Boiler water heating control by bi-metallic strip Essay Example

Boiler water heating control by bi-metallic strip

Executive Summary

in the low mode. Boiler water heating control by bi-metallic strip 3 to 40Boiler water heating control by bi-metallic strip 2 in high mode 50Boiler water heating control by bi-metallic strip 1 to 70Boiler water heating control by bi-metallic stripThis project report highlights the use of bi-metallic thermostat in regulating the heating of water for domestic use. The project involves use of two heating elements of different heating capacity. The water heater can maintain water at 80


In a bi-metallic thermostat two metals are joined together and when the heat up they will bend and disconnect from the contact. Since the contact is responsible for connecting the heating power heating will stop when there is disconnection.

In this project focus was on setting of temperature of operation of a domestic electrical heating system.


3Introduction 1.0

41.1 Project description

41.2.1Abstracting the Problem

41.2.2Division of Tasks

51.2.3Problems Faced

51.3Sensor Selection

51.3.1Identification of the Sensor Type

51.3.2Performance Test of the Sensor

61.4Measurement System Implementation

61.4.1Hardware Configuration

81.4.2Software Configuration


  1. Introduction

Having an automatic controller which is tuned as required makes it possible for correct adjustment to be achieved in the desired time and this brings upsets to a minimal level and thus making the entire system work in a more reliable way.

There is need for taking special care in the process of boiler temperature control instrumentation.

Boiler temperature is incorporated into a system so as to serve as a limit switch acting as linkage between the burner and the circulator operation. Boiler temperature control usually will adjustable temperature sensing used for limit control and this are made to suit different application.

1.1 Project description

This project involves control of boiler temperature and it incorporates a high limit function that switches on and off at present temperatures. The high limit value of the boiler is the highest allowable temperature the boiler is allowed to attain and when this temperature is reached the heat turns off automatically. The setting for high limit differential is about 10 below the high limit setting. The heating system has two levels of heating: higher heating level and lower heating level.

1.2. Implementation

1.2.1Abstracting the Problem

The level to which water is heated is determined by the current amount that is passing through the heating element and the total time the current is passing. There is also need to have flexibility in the levels at which the action are taken. The system should also be connected to a display unit which will display the state of the system.

1.2.2Division of Tasks

The first stem is to choose the right bi-metallic strip element size that will give the desired temperature controls. The second task was to have the select two heating elements of the right size that will match the two bimetallic thermostats.

1.2.3Problems Faced

The problem faced is being able to maintain the desire temperature levels when the amount of water is the tank is expected to vary as it is being used.

1.3Sensor Selection

1.3.1Identification of the Sensor Type

The sensors to be used in this project are to be able to sense temperature. The sensors need to be able to have the desired level of sensitivity and to be able to work in the desired range of temperature. The sensors are also to be able to function with high reliability. The sensors are to be used in wet and hot environment and thus should be able to withstand such environment.

In this project a bi-metallic thermostat as the sensor of choice. Thermostat have temperature range which is required in this project.

1.3.2Performance Test of the Sensor

The bi-metallic thermostats were tested to establish the switching off pattern exhibited in relation to the temperature water in the tank. The temperature in the water tank was measured using mercury in class thermometer. The bimetallic strip thermostat was made it disconnect at the desired temperature in the tank by adjusting the current passing though it through the variable resistance.

1.4Measurement System Implementation

1.4.1Hardware Configuration

The system consists of two bimetallic strips each connected to a heating element of appropriate capacity. The heating element of be used in heating is chosen by choosing the mode of heating either of, low or high. In the high mode a more powerful hater is connected and the bimetallic strip allows heat to take place to a higher degree of 80c. After disconnected there is reconnection when the water drops to 70 C. at lower mode the water is heated to 50 C and reconnected occurs when water temperature drops to 40C. The bimetallic strips are connected outside the water tank and their switching on and off depends on the level of current passing through. In order to select the current which will correspond to the desired temperature levels a variable resister is introduced in series with the thermostats.

Boiler water heating control by bi-metallic strip 4

Figure 1: water heating element (lower heating)

Boiler water heating control by bi-metallic strip 5
Figure 2: Water heating circuit

1.4.2Software Configuration

In this system the there are there modes of operation: off, low and high. The display unit incorporates the switch mode keys and is able to indicate to the mode at which the system is operating.


The temperature control system is expected to function with high level of reliability as its operation is simple. The use of this system can help in managing power consumption. The system also is simple to repair in case of component failure such as the bimetallic thermostat.


Agilent technologies (2012). Hint for selecting the correct temperature sensor for your application.