Figure 5-36. - Connection points for thawing frozen service lines.

Table 5-3. - Relation of Current and Voltage Required for Thawing

*Cast Iron

the frozen sections. Some data on current and voltage required for electrical thawing of various sizes of wrought-iron and cast-iron pipes are presented in table 5-3.

The time for electrical thawing may vary from 5 minutes to over 2 hours, depending on pipe size and length, intensity of freezing, and other factors. The best practice is to apply current until the water flows freely.

Use the following procedures in electrical thawing:

1. DIRECT-CURRENT GENERATOR. To thaw pipes with a welding generator or similar direct-current source, set the generator to the correct amperage for the pipe to be thawed and connect the leads to the pipe.

2. ALTERNATING-CURRENT CIRCUIT. Transformers are required to adjust amperage of an