Introduction: Pilot Light and Water Heater Monitor

It’s been said that there’s more than one way to skin a

cat. One strategy involves a highly skilled technician and precision instruments. Another involves a redneck, a butter knife, and a ball peen hammer. This project is probably closer to the later on the scale of Arduino projects.

We own a late model natural gas water heater manufactured by one of the nation’s largest appliance suppliers. One of the heater’s safety features shuts off the standing pilot when the combustion chamber overheats. It can be reset easily enough, but the condition is most commonly discovered when I’m standing next to the shower waiting for hot water which never arrives. It then occurs to me that the pilot light has failed again. When I went looking for a device that would alert me to the fact that the pilot light has failed, I was unable to find a suitable product intended for residential use. It seemed that there was a solution offered by using a microprocessor and a few simple sensors.

The intended purpose of the device is as follows:

· Report the condition of the standing pilot and set an alert and/or alarm condition in the event of a pilot failure.

· Report the hot water supply temperature as a back up to the pilot monitor and set an alert and/or alarm condition when the temperature falls below a set point.

· Monitor the space for a natural gas leak and set an alarm condition when a set point is reached.

· Monitor the space for a water leak on the floor around the water heater and set an alarm when water is detected.

· Automatically silence alarms for pilot failure and water temperature failure between the hours of 10PM and 7AM.

· Provide an ACKNOWLEDGE feature that allows the user to silence an active alarm for a specified time period while the water heater recovers from an alarm condition and then automatically returns to normal operation if conditions warrant.

· Provide a Silence feature that disables audible alarms indefinitely.

· Set biannual reminder alarms on the first of June and December to remind me to clean the water heater’s flame arrestor. It is reported that a clogged flame arrestor is the root cause of the standing pilot failure in the first place. (So why not just mark a calendar on the wall? See paragraph one).

· Enable the end user to easily modify the set points, date, and time.

Natural Gas water heaters are fairly simple appliances, but they are none the less potentially dangerous. Designers go to great lengths to make them safe for residential use. For this reason, I wanted a solution that was separate and apart from the appliance. That is, I did not want to engage, modify, or defeat any part of the water heater’s circuitry or safety systems. All of the power, sensors, circuits, wiring, etc are stand alone. There are a couple of thermometers physically attached to the appliance, but they are positioned so that they do not interfere with the appliance in any way. Our water heater is in a closet with climate control. The parameters I’ve set have proven very reliable. Your results will be dependent on your appliances location and condition. The thermometers I’ve used in this project are very fast acting devices, but 40 gallons of water are slow acting. It may take 60-90 minutes for temperatures to drop below the set point. The water detector sensor is mounted in an Altoid tin and the thermopile sensor for the pilot detector is mounted in a mini-Altoid tin which is then mounted to the cowling at the bottom of the water heater.

Materials List:

Arduino Nano


DROK® LM2596 Adjustable Voltage Regulator

3 mm standoffs

Adafruit TMP-006 Thermopile Sensor PRODUCT ID: 381

Adafruit Pi Cobbler Breakout Kit for Raspberry Pi

IIC I2C Level 5V-3V System converter Module for Arduino Sensor

Dallas DS18B20 Thermometer PRODUCT ID: 381

MQ-5 Natural Gas Sensor

Rain Sensor Rainwater Module Rain Detection Module 3.3V-5V

2-10K Potentiometer

4 x 20 I2C LCD Display

DS3231 RTC

4 SPDT switches

8 Momentary switches

Fuse holder

Circuit board

2-white 5mm LED with holder

2-yellow 5mm LED with holder

2-blue 5mm LED with holder

2-red 5mm LED with holder

10-10K ¼ watt resistor

1-1k ¼ watt resistor

Adafruit CAT 5 panel mount connector

Adafruit mini USB panel mount connector

DC panel mount jack

1/8” stereo jack and plug

Assorted connectors and wiring

2 buzzers

ribbon cable