Frost protection system for condensate drain pipe

Abstract

A frost protection system is described for a condensate drain pipe for a boiler, air-conditioning unit etc to protect an outdoors run of the pipe. The system comprises an outdoors temperature sensor, a heater, and a controller for activating the heater in dependence upon the temperature sensed by the sensor. The heater is in the form of a flexible line (for example an electrical cable with a resistive filament). The heater (or a connection for it) passes through a fitting in the pipe indoors, and the heater extends along the inside of the outdoors run of the pipe. In cold weather, the controller activates the heater to produce heat inside the drain pipe and thus reduce the risk of the condensate freezing.

1 . A frost protection system for an apparatus having a condensate drain pipe, the system comprising:
 a temperature sensor;   a heater; and   a controller for activating the heater in dependence upon the temperature sensed by the sensor;   
       wherein:
 the heater is in the form of a flexible line for disposal in the drain pipe; and 
 the system further comprises a fitting for the drain pipe to enable the flexible line, or a connection between the controller and the flexible line, to pass from the controller to the inside of the pipe. 
 
     
     
         2 . A system as claimed in  claim 1 , wherein:
 the fitting is in a form of a tee or coupler having first and second portions for connection to a first upstream portion and a second downstream portion, respectively, of the condensate drain pipe and a third portion to enable entry of the flexible line or the connection therefor.   
     
     
         3 . A system as claimed in  claim 2 , wherein:
 the tee or coupler has a fourth portion arranged to be fitted to a further pipe having a larger internal diameter than the external diameter of the second portion of the condensate drain pipe so that the second portion of the condensate drain pipe can run inside the further pipe.   
     
     
         4 . A system as claimed in  claim 3 , wherein:
 the system is provided in combination with the second portion of the condensate drain pipe; and   the second portion of the condensate drain pipe is flexible.   
     
     
         5 . A system as claimed in  claim 3 , wherein:
 the second portion of the tee or coupler is provided as a separate element which is arranged to be connected to the remainder of the tee or coupler when the further pipe is fitted to the fourth portion of the tee or coupler.   
     
     
         6 . A system as claimed in  claim 1 , wherein:
 the heater is electrical and has a resistive filament extending along the line.   
     
     
         7 . A system as claimed in  claim 6 , wherein:
 the line is a coaxial cable.   
     
     
         8 . A system as claimed in  claim 6 , wherein:
 the line is a coaxial cable; and   the resistive filament forms a central core of the coaxial cable.   
     
     
         9 . A system as claimed in  claim 6 , wherein:
 the controller is operable to control the current flow through the resistive filament.   
     
     
         10 . A system as claimed in  claim 6 , wherein:
 the controller is operable to control the voltage applied across the resistive filament.   
     
     
         11 . A system as claimed in  claim 6 , further including:
 a limiter for limiting the flow of electrical current through the resistive element.   
     
     
         12 . A system as claimed in  claim 1 , wherein:
 the controller is operable to activate the heater when the temperature sensed by the sensor falls below a predetermined value   
     
     
         13 . A system as claimed in  claim 1 , wherein:
 the controller is operable to control the heater in dependence upon the amount by which the sensed temperature is below the predetermined value.   
     
     
         14 . A system as claimed in  claim 1 , wherein:
 the controller employs pulse-width modulation to control the heater.   
     
     
         15 . A system as claimed in  claim 1 , further including:
 a sensor line for connecting the sensor to the controller.   
     
     
         16 . A system as claimed in  claim 15 , wherein:
 the fitting is arranged to enable the sensor line to pass from the controller to the inside of the condensate drain pipe.   
     
     
         17 . A system as claimed in  claim 15 , further including:
 a second fitting to enable the sensor line to pass from the controller to the inside of the condensate drain pipe, or to enable the sensor line to pass from the inside of the condensate drain pipe to the sensor outside the condensate drain pipe.   
     
     
         18 . A building having:
 an external wall;   an apparatus disposed inside the building and having a condensate drain pipe that passes through a hole in the wall; and   a frost protection system for the apparatus, the system comprising:
 a temperature sensor disposed outside the building; 
 a heater in the form of a flexible line at least part of which is disposed in the drain pipe outside the building; 
 a controller for activating the heater in dependence upon the temperature sensed by the sensor; and 
 a fitting fitted to the drain pipe inside the building to enable the flexible line, or 
 a connection between the controller and the flexible line, to pass from the controller to the inside of the pipe. 
   
     
     
         19 . A building as claimed in  claim 18 , wherein:
 the fitting is in a form of a tee or coupler having:
 first and second portions connected to a first upstream portion and a second downstream portion, respectively, of the condensate drain pipe; 
 a third portion through which the flexible line or the connection therefor enters; and 
 a fourth portion fitted to a further pipe having a larger internal diameter than the external diameter of the second portion of the condensate drain pipe, the second portion of the condensate drain pipe running inside the further pipe; and 
   the second portion of the condensate drain pipe is flexible.   
     
     
         20 . A building as claimed in  claim 19 , wherein:
 the apparatus is one of a boiler, a refrigerator, a freezer and an air-conditioning unit.