[0001] The invention relates to header tanks. Header tanks are typically open cisterns made
from a plastics material and are used to supply cold water, for example to a central
heating system. Header tanks are typically located above hot water tanks in, for example,
the attic of a house. In use, a header tank supplies replacement cold water to a hot
water tank through a supply pipe. The replacement cold water is supplied when hot
water is drawn from the hot water tank as a result of for example, someone having
a shower.
[0002] Throughout the day, a hot water tank is operated to heat and maintain the temperature
of the water to be at a desired level. Typically, heating the water and maintaining
the temperature of the water is controlled by a thermostat and for safety purposes
a vent pipe is also used to allow excess pressure, air bubbles and steam that may
build up in the hot water tank, to be removed through the header tank.
[0003] However, if the thermostat is faulty or fails, the water in the hot water tank can
be heated undesirably. This can lead to the hot water tank causing the water in the
supply tank and the header tank also to be heated, which can result in the temperature
of the normally cold water in the header tank increasing undesirably. As the header
tank is typically made from a plastics material not designed to hold hot water, the
header tank may melt, leading to hot, potentially scolding hot water, leaking out
through the floor of the attic into any room below. This is clearly highly undesirable
and should a person be situated beneath the header tank when it leaks, injury and
possibly death may occur.
[0004] It is an aim of the invention to address problems associated with header tanks that
are identified herein or otherwise.
[0005] The invention provides a safety device for a header tank, the safety device having
means for connecting the safety device to a header tank, the safety device being heat
sensitive such that if water in the header tank rises undesirably, the safety device
acts to empty at least some of the water from the header tank in a controlled and
safe manner.
[0006] Usually the header tank will have means such as a ball-cock, to supply fresh cold
water to the header tank, when the level of water in the tank falls below a predetermined
level. Thus actuation of the safety device according to the invention will result
in fresh cold water replacing heated water in the header tank, resulting in a safe
condition.
[0007] The safety device may comprise a valve which at one temperature is closed, and at
a higher temperature is open.
[0008] The valve may incorporate a control member which melts above a threshold temperature.
[0009] The threshold temperature may be between 60 to 66°C.
[0010] The control member may comprise a heat sensitive membrane.
[0011] The membrane may be made of wax.
[0012] The valve member may have first and second body parts, the membrane being sandwiched
between the body parts.
[0013] One of the body parts may have a recess dimensioned to receive the membrane.
[0014] The membrane may comprise a disc, the recess being shaped and dimensioned such that
the disc is a tight fit within the recess to reduce the risk of leakage.
[0015] Each body part may have at least one aperture through which water can flow, in use,
once the membrane has melted.
[0016] One of the body parts may have more apertures than the other body part.
[0017] A sealing element may be provided between the body parts arranged to prevent water
from leaking out between the body parts.
[0018] The safety device may have means for clamping the body parts together.
[0019] The means for clamping the body parts together may comprise part of a threaded plumbing
fitting arrangeable to mount the safety device in an aperture in a header tank, below
the maximum water level of the header tank.
[0020] The invention includes a header tank having a safety device according to the invention.
[0021] The header tank may have a ball-cock system such that additional cold water will
be supplied to the header tank if the safety device operates to empty at least some
of the water from the header tank.
[0022] The safety device may be mounted in the side wall of the header tank, for example
at a position 30 to 70mm below the maximum water level in the header tank.
[0023] Preferably the safety device includes a water conduit which directs heated water
to a safe point, should the safety device operate.
[0024] The conduit may be connected to a conventional overflow pipe of the header tank.
[0025] The present invention may be carried out in practice in various ways but a specific
embodiment will now be described, by way of example and with reference to the accompanying
drawings, in which:
Figure 1 shows a side view of a header tank assembly of an embodiment of the present
invention;
Figure 2 shows a perspective view of the header tank assembly;
Figure 3 shows an exploded side view of a heat sensitive element for the header tank
assembly;
Figure 4 shows a front view a heat sensitive membrane for the heat sensitive element;
Figure 5 shows a side view of the heat sensitive membrane;
Figure 6 shows a front view of a first body part for the heat sensitive element; and
Figure 7 shows a front view of a second body part for the heat sensitive element.
[0026] Figure 1 shows a header tank assembly 1 of an embodiment of the present invention.
The header tank assembly 1 has a heat sensitive valve 2, a header tank 3, a water
supply apparatus 4 and a drainage pipe 5. The heat sensitive valve 2 is arranged to
empty some of the water into the drainage pipe 5 in response to the water held in
the header tank 3 reaching a threshold temperature. The drainage pipe 5 is connected
to an overflow pipe O of a central heating system to dispose of the water emptied
from the header tank 3, in use.
[0027] As a result of the emptying of water, the level of water in the header tank 3 is
reduced, which in turn triggers the apparatus 4 to supply water into the header tank
3 from, for example, a mains water supply. The supplied water is of a temperature
lower than the threshold temperature thereby causing the temperature of the water
held in the header tank 3 to be maintained or reduced to a temperature lower than
the temperature at which the header tank would melt.
[0028] To ensure that the water can be drained from the header tank 3, the heat sensitive
valve 2 is positioned on a side wall of the header tank 3 beneath a "full" water level
(shown for exemplary purposes as a line WL). The "full" water level WL of the header
tank 3 is in the region of between 50mm to 150mm from a top edge of the header tank
3. The heat sensitive valve 2 is positioned in the region of between 25mm to 100mm
beneath the full water level WL.
[0029] Figure 2 shows that the heat sensitive valve 2 is positioned to extend from an external
surface of the header tank 3 through the side wall to an internal surface of the header
tank 3. The internal surface forms a water holding area of the header tank 3 in which
a reservoir of water is held. A first end 20 of the heat sensitive valve 2 is situated
in a region external to the header tank 3. A second end 21 is situated in a region
internal to the header tank 3. The first end 20 is connected to the drainage pipe
5 to allow water to be drained from the header tank 3 through the second end 21, in
use. The second end 21 has a heat sensitive element that opens the heat sensitive
valve 2 when the temperature of the water is above a threshold temperature, for example,
60°C.
[0030] The heat sensitive valve 2 has a tubing to direct the water drained from the header
tank 3 to the drainage pipe 5. The tubing comprises a plumbing fitting comprising
a plurality of securement means 22, 23, 24 having screw threads and nuts to allow
the valve to be secured. The first securement means 22 is for connecting the valve
to the drainage pipe 5. The second securement means 23 is for holding the valve in
position on the side wall of the header tank. The third securement means 24 is for
holding a valve end cap 25 in position on the heat sensitive valve 2. The securement
means 22, 23, 24 also have sealing means to reduce the amount of water that can leak
from the header tank 3 through the heat sensitive valve 2.
[0031] The tubing is substantially L-shaped, i.e., the tubing has an approximately 90° bend.
The tubing is bent to allow the drainage pipe 5 to be connected to an overflow pipe
O of a central heating system. With the drainage pipe 5 connected in this way, the
heat sensitive valve 2 uses the typical facilities of the central heating system to
dispose of water emptied from the header tank 3.
[0032] The valve 2 components can be constructed from any suitable material, such as, plastics
materials, steel, stainless steel, brass and copper.
[0033] Figure 3 shows the heat sensitive element as having body parts in the form of an
end cap 25 and a plug 26. A meltable membrane 27 is sandwiched between the body parts.
These components 25, 26, 27 are used to control the flow of hot water from the header
tank 3. To form the heat sensitive element the meltable membrane 27 is positioned
in a recess 28 of the plug 26 and the end cap 25 is positioned to form a sandwich
of the membrane 27 with the plug 26.
[0034] The membrane 27 is disc shaped as shown by Figures 4 and 5. The membrane is dimensioned
to tightly fit into the recess 28. The membrane 27 is manufactured from a material,
for example wax, that melts when a predetermined threshold temperature is reached.
The threshold temperature is set to be beneath the temperature at which the header
tank melts. For example, if the plastics material used for the header tank melts at
a temperature between of 70°C to 90°C, then the membrane is made from a material that
melts at around 60-66°C.
[0035] Figures 6 and 7 show a front view of the end cap 25 and plug 26 used to hold the
membrane 27 in position on the header tank 3. The end cap 25 and plug 26 have apertures
through which the water drains from the header tank 3. The end cap 25 has a plurality
of apertures and the plug has one aperture. Both the end cap 25 and plug 26 have a
sealing element so that a seal is formed between them when positioned in the heat
sensitive valve 2.
[0036] To fit the valve 2 to the header tank 3, firstly, the header tank is drained and
prevented from filling with water. An aperture is then created in the side wall of
the header tank beneath the "full" water level by drilling a hole into a side wall
of the tank. The second end 21 is then positioned through the header tank aperture.
A nut is then positioned on a screw thread of the second securement means 23 and then
tightened to fix the valve 2 to the header tank 3. The plug 26, membrane 27 and end
cap 25 sandwich is then inserted into the second end 21 and secured to the valve 2
using the third securement means 24. Additional sealant is then optionally added.
The header tank 3 is then allowed to refill to immerse the heat sensitive valve 2
in water.
[0037] To allow the hot water to be drained out the tank 3, the first securement means 22
is then used to connect the valve 2 to the drainage pipe 5. The drainage pipe 5 is
then connected to an overflow pipe O.
[0038] As described below, with the valve 2 immersed in the water held in the header tank,
the risk of that water exceeding a temperature above which the header tank will melt
is reduced.
[0039] During a normal daily cycle the header tank 3 supplies water to a hot water tank
as and when it is required. Whilst water is being supplied to the hot water tank,
the amount of water in the header tank is reduced. Referring to figure 1, the water
supply apparatus 4 recognises this reduction through use of a ball cock system 40.
The ball cock system 40 comprises an arm 41 that is pivotally connected at one end
to a water supply valve 42 and at the opposed end to a float 43. The float 43 rests
on top of the surface of the water in the header tank. The float 43 is buoyant and
moves upwards and downwards in the header tank 3 in response to a change in level
of the water in the header tank 3. In a first position, when the water is at the "full"
water level, the float 43 moves the arm 41 to close the valve 42. In a second position,
when the water is lower than the "full" water level, the float moves the arm 41 to
open the water supply valve 42 and supply water into the header tank 3.
[0040] The heat sensitive valve 2 takes advantage of the water supply apparatus 4 to control
the temperature of the water held in the header tank 3. During a temperature control
cycle, if the water in the header tank reaches the threshold temperature, the membrane
27 melts. The melting of the membrane 27 opens the heat sensitive valve 2 and allows
water to be drawn from the tank 3, which is directed to the overflow pipe O using
the drainage pipe 5. As a result the water level in the tank 3 lowers, and triggers
the water supply apparatus 4 as described for the normal daily cycle. As water continues
to drain through the heat sensitive valve 2 the water supply apparatus 4 continuously
supplies water causing the temperature in the header tank to be kept at the threshold
temperature or be lowered. This maintaining or lowering of the temperature reduces
the risk of the reservoir of water from rising above the threshold temperature due
to a faulty thermostat.
[0041] The valve 2 reduces the problems associated with faulty thermostats causing a header
tank to melt. The valve 2 is of a simple construction and takes advantage of typical
central heating components so that it can be easily fitted to already installed header
tanks or on new header tanks awaiting installation.
[0042] Attention is directed to all papers and documents which are filed concurrently with
or previous to this specification in connection with this application and which are
open to public inspection with this specification, and the contents of all such papers
and documents are incorporated herein by reference.
[0043] All of the features disclosed in this specification (including any accompanying claims,
abstract and drawings), and/or all of the steps of any method or process so disclosed,
may be combined in any combination, except combinations where at least some of such
features and/or steps are mutually exclusive.
[0044] Each feature disclosed in this specification (including any accompanying claims,
abstract and drawings) may be replaced by alternative features serving the same, equivalent
or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated
otherwise, each feature disclosed is one example only of a generic series of equivalent
or similar features.
[0045] The invention is not restricted to the details of the foregoing embodiment(s). The
invention extends to any novel one, or any novel combination, of the features disclosed
in this specification (including any accompanying claims, abstract and drawings),
or to any novel one, or any novel combination, of the steps of any method or process
so disclosed.
1. A safety device for a header tank, the safety device having means for connecting the
safety device to the header tank, the safety device being heat sensitive such that
if water in the header tank rises undesirably, the safety device acts to empty at
least some of the water from the header tank in a controlled and safe manner.
2. A safety device as claimed in Claim 1, comprising a valve which at one temperature
is closed, and at a higher temperature is open.
3. A safety device as claimed in Claim 2, in which the valve incorporates a control member
which melts above a threshold temperature.
4. A safety device as claimed in Claim 3, in which the threshold temperature is between
60 and 66°.
5. A safety device as claimed in Claim 3 or Claim 4, in which the control member comprises
a heat sensitive membrane.
6. A safety device as claimed in Claim 5, in which the membrane is made of wax.
7. A safety device as claimed in Claim 5 or Claim 6, the valve member having first and
second body parts, the membrane being sandwiched between the body parts.
8. A safety device as claimed in Claim 7, in which one of the body parts has a recess
dimensioned to receive the membrane.
9. A safety device as claimed in Claim 8, in which the membrane comprises a disc, the
recess being shaped and dimensioned such that the disc is a tight fit within the recess
to reduce the risk of leakage.
10. A safety device as claimed in any one of Claims 7 to 9, in which each body part has
at least one aperture through which water can flow, in use, once the membrane has
melted.
11. A safety device as claimed in Claim 10, in which one of the body parts has more apertures
than the other body part.
12. A safety device as claimed in any one of Claims 7 to 11, in which a sealing element
is provided between the body parts arranged to prevent water from leaking out between
the body parts.
13. A safety device as claimed in any one of Claims 7 to 12, having means for clamping
the body parts together.
14. A safety device as claimed in Claim 13, in which the means for clamping the body parts
together comprises part of a threaded plumbing fitting arrangeable to mount the safety
device in an aperture in a header tank, below the maximum water level of the header
tank.
15. A header tank fitted with a safety device as claimed in any one of the preceding claims.