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.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a frost protection system for an apparatus having a condensate drain pipe.[0003]2. Description of the Related Art[0004]Various apparatuses produce condensate during normal operation, examples being condensing boilers, freezers, refrigerators and air-conditioning units. It is necessary to dispose of the condensate. Some small apparatuses are able to do this by evaporation. However, for larger apparatuses, it is necessary to drain the condensate away through a drain pipe. In some situations, the drain pipe can be routed internally of the building to the drainage system of the building in which the apparatus is sited. However, in other situations, for example when replacing a non-condensing boiler with a condensing boiler, it can often be very inconvenient and costly to access the building's drainage system internally of the building, and it is far more convenient to route the condensate drain pip...

AI Technical Summary

Benefits of technology

[0006]An aim of the present invention, or at least of specific embodiments of it, is to prevent freezing in cold weather of condensate in such drain pipes and to do so in a convenient and unobtrusive way.

[0009]Accordingly, in cold weather, the controller can activate the heater to produce heat inside the drain pipe and thus reduce the risk of the condensate freezing. Because the heat is produced inside the pipe, it can act more directly on the water and less directly on the air surrounding the pipe than if the pipe were heated from the outside, and thus the amount of heat required is less. It is expected that, with the invention, it will even be possible to reduce the diameter of the drain pipe compared with the size that is typically used absent the invention. In addition to reducing the pipe cost, reducing the pipe size results in less air being heated in the pipe and possibly convecting the heat away.

[0010]In a specific embodiment of the invention, 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. The tee or coupler may also have 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. It has been found that less heat is required to prevent freezing of the condensate in a smaller diameter pipe (for example of 10 mm diameter compared to 22 mm diameter). Furthermore, the air gap that remains between the inner second portion of the condensate drain pipe and the further outer pipe provides thermal insulation which reduces heat loss from the inside of the inner second portion of the condensate drain pipe.

[0011]The system is preferably provided in combination with the second portion of the condensate drain pipe. It has been found that less heat is required to prevent freezing of the condensate the fewer the number of cold joints in the condensate drain pipe. Therefore, the second portion of the condensate drain pipe is preferably flexible (for example a length of polyethene hose). Accordingly, despite any elbows that may be required in the further pipe, the second portion of the condensate drain pipe can wind its way along the inside of the further pipe without any joints.

[0016]The controller is preferably operable to control the heater in dependence upon the amount by which the sensed temperature is below a threshold value, for example, increasing the heating effect linearly the greater the temperature difference. The controller preferably employs pulse-width modulation to control the heater.

Problems solved by technology

In addition to reducing the pipe cost, reducing the pipe size results in less air being heated in the pipe and possibly convecting the heat away.

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