On-demand water heating system
An on-demand, closed-loop fluid heating system with a control system for providing fluid on-demand at consistent desired precise temperatures. The closed loop assembly may include a heating system, an air separation chamber with an air vent valve, a circulation pump, a small fluid accumulation tank, and plumbing forming the closed loop. Various sensors related to flow and temperature of fluids provide input to the combined feed forward and feed back temperature control system, such as a Programmable Logic Controller that precisely adjusts intermittently outgoing fluid temperature by immediately controlling the amount of heating to the fluid at precisely near usage temperature. Output from the control system can regulate various aspects of the system. A check valve in the closed loop between the system inlet and the system outlet avoids incoming fluid from being mixed with heated outlet fluid.
1. A fluid heating system for providing fluid on-demand at consistent desired precise temperatures comprising:
a closed loop with a heating system, an air separation chamber with an air vent valve, a circulation pump, a small fluid accumulation tank, a flow indicating sensor and plumbing forming the closed loop;
a system inlet allowing entry of incoming fluid to the closed loop;
an incoming temperature sensor after the system inlet in the closed loop;
a system outlet that allows heated fluid to exit the closed loop;
a fluid feed temperature sensor in the closed loop adjacent to the system outlet, which measures the temperature of the fluid just before the fluid exits the closed loop;
a control system that receives input from the flow indicating sensor, the incoming temperature sensor and the fluid feed temperature sensor to control the heating system; and
a check valve between the system inlet and the system outlet that avoids incoming fluid from being mixed with heated outlet fluid;
wherein the control system determines a modulated power setting level to enable the heating system to supply proper input into the closed loop to again recover to set point with the following calculation:
Watts
Required
=
(
SP
-
M
)
×
GPM
×
1000
watts
1
kw
×
1
6.824
°
F
.
GPM
/
kw
Where:
SP=Set Point Value in ° F.
M=Mix Temp. @ the incoming temperature sensor in ° F.
GPM=Flow around the Closed Loop in gallons/minute
Then:
%
Output
(
Required
Power
Level
)
=
Watts
Required
Watts
Available
Where: Watts Available is a program value determined at build.
2. The fluid heating system of claim 1 further comprising a heater temperature control sensor after the heating system in the closed loop for measuring temperature of the fluid as it exits the heating system and is connected to an input to the control system to control the heating system and the temperature of the fluid exiting the heating system.
3. The fluid heating system of claim 1 wherein the circulation pump is of sufficient size to create a flow around and within the closed loop of a rate of 4-6 times of flow in and out of the system.
4. The fluid heating system of claim 1 wherein the small fluid accumulation tank is less than a six gallon capacity without an internal heat source.
5. The fluid heating system of claim 1 further comprising an expansion tank connected to the closed loop.
6. The fluid heating system of claim 1 wherein the heating system is electric having a plurality of heating chambers with a portion of a top manifold and bottom manifold, a connecting tube between the manifolds, and a heating element immersed in the fluid.
7. The fluid heating system of claim 1 wherein the control system includes a combined feed forward and feed back temperature control Programmable Logic Controller that precisely adjusts intermittently outgoing fluid temperature by immediately controlling the amount of heating to the fluid at precisely the usage temperature within a deviation of ±2° F.
8. The fluid heating system of claim 1 wherein the control system provides output to control the system to a heated water feed solenoid valve and to a drain solenoid valve that can be opened to drain unused fluid in the system outlet as controlled by output signals from the control system.
9. A water heating system for providing water on-demand at consistent desired precise temperatures comprising:
a closed loop assembly including
an electric heating system with heating elements in a plurality of heating chambers,
an air separation chamber with an air vent valve to evacuate air from a closed loop,
a circulation pump of sufficient size to create a flow around and within the closed loop of a rate of 4-6 times of flow in and out of the system,
a small water accumulation tank that is less than a six gallon capacity without an internal heat source,
a flow indicating sensor used to verify that the closed loop has a minimum of a threshold flow rate within the closed loop,
an expansion tank with a bladder to provide thermal expansion space,
with plumbing forming the closed loop
in conjunction with
a system inlet with an inlet pressure regulator to regulate the pressure of the incoming water to the closed loop;
an incoming temperature sensor after the system inlet in the closed loop;
a system outlet that allows heated water to exit the closed loop;
a water feed temperature sensor in the closed loop adjacent to the system outlet, which measures the temperature of the water just before the water exits the closed loop;
a heater temperature control sensor after the heating system in the closed loop for measuring temperature of the water as it exits the heating system;
a combined feed forward and feed back temperature control system being a microprocessor programmable logic controller that receives input from the flow indicating sensor, the incoming temperature sensor, the heater temperature control sensor, and the water feed temperature sensor to precisely adjust intermittently outgoing water temperatures by immediately controlling the amount of voltage to the heating elements to heat the water at precisely a usage temperature within a deviation of ±2° F.; and
a check valve in the closed loop between the system inlet and the system outlet that avoids incoming water from being mixed with heated outlet water wherein the system does not use cool water to mix with heated water in mechanical thermostatic mixing and the water is not heated more than ±2° F. of the desired temperature.
10. The water heating system of claim 9 further comprising a display for entering command inputs into the control system.
11. The water heating system of claim 9 wherein the closed loop assembly is surrounded by insulation.
12. The water heating system of claim 9 wherein the system outlet includes a drain solenoid valve that can be opened to drain unused water in the system outlet as controlled by an output signal from the control system.
13. The water heating system of claim 9 wherein the control system provides output to control the system to a heated water feed solenoid valve and a drain solenoid valve.
14. The water heating system of claim 9 wherein an output signal from the control system to provide voltage to the heating elements is a variable rate that changes an on-time or modulation rate of the heating elements to provide controlled modulated heat output of the heating elements.
15. The water heating system of claim 9 wherein the system inlet further includes an inlet flow sensor to indicate the flow rate and flow start and stop sequence as a signal to the control system.