Furnace Sequence Of Operation

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 10 January 2019

⏱️ 42 minutes

🔗️ Recording | iTunes | RSS

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Summary

Jason Obrzut comes on the podcast and talks us through his furnace sequence of operation training: "Take It Slow, It's Gonna Blow!"

There are 6 main steps in Jason's furnace sequence of operation training. The phrase, "Take It Slow, It's Gonna Blow!" should help you remember the sequence (Thermostat, Inducer motor, Safety switch, Igniter, Gas valve, Blower motor).

The first component in the furnace sequence of operation is the thermostat, which initiates the call for heat. So, the thermostat has to send the signal to the circuit board. After the board receives that signal, it sends 120v out of the board to the inducer motor.

Next, the inducer pulls the gas combustion air into the heat exchanger. That air will then be deposited into the exhaust. The inducer is what aids the venting action and is a critical part of a furnace.

The safety switch is a general term for a negative pressure switch with a hose connected to the inducer housing or heat exchangers. Negative pressure from the inducer motor will close that switch. When that switch closes, 24v goes back into the board.

Then, the board sends a signal to the igniter. Now, you will finally begin to see heat delays. Silicon carbide and silicon nitride are common igniter materials nowadays, but they are fragile.

Once the igniter has worked long enough, the gas valve opens. We get 24v from the board to the gas valve, which brings on the gas flow and starts a timer.

When the timer expires, the blower motor will come on. This component is the LAST one to come on.

Jason and Bryan also discuss:

Pressures on the flue
Cracked heat exchangers
Safeties not closing
Hot-surface vs. intermittent-spark vs. direct-spark ignition
Flame sensors and proving flame
DIP switches

Learn more about Refrigeration Technologies HERE.

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Transcript

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0:00.0	and This episode of the HVAC School podcast is made possible by some pretty good companies,
0:21.6	our sponsors.
0:22.8	And those are Field Piece.
0:24.6	Field Piece is going to be at the AHR conference.
0:27.2	I'm going to ask you to stop by their booth at C-6359
0:32.0	at the AHR conference or AHR Expo, as it is properly called in Atlanta.
0:37.0	I'm going to be by the booth a couple different times, so if you swing by there's a good chance I might be there.
0:42.0	We have been trying out their new
0:43.4	job link probes the GL3 series of probes we really like them. They are one of the
0:48.3	best options for using Measure Quick out there because of the tremendous range. They
0:52.4	have listed on them I think 300 foot
0:54.0	range and as long as there aren't any maybe thick concrete block floors or something in between,
0:59.2	you're going to get all of that with the jabbling probes. They really are great and you can use them to have some of your
1:05.3	air probes on the inside and your refrigerant probes on the outside and pull those all into
1:08.8	measure quick. So if you haven't looked at field piece yet I would suggest that you do so and take a look at the products at AHR at Booth C6359.
1:18.1	Also a big thanks to refrigeration technologies at refrigetech.com.
1:22.2	They're going to be at B4 417 and I'm going to be at their booth on
1:26.4	Monday at 3 p.m. So stop on by and it's refrigeration technologies they make,
1:31.0	Viper Cleaners and Nylog and all sorts of other things.
1:34.8	Also big thanks to Navac and Navac Global.com and then finally carrier and carrier.com. This is the guy who once had to have a bank evacuated because he tested the heat strips during a maintenance.
1:57.0	Brian All.
1:58.0	Today on the podcast, oh hey, hey this is Brian, this is the podcast that helps remember some things
	...

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