Hello, I just purchased a home with a HVAC unit installed in the attic that is 4 years old. Last night was the first time I've attempted to use the heat and it only blows cold air. Upon further inspection i find the burners are not burning at all. It is a conventional unit with A/C and only 5 wires going to the thermostat (W, Y, G, R and blue (C)).

I have tried connecting red & white wire together to rule out the thermostat.

I have tried to turn off the 15amp breaker and turn it back on.

Fan on thermostat is set to auto, heat set 10 degrees higher than room temp

When I take the door off I can see it is electric ignitor, I will post a picture.

Unit it a rheem brand. Natural gas. I have checked the 3 valves in the gas line (including the two on the contraption where gas comes in from the street) - all are open position.

When heat is turned on I hear a little whine noise then the blower turns on. I tried dimming the light and I don't think I see a spark or anything.

What else should I check?
Thank you!

 

Welcome to the forums.

Remove the lower blower cover. Read the back of the door for trouble codes.
Locate the control board in the blower area.

While the blower cover is off the furnace has no power. Hold in the door safety switch or put the cover back on and look thru the sight glass for the blinking LED. Allow it to try to fire and count the flashes.

 

Cool beans, thanks! I'll give that a try

 

Here's the 2 pictures... I did the light check - and got 3 blinks from the green light in the middle. I was unable to find a glossary or what that means...

 

The codes are on the back of one of the service panels. Usually the blower one.

Preliminary..... Rheem three flash code signifies open safety sensor. Possibly a heat sensor near the burner/flue area. The switches are oval in shape. You're looking for one with a tiny red reset button on it.

You may need to post the model number off the ID plate.

 

There were some labels on the back of each panel, but nothing to do with flashes. Might have to look closer. Here's another pic I took of some identifying material.

 

No help. Post the model number off the ID tag on the sidewall near the burner.

 

Wanted to let you all know I called a professional and turns out there was water in the piping where the burners blow the flames/hot air. The A/C is blowing it's humid air through the furnace in the summer time probably causing the condensation. Whoever installed this unit did it in reverse so the professional recommends I have it fixed or else I may have to do this every year and maybe the furnace will rust out? Bummer. Also learned they never bonded/grounded the yellow flex gas line and the condensate line runs into the main stack ruining my dry vent. Oh the joys of home ownership... No idea why none of this was picked up on the inspection.

 

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Sounds like you had a VERY good repairman!

That sounds like a bunch of quite subtle problems. Home inspectors have only a basic knowledge of HVAC systems. Usually if they think they see a problem, they will recommend an inspection by a capable repairman.

Even a capable repairman might have missed some of the things you mention, absent an actual problem that needed to be diagnosed. That is to say, I might have missed some of that!