1 Basic Electrical Series and Parallel Circuits

2 Introduction So far we have looked at circuits that have one path for electricity to go as well as a single switching device. The majority of circuits you work in with HVAC will be more complex Therefore we must understand the two ways circuits are designed. So far we have looked at circuits that have one path for electricity to go as well as a single switching device. The majority of circuits you work in with HVAC will be more complex Therefore we must understand the two ways circuits are designed.

3 Series Circuits Series circuits exist when: –The flow of electrons (current) must pass through a series of components. –Switches that control loads are wired in series with these loads. Series circuits exist when: –The flow of electrons (current) must pass through a series of components. –Switches that control loads are wired in series with these loads.

4 Series Circuits L N SW1SW2 B1 B2 120 Volts

5 Series Circuits SW1 is in series with SW2 which is in series with B1 and B2 If any one of of the components in this circuit is open of fails the remainder of the circuit will not work. Loads in series split the source voltage based on their resistance. Neither B1 or B2 will be getting full source voltage. SW1 is in series with SW2 which is in series with B1 and B2 If any one of of the components in this circuit is open of fails the remainder of the circuit will not work. Loads in series split the source voltage based on their resistance. Neither B1 or B2 will be getting full source voltage.

6 Series Circuits The amperage is the same through the entire circuit. The total resistance is the sum of all the individual components resistance. The amperage is the same through the entire circuit. The total resistance is the sum of all the individual components resistance.

7 Series Circuits In the HVAC industry it is rare to see loads in series. It is frequent to see switches in series. Both switches must be closed to provide a path for electricity. In a series circuit any open will cause the circuit not to work. In the HVAC industry it is rare to see loads in series. It is frequent to see switches in series. Both switches must be closed to provide a path for electricity. In a series circuit any open will cause the circuit not to work.

8 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Start with making sure all switches that you can close are closed.

9 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage across the source. 120 V

10 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage across the first switch (Service Switch) 0 V

11 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Line side of SW1 0 V

12 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Load side of SW1 0 V

13 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Line side of SW2 0 V

14 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Load side of SW2 0 V

15 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Line side of B1 0 V

16 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Neutral side of B1 60 V

17 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Line side of B2 60 V

18 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Neutral side of B2 120 V

19 Troubleshooting Series Circuits L N SW1SW2 B1 B2 120 Volts Now check voltage Source to Neutral side of circuit 120 V

20 Troubleshooting Series Circuits When troubleshooting a series circuit if you get source voltage across any switching device that switch is open. When troubleshooting a series circuit if you get source voltage across a load and that load is not operating the load is bad. When troubleshooting a series circuit if you get source voltage across any switching device that switch is open. When troubleshooting a series circuit if you get source voltage across a load and that load is not operating the load is bad.

21 Parallel Circuits Parallel circuits are the most common circuit in the HVAC industry for loads. These are the circuits that do the work. All loads in parallel receive full source potential (voltage) Parallel circuits exist when a circuit has more than one load, but none of the loads receive voltage from another load. Parallel circuits are the most common circuit in the HVAC industry for loads. These are the circuits that do the work. All loads in parallel receive full source potential (voltage) Parallel circuits exist when a circuit has more than one load, but none of the loads receive voltage from another load.

22 Parallel Circuits If one load burns out or goes bad the remaining loads will continue to operate. All loads get full source voltage. The total amperage of the circuit is the sum of all the amperages of the loads. If one load burns out or goes bad the remaining loads will continue to operate. All loads get full source voltage. The total amperage of the circuit is the sum of all the amperages of the loads.

23 Parallel Circuit L1 L2 B1 B2 SW1 Example of one switch controlling two loads in parallel.

24 Parallel Circuit L1 L2 B1 B2 SW1 Example of two loads in parallel each controlled by a switch. SW2

25 Troubleshooting parallel circuits The same basic procedure as a series circuit. Start at the source. The same basic procedure as a series circuit. Start at the source.

26 Parallel Circuit L1 L2 B1 B2 SW1 First make sure all switches you can control are closed. SW1

27 Parallel Circuit L1 L2 B1 B2 SW1 Next use your meter and check to make sure there is source. SW2 240 V

28 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and the start of the branch. SW2 0 V

29 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and line side of SW1. SW2 0 V

30 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and load side of SW1. SW2 0 V

31 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and line side of B1. SW2 0 V

32 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and load side of B1. SW2 240 V

33 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and then the connection to neutral. SW2 240 V

34 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and line side of SW2. SW2 0 V

35 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and load side of SW2. SW2 0 V

36 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and line side of B2. SW2 0 V

37 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and load side of B2. SW2 240 V

38 Parallel Circuit L1 L2 B1 B2 SW1 Next check voltage between L1 and and then the connection to neutral. SW2 240 V

39 Troubleshooting Parallel Circuits When troubleshooting a parallel circuit if you get source voltage across any switching device that switch is open. When troubleshooting a parallel circuit if you get source voltage across a load and that load is not operating the load is bad. When troubleshooting a parallel circuit if you get source voltage across any switching device that switch is open. When troubleshooting a parallel circuit if you get source voltage across a load and that load is not operating the load is bad.

40 Troubleshooting rules Start at source and work your way from there. If you get any voltage across a switch that switch is open (or bad). If you get voltage at a load and the load is not working it has failed. Replace it. Start at source and work your way from there. If you get any voltage across a switch that switch is open (or bad). If you get voltage at a load and the load is not working it has failed. Replace it.

41 Shop Projects Build and check a series circuit using your meter. Build and check a parallel circuit using your meter. Make sure to get appropriate sign offs from instructor and each person participates in the project. Build and check a series circuit using your meter. Build and check a parallel circuit using your meter. Make sure to get appropriate sign offs from instructor and each person participates in the project.