US 3812872 A
A control system to prevent freezing of heating units, such as boilers, particularly those which may be outdoors, such as on a rooftop. A drain valve is provided to automatically drain the water from the unit in the event of power failure which would prevent heating of the water, or in the event of the occurrence of a low temperature of the water approaching freezing, or both. The system may also include a valve which closes in response to one or both of these conditions to prevent admission of water to the unit. The drain valve embodies a time delay feature so as to not respond to power failures of minimum predetermined duration.
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Description (OCR text may contain errors)
United Sttes Block et a1.
atttt [1 1 [451 May 28, 1974 SYSTEM TO PREVENT FREEZING 0F HEATING UNITS SUCH AS BOILERS  Assignee: Raypak, 1nc., Westlake Village,
22 Filed: June 22,1972
211 App]. No.: 265,125
3,446,226 5/1969 Canterbury I: 137/62 FOREIGN PATENTS OR APPLlCATlONS 1,137,405 12/1968 Great Britain 137/62 Primary Examiner-Alan Cohan Assistant Examiner-Richard Gerard Attorney, Agent, or Firm-Herzig & Walsh [5 7 ABSTRACT A control system to prevent freezing of heating units, such as boilers, particularly those which may be outdoors, such as on a rooftop. A drain valve is provided to automatically drain the water from the unit in the event of power failure which would prevent heating of the water, or in the event of the occurrence of a low temperature of the water approaching freezing, or both. The system may also include a valve which closes in response to one or both of these conditions to prevent admission of water to the unit. The drain valve embodies a time delay feature so as to not respond to power failures of minimum predetermined duration.
1 Claim, 3 Drawing Figures SYSTEM TO PREVENT FREEZING OF HEATING UNITS SUCH AS BOILERS SUMMARY OF THE INVENTION The invention is an automatic control system adapted for use with heating units, such as boilers and particularly boilers which are situated outdoors, such as for example on a rooftop. Such heating units or boilers are particularly subject to the hazard of damage resulting from freezing of the liquid in the boiler which typically would be water. Freezing could result from inoperation of the boiler caused by various occurrences, such as power failure, particularly; interruption of gas or fuel supply; safety shutdown due to pilot outage; or other comparable reasons including inadequate or insufficient water flow; etc.
The primary object of the invention is to provide an automatic control means to protect the boiler from freezing from any of the above ennumerated contigencies.
In a typical type of installation, the heating unit or boiler may be one that is gas fired, although the invention is adaptable in any type of system wherein it is desired to protect the heating unit against the hazard of damage from freezing. The invention is described in detail herein as adapted in a gas fired water heating system wherein the boiler (heating unit) is installed on a rooftop.
In a preferred exemplary form of the invention, an automatic normally closed (The word normal herein means normal or ordinary operation of the system rather than referring to a valve position as related to its being energized or de-energized.) valve is provided to automatically open and drain the boiler in the event of power failure. The valve may also be caused to open in response to the occurrence of a low temperature of the water in the boiler approaching freezing. The valve can be made responsive to both conditions. Additional valve means may be optionally provided, that is, a normally open valve means controlling the supply of water to the boiler which closes when one or both of said conditions occur. In some installations, it is desirable and more economical to not provide the normally open valve, but in the event of occurrence of the said condition or conditions, water is allowed to be continued to be supplied to flow through the boiler and to drain therefrom while the condition prevails. Preferably, a boiler vent valve is provided which is opened in response to the condition or conditions to insure that the drain will take place.
A further object is to provide a control system for protection of a boiler as referred to wherein a normally closed valve is provided to automatically open and drain the boiler in the event of a power failure condition and/or a low temperature in the boiler or other condition indicative of the hazard that there might be freezing of the boiler.
A further object is to provide a system as in the foregoing object providing further, a normally open valve which closes to prevent flow of water to the boiler in the event of occurrence of the condition.
BRIEF DESCRIPTION OF THE DRAWINGS Further objects and additional advantages of the invention will become apparent from the following detailed description and annexed drawings, wherein:
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, a typical rooftop type installation is illustrated. The roof level is designated at 10 and the boiler is designated at 12. The heating unit which is typically referred to in the art as a boiler may be of a conventional type fired by gas such as the one shown in US. Pat. No. 3,575,157.
Numeral M indicates a line or pipe connected to a city water supply which connects to pipes l6, l7, and 19 and to the boiler. In pipe 22, there is provided an expansion tank 18. The discharge line from the boiler is designated at 22. These lines are connected to a typical heating system which may be a space heating system as designated at 24.
In line 14-16 there is provided a normally open valve 30 which may be a solenoid type valve that controls supply of water to the system.
Numeral 34 designates a branch line connected to return line 17 having in it a normally closed bellows operated valve 35. This valve is of a time delay type which although it is normally closed, in the event of a power failure it will automatically open after a predetermined time delay of an established number of seconds. The valve is of this type so that in the event of momentary power failures of a few seconds, it will not open undesirably. As will be noted, drain valve 35 has a valve member 36 connected to bellows 37. Surrounding the bellows is an electrical heating coil 39. Whenever this coil is energized, the fluid in the bellows expands seating valve member 36 and thus closing the valve. Whenever coil 39 is deenergized, the fluid in bellows 37 will cool and contract, and in a predetermined number of seconds will open the valve.
Numerals 38 and 40 designate flow switches which may be of a conventional type and may be connected in the control system for the heating apparatus of the boiler which may involve a typical gas control valve, a safety valve, a pilot operated switch, etc. as is already well known in the art. It is therefore not shown in detail herein.
Numeral 44 designates a temperature actuated switch actuatable in response to thermostatic bulb 46 and tube 48 as shown responsive to temperature of water in the lower part of the boiler.
Numeral 50 designates the drain linefrom valve 35 arranged to drain into a funnel 52 and into the end of a line 54. Line 50 is provided with an orifice 56 ahead of which is line 58 connected to pressure responsive diaphragm switch 60. This switch is connected in a battery powered circuit controlling an alarm 64 which may be of various types, such as visual or audible. Such alarm would be located at an appropriate control center or station to advise supervisory personnel that valve 36 is open and the boiler is draining.
Numeral 62 designates a vent valve connected to the boiler in such a way so as to be able to vent its water system to the atmosphere to insure that the boiler would drain in the event that valve 35 opens.
The system as shown is electrically controlled. Numeral 70 designates a transformer having a primary winding 71 and secondary winding 72. It will be noted that secondary winding is connected to thermostatic switch 44 which controls parallel circuits for all three valves.
In the event of power failure or opening of switch 44 in response to low temperature, valve 30 closes (deenergized); valve 62 opens (deenergized); coil 39 is deenergized and valve 35 opens.
As pointed out in the foregoing, the basic system itself may be of various alternative types embodying various different features and arrangements. The expansion tank, for example, might be below the level of the rooftop. The system might be one having an accumulator or storage tank or one without such a tank as in known in the art as for example in the patent referred to above. The heated water distribution system may be connected directly to the boiler or on the other hand, it may be connected to the accumulator or storage tank. FIG. 3 shows such a system having an accumulator or storage tank 76 having connections 77 and 78 to a water distribution system. Pipe 22 connects to tank 76, and pipe 81 connects the tank to pipe 16.
FIG. 2 shows a possible alternative or modification wherein drain valve 35 is a mechanically operated type responsive to a thermostatic bulb 84 adjacent discharge line 22 and connected to the valve by tube 85. The thermostat normally will maintain the valve closed and at a predetermined relatively low temperature indicating' that freezing of the water has become a possible hazard, the fluid in the bulb will contract sufficiently to cause the drain valve to open allowing the boiler to drain. If desired, a similar mechanically actuated normally open thermostatic valve can be provided to control the flow of water to the boiler. In a system as shown in FIG. 2, power failure protection can be embodied also if'desired.
Fromthe foregoing, those skilled in the art will readily understand the nature and operation of the system of the invention. As pointed out, the system may or may not embody the normally open inlet control valve, and the controls can be responsive to power failure or temperature or both as shown. In some hydronics systems which are closed systems, it is undesirable to continuously circulate water through the system; and thus, the inlet control valve is used. In some instances, it can be dispensed with, thus reducing expense. In the system as shown, in the event of power failure, valve 35 will open after a predetermined number of seconds, the normally open valve 30 will close shutting off flow of water to the boiler. The system may be provided without valve 35, in which event water from the source will continually flow through the boiler and drain therefrom during the time the hazardous condition prevails. The temperature of such water will always be such as to preclude freezing of the boiler.
The foregoing disclosure is representative of preferred forms of the invention and is to be interpreted in an illustrative rather than a limiting sense, the invention to be accorded the full scope of the claim appended hereto.
1. A freeze damage prevention system for a heating unit for heating water and the like wherein said unit is situated to be subject to damage from freezing of the liquid within it, the system comprising: normally closed valve means connected to the unit in a position whereby to drain the liquid from the unit sufficiently to prevent damage from freezing in the unit; and means controlling said valve means responsive to a condition indicative of possible or imminent freezing of liquid within the unit, said responsive means comprising mechanism actuatable in response to power failure whereby to cause said normally closed valve to open, said valve means embodying a time delay mechanism whereby said valve means is prevented from opening in response to a power failure of a predetermined relatively short duration.