Method for threading a string through HVAC ducts
The invention is a method for threading a thin string through an HVAC duct system from a vent to the HVAC equipment supply plenum where the vent is connected to a small supply duct which in turn is connected to a large supply trunk connected to the plenum. The method uses a high speed blower at the vent to propel a small resistance object connected to the string through the small duct until it reaches the trunk. Then a capture mechanism is used from the HVAC plenum to capture the object and pull the string to the plenum. In an example of the method, the resistant object includes a packed parachute that is released after it travels a predetermined distance.
1 . In a forced air HVAC system having a network of air ducts connecting a central supply plenum to a plurality of air vents, a method for threading a string from at least one of said air vents to said plenum, comprising:
a. providing a light weight resistance object that easily fits inside the duct connected to said one of air vents, said duct being in said network;
b. connecting said object to a string;
c. providing a blower at one of said vents;
d. using said blower to propel said object from one of said vents through said duct to where said duct connects to a large duct of said network;
e. providing at said plenum a capture means for pushing into said network and capturing said object;
f. pushing said capture means into said plenum and said network toward said object;
g. capturing said object;
h. pulling said object and said string back to said plenum;
thereby threading said string from one of said vents to said plenum.
2 . The method of claim 1 where said object approximates the shape of a sphere.
3 . The method of claim 1 where said object approximates the shape of a sphere and is composed of foam plastic.
4 . The method of claim 1 where said capture means is a semi flexible element suitable for pushing with a snag tool attached to one end of said element.
5 . The method of claim 1 where said capture means is a semi flexible hose suitable for pushing, said hose attached to a source of vacuum airflow.
6 . The method of claim 1 where capture means is an apparatus for cleaning ducts.
7 . In a forced air HVAC system having a network of air ducts connecting a central supply plenum to a plurality of air vents, a method for threading a string from at least one of said air vents to said plenum, comprising:
a. providing a light weight object with two resistance states that easily fits inside the duct connected to said one of air vents, said duct being in said network;
b. connecting said object to a string;
c. providing a blower at one of said vents;
d. using said blower to propel said object in low resistance state from one of said vents through said duct to where said duct connects to a large duct of said network;
e. providing at said plenum a vacuum blower;
f. connecting said vacuum blower to said plenum and creating an airflow toward said plenum;
g. providing a means for said object to transition to high resistance state;
h. allowing said object and said string to be pulled back to said plenum by said airflow;
thereby threading said string from one of said vents to said plenum.
8 . The method of claim 7 where said object includes a packed parachute with a means for controlling unpacking of said parachute.
9 . The method of claim 7 where said object is a packed parachute with a mechanism that unpacks said parachute after a predetermined distance traveled in said duct.
10 . The method of claim 7 where said object is a combination of a parachute and a spool suitable for winding said parachute and a length of string into a shape suitable for rolling, said length of string being longer than the length of said duct.
11 . In a forced air HVAC system having a network of air ducts connecting a central supply plenum to a plurality of air vents, a method for threading a string from at least one of said air vents to said plenum, comprising:
a. providing a light weight resistance object that easily fits inside the duct connected to said one of air vents;
b. winding a length of string onto said object;
c. providing a means for generating an airflow from one of said vents to said plenum;
d. using said airflow to propel said object from one of said vents through said network and unwinding said length of string in said network as said object is propelled;
e. recovering said object at said plenum;
thereby threading said string from one of said vents to said plenum.
12 . The method of claim 11 where said airflow is generated by a combination of a blower at one of said vents and a blower at said plenum.
13 . The method of claim 11 where said resistance object approximates the shape of a sphere.
14 . The method of claim 11 where said object approximates the shape of a sphere composed of foam plastic.
15 . The method of claim 11 where said object has a low air resistance state and a high air resistance state.
16 . The method of claim 11 where said object has a low air resistance state and a high air resistance state, and is in said low resistance state when at said one of vents, and transitions to said high resistance state after being propelled a predetermined distance in said network.