Automatic control of steam heating systems using remote sensors and switches utilizing thermodynamic qualities of steam with the existing system characteristics to increase heating cycle efficiency

Abstract

An electromechanical analog or digital system that controls a steam heating cycle in one or more spaces is revealed herein. Said electromechanical system is comprised of pressure and temperature sensors, and pressure and temperature switches. Said sensors are installed into or onto a steam heating system, at the furthest steam circulation point physically accessible of said steam heating system. Said switches, by either mechanical or electrical means, receive temperature and pressure data from said sensors, respectively. Pressure and temperature switches are interposed between a thermostat and steam supply, as to oscillate steam supply until pressure and temperature set points of switches are achieved or set point of thermostat is achieved. The same aforementioned system can be controlled using a digital controller to take pressure and temperature sensors information into a controller that will interrupt or continue the call for heat from a thermostat to a steam supply.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS.

U.S. Pat. No. 1,992,846 relates to a system in which the temperature of the radiator rather than the surrounding space controls the steam supply. Accordingly, the time of steam flow is a function of air temperature surrounding a pilot radiator, rather than purely a function of the condition of the temperature adjacent the thermostat. Another disadvantage is that temperature is not the only property of steam and nothing in this particular invention takes into account the latent energy of the steam, as it should. U.S. Pat. No. 2,468,268 discloses an intermittently fired steam producer in combination with means for heating radiators between cycles, the heating being dependent upon the differential of indoor and outdoor temperatures. When pressure drops due to a high temperature differential, the pressure drop induces a heat flow through the heating circuit even during the off cycle of the boiler. This system is flawed due to no control of the elements heating the space. U.S. Pat. No. 5,056,714 (Cohen) uses a timer that after a certain pressure is established within a radiator, the heat cycle will stop. The problem with this patent is that the timer can be very subjective to the settings of the installer and does not necessarily emit the maximum amount of heat possible by the system. Ambient conditions change constantly and there is no way of setting the optimum time correctly for the proper heat transfer from a radiator to one or more spaces to be heated. Other examples of steam heating systems may be found the following additional U.S. Pat. No. 1,985,215 (Shivers) U.S. Pat. No. 2,030,544 (Ross) U.S. Pat. No. 2,062,565 (Ferguson et al) U.S. Pat. No. 2,065,198 (Rohlin) U.S. Pat. No. 2,152,699 (Kuester et al) U.S. Pat. No. 2,153,382 (Martin Jr.) U.S. Pat. No. 2,249,706 (Furguson) U.S. Pat. No. 2,378,760 (Ferguson) U.S. Pat. No. 2,387,576 (Graves) U.S. Pat. No. 2,668,664 (Williams)

All of the aforementioned patents do not take into account the latent heat of vaporization of steam and the energy that it has to transfer to the heated space. Nor do they attempt to modulate the system based on the physical state of the steam being liquid, vapor or superheated state of matter. They do not account for the frictional and mechanical losses of the system and try to provide the minimum energy needed to heat the space(s). None of the previous patents put all of this data together in an electromechanical system to control the steam supply for maximum efficiency. That is what makes the previous patents obsolete when it comes to controlling temperature in a space.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAMES OF THE PARTIES TO A JOIN RESEARCH AGREEMENT

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INCORPORATION-BY-REFRENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF INVENTION

(1) Field of the Invention

The field of the invention relates to controlling steam-induced heat in a steam heating system that heats one or more spaces. In particular the invention makes use of remote electro-mechanical temperature and pressure sensors connected to analog or digital switches installed or onto a conduit(s) or heating element(s) of a steam heating system to control the steam cycle that supplies steam induced heat to one or more spaces. Through the use of this invention a steam heating system will work more efficiently by using less energy to keep the desired temperature setting in a space or spaces and maintain a constant desired temperature setting in the heating area.

(2) Description of the Related Art

Most conventional steam heating systems are inefficient and poorly controlled. The temperature in a space is rarely maintained at or near a desired temperature set point. A typical steam heating system employs a thermostat, which controls to call for steam from the steam supply source to heat one or more spaces. A steam supply source or example could be, but is not limited to, an oil or natural gas fired boiler.

When the temperature of a space(s) falls below a set temperature point that has been programmed into a thermostat, a signal/call for heat is sent from a thermostat to a steam supply source. Steam is emitted from a steam supply source, which enters the heating conduit system, also known as a piping system, forcing cool air through the thermostatic vent valves. These valves open to allow cool air within the radiators and heating conduit/piping system to vent out. Once the steam enters a radiator(s) the valves close.

After venting out the cool air, the heated steam heats a radiator(s), which transfers the heat energy to one or more spaces to be heated, thus heating the space(s). A steam supply source, such as an aforementioned boiler, continues to emit steam until either the operating limit control of a steam supply source is reached or the temperature setting of a thermostat is reached. At this point a steam supply source receives a signal from a thermostat or from its operating limit control mechanism to deactivate. It should be noted that the signal/call for heat from a thermostat continues until a desired set temperature point in one or more spaces to be heated is reached. The operating limit control functions to protect a steam supply source from reaching excessive pressures and acts strictly as a control function for a steam supply source, not as a control function of the temperature of a space.

A significant drawback of such conventional systems resides in that heat emitting element of said system, such as a radiator, will continue to emit heat after a desired set point is reached and, also that, after a burner/heat supply source is deactivated, such residual heat raises the temperature within a space beyond the desired temperature set point. As a result, there is a continuous “hunting” cycle wherein the temperature in a space continuously varies from a temperature below the set point to a temperature above the set point; the higher temperature being developed, as noted, due to the continued emission of heat after the desired temperature set point has been reached.

Numerous control systems have been proposed which incorporate complex valves, multiple sensors, timers etc. in an attempt to provide a relatively constant temperature within one or more spaces to be heated. Such assemblies have failed to control the heat cycle effectively and have made steam heat expensive and inefficient to operate and maintain as compared to other non-steam source heating systems and methods.

BRIEF SUMMARY OF INVENTION

The herein disclosed invention controls a steam heating cycle using thermodynamic qualities of steam. Quality of steam is a calculated value based on pressure and temperature properties of steam, best represented by a Mollier diagram (FIG. 4). The Mollier (FIG. 4) diagram embodies the principle that a higher “quality” steam has more available latent energy to transfer to a space to be heated.

EXAMPLE I

Start of cycle or cut in pressure and temperature

P1=15 psia

T1=130 Deg F.

x1=sub cooled quality %

h1=98 BTU/lbm

End of cycle or cut out pressure and temperature.

P2=16 psia

T2=217 Deg F

x2=superheated quality %

h2=1132 BTU/lbm

End of cycle or cut out pressure and temperature with 2 psia of steam higher than necessary.

P3=18 psia

T3=222 Deg F.

x3=superheated quality %

h3=1154 BTU/lbm

Calculations

Q=MCpΔT

Where M=mass flow (lb/hr)

Cp=specific heat (Btu/lbm*R)

ΔT=Change in temperature (deg F)

Q=rate of heat transfer (Btu/Hr)

Where M,Cp are same for both situations

Q2=(T3−T1)=92

Q1=(T2−T1)=87

Q2−Q1=5 Deg F.

H3−H2 22 btu/Ibm

Negligible temperature change and btu/lbm for minor steam pressure and run boiler excessively. Steam at a lower pressure but higher quality can have a higher enthalpy value than steam at a higher pressure but lower quality. The higher enthalpy steam has more energy per unit mass to transfer to a space that requires heating. No current system takes the above mentioned thermodynamic properties of steam into account and instead relies on the settings of the thermostat to cycle steam supply source, such as a boiler, on or off till desired thermostat temperature is met. If the call for heat from the steam supply source was “off” and the desired temperature in a space(s) was reached, the heating elements are still transferring heat from the heating element. Current systems do not accurately account for the operating control of the steam supply and its settings. These settings can allow too much steam to be supplied to the system wasting energy. This results in temperature variations in the space(s) to be heated and wasting energy by either over or undersupplying the system with steam. That is a major flaw of the current systems in place, which result in wasted energy, temperature swings and mechanical issues within the steam heating system itself. My patent accounts for the heat transferred after the steam supply by using the method I developed. The herein disclosed invention also accurately adjusts and compensates installation settings and system characteristics that were previously subject to the existing conduit/pipe installation and

the control setting subjectively set by the installer. The herein disclosed invention takes into account mechanical losses in the heating conduit/piping system leading to and from a heating element, such as a radiator(s), supplying heat to one or more spaces. It allows

a heat cycle to remain active until the minimum pressure needed to circulate the steam through the system to be heated is reached, then and only then does it deactivate. This optimally efficient heat cycle is accomplished by strategically placing sensors into the heating conduit/piping system as far removed from the steam supply source as physically possible. By installing said sensors at the farthest point physically accessible to the installer, such strategic placement will take into account a steam heating system's inherent properties, including but not limited to: fluid friction, pipe losses, gravitational energy losses and thermodynamic properties of steam. Once the steam reaches said

farthest point in a steam heating system, circulation of steam will have reached all other points in a steam heating systems conduit as well. Said sensor(s) will send a signal to one or more pressure and temperature switches, respectively. Accordingly an advantage of one or more aspects is as follows: electromechanical system, which is the invention revealed herein, will function as to allow for minimum operating time of a steam supply

source that is needed to circulate steam (with sufficient latent heat through out space). Previously the individual that set the operating control of the steam supply source determined this. Thus the aforementioned setting was very subjective as it was based on the installer's discretion, affected by human error or lack of knowledge, and was often set much higher or lower than at the optimally efficient setting possible. This created conditions that either caused one or more spaces to be overheated or caused an inadequate heating of one or more spaces. The herein disclosed invention also would eliminate short cycling of a steam supply source because it ensures that all of the useful latent and sensible heat is transferred from the steam in the conduit/piping part of the system to a heating element, such as a radiator(s), to one or more spaces to be heated before the heat cycle would start again. These characteristics allow for more even heating of a space or spaces as well as lower maintenance and/or reduce steam heating system failures due to over pressurizing or under pressuring of the steam heating system.

In accordance with one embodiment an electromechanical system that controls a steam heating system to regulate temperature in a space or spaces to be heated by a steam supply, a heating element(s) in space(s) to be heated, conduit supplying steam operatively connecting steam supply to heating element(s), thermostat(s) located in space(s) being operatively connected to a conduit supplying steam as to initiate a heating cycle from steam supply, thermostat(s) being responsive to a sensed temperature below a predetermined temperature for space(s). Pressure senor(s) being responsive to the pressure in said steam conduit, temperature sensor(s) being responsive to temperatures in said steam conduit, normally closed temperature switch that activates open or closed based on the temperatures sent from the temperature sensors, normally closed pressure switch that activates open or closed based on the pressure sent from the pressure sensor(s), electrical conduit or wireless connection for providing interface between switch(s), sensor(s), thermostat(s), steam generator. Temperature and pressure sensors are installed into or onto the heating conduit/piping part of a steam heating system at the furthest steam circulation point physically accessible for that steam heating system. Pressure and temperature switches receive temperature and pressure data from said sensors, respectively. Pressure and temperature switches are interposed electrically between a thermostat and steam supply. Pressure and temperature switches will have high and low value set points that will oscillate to switch on or off when high or low values of pressure or temperature are achieved respectively. The switches are both normally closed switches until the set point is achieved and the switch is opened which will open the circuit. The pressure and temperature switches are electrically connected in parallel with each other and in series between the thermostat and steam supply. There is a bypass switch that bypasses the electrical circuit of the pressure and temperature switches incase such action is desired or necessary.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary as well as the following detailed description will be better understood when read in conjunction with the drawings, wherein;

FIG. 1 is a schematic of the invention incorporating pressure switches controlling steam enthalpy through mechanical means;

FIG. 2 is a flow chart of a known control sequence on a conventional steam heating system;

FIG. 3 is a flow chart of the invention's control sequence;

FIG. 4 is a copy of a known “Mollier Diagram” representing steam properties using enthalpy and entropy;

FIG. 5 is a list of parts claimed in the invention;

FIG. 6 is a schematic of the invention incorporating electrical control as means for controlling heat.

DETAILED DESCRIPTION OF THE INVENTION

The accompanying diagram FIG. 1 depicts a steam heating system. The purpose of the system is to heat one or more spaces to a desired temperature and then maintain that temperature in said space(s) as evenly as possible. There is a steam supply source (14) that supplies hot steam throughout a steam heating system. The heavy dark lines represent a pathway for which steam is supplied throughout a steam heating system, referred to as a heating conduit/piping part of the steam heating system. There is a heating element, commonly referred to as a radiator, that heats one or more spaces (12) by being supplied hot steam from a steam supply source via a heating conduit or piping system. There is a thermostat (10) that gives the call for heat and initiates the heat cycle. Said thermostat is a switch wired in series to a steam supply source, (10) that sends a signal to a steam supply source to start a heat cycle. There is a normally closed pressure switch (16) measures the pressure of the steam in the heating conduit/piping system. Said pressure switch (16) is installed at the farthest steam circulation point physically accessible to the installer in or on the heating conduit/piping element of a steam heating system. There is a normally closed temperature switch (18) that measures the temperature of the steam in the heating cycle in said heating conduit system. The temperature switch should be installed as close to the pressure switch as physically possible, sensing from the same line as the pressure switch. There is a bypass switch (29) that is normally open but can be closed for maintenance or repair purposes.

Elements (18) and (16) are wired in series with a thermostat (10) and in parallel with each other. Upon a call for heat from a thermostat, a steam heating system will initiate its heat cycle. When the desired pressure and temperature of the steam in a steam heating system are met, the pressure (16) and temperature (18) switches will open and the cycle will stop. The steam supply source will stop producing a heat cycle because all the switches will be in an open state and, thus,

interrupt any signal from the thermostat (10) calling for heat. The cycle will remain interrupted until the thermostat (10) set point is reached or the temperature and pressure conditions at the heating element (12) where the sensors are located, have reached a value where all of the effective latent and sensible heat from a heating element has been transferred to one or more spaces. The pressure and temperature setting that determines when the steam supply source oscillates on or off are based on calculated steam quality properties from a Mollier diagram (FIG. 4). A calculated quality of steam close to or equal to 1 will cut out the cycle. The cut in of the cycle will occur when the calculated steam quality reaches 0 or a sub cooled state. At that point the (16) and (18) switches will close again completing the circuit. The signal from a thermostat (10) to call for heat will close and the heat cycle will resume unless the thermostat (10) set point in said space has been reached.

The accompanying diagram FIG. 6 depicts a steam heating system. The purpose of the system is to heat one or more spaces to a desired temperature and then maintain that temperature in said space(s) as evenly as possible. There is a steam supply source (14) that supplies hot steam throughout a steam heating system. The heavy dark lines represent a pathway for which steam is supplied

throughout a steam heating system, referred to as a heating conduit/piping part of the steam heating system. There is a heating element, sometimes referred to as a radiator, that heats one or more spaces (12) by being supplied hot steam from a steam supply source via a heating conduit or piping system. There is a thermostat (10) that gives the call for heat and initiates the heat cycle. Said thermostat is a switch wired in series to a steam supply source, (10) that sends a signal to a steam supply source to start a heat cycle. There is a pressure sensor (36) measures the pressure of the steam in the heating conduit/piping system. Said pressure sensor (36) is installed at the farthest steam circulation point physically accessible to the

installer in or on the heating conduit/piping element of a steam heating system. There is a temperature sensor (38) that measures the temperature of the steam in the heating cycle in said heating conduit system. The temperature sensor should be installed as close to the pressure switch as physically possible, sensing from the same line as the pressure switch. There is a bypass switch (29) that is normally open but can be closed for maintenance or repair purposes.

Elements (38) and (36) are connected to an analog or digital controller (34). The analog or digital controller (34) will take the inputs from sensors (38) and (36) and based on settings calculated from a Mollier diagram (FIG. 4) will open or close the circuit based on the pressure or temperature setting from sensors (38), (36). The analog or digital controller (34) is wired in series with a thermostat (10) and steam supply (14). Upon a call for heat from a thermostat, a steam heating system will initiate its beat cycle. When the desired pressure and temperature of the steam in a steam heating system are met, the pressure (36) and temperature (38) sensors will transmit to the analog or digital controller (34). The controller will compute the data based on the Mollier diagram (FIG. 4) will stop the cycle. The steam supply source will stop producing a heat cycle because the analog or digital controller (34) will be in an open state and, thus, interrupt any signal from the thermostat (10) calling for heat. The cycle will remain interrupted until the thermostat (10) set point is reached or the temperature and pressure conditions at the heating clement (12) where the sensors are located, have reached a value where all of the effective latent and sensible heat from a heating element has been transferred to one or more spaces. The pressure and temperature setting that determines when the steam supply source oscillates on or off are based on calculated steam quality properties from a Mollier diagram (FIG. 4). A calculated quality of steam close to or equal to 1 will cut out the cycle. The cut in of the cycle will occur when the calculated steam quality reaches 0 or a sub cooled state. At that point the analog or digital controller (34) will close again completing the circuit. The signal from a thermostat (10) to call for heat will close and the heat cycle will resume unless the thermostat (10) set point in said space has been reached.

Mollier diagram (FIG. 4)
EX.1
Start of cycle or cut in pressure and temperature
P1 = 15 psia
T1 = 130 Deg F.
x1 = subcooled quality %
h1 = 98 BTU/lbm
End of cycle or cut out pressure and temperature.
P2 = 16 psia
T2 = 217 Deg F.
x2 = superheated quality %
h2 = 1132 BTU/lbm
End of cycle or cut out pressure and temperature with 2 psia of steam
higher than necessary.
P3 = 18 psia
T3 = 222 Deg F.
x3 = superheated quality %
h3 = 1154 BTU/lbm
Calculations
Q = MCp(delta)T
Where
M = massflow(lb/hr)
Cp = specific heat (Btu/lbm*R)
(Delta)T = Change in temperature(deg F.)
Q = rate of heat transfer(Btu/Hr)
Where M,Cp are same for both situations
Q2 = (T3 − T1) = 92
Q1 = (T2 − T1) = 87
Q2 − Q1 = 5 Deg F.
H3 − H2 22 btu/lbm
Negligible temperature change and btu/lbm for minor steam pressure
and run boiler excessively
FIG.8

Claims

1. An electro-mechanical regulating system heating system comprising of:

A steam supply means;

A heating element in a space to be heated;

A steam conduit means connected to said steam supply means and said heating element means;

A thermostat element in said space to be connected to said steam supply means;

Pressure sensing means;

Temperature sensing:

A pressure electrical switching means;

A temperature electrical switching means;

A triggering element for sensing pressure and temperature within the system for cycling steam supply on and off within the system.

2. A system according to claim 1, wherein;

said pressure sensors in communication with said pressure switches, for sensing pressures in said system and pressure element responds to existing system pressure requirement based on calculated settings derived form Mollier diagram, said temperature sensors in communication, with said temperature switches, switching-means for sensing temperature of the steam means responsive to existing system temperature requirement based on calculated-settings derived from Mollier diagram. Pressure and temperature switches, to be connected to said pressure and temperature sensors for sensing of atmospheric pressures and temperatures triggering said steam supply means till desired pressure and temperature settings are achieved in said conduit or said heating element whereby said steam supply means is cyclically energized and de-energized until said desired temperature setting of said space to be heated is reached.

3. An electro-mechanical regulating system heating system according to claim 1 further comprising; said pressure and temperature sensors means are installed at the furthest steam circulation point of said steam heating system, physically accessible by the installer of this invention.

4. A method for dampening an existing steam heating system comprising;

said pressure and temperature switches, are activated and deactivated through sensed pressures and temperatures within the steam system, interrupting and continuing signal from thermostat, respectively using the Mother diagram to calculate quality of the steam based on pressure and temperature magnitude requirements of the existing system in order to cycle said steam supply means.

5. An electro-mechanical regulating system heating system according to claim 1 further comprising;

where said pressure and temperature switches, means are wired in series circuit in between the thermostat and steam supply controlling the signal between the thermostat and said steam supply.

6. An electro-mechanical regulating system heating system according to claim 1 further comprising;

where said pressure and temperature sensors are connected wirelessly through the use of a wireless communications element which sends a signal to pressure and temperature switches, switching means wired in series circuit between the thermostat and steam supply means.

7. An electro-mechanical regulating system heating system according to claim 1 further comprising:

said pressure and temperature switches are wired in parallel circuit with each other and in series circuit between the thermostat and steam supply means acting to interrupt the signal for the thermostat if both switches thereby de-energizing the ON circuit for the steam supply by requiring the opening of both pressure and temperature switches in order to deactivate the steam supply, where by the said system requires only one pressure or temperature switch to be closed in order to send signal from thermostat to steam supply to initiate a signal for heat from steam supply.

8. An electro-mechanical regulating system heating system according to claim 1 further comprising;

a bypass/maintenance switch which is wired in a series circuit directly between the steam supply means and the thermostat but in a parallel circuit with temperature and pressure switching means, allowing direct connection to the steam supply and thermostat for conventional operation of an existing steam system.

9. (canceled)

10. An electro-mechanical regulating system heating system according to claim 1 wherein two walls are respectively associated with at least two heating zones within the interior of a heating space;

pressure and temperature sensors are located in individual heating zones;

pressure and temperature switches are located in individual heating zones;

wherein switching means is activated or deactivated responsive to sensed pressures and temperatures within the steam system(s), interrupting or continuing signal from thermostat, dampening steam supply valves designated to control that heating zone based on the Mollier diagram without impacting remaining zones within the system.