Gas Furnace service, repairs and efficiency improvement

by G&S Mechanical Services:

With emphasis on service and repair not replacement

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    We can improve the performance and efficiency of your furnace and save you money on repairs and fuel use.

    I get many inquires about problems with the pilots on gas furnaces. Unless you have a newer furnace with an electronic or electric ignition system you probably have a standing pilot. That is a system where the pilot is always burning and is used to light the main burner. There are two basic systems used with standing pilots. The first is the thermocouple system that uses two dissimilar metals to provide electricity to hold open the pilot valve on the gas valve, once you light the pilot. The main valve is operated by 24 volts from a transformer.

    The second system is called a Milli Volt system. The pilot heats a larger device that generates a bit more electricity, enough to operate the main valve too. The theory is that if the pilot is not lit then the main burner won't work. This system is used a lot on mobile home and RV furnaces because they will work with out utility power.

    To tell the two systems apart look at the device that sits in the pilot flame. If it is a piece of small tubing like a capillary then you have a thermocouple. If you have what looks like a cable with wires coming off of it they you have a Milli volt system. I always replace milli volt systems with conventional 24 volt systems.

    I will add some information shortly explaining what should be done as routine service on a gas furnace.

Read more that I have written on this subject at the freegas page
 and the question page . To see images of gas valve systems click here.
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