How Do Relays and Transformers Work in HVAC?

Learn the basics of HVAC transformer and relays in this informative video! Perfect for those looking to learn more about the HVAC industry and how to become an HVAC technician.

In this video you will learn

How to wire a transformer?
What a transformer is used for?
How to wire a relay?
What a relay controls?
What is a normally open contact?
What is a normally closed contact?
How to use your meter to check coil voltage?
How to wire a motor?
What is a sequencer?
What does a sequencer control?
How to wire a thermostat?

Fieldpiece SC440 True RMS Clamp Meter

Yellow Jacket 42004 Series 41 Manifold with 3-1/8" Gauge

Go check out Fieldpiece Products to learn more about there multimeter the SC440

#thermostat #wiring #hvac #relays #contactor #sequencer

Taddy Digest Website

[timothygardner]

Some people just have the gift to explain things and make it simple. You Sir have that gift. Thank you From a avid DIY’er, one of the best vids I’ve seen on ANY subject

[lukehall]

Feel like imma have to watch this a few times lol

[mrlegendary]

@taddydigest You should show the proper usage of those crimping pliers. The part you used @15:06 is labeled NON, for use with NON insulated terminals. You should use the section labeled INS, designed for insulated terminals as shown. It makes a difference, as the one tends to damage the nylon barrel.

[TheMaster]

I completely understand both relays on how the 24 volts changes each pole from open to close. The only problem I'm having is that you didn't discuss the wiring on the connectors and their purpose. For instance, on pole 1, 2, and 3, are they all hot wires? Why would you need power to 2, then shut it down and send power to 3?

[RC-Heli]

Thanks for sharing this man. I did not know that these relays function with normally closed and normally open switches. I'm pretty positive that I have a bad relay right now not letting 24 v get to one terminal of the honeywell S86F igniter.on my furnace.

[jillfoster]

Hi Tad, I have an electric ac/furnace unit. It has a safety alert to tell me when there's water in the bottom pan. My thermostat went bad. I changed it and blew a fuse, I fixed that. So now I have my thermostat on nothing runs. I wire my Yello, green & ref low voltage wires all together. I can then run my ac & blower, but the blower won't shut off. Do you know any reason the safety alert might have something to do with the fan always on?? OMG, I'm on my fourth day of trouble shooting, and it was 90 today😢 unemployed until next month, so here I am on YouTube University. I've now watched all of your videos. Thank you for them!

[coreyschultz]

First year hvac student here and I'm loving the info, but feel like you are going too fast for my brain. I am add and most likely undiagnosed mildly dyslexic as well. I keep getting tripped up with which ones are n/o and n/c. I also realize that some are pressure and some are temp, but any advice other than reading the manual (if it's there?) I seem to do well with most bugs in the lab, but that is not the same at all as walking up to a furnace/ac in the field.
Thank you for any input or advice

[mgm]

With winter approaching I’m finally getting to installing my basement smart thermostat that has line voltage inputs. It was at the bottom of my list since my heat only system is not needed in the summer here.

Do you have any recommendations for what brand/model relay to use for controlling the HV switched boiler heat with the smart thermostat? I already have the boiler transformer I’m tapping and ran the LV lines to power the smart thermostats, so I don’t need a transformer/relay, just a regular one. Much appreciated. I feel as though the knowledge and confidence I acquired months ago has faded from my mind 😅

[charleswashington]

Good video, I want to share some info on a comment you made. Correct me if I'm wrong. Yes, sequencers do have timed delays built in and that's not the only difference. Additionally, sequencers are design to support the high amp demand that heating elements draw. Those relays like the 90340 you demonstrated are design to carry inductive loads like a condenser or blower motor. NOT resistive load like heat stripes. Those relays would turn into hot fudge sundays. Now, the contactor relay would do well. Sir, you handle those probes like Chinese chop sticks, best i have ever seen. Great job, I enjoy the channel.

[rubenibarra]

Question I have a Jard 17325, How can you tell which side is the Load or Power. Their no label on either side?

[Almtyhalfbreed]

Do you have budget friendly must have tools for beginning HVAC techs?

[dgmenace]

Thanks for the video. I've been troubleshooting a Hallmark horizontal oil fired furnace. I'm having an issue with it going into a lockout. Sometimes it will work for a couple days, others just a few hours. Order of replaced parts are...oil Filter, pump screen/strainer, nozzle, electrodes (adusted properly), and cad sensor have all been replaced in the last 2wks. I added a pressure gauge to the pump and its reading 140psi...single oil line, above ground, gravity oil tank. This is an older pump, no shutoff solenoid. The flame looks great & the limit switch seems to be operating properly. The ignition transformer throws an arc at least an inch. No smoke or soot. Have you ever run into an intermittent problem like this that was the transformer or fan relay? Any suggestions would GREATLY be appreciated. Once I press the red reset button the furnace fires right up and I can never get it to act up while watching it. Thanks in advance.

[dlowe]

I've had to learn basic controls for the plumbing course I'm taking, nothing really makes sense. This video was explained very well and simplified for beginners like myself. Thanks!

[mgm]

This video was great! I was trying to make sure I knew exactly what I was doing before attempting to replace an old mercury line voltage thermostat in my basement with a new smart thermostat. The main floor Tstat was LV already, but the basement zone was HV for some reason. You made it super easy to understand that I want the heat call wire off the thermostat and the common wire to power the relay, and then the HV lines will be connected to the normally open poles that close the circuit when the control side provides power.

[jt.]

Brother thank you so much for this demonstration! I'm actually doing this in hvac school right now. You definitely have a teaching gift!

[ittech]

Great, where is the 24 volt transformer located ( for the contractor ) I have no 24 volts there when I turn it on. Thank you

[oscarcaro]

This informative video covers relays, Contactors, transformers, Thermostats, motors. It goes to the point and covers a lot of useful information.
Thank you for showing and sharing your knowledge in a simple but extremely valuable way. Please post more HVAC videos.

[rozilla_the_savage]

New to the field. Got a package unit that was freezing up. Noticed the blower doesn't come on when i call for fan, but the compressor and condenser fan comes on when I call for cool. Possibly the fan relay?

[Ray-wrwr]

is the common wire on the air handler board always energized 24v ? coming from transformer C wire usually closed contacts on the condenser relay, just left a job site, jump R to Y & O terminals on the heat pump condenser so people can have acold air) im in NYC & we have a heatwave ( solenoid valve was making buzzing sound i check the voltage 27v not sure what is the issue here going back to the job site tomorrow it was a late call . any advice appreciate it

[tylerluu]

I love your videos. I watch it over & over until it burns my brain.
Question: I am working on Carrier HVAC which is 25 years old. I replaced the transformer and I checked all the wires. I got all the power but My Control Board has no red light. Any suggestions I appreciate it.