BY GEORGE LANTHIER

We ’ re going to look at a simple solution that can prevent a catastrophe and the simple cure we call ‘ the Boston trick ’. We have a lot of steam in the Greater Boston and Worcester area and so we ’ re pretty good at working on steam .

First off , we need to establish the parameters . Let ’ s say you have a water boiler that holds 12 gallons of water . Then as a steam boiler it will hold 9 gallons to the working water line . Did you know

the average four section steam boiler currently holds about nine to 14 gallons to the working water line ? Did you know that at 55 pounds per square inch ( psi ) of water pressure you can flow about 10 gallons of water per minute ( gpm ) through a ½ inch pipe ? That means that a gallon of water can be fed into that boiler in about six seconds and that ’ s not a long time .

The proper level of water in a steam boiler is essential for correct and safe operation . The most common of the water controls is the

Figure 1

Figure 2

low-water cutoff . In addition , there are water feeders , pump controllers and combinations of low water cutoff / feeders , and low water cutoff / pump controllers . Let ’ s start with one of the easiest .

The low water cutoff shown in Figure 1 is a float-type cutoff . The model shown is the last of its type made . The # 67 from McDonnell & Miller has been in use for almost 100 years and serves its purpose . It once had many competitors from companies such as Watts , Econo and Honeywell , but these products are no more .

Figure 3 The # 67 works with a simple float Figure 6

attached through a bellows to a switch mechanism . The switch will close on a water rise in the boiler and while water is in the boiler remain closed , see Figure 2A . The burner circuit is connected in series to terminals 1 and 2 . If the water drops in the boiler to an unsafe level the

float drops , the switch breaks , and the contacts open . The switch terminals are shown in Figure 3 , and a typical wiring diagram using this control is shown in Figure 4 for oil . The # 67 can also be used to electrically control an automatic water feeder .

The feeder , as shown in Figure 5 , is also connected in series to terminals 3 and 4 . When power reaches terminal 4 of the diagram in Figure 3 it energizes the feeder that starts to feed water to the boiler . The contacts are made as the float falls in reaction to a low-water condition , see Figure 2B .

If the feeder refills the boiler , the

Figure 4

Figure 5

float rises , the feeder shuts off , and the burner continues to run . If the feeder fails to fill the boiler , and the float continues to drop , the contacts across 1 and 2 open , and the burner shuts off , see Figure 2C . The feeder will continue to be powered , and if enough water raises the float , the burner restarts . What happens if a wet return fails ? Or a 28 JUNE 2024 | FUEL OIL NEWS | www . fueloilnews . com