Smell (not gas).... and a bang

Problems related to residential installations.

Smell (not gas).... and a bang

Postby danrad » Sat Nov 19, 2011 8:08 pm

Hello all, This is my first post.

I have been struggling with a new furnace for my second winter now. It is a GoodmanCvC9/MVC95- Two stage. We noticed that this new furnace was making a banging sound every time it would light. Also around the same time we noticed an odour constantly around the furnace. I had called the installer and they told me I just needed to take the plastic plug off the side of the furnace and banging would stop. Fair enough I did this and the banging had stopped, however the odour increased.

I called out our local gas company and they came up with a reading always near the third burner. They tagged the furnace and the installer came out switched out the gas valve. This continued for 8 calls to the gas company and I am on the 4th gas valve. At times after a burn (this is when the smell is typically the strongest) the gas company was get readings of 12,000 ppm from what I recall. (Could of been 1200 if the first number seems ridiculous)

My gas meter was also changed outside to make sure there was no movement in the gas lines.

I am wondering if it is the venting (there is nothing stopping the flow, but why would I get a backdraft) since when the plastic plug is out I feel a draft coming through the hole.. even while it is on and running.

Lastly should I have any smell what so ever from this furnace? I have sniffed around other furnaces and smell nothing.. slowly I am going a little crazy.

Thanks for any and all suggestions/replies.
danrad
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- Smell (not gas).... and a bang

Postby Freon » Sun Nov 20, 2011 10:16 am

First thing I suggest is you watch the furnace light when someone else calls for heat at the thermostat. You need to watch carefully as the ignition sequence happens. Take notes. Do all the burners light? Do they light smoothly? Is the flame blue or a mix of blue and yellow?

Can you check the drain line for the condensation? See if you see any signs of leaks. Try and localize the smell so you can narrow down the possible causes. The most difficult part of fixing your furnace is knowing exactly what is wrong. Also, those gas company readings... what where they measuring... CO, CO2 oxygen?
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- Smell (not gas).... and a bang

Postby danrad » Sun Nov 20, 2011 11:45 am

After doing quite a bit of research lastnight I believe I found out that my problem is a combustion leak. When the odour is strongest is right after a burn. I have both carbon and natural gas detector and they never go off. But the odour is present, mostly confined to around my furnace as it is in a small room.. with a door way and a vent near one of the walls near the floor.

I put my hand where the exhaust pipe connects to the furnace and i feel a draft coming out of the pipe.

This furnace is a supposed to be a 'closed chamber' however by doing what the installer told me to remove a plastic plug on the side to stop the banging on startup, would this not defeat the purpose of a 'closed chamber'?

As for the a possible delayed ignition, that is why they replace the gas valve the first time.

My questions are

1. Is removing the plug on the side to stop the banging appropriate or just a quick fix to get me off his back.

2. is it possible that I have negative pressure in my house cause the backdraft. What could be done to reverse this.. or has the installer put the venting stack in wrong?

thanks again for any replies/
danrad
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- Smell (not gas).... and a bang

Postby heatseeker » Mon Nov 21, 2011 10:23 am

LET ME GET THIS STRAIGHT they changed the gas valve four times????? What's the definition of insanity? Four gas valves and they can't figure out what's wrong with it? What's the name of that company Morons are us. Seriously this is ridiculous. Call another contractor and have them repay your out of pocket to have it repaired correctly.
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- Smell (not gas).... and a bang

Postby Freon » Tue Nov 22, 2011 4:35 pm

You should not feel air exiting the exhaust piping anywhere. Check CAREFULLY that there is no blockage in the entire exhaust piping. Try and find the exact place the air you feel is coming from. Possibly you can fix it or else call in a duct person. Check that the exhaust was installed correctly. Sometimes elevation of the outside piping (stack) is important. Also if there's a prevailing wind and the exhaust stack is on the lee side, it is possible you have back flow happening.
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