HVAC PICTORIAL DIAGRAM MANUAL

Firstly, the source is the source of power or electricity. In the above control drawing is a basic electric circuit. If you have a gas furnace or other type of heating system the fan will be controlled differently either by time delay or temperature.

HVAC PICTORIAL DIAGRAM MANUAL

Whether the system is in air conditioning mode or if the manual switch for the fan is turned to the on position. The thermostat controls the circuit for the blower fan. Lastly, this energizes the coil closing the contacts and turning on the blower motor.

When the switch in the thermostat closes it completes the circuit. And then to the other side of the relay coil. The 24 hot leg of the transformer will go through the thermostat. Then go to one side of a coil on the relay. The 24-volt neutral leg will run from the transformer. Furthermore, this particular relay is controlled by the thermostat. The relay in the above control diagram controls a blower motor as shown. Some relays are controlled by other relays depending on the components in the system and the sequence of operation. It works through the 24-volt control circuit. The relay or contactor is nothing more than a switch that turns on a motor or compressor. Control Circuits for Air Conditioning and Heating - How It All Works If a relay or contactor needs to be replaced it needs to be replaced with an exact match relay or contactor. If a relay with a 5 amp rating for the contacts is used to control a motor with a 10 amp rating then the contacts will burn out and the relay or contactor will be useless. One is the voltage that controls the coil on the relay or contactor and the other is the amp rating of the contacts.Ī relay or contactor with a 24-volt coil will blow out if 120 volts is used on the coil. Relays and contactors have a few very important ratings on them. They are both normally controlled by 24 volts and they typically pass line voltage to a motor or compressor. Furthermore, contactors and relays work in much the same way in a typical HVAC control circuit. Relays and contactors are used in HVAC control circuits to turn things on and off such as a blower motor, condenser fan motor, or compressor. Resource Link: Ohms Law and HVAC | Heating and Cooling Technical Furthermore, in case there is a dead short in the control circuit the fuse will prevent the transformer from blowing. Additionally, it is important that an inline fuse is placed on the hot leg or 24V hot side of the transformer. If the VA rating on the transformer is exceeded by the number of loads in the system then the control circuit will not work properly and the transformer will fail. The sum of these VA ratings for all the loads in the circuit cannot exceed the VA rating on the transformer. Control transformers always come with a VA rating and that gives the maximum rating for which the maximum number of loads can be used for that transformer.Įach relay or load in the control system has a VA rating. Some control transformers are multi-tap transformers that can be used on either 120V or 240V to step down the voltage to 24 volts. Transformers (step-down) can be 120V to 24V, 240V to 24V, and many other combinations. Step-down transformers are used for air conditioning and heating systems to step down the voltage from a line voltage to a safer and more efficient voltage for use in the control of the system.

Hvac pictorial diagram