Steam heated hot air furnace having an electric steam boiler

In a furnace having a boiler in which a pair of spaced electrode plates are supported, electric current is applied to the electrodes to generate steam which flows out of the boiler through a steam conduit to a heat exchanger. A blower forces air across the heat exchanger and out of the furnace through duct work for distribution to the rooms that are to be heated. An equalizer line is connected from the steam conduit to the bottom of the boiler. A return line, having a Hartford loop located above the bottom of the boiler but below the water level of the boiler, returns condensate from the heat exchanger to the boiler through the equalizer line.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates generally to warm air furnaces and deals more 
particularly with a furnace that includes an electrically heated boiler. 
Closed steam heating systems have long been used to heat homes and other 
buildings. Among the advantages of steam heating are its overall 
simplicity and reliability, while the disadvantages include radiator noise 
and the plumbing costs of the extensive piping that is required. In recent 
years, forced air furnaces have been considerably more popular than steam 
system, principally because of their quieter operation and reduced 
maintenance requirements. Since both types of heating systems are 
typically fired by coal, fuel oil or natural gas, they have been greatly 
affected by the recent cost increases in these shortage fuels. 
A need therefore remains for an improved furnace which is able to heat 
effectively without consuming an excessive amount of fuel or power. It is 
the primary goal of the present invention to meet this need by providing a 
furnace that combines the simplicity and efficiency of steam heating with 
the advantages of forced air systems and electric furnaces. 
An object of the invention is to provide a furnace of the character 
described in which the heat of the steam is transferred to circulating air 
for distribution to the rooms that are to be heated. The use of forced air 
in combination with a steam system retains the simplicity and efficiency 
of steam heating while eliminating the need for extensive piping and for 
radiators or the like in the rooms. 
In summary, the invention is directed to an electric boiler furnace having 
an insulated boiler in which a pair of spaced electrodes are supported. 
Electric circuit applied to the electrodes generates steam which flows out 
of the boiler through a steam conduit to a heat exchanger. A blower forces 
air across the heat exchanger and out the furnace through duct work for 
distribution. An equalizer line is connected from the steam conduit to the 
bottom of the boiler. A return line, having a Hartford loop located above 
the bottom of the boiler but below the water level of the boiler, returns 
condensate from the heat exchanger to the boiler.

Referring now to the drawing in detail, a furnace constructed according to 
the present invention is generally designated by reference numeral 10. A 
blower 11 is mounted on a support 11a and driven by a motor 12. Blower 11 
and motor 12 are housed within a compartment 13 located at the bottom of 
the furnace housing. Compartment 13 is presented between walls 14, a floor 
15, and an upper horizontal partition 16. An outlet opening 17 through 
which blower 11 discharges air is formed in partition 16. 
A boiler 18 is located on top of partition 16 within the upper portion 19 
of the furnace housing. Housing portion 19 is bounded by walls 20 and a 
ceiling 21 that are lined with thermal insulation 22. An outlet opening 23 
is formed through ceiling 21, and a duct 24 connects to the outlet to 
receive and distribute warm air to the rooms that are to be heated. A 
generally vertical baffle 25 is mounted between one of the furnace walls 
20 and the boiler 18 in order to assist in directing the air from blower 
11 toward the outlet duct 24. 
Referring now to FIG. 2 in particular, boiler 18 is rectangular in shape 
with opposite side walls 26 which comprise flat metal plates. The end 
walls 27 of the boiler are metal channels having flanges that are bolted 
at 28 to the side walls 26. The floor 29 and ceiling 30 of the boiler are 
also channels which are bolted to the end and side walls, as best shown in 
FIG. 1. The entire interior surface area of the boiler is lined with a 
coating of asbestos insulation 31a, and gaskets 31b are provided at the 
junctions between the boiler walls, floor and ceiling for sealing 
purposes. 
A pair of electrodes 32 and 33 are located within boiler 18 in order to 
electrically heat the water therein. A pair of insulators 34 extend 
through one of the boiler side walls 26 in a leakproof manner. A conductor 
rod 35 extends through each insulator 34, and the electrodes 32 and 33 are 
connected to the ends of rods 35. Conductor wires 36 lead to conductors 35 
in order to supply current thereto, while a ground wire 37 is grounded to 
the boiler. The wires lead to a panel 38 which is mounted to one of the 
furnace walls 20. An access opening 39 is formed through wall 20 and is 
normally covered by a door 40. 
In the preferred embodiment, electrodes 32 and 33 are flat, rectangular 
stainless steel plates that are parallel to one another. Preferably, the 
electrode plates are approximately 3/16 inch thick and are spaced 
uniformly from one another a distance of about 5/8 inch. Insulated spacers 
42 are provided to maintain the uniform spacing and alignment of the 
electrodes 32 and 33. There are preferably a pair of spacers 42 near the 
lower ends of the electrodes and a second pair near the upper ends of the 
electrodes. As shown in FIG. 2, a rigid insulative rod 43 extends through 
each electrode 32 and 33 and between the boiler side walls 26, to which 
the rod is connected at its ends. The spacers 42 are supported around rods 
43 and include central portions which are located between the electrodes 
32 and 33 to maintain the spacing and alignment thereof. End portions of 
the spacers are located tightly between walls 26 and the electrode plates. 
Electrodes 32 and 33 are spaced well away from the walls, floor and 
ceiling of the boiler. Electrode 32 is somewhat greater in height than 
electrode 33, with its end located above that of electrode 33. The normal 
water level within boiler 18 is indicated at 44, and the top end of each 
electrode is located well above this level. 
A steam conduit 46 connects to boiler 18 to receive the steam that is 
generated therein. Conduit 46 extends generally upwardly at an inclined 
angle from the top of the boiler and connects at its top end to a steam 
header pipe 47. The header pipe 47 extends generally horizontally and is 
preferably a copper pipe. A steam gauge 48 connects to pipe 47 and 
indicates the steam pressure therein. 
A plurality of finned heat exchangers 50 extend at a slightly downwardly 
inclined angle from connection with header 47. Heat exchangers 50 are 
arranged to extend parallel to one another. Each heat exchanger 50 
preferably comprises a coil of copper tubing having a diameter of 
approximately 1/2 inch. Each heat exchanger connects at its lower or left 
end to condensate return header pipe 51 which extends substantially 
horizontally and which receives the water that condenses on the heat 
exchangers. An air vent 52 vents to the atmosphere to permit the escape of 
air from pipe 51. 
A return line 54 extends generally downwardly and inwardly toward boiler 18 
from the return header 51. Line 54 is bent back upwardly at its lower 
portion and is connected with a Hartford loop 55, the horizontal portion 
of which is located approximately 2 inches below the water level line 44 
in the boiler. The Hartford loop 55 connects at its end with an equalizer 
line 56 which extends upwardly and is then bent horizontally to connect 
with the steam conduit 46 at a location above the boiler. The condensate 
return path includes a downward continuation 56a of the equalizer line 
which extends from the Hartford loop 55 downwardly to connection with a 
horizontal fill line 57. Line 57 connects with the bottom portion of the 
boiler to supply fresh water and condensate thereto. 
An automatic fill mechanism for supplying water to the boiler includes a 
casing 58 from which a pair of generally horizontal pipes 59 extend. A 
vertical gauge glass 60 is connected between the ends of lines 59 and 
serves to visually indicate the water level in the boiler. A vertical pipe 
61 extends upwardly from the fill pipe 57 to connect same with the 
automatic fill mechanism. A float valve (not shown) within casing 58 
operates a valve 62 in the fill line 57 when the water level in the casing 
drops below a preselected level. When this occurs, valve 62 admits water 
to the boiler through line 57 which connects to a water supply. A drain 
pipe 63 equipped with a manual valve 64 connects to an intermediate 
portion of pipe 57. 
In use, a conventional room thermostat (not shown) controls blower 11 and 
the current supply to conductor rods 35. When current is applied to 
electrodes 32 and 33 to create a voltage differential therebetween, the 
electrical charge flows through the water between the electrodes, and the 
water is thereby heated to quickly reach the boiling temperature. The 
steam that is generated in the boiler passes through steam pipe 46 and 
into the header pipe 47. The steam then flows through the heat exchangers 
50 in equal amounts, and the action of blower 11 forces a flow of air 
across the heat exchangers. The baffle 25 assists in directing the air 
toward the heat exchangers and the outlet duct 24. The air that flows past 
heat exchangers 50 picks up heat from the steam therein, and the warm air 
passes out through duct 24 and is distributed to the rooms that are to be 
heated. 
The water that condenses in heat exchangers 50 flows along the length 
thereof into the return header pipe 51. From pipe 51, the condensate flows 
through pipe 54 and the Hartford loop 55 back into the boiler through line 
56a and the fill line 57. The Hartford loop acts essentially to trap water 
since it is located below the water level of the boiler. The equalizer 
line 56 applies downward steam pressure at the bottom portion of the 
boiler and thus cooperates with the Hartford loop to prevent a backflow of 
steam from the boiler. It is contemplated that suitable automatic switch 
controls (not shown) will shut off current to electrodes 32 and 33 if the 
water level in the boiler is too low or if the boiler floods, and also if 
blower 11 should malfunction. 
It has been found that the electrical energy applied to the electrodes is 
converted into heat for boiling the water. As an example of the 
efficiencies that have been obtained, 40 kilowatts were consumed in a 
typical 24 hour period during which the furnace maintained the average 
size house in which it was installed at a temperature of 73.degree. F. The 
outside temperature varied between 38.degree. F and 64.degree. F during 
the 24 hours. During another typical 24 hour period in which the outside 
temperature varied between 50.degree. F and 60.degree. F, the house was 
maintained at 73.degree. F with the furnace consuming 30 kilowatts of 
power. 
From the foregoing it will be seen that this invention is one well adapted 
to attain all ends and objects hereinabove set forth together with the 
other advantages which are obvious and which are inherent to the 
structure. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
Since many possible embodiments may be made of the invention without 
departing from the scope thereof, it is to be understood that all matter 
herein set forth or shown in the accompanying drawings is to be 
interpreted as illustrative and not in a limiting sense.