how a basic electric residential hvac system works...

okay so here we are with your basic electric HVAC system with all the controls exposed so that you can see what's going on behind closed doors okay so first things first we got a breaker that your main power supply for all your controls inside your air handler which gets its power from the mains power supply of the house then we got your transformer which transforms your main power supply to 24 volts so that can it can be used to control your thermostat your fan relay your sequencer your your contactor and all that other good stuff okay so basically what's going on when you turn on the power power from the main power supply is passing through the breaker and it's going into this transformer and it's being transformed to 24 volts which is a small voltage so it can be used inside these little coils of the controls one side of these controls is always going to be hot and the reason for that is because it's being broken with the controls and this thermostat here controls pretty much everything and has a name for everything so when you turn it on fan on this fan relay within have 24 votes being provided to here which has a piece of bi-metal these two top Spade clips are what they call normally open so they're broken right here but when this has 24 volts applied to it this piece of bi-metal then pushes up and passes power from this side to this side which then will energize your blower motor okay I'm gonna give you an example of that fan on so right now power is being passed from here through the piece of bi-metal which has made a closed circuit now on the top Spade clips and turned on your blower motor when you turn it off the 24 volts de-energize this from here this bi-metal pulls back down and breaks the circuit up here and then it stops power from the blower motor so when you turn on the air-conditioner pretty much everything that I just told you still happens here you have that 24 votes being applied here the bi-metal goes up and closes this normally open circuit and turns on the blower motor but at the same time you also have 24 volts being distributed or pushed to the outside contactor which will then be energized and pass power from this through and turn on your compressor and fan motor and then you have air conditioning let's do that so right now you're getting your 24 volts going to the fan relay it's making a circuit at the normally closed and turning on your blower you're also getting 24 votes being distributed outside to your contactor which is turning on your outside unit thus you have air conditioning turn that off when you run the heater it's a little bit different so when you run the heater power is still going through this fan relay but the bottom the middle set of Spade clips are what they call normally closed so if you were to get an ohmmeter and put a lead here in the lead here it would amount because this circuit is normally closed while there is no power to here this will close it is normally closed and when there is 24 volts here that this piece of bi-metal pushes up the power will then break at the at the middle ones and close the top ones but in when there is no power the top ones are open which are normally open and the middle ones are closed so then your call for white will push 24 volts to this white wire which is on your sequencer and then you have almost the same thing going on in the sequencer there's a piece of by metal in here that will then be energized push up and this power will then pass through this sequencer and go through the normally closed circuit and then turn on your blower motor at the same time that that's happening these here are on a time delay or on what they call a time sequence so this one will energize first meanwhile a minute to two minutes later this one will energize which is hooked up to the heater side of the system and there's a specific reason for that so now let's put our thermostat over to heat and like I was explaining before the 24 volts is not going to the fan relay but it's going to the sequencer and your powers being passed through because it has made a circuit it's going through the center part and it turned on your flower-mobile so it's been about a minute and 20 seconds as you can see your meter is now energized turned on so the reason for the time delay in the time sequence is this when your meter turns off or you turn your heater off the first sequencer would be energized first turning off the heater there will be no more 24 votes at the sequencer so it would shut off but it shuts off and a time sequence so the first one will show off that shuts off is going to be this one which will shut off your heater and once your heater is shut off after about another 45 seconds your fan will shut off and the reason why it stays running is to cool off your heating elements inside the air handlers to their to where they are a safe temperature to be off then your fan will come off and that's the reason for this time sequence relay or sequencer now your heater is at a safe temperature now it's okay for your fan to shut off and that my friends is how an HVAC system works behind closed doors you

Channel: Engineered Comfort HVAC

Views: 103,041

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Id: RTJlq9acCSw

Length: 7min 22sec (442 seconds)

Published: Fri Jan 31 2020