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Atmosphere Furnace Maintenance Tips |
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Intermittent Drop Out of the Combustion System |
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One of the common problems encountered in furnace operations is
intermittent drop out of the combustion system. One of the possible causes of this is due to pressure
switches in various points of the lines sensing a momentary
abnormality or opening under vibration.
We have had cases where we have suspected this to be a
problem and a person has stood and watched a pressure switch for a
considerable period of time.
Someone will ask a question or mention something,
and the person turns to answer, the failure occurs, and they miss
it.
One of the tricks we have developed for determining if a pressure switch is causing a problem is the installation of a very small amperage fuse. We are all familiar with the glass type fuses used in automobiles. These inline fuse holders can be purchased from any automotive store. The fuse size should be less than .1 amp and are usually purchased from a small radio parts outlet. The procedure for using the fuse is that after the equipment is up and running, the fuses are clipped across the normally closed contact of the pressure switches. The reason for the use of such a low amperage fuse is that it is not large enough to carry the current required by the safety shutoff solenoid or other solenoids. Now, should one of the pressure switches in the circuit vibrate open or senses a momentary abnormality, the contact will open. When this occurs, the fuse, being too small to carry the current, will blow. Now, all we need to do after we have a drop out is to go and check out all the fuses and find out which one is blown. This has isolated the particular switch and we can look for the abnormality or vibration problem. The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement. |
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