Furnace Gas Valve won't open consistently

Jamie2666

I have a Napolean NBM060S2A furnace and having a strange issue with it firing up hoping someone can offer some advice on things I haven't thought of yet.

So if the furnace has been off for awhile, an hour or so, and you call for heat it fires right up no problem and will heat the house up to the temperature being called for. Once it shuts off and the temp drops and the next call for heat is up it won't fire. Inducer starts up, igniter glows orange, the valve clicks but no gas comes out and then it shuts down and starts all over again. There is 24 volt coming to the valve consistently when it's suppose to be opening. My initial thought is that it's a faulty gas valve but the other weird thing is that after it tries to fire up three times the furnace doesn't shut off, the blower starts up and just blows cold air until I turn it off.

Anyway I've located a new gas valve but before I pull the trigger on buying that thought I'd see if anyone else has any input….if it didn't work all the time and was getting 24v I would think gas valve. But seems like it could be board or valve ? Thanks in advance!

mattmia2

replacing the gas valve isn't a diy job, you need someone that understands combustion to set up the new valve. the blower runs on a timer, if the burner doesn't come on the blower still comes on x seconds after the start of the heat call.

if there really is 24v to the gas valve and no gas, assuming there is gas to the appliance, it is the valve. be a good idea to put a manometer on the gas input before condemning the valve, especially if it is lp

Jamie2666

Thanks! I definitely wasn't going to tackle a new valve myself, I'm trying to get a hold of the company that did the Natural Gas to LP conversion on the furnace last week to come back and look at it. Of course, it's the long weekend and he's not getting back to me.

Maybe you can answer one more question for me, if someone did a natural gas to lp conversion, would you put a manometer on it with the lp gas flowing to the regulator ? Or is that something that happens before the gas is hooked up ? Cause i watched him turn the gas on for the first time and he just fired up the furnace and said it was all good to go. Just wondering if he would have done that test before ? Or maybe didn't do it at all and that's why this is happening. It's just strange that it will function properly on the first start up after sitting for a while and then immediately after it shuts off it won't start up again without sitting for awhile.

mattmia2

if the pressure isn't in the specified range the regulator in the valve may shut down completely. does the valve click when it is energized but doesn't fire?

EdTheHeaterMan

I have seen stranger things…

If a burner operated correctly from a cold start, but does not run corretly after it heats up then maybe goes off by limit, then has a second trial for ignition after just a short time, then I believe it is heat related. A hot burner or pilot or HSI or sparker electrode, may be in one position when cold, and another position when hot. That small adjustment may be the reason for your failed trial for ignition. Gas pressure or a slight adjustment of the ignitor. Your professional may need to look into the proper adjustments on that burner.

You (or your Pro) might feel really dumb if you replace the gas valve and you have the same problem. I usually do the process of elimination with the lowest cost items first then go to the more expensive ones if all else fails.

mattmia2

This isn't a valve with the ignition control built in, is it?

Jamie2666

mattmia2 - Yes it does click but then doesn't fire and doesn't have the ignition control built in.

EdTheHeaterMan - I had the same thought, that something is moving and that once it gets back to normal temperature it's able to start up again.

Seems like it should be an easy fix although parts aren't able to be sourced locally and we're heading down to chilly temps this week. Time for a new sweater or two!

EdTheHeaterMan

How old is the furnace? When did this issue start? Have you had maintenance performed in accordance with the homeowner's user manual? it starts on page 66 and goes to page 69.

https://www.manualslib.com/products/Napoleon-Nbm060s2a-3839153.html

• If yes to annual maintenance, how long ago?
• Did the issue co-inside with completing the maintenance?
• Is it possible that the HSI was moved away from the gas flow at the burner just enough to cause this problem?
• When was the last time the HSI was replaced?

All the above assumes that there is no flame at all during trial for ignition.  Below assumes the flame ignites and goes out right away.

• Is it possible that the flame sensor was moved away from the gas flow at the burner just enough to cause this problem?
• When was the last time the flame sensor was cleaned, adjusted, or replaced?

• Are the wires to the flame sensor connected securely to the ignition control?
• Is the furnace properly grounded?
• Are there signs of corrosion at any of the burner connections, manifold connections or cabinets?  

The last three have to do with Flame Rectification.  The flame acts as a rectifier in the proof of flame circuit.  There is an AC electric current that is sent out to the flame sensor.  The flame converts that to a DC circuit at the point where the electrons pass thru the flame and return to the control via the chassis ground circuit.   The actual metal cabinet of the furnace or boiler, the burners and the metal pipes are the conductor to the control.  If there is corrosion on any cabinet screws, then your return path for the DC circuit via the chassis ground may be compromised. The amount that is compromised may have to do with the temperature of the metal near the burner close to the flame sensor.

When this is the case, I have found that installing a grounding wire from a screw near the burner, close to the flame sensor, will make a better ground path.  Connect the other end of the ground wire to the screw terminal on the control that has the ground path. Sometimes the ignition control has a burner ground terminal that you can plug a spade connector to your ignition control ground.

Jamie2666

Thanks Ed for all that information, Honestly I have no idea how old the furnace is, I bought if off a heating company about 5 years ago and it's sat in my basement until now. This is the first time it's been hooked up. That said I did ask the heating and plumbing company who did the natural gas to LP conversion to check everything over….whether they did or not, I don't know. They just said it was good to go.

All that said, I'm pretty sure we can rule out flame sensor as there is no flame at all when trying to ignite. I did clean the sensor anyway. We get the bright orange glow of the HSI and the valve clicks but no gas is released. So I'm thinking it must be something from your first list. Something else I didn't mention was this issue also happens if you start up the furnace ( so flame and it's producing heat ), turn it off right away and then try to restart the issue happens….so it's not just after it's been running for awhile, it could be running for 5-10 seconds and if you shut it off and turn it back on it won't fire again unless you let it sit for an hour or so.

I think I have a guy coming in this Friday to look at it, I just wanted to order any part that could be the problem before he gets here…and even though that really sucks for my pocket book with the weather coming next week I don't think I have time to have him out and then order parts, that'll push the repair two weeks down the road. I mean, I can run this thing manually….so heat the house up to 75F and then turn the thermostat down to like 60F so it doesn't fire up again….then after and hour turn the thermostat back up again. The only thing that worries me ( probably cause i've read too many forums on the internet ) is that if the gas valve is not functioning properly or someone put too much psi through it for whatever reason that it's pretty dangerous to run it. with that failing valve. I would never run it over night but I have used it to warm up the house right before bed and then I turn it off for the night. Anyway I've done a lot of stupid things during the build of this house but buying a used furnace is at the top of the list. I just need it to get through the winter and then I'm going to buy a new one.

Thanks again for taking the time to chime in on all this, I do appreciate it.

JUGHNE

With a gas manometer on the valve inlet and volt meter on the gas valve connections so you can verify both those factors, then when it clicks and no gas to slightly whack the side of the gas valve with the rubber handle of a large screwdriver……..if that opens the valve then you know it is in fact the gas valve itself.

The presence of a repairman will make the valve work consistently for him, but not for you if he leaves without changing anything.😯

Be sure he is aware of having to convert the valve to LP. You want him to observe the inlet gas pressure with the burners operating.