September is start up month!  All maintenance should be done by now, and your system test fired – so you are ready to go when the weather gets cold.

As the weather changes frequently so does the requirements for heat.  It may be cold overnight, requiring the system to be on in the morning, and warmer in the afternoon so no heat would be required.  Under these conditions it is tempting to switch the burner on and off manually.

This is not a good practise and can create all kinds of problems.  For example on a steam vacuum system, shutting off the burner allows the boiler water to cool down and take up less volume in the boiler vessel.  As the volume has been reduced a vacuum is created in the boiler causing the water in the condensate tank to be drawn into the boiler through the condensate pump and piping and as a result could lead to the boiler flooding, excessive make up, possible priming and water hammer in the steam header piping.  This condition can happen to a lesser degree in a conventional two pipe steam system.

Repeated heating and cooling of the boiler causing expansion and contraction can lead to leaky tubes, failure of gaskets and push nipples in cast iron boilers.  Ideally once the boiler has been started, it should be kept running for the rest of the season, and the steam controlled by the main steam valve or zone valves.

The main steam valve is essential to the most efficient operation of a vacuum system and will the the next topic I will discuss in my Tips and Tricks!