Direct Vent Ignite Problem?

[Jerry Simon]

One of those barbeque-like spark igniters to light the pilot, then rotate valve for flame-on. Showed my client how to light pilot & flames; no problem doing so. Turned unit off, then she tried, and pilot would not light. Waited a few minutes, then it lit. Shut off, tried again right away, and pilot would not light again, but it did light after waiting again for a few minutes.

Normal? Some sort of safety device?

[Brandon Whitmore]

With a piezo (BBQ spark) lit standing pilot type fireplace, the only safety is the ASO (automatic shut off) valve. The thermocouple or thermopile must generate enough milli-voltage to energize the electromagnet built into the gas control valve. That magnet is what you are manually holding in by pushing in the gas control knob on the pilot setting. Once enough voltage is generated, the magnet then keeps the magnet in place and allows gas to flow.

Off the top of my head, I don't know why the fireplace would act that way....

[John Kogel]

Air in the line, maybe. Failing to hold the knob in all the way?

I show the people the card with the instructions, but never mess with other people's pilot lights. Maybe for the home owner I would, but never a buyer.

I know you are trying to teach and help, but it can lead to trouble, such as what happened here - she couldn't get it right. A month from now, she might try again and burn off her eyebrows.

[Brandon Whitmore]

I often find intermittently firing pilots when the sparker tip is out of adjustment or the pilot assembly is dirty.

[hausdok]

When you turn a gas valve off on a gas fireplace you usually have to wait a minute or so for a clicking sound before you can relight it. Turn it off and then try to turn it on and it won't light. Wait for the click and then proceed as normal and it lights.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

One of those barbeque-like spark igniters to light the pilot, then rotate valve for flame-on. Showed my client how to light pilot & flames; no problem doing so. Turned unit off, then she tried, and pilot would not light. Waited a few minutes, then it lit. Shut off, tried again right away, and pilot would not light again, but it did light after waiting again for a few minutes.

Normal? Some sort of safety device?

I think she was "flooding" the pilot area with gas and there wasn't enough oxygen to support combustion. Wait a minute or blow into the area to air it out and it'll light right away.

[Jerry Simon]

One of those barbeque-like spark igniters to light the pilot, then rotate valve for flame-on. Showed my client how to light pilot & flames; no problem doing so. Turned unit off, then she tried, and pilot would not light. Waited a few minutes, then it lit. Shut off, tried again right away, and pilot would not light again, but it did light after waiting again for a few minutes.

Normal? Some sort of safety device?

I think she was "flooding" the pilot area with gas and there wasn't enough oxygen to support combustion. Wait a minute or blow into the area to air it out and it'll light right away.

That seems to fit. TY

[Brandon Whitmore]

I think she was "flooding" the pilot area with gas and there wasn't enough oxygen to support combustion. Wait a minute or blow into the area to air it out and it'll light right away.

If natural gas and not propane, I doubt this is possible. When I go into a home to fire equipment, I stick a small screwdriver in at the control knob to hold the magnet down. Then, I walk away to fire all of the other equipment for anywhere from 2-20+ minutes- this helps purge the line of any air. When I come back and fire these things up, the biggest "flash" I've gotten is maybe the size of a golf ball. Nat. gas can ignite at anywhere from appx. 4.7- 15% , and has a specific gravity of .60 ish. That means that the gas just vents out of the fireplace as the line is being purged.

[Jim Katen]

I think she was "flooding" the pilot area with gas and there wasn't enough oxygen to support combustion. Wait a minute or blow into the area to air it out and it'll light right away.

If natural gas and not propane, I doubt this is possible. When I go into a home to fire equipment, I stick a small screwdriver in at the control knob to hold the magnet down. Then, I walk away to fire all of the other equipment for anywhere from 2-20+ minutes- this helps purge the line of any air. When I come back and fire these things up, the biggest "flash" I've gotten is maybe the size of a golf ball. Nat. gas can ignite at anywhere from appx. 4.7- 15% , and has a specific gravity of .60 ish. That means that the gas just vents out of the fireplace as the line is being purged.

Now I'll have to do some experiments. . .

[Hearthman]

Originally posted by Brandon Whitmore

I think she was "flooding" the pilot area with gas and there wasn't enough oxygen to support combustion. Wait a minute or blow into the area to air it out and it'll light right away.

If natural gas and not propane, I doubt this is possible. When I go into a home to fire equipment, I stick a small screwdriver in at the control knob to hold the magnet down. Then, I walk away to fire all of the other equipment for anywhere from 2-20+ minutes- this helps purge the line of any air. When I come back and fire these things up, the biggest "flash" I've gotten is maybe the size of a golf ball. Nat. gas can ignite at anywhere from appx. 4.7- 15% , and has a specific gravity of .60 ish. That means that the gas just vents out of the fireplace as the line is being purged.

This is inherently dangerous. You are deliberately trying to replicate the delayed ignition test when usually detonate like a bomb. When attempting to light a pilot, you should be creating a spark every 3-5 seconds with gas flowing to the pilot. If you cannot get the pilot to light within 30-60 seconds at this, shut the unit off and have someone disconnect the gas line to the valve or pilot tube and bleed the air out. If this reveals gas is to the valve, use an open flame held at the pilot to ascertain if there is gas to the pilot but the sparks is failing to cause ignition. Sometimes, you have plenty of gas but the igniter fails to generate a sufficient spark at the gas. This can be anything from a cracked ceramic insulator to compromised wire lead to a bad piezo or diry electrode. The spark gap, just as with autos is critical as well.

As for flooding the unit with gas, absolutely. I see it all the time with both fuels. The venting has a lot to do with this but the dissipation of NG due to its lower Sp. Gr. takes time. I've worked on CPSC recalls on units that experienced severe delayed ignition due to a restrictive vent system when all else worked fine.

When lighting a pilot on LPG units, it is a good idea to remove the glass front and hold your face off to the side during lighting. I've investigated enough incidents of delayed ignition injuries on LP units.

[Brandon Whitmore]

Now I'll have to do some experiments. . .

Here's a fun one for you....

Fill a metal coffee can with natural gas by laying it upside down (lid down) and running a gas hose/tube into a partially open lid. Then, punch a small hole in the top of the can (punch thru metal) and light the "hole" area-- this will make a candle. Then, let the coffee can candle burn until you get down to 15% concentration of gas inside of the can-- you'll enjoy what happens next. It's much more explosive impressive while doing this in a dark room.

[Brandon Whitmore]

This is inherently dangerous. You are deliberately trying to replicate the delayed ignition test when usually detonate like a bomb. When attempting to light a pilot, you should be creating a spark every 3-5 seconds with gas flowing to the pilot. If you cannot get the pilot to light within 30-60 seconds at this, shut the unit off and have someone disconnect the gas line to the valve or pilot tube and bleed the air out. If this reveals gas is to the valve, use an open flame held at the pilot to ascertain if there is gas to the pilot but the sparks is failing to cause ignition. Sometimes, you have plenty of gas but the igniter fails to generate a sufficient spark at the gas. This can be anything from a cracked ceramic insulator to compromised wire lead to a bad piezo or diry electrode. The spark gap, just as with autos is critical as well.

I know what the manufacturer's lighting instructions say, and expected someone to chime in that what I was doing was technically wrong.

I work for the local gas company as a service tech., and do this procedue daily, as do many others, with absolutely no problems.

You are deliberately trying to replicate the delayed ignition test

I'm far from attempting to cause delayed igntion. The only time I've run into a delayed ignition concern is when the burner gas is flowing, and ignition doesn't occur when it should, or if the ASO has failed. The pilot orifices are tiny, and I think it would take a very long time to pool natural gas up to that 4.7% range even if the vent were partially obstructed. Now if there were no vent, and the unit were sealed, I wouldn't be purging for a long period of time through the pilot.

[Brandon Whitmore]

I've worked on CPSC recalls on units that experienced severe delayed ignition due to a restrictive vent system when all else worked fine.

Can I get more details?

I'm going to guess that the delayed ignition wasn't due to someone trying to light a pilot, but am curious.

[Jim Katen]

Now I'll have to do some experiments. . .

Here's a fun one for you....

Fill a metal coffee can with natural gas by laying it upside down (lid down) and running a gas hose/tube into a partially open lid. Then, punch a small hole in the top of the can (punch thru metal) and light the "hole" area-- this will make a candle. Then, let the coffee can candle burn until you get down to 15% concentration of gas inside of the can-- you'll enjoy what happens next. It's much more explosive impressive while doing this in a dark room.

And one for you:

Take an empty 2-liter pop bottle, stick the neck of a propane torch into it and fill it with propane. Then lay the bottle on its side on the kitchen table. Ignite your torch and move it slowly toward the open neck of the bottle. The propane will ignite, forming a long jet of flame which will propel the bottle across the room. If you aim it correctly, it will conk the cat on the head.

[Tom Raymond]

I watched my step father and his brother fill a balloon with acetelyne to the size of a small beach ball. They tied a line on the balloon and pulled it over a lit candle they had placed on the front lawn. The kaboom nearly blew the windows out of the house.

Jim, I think your experiments deserve a youtube channel. Please?

[Hearthman]

http://www.cpsc.gov/en/Recalls/2005/CPS ... replaces-/

This unit was designed as a high efficiency heater with a restrictive heat exchanger. This prevented the air in the combustion chamber from easily purging up the vent to make room for fuel gas as the valve operator opened. Gas continued to flood the combustion chamber as the IPI pilot was getting good flame rectification to the point a nice explosive vapor cloud had accumulated in the combustion chamber before it reached the pilot flame and boom! We had one unit at a trade show in a convention center. The salesmen went to light off the various fireplaces and this unit detonated. The vent termination shot to the rafters 47 feet where it was smashed by the force then fell down. Part of the recall fix was a delay mechanism that allowed the IPI pilot to burn 45 seconds to "prime" the exhaust vent so the mixed fuel/ air could flow properly through the burner and ignite properly, within 4 seconds per ANSI. We also had to install a reinforced frame for the glass front made of 1" tube steel so the glass would not bow out and shatter throwing shrapnel all over the room.

Brandon, if you're doing this procedure with the glass removed I don't have a major problem with it for up to 5Min as long as you remain in the room supervising it. If the glass remains installed or you bleed it longer, I'd say you've been extremely lucky. Personally, I think it is irresponsible for a qualified technician to do this and walk away leaving the unit unattended when he could take a 7/16" open wrench and crack the pilot tube then speed bleed it or if it is a longer run, crack the gas line and bleed the air up to the unit then light as normal.

I will also warn you if the unit has had its fuel type converted beware the tech could have left the pilot orifice spud off, which would then flow a quite significant amount of gas, which happened to me once. It cost me some body hair but was a close call. I agree NG is not as tricky as LP but still it should be respected all the same. When you're doing this procedure do you have your sniffer sampling inside the fireplace set to % volume?

[Brandon Whitmore]

agree NG is not as tricky as LP but still it should be respected all the same. When you're doing this procedure do you have your sniffer sampling inside the fireplace set to % volume?

Yes, I carry a sniffer, set to PPM. No, I don't sample inside the fireplace. If I sense something is wrong, I stop and figure it out. My nose will often let me know if raw gas or air has been bleeding for some time, even with the glass in place. Gas log fireplaces/ appliances are typically not 100% sealed,

Bleeding thru the flex connector/union, etc. beneath the "firebox" isn't always simple, and then we get call backs on odor/gas leak calls because the smell lingers.

There are other ways to purge such as using a battery that I won't use due to the concern of gas build up in the unit.

I think it all comes down to experience, what you are comfortable with on a given piece of equipment, etc. Also, I can tell how much air is in the lines based on how other pieces of equip. are firing, so I'm not really bleeding gas through the pilot tube the entire time.

The reason I used my example wasn't to say that it was the best, or even a good way of doing things. It was used to say that I don't believe the customer was "flooding" the fireplace during the light up attempt. Would you agree with that statment?

Oh, and thanks for posting your example, I appreciate it.

[Hearthman]

The incidence of flooding around a pilot above the UFL preventing ignition is dependent upon a lot of things. The type of pilot, orientation of the pilot to the burner, which can often tend to trap a small cloud of gas in front of the pilot, and as I said before, the venting can sometimes combine to result in a combustible vapor cloud above the UFL. With NG, it is a simple matter of waiting 30 seconds and as you said, the gas usually dissipates unlike LPG. Old two diverter pilot hoods usually require 800-1,200 BTU/hr input whereas a pilot that includes a thermocouple and thermopile or an ODS on a ventfree can burn as much as 1,600 BTU/hr. These flow rates are about double that of a simple TC only pilot such as on water heaters, boilers, and manual control gas logsets. That higher flow rate pilot was the usual culprit with flooding.

When I was a Regional Quality Assurance Mgr. for a fireplace installing distributor, I set a policy on LP start-ups of removing the glass and using an open flame at the pilot until the pilot lit. Then shut it off and light pilot using piezo igniter or IPI with the burner off first. Once the pilot stays lit, you blow out the pilot and confirm the safety shutoff function. Then you can close the glass and start up per usual.

I investigated a number of LP systems that blew upon ignition resulting in injuries and the termination cap shot over 100ft. NG is safer but not bullet proof. An open fireplace is rarely a problem except when there is a leak in the gas tubing. That gets exciting.

[Jerry Simon]

So, can anyone answer my original question with any authority?