New High Efficiency Furnace Problem

Buster 567 · 01-10-2007, 05:46 PM

Hello,

Excuse my choice of words but my knowledge of furnances is limited at best.

In the Spring we purchased a new American Standard 90+ high efficiency, single stage, furnace.

Periodically, usually once a day, the furnance will attempt to come on then will make a banging noise and then shut off. It will then attempt to re-start. Sometimes this will repeat up to 4 times before the fan comes on and the furnace is operational. We noticed that it also vents a small amount of natural gas outside when it shuts down (pvc pipe).

Most times the furnace starts up without any problems.

The furnance is still under warranty so I had the installer back out to look at it. On the phone he thought it was the flame sensor but he said that in order for it to be the flame sensor this problem would need to be consistently occuring.

His assessment was that there was nothing wrong with the furnance. Unfortuneately the problem did not occur when he was testing it.

Any ideas what might be causing this.

Thanks

#CARRIERMAN · 01-10-2007, 05:56 PM

Hi Buster 567

There are several things that cause this problem. One is the gas pressure is too high or too low. The second is the ignitor is out of adjustment. My guess by what you have written is gas pressure too high. Third is a burner out of alignment. Fourth is the air intake or exhaust is not installed properly or is restricted. Print this out and have your installer or service tech check these items.

Good luck
Rusty

Buster 567 · 01-10-2007, 06:01 PM

Thanks for the info.

I appreciate it.

lrfllc · 12-07-2008, 02:05 PM

The way this furnace is designed to to work:
1) The vent motor comes up to speed, clears the cumbustion area and pulls up a diaphram switch:
2) Once the swithch is closed the ignitor (hot surhafe ignition on this model - HSI) turns on.
3) Then the gas valve opens and the burner lights
4) The flame sensor senses the flame and the furnace continues to burn.

I think the key here is you can smell raw gas outside the house, which means everything is working until we get to the HSI igniting the gas. Make sure the cubustion area is completly sealed off, all grommetts in place and all doors are in place and closed. If this model has a sealed cumbustion area make sure the wires leading to the HSI have the gromett in place.

Larry pickeringtonhvac.com

ontheeaglesnest · 12-12-2010, 07:32 PM

I have the same furnace but sometimes will not start up at all to heating phase. Motor to clear combustion chamber comes on and igniter comes on but no gas. I am instucted to take cover off and pull small black hose off and blow then replace. Ya this works but what is causing the problem to begin with? The furnace diagnostic flashes 3 blinks .

lrfllc · 12-13-2010, 03:12 PM

Not sure what tube you are blowing on, but in most cases condensation in 90% furnaces collect in a trap and if it is stopped up the furnace won't allow the pressure switch to close. If blowing on the thing causes it to work, then take the assembly apart and clean it.

Hope this helps.

Regards, Larry@lrfmaintenance.com

www.lrfmaintenance.com

lrfllc · 12-13-2010, 03:14 PM

Not sure what tube you are blowing on, but in most cases condensation in 90% furnaces collect in a trap and if it is stopped up the furnace won't allow the pressure switch to close. If blowing on the thing causes it to work, then take the assembly apart and clean it.

Hope this helps.

Regards, Larry@lrfmaintenance.com

www.lrfmaintenance.com[/quote]

Hixheat1 · 12-13-2010, 05:33 PM

Quote:

Originally Posted by Buster 567

Hello,

Excuse my choice of words but my knowledge of furnances is limited at best.

In the Spring we purchased a new American Standard 90+ high efficiency, single stage, furnace.

Periodically, usually once a day, the furnance will attempt to come on then will make a banging noise and then shut off. It will then attempt to re-start. Sometimes this will repeat up to 4 times before the fan comes on and the furnace is operational. We noticed that it also vents a small amount of natural gas outside when it shuts down (pvc pipe).

Most times the furnace starts up without any problems.

The furnance is still under warranty so I had the installer back out to look at it. On the phone he thought it was the flame sensor but he said that in order for it to be the flame sensor this problem would need to be consistently occuring.

His assessment was that there was nothing wrong with the furnance. Unfortuneately the problem did not occur when he was testing it.

Any ideas what might be causing this.

Thanks

I'm a train dealer same as American standard. Is the furnace in the horz position. If so you have to re configure drain line on combustion housing. It could be a drain issue. Is it a two pipe system. Also it could be a gas pressure issue. Did you have gas before or is this a new install. If flue does not have enough fall your back to your unit. 1/4 inch per foot. Make sure flue is not frozen or drain line. Is clear.

ontheeaglesnest · 12-13-2010, 09:36 PM

I kind of thought of that on this new install bout the drain and made sure it was gradually fallin all the way to drain cuz the way installer left it the drain would hold water before coming out the end. I did this a couple of days ago so i will see if that smartens it up but other than that will do as u say and call the gas company. Thx so much for the reply. Brian