The ELECTRODE PROBE TYPE of feedwater control (fig. 1-9) and low-water cutoff consists of an electrode assembly and a water level relay. The electrode assembly contains three electrodes of different lengths correspondin g to high. low, and burner cutout in the boiler drum.

To understand the operation of a boiler circuit, refer to figures 1-9 and 1-10 as you read the information in table 1-1. Although this information is not complete. it is presented here to acquaint you with the operation of the electrode type of boiler water level control.

Try Cocks

The location of the try cocks is shown as item 6 in figure 1-6. The purpose of the try cocks is to prove the water level in the boiler. You may see water in the gauge glass. but that does not mean that the water level is at that position in the boiler. lf the gauge glass is clogged up. the water could stay in the glass giving a false reading. The try cocks, on the other hand, will blow water. steam. or a mixture of steam and water out of them when they are

Figure 1-9. - Electrode type of water level control.

manually opened. When steam is discharged from the lowest try cock, you have a low-water condition.

Table 1-1. - Operation of a Boiler Circuit

*Relay = Relay