and a plunger rod, which contacts an operating member of a microswitch. When the hot water handle of a faucet is opened, water travels from each of the separate hot water chambers to lower the cold water pressure in each of the second chambers and flex each of the diaphragms toward its respective microswitch, to move the abutting operating members and actuate the microswitches so that each of the heating elements is switched on. When the hot water handle is closed, the pressure in each of the two chambers will be equalized, and the springs will force the diaphragms to their starting positions to shut off the two heating elements. A sheet metal stepped plate is held in a fully sealed enclosure and secured to temperature limit switches for added safety and security.

An improved "in-line" tankless electrical resistance water heater includes a top having a cold water inlet and a hot water outlet for connection to the cold, and hot water lines of a faucet in a sink. The water heater includes a body with a passageway through which cold water travels, from the top towards the bottom, where it is fed into two separate chambers on opposed sides of a diaphragm. A first of the two chambers has no outlet, and the pressure of cold water therein presses against a first side of the diaphragm, while the second chamber includes an outlet to a further chamber having a heating element therein. The second chamber also includes a plunger, biased by a spring against a second side of diaphragm, and a plunger rod, which contacts an operating member of a microswitch. When a hot water handle of the faucet is opened, water travels from the further chamber to lower the cold water pressure in the second chamber and flex the resilient member toward the microswitch, to move the operating member and actuate the microswitch, so that the heating element is switched on. When the hot water handle is closed, the pressure in the two chambers will be equalized, and the spring will push the resilient member back to shut off the heating element.

A water jacket assembly for an instantaneous gas fired water heater, the assembly including pressed profiled plates made of copper or copper coated steel, one plate being the inverted image of the other, said plates being placed together in pairs, the pairs of plates being arranged in a parallel array to form a heat exchanger, the heat exchanger being bordered by a water jacket comprising overlapping side and end panels of copper or copper coated steel attached to the array of plates, the assembly being fused together to define a combustion chamber with discrete combusted gases and water passages within said assembly.

A method whereby application and network services (such as access control and electronic mailing list servers) can use a directory service to define groups of directory members using a directory search specification evaluated at service delivery time (dynamic group membership.) Traditionally, network services have been delivered to groups of users defined in relatively narrow manners: either by keeping a list of all users who are members of the group, or by attaching specific group membership attribute information to the information maintained about each specific user. Dynamic group membership allows these services to be delivered to groups of users who can be defined by a completely arbitrary specification of user attribute information. For example, electronic mail can be sent to a group of users whose office was located in a certain building (specifically, whose office location attribute matched a specific value.) Another example is that users may be permitted to access a network service, such as a printer, based on whether the printer is in the same building as the user (specifically, whether the printer's location attribute matches the user's office location attribute).

In various embodiments, the invention provides a system for heating a liquid, such as, for example, water, comprising a plurality of liquid heaters, the inlets and outlets of which are respectively connected in a parallel flow relationship by respective manifolds, and configured to provide liquid having a temperature of greater than about 90 degrees Fahrenheit at a flow rate of greater than about 10 gallons per minute. In various embodiments, the present invention provides an electric tankless liquid heater system capable of delivering hot liquids, and in particular water, at even higher flow rates and or temperatures, including, but not limited to, flow rates greater than about: (1) 12 gpm; (2) 18 gpm; (3) 20 gpm; and (5) 20 gpm; and/or temperatures of greater than about: (1) 100.degree. F.; (2) 120.degree. F.; (3) 140.degree. F.; and (4) 180.degree. F.