new furnace won't stay lit, unitary by York, 80%, 75,000 btu GF8

[stevek]

I just installed a new furnace. It was quite easy. Once turned on by the thermastat, the burner lights for about 7 seconds than turns off. This will continue three times then the control locks out for an hour, then it will repeat. The error code says flame could not be established. That is correct, but why. The manual says caused by low gas pressure, faulty gas valve, faulty hot surface igniter or burner problem. The igniter glows red and it seems to have a strong flow of gas until it shuts off. The house has a new gas meter. The house was empty and without heat last winter. I believe the thermostat is hooked up right, it is new, and it is a cheap simple model. The furnace is in a basement with the appropriate ammount of cubic feet to not require outside makeup air, as I read the instructions.

Let the experts speak, I will listen. stevek

[hvacdrd]

Sounds like the furnace is not detecting the flame. Opposite from the ignitor(which is usually on the right burner) is the flame sensor(would be on the left, white ceramic body diameter of a pencil with a metal rod that is in the flame when running). Make sure the wire is connected here and at the ignition control. Verify that the metal rod is not touching any thing either

Verify that your electrical supply has a proper ground, the flame sensing circuit will not work properly without it.

[AccApp]

On the opposite side of the ignitor will be a straight metal rod inside a white ceramic insulator. The rod will have one wire coming from it's end and going to the control board. This is the flame sensor. It has a very thin, invisible coating of oxides which are preventing the system from realizing flame has been established. Take it out and using some steel wool or emery cloth clean the part of the metal rod which gets washed by the flame until it is bright and shiny. I always clean it using lengthwise strokes as I used to be a TIG welder but you just want it to work. Reinstall it and report back. I have some customers who require this every year and others who get it once and never again. Lots of early season jobs require this.

[hvacdrd]

See...great minds do think alike.

(this gets me to 400)

[stevek]

No luck. I cleaned the flame senser with emory cloth and checked the conector. It still burned for 7 seconds and went out with the same error code. The power supply to the furnace isn't a grounded circuit, nothing in the house is. I tried to ground the the power supply at the shutoff switch. This didn't work. It seems to me that if the circuit not being grounded was the problem then the furnace would not light at all, not light and then go off. I am going to have an electrician run a ground cable to the box and will have him run a grounded circuit to the furnace. I appreciate the advice, I am learning alot about furnaces. thanks

stevek

[AccApp]

Get a good ground to the furnace and report back. Is the polarity correct? Power can have bizarre effects if not properly applied.

[dkpd1581]

Look to see if the gas line serving your new unit has a gas regulator.  Start from where the gas line enters your unit and work backwards.  It could quite possibly look like a little square box or a pancake. 

If there is one there, it could be A: Defective or B: Unecessary. 

I have had older furnaces that required or had gas regulators and the new one does not.  My experience is that upon start up there is enough pressure in the line to hold open the regulator but as the furnace lights and consumes the gas, it lowers the pressure to the point that the diaphram inside the regulator closes.  Your furnace only realizes that the flame goes out (due to not enough gas pressure making its way through the regulator).  It shuts off, the gas pressure builds back up while the unit purges and goes through its start up procedures.

After 3 times of this off and on, the idiot light on the board says flame not detected.  If you do have a regulator, try removing it and then starting the system and see if this will give you better results

[applianceman18007260692]

maybe you have air in the gas line did you bleed it good?

[Guest ahammer48]

Hello

I agree with applman & dkpd. Especially since in your post you say a new gas meter was installed. Wouldn't be the 1st time the gas company forgot to open a valve up after a meter replacement. Go out to the meter and C if all the valves are open.

Do you own any other gas appliances and are they working ok?

Are U on natural gas or LP and is the unit possibly the wrong type?

Is there a knob on your gas valve that is set to pilot and need to be turned to main flame.

You need to check the gas  pressure :poison: before and after your gas valve. Had a job that the entering pressure was to high and the units valve would shut down, just like Urs is doing.

Have a tech come out and check it. Gas is not something U want to mess around with if your not qualified. Ur gas company may also do it for free. Call them.

 

Hope this helps:)

[stevek]

I had not done anything with the furnace problem until the last couple of days. I lit the new hot water heater the other day to make sure the gas flow was alright. It worked fine. While it was heating, I turned on the furnace, it stayed lit longer than before although it still turned off way too soon. I thought it would have the opposite effect if gas flow was the problem. I got to thinking maybe there was too much gas pressure, so I closed the gas supply valve about halfway. It is a simply gate valve. I turned on the furnace and now everything works fine. My question is, do I need a new regulator on the gas meter? It is a new meter and regulator, or is this somehow a problem with the gas supply valve on the furnace? It is a new furnace.

[applianceman18007260692]

when they changed the outside meter did they use the old outside pressure reg? I think you need to call the gas company . the safety valve itself has a reg built in to it if its a newer model. but the pressure can be checked on it through the pressure tap

[hvacdrd]

First verify the furnace is set up for the type of gas you are using. I am assuming that you are on natural gas given the information you provided so far. An LP furnace won't work on Natural and vice versa.

Measure, measure, measure. An overfired or underfired burner will not work properly.

The two things you need to know -

1) inlet gas supply pressure (natural gas typical supply pressure is 7"w.c.(water column) equivalent to 1/4 psi. Your supplier should be able to give you this information upon request.

2) manifold pressure(pressure after the gas valve in your furnace) typical is 3.5"w.c. - see your nameplate for specific value.

If you are choking down the inlet pressure it will decrease the manifold pressure. On a new furnace start up the manifold pressure must be checked.

 

[Brew Man]

Hey,

Check on any recalls that could be on your furnace. Other than that you could check on a gas piping sizing chart to see if you have the right size piping to your furnace. depending on your house size you would need a 90,000 btu furnace for an 1800 sq ft home.