Gas fireplace problem (SE)

Bob Harper

I agree w/ you on the O2. That's why I focused on the venting. If it works with the glass off, the gas train is ok. Now, its the venting or the secondary air circulation inside the Fp.

S Ebels

This thing is driving me crazy

The unit in question is a direct vent (through the roof)Heatilator LP gas fireplace that we installed 2 years ago. It worked flawlessly until about a month ago. At that time it began to act thusly................The pilot will stay on indefinitely, when the owner turns on the main burner it will light and burn great until 14 minutes have passed. I mean 14 minutes, you can time it with a stopwatch and it'll be within a few seconds every time. At that point the pilot will begin lifting away from the thermocouple and thermopile. It will turn long, lazy and yellow from it's normal sharp blue pattern in a matter of about 15 seconds. Shortly thereafter the thermocouple will lose temp because of the flame being pulled away and the main and pilot valves will shut down. At that point, the pilot can be immediately re-lit and the sequence will repeat for the duration of the whole 14 minute period. The two pipe chimney goes vertical from the unit for 6', then angles over at about 15* for 8', then goes vertical again for the last 8 feet.

Here's what I've done and checked so far and I'm out of ideas. Checked gas pressure, OK. Checked the entire length of the chimney for obstructions, none. Checked inlet air passageways internal to the firebox, OK too. Tried running the fireplace with the bottom of the glass propped open 1/4" AHA!!! The flame didn't get wierd and it stayed lit past until I turned it off. Called Heatilator to quiz tech service about this and they basically said Hhhmmmmmmm, mentioned something about a vent restrictor. I found out what the dimensions and placement were supposed to be and fabricated one out of sheet metal. It inserts in the round flue hole at the top of the firebox. No difference. The exact same thing happened in the exact time sequence as before. Now I'm thinking there has to be an issue with the draft if the factory guys are suggesting something like that. So up on the housetop I go to bore a couple test holes for the draft gauge. At start up the intake and the exhaust pipe read _.04" wc. The reading stays the same until about 13 minutes into the burn at which point both intake and exhaust drop to 0.0 in a space of about 10 seconds. Shortly after that is when everything goes out. I hustled down to relight the pilot and main, went back on the roof no more than 2 minutes after the thing had extinguished and the draft read -.04 again. Held it right there for another burn of 13 minutes and then began to drop until hitting zero once more.

The Heatilator guys are stumped too. Nothing has changed in the house. (new construction) No changes to the exterior as far as trees being planted or removed.No new fans or exhausts. The fresh air intake to the heating system duct is not plugged or blocked off......... I am absolutely stumped as to why the draft is disappearing the way it is.

Looking for the wisdom of the Wall. If it was mine, I'd have put a bullet in it long ago.

The pics are in numerical sequence with number 5 being shortly after start up, 11 at about 10 minutes, 14 at 12 1/2 minutes and finally 18 at 13 minutes showing hoe the pilot has pulled away from the thermocouple and become long and yellow.

EBEBRATT-Ed

I don't have much of a clue but obviously this thing is running out of air somehow. You talk about intake and exhaust. Where is the makeup air(intake) coming from?? Inlets around the glass doors? Are you getting a downdraft. Somehow this thing is starving itself for air. Something seems backwards. You would think that after running 14 min. you would get better draft from a hot chimney. Almost seems like a down draft or reverse flow is somethering the fire with it's own flue gasses.

I think you checked this but your sure there is no exhaust, attic fan, another fireplace with an open damper? How is the chimney compared to the roof line? higher than the peak or at least 10 feet from it, Any trees over chimney??

ED

S Ebels

Exactly right

The flame is running out of air the way it looks to me also. The vent assembly is concentric, exhaust inside the intake like a sealed combustion boiler or furnace. The thing that puzzles me is that the main flame doesn;t appear to change much, if at all when this happens. The pilot just starts pulling off the thermocouple like it's being blown off. The fact that it turns yellow (pic 18) makes me think it's starved for O2 somehow.

Chimney is good on all the things you mentioned.

Ron Schroeder

This thing is driving me crazy

And rightfully so, the only other thing I can think of if there are no blockages is cross contamination and the flue gases are circulating in the termination assembly or inernal intake channel instead of rising

Bob Harper

HL direct vent troubleshooting

Steve, can you furnish the gas pressures you recorded just for the heck of it? Having said that, if the unit burns fine with the glass off, the problem is in the venting. Since this is a double walled thermosyphon vent, it probably has a shunt somewhere in the run. Think of it this way:
At a cold startup, there is a slight draft up the exhaust and the intake, being full of colder denser air is flowing down into the Fp. Now, you light the burner. As the inner 5" pipe heats up, a boundary layer of incoming air heats up and actually begins a flow reversal. This explains why the burner is so blue at start up and takes about 15 minutes to get yellow tips. Now, if one of the pipe joints is buggered, it may start off as a venturi. However, as it heats up and starts this reverse convection, it can draw flue gasses into the otherwise fresh incoming air. The only way to prove this would be to somehow sample the incoming air with a combustion analyzer right as the air enters the firebox at the rear.

I hate to say it but a plumbing snake camera might be the only way to find it without opening walls. Just visualizing the outer pipe joints doesn't tell you about those inner ones. Also check the vent termination. If you used the DVP-TV, try the DVP-TVHW high wind top. Even if you don't have wind problems, it breathes better. In fact, as a test, take off the termination and stick a short length of 5" smoke pipe into the exhaust.

Keep HL Tech Service in the loop. They'll work with you until it is cured.
HTH,

Larry Savino

OK couple of things I can share. And your welcome to call me just drop me an email.I am on the east coast and will be working tomorrow Ill give you my cell phone. Lets start with the easy stuff, What if anything has changed in the house? have they added a new gas apliance,The pilot light on these are soft an susceptible to weak pressure, if your losing pressure(another appliance coming on further upstream of the FP) it will pull out the pilot

its important to take a pressure reading while its running, to see if it drops.

these direct vents love air. You may have a problem with a cross contamination exhaust into inlet air, but when its starving for air you normally see the flames on the burners ghosting (they actually disconnect from the burners and are like floating above the burners like a ghost) because the flame is reaching up into the box searching for air.

See if you can down load a manual on this to see if the flue is done as per the manufacturer's recommendations, Each and every pipe joint is supposed to be sealed on the inside with a material called milpack.If its not there the more joints you have the more cross contamination you will get. Also there should be an air shudder on the main burner that could have been adjusted to small.

Every one i go to service I make sure I have a installation manual on it to make sure the guy before me installed it correct and also to confirm log-set placement.

Jim Bergmann_2

Pilot problems

What you are seeing is a working oxygen depletion sensor; the manufacture has designed the pilot for this purpose. It is usually an aerated pilot that is very sensitive to the surrounding O2 level. (Secondary air) As the O2 in the fireplace depletes, the pitot will pull away form the flame just like you described. I would check for a recirculation problem. The flue gasses may either be leaking from pipe to pipe, or recirculating at the roof. Make sure the vent cap has not been damaged.
Attached is a shhet I made for my students, I hope the ideas help

Jim Bergmann
HVAC/R Technical Specialist
Testo

big bob

possible answer?

this problem you are talking about sounds identical to one we had at our plant three years ago.the only difference was that it was a vermont castings.all of our other techs had been there tested stuff and found pretty similar results to yours.my boss asked me to go over with him and take a look at it.i found pretty much the same type of results they did and you are.so after 3hrs on the phone with there tech support i asked what the max vent length was on a dv unit.they said there's were 26ft i had 21ft.the guy said that should be fine there had 2 be another problem.i kept looking at the unit scrathing my head thinking i'm overlooking the obvious here.then it came to me and i asked there tech support what they were eqauting for restriction in a bend or elbow.they said add 5 ft to eqation for each.2 bends in mine add that 10 to my 21 and i was over by 5 feet.i still wasn't convinced. it had been in for 2yrs why now.they explained that what it does over time is weaken the diaghram in the gas valve and keep it from creating the steady flame.they suggeted we change it to a natural vent.we ate the cost and did and it.it has been 3yrs and 13 service calls less than the old unit and no problems yet knock on wood.

rich pickering

milpack

To add to Larry's post, high temp red silicone tends to dry out and crack. Milpack is not supposed to.

Bob Harper

ODS?

Jim I hate to tell you but Heatilator and all Hearth & Home Technologies fireplaces do NOT use an ODS pilot such as required with ventfree units. In fact, the only ventfree HHT makes are electric and hydrogen fireplaces.

Also, they are moving away from standing pilot to their own proprietory Intermittent Pilot Ignition system called Intellifire.

HTH,

Jim Bergmann_2

ODS?

> Jim I hate to tell you but Heatilator and all

> Hearth & Home Technologies fireplaces do NOT use

> an ODS pilot such as required with ventfree

> units. In fact, the only ventfree HHT makes are

> electric and hydrogen fireplaces.

>

> Also, they

> are moving away from standing pilot to their own

> proprietory Intermittent Pilot Ignition system

> called Intellifire.

>

> HTH,

Jim Bergmann_2

ODS?

I stand corrected, however the heater is still showing symptoms of being short of O2 at the pilot, and I would still make the same checks. The manufacture may have not intended the pilot to work as an O2 depletion sensor, but it looks like it is. Looking closer at the pilot in the pictures I cannot argue. You are correct. An O2 depletion sensor would have been mounted at an angle. I might also check the pilot air inlet for dirt, if the pilot was dirty and the O2 level dropped in the unit after several minutes of operation, the pilot still might yellow and pull away.

Thanks
Jim

Weezbo

I 2 have spent three hours today with a heatilator

propane fireplace:( different fuel different deal..

whatever...to me it sounds like either a temp sensor or some limiting devise is goofing yours over. does yours have remote control? i cannot find the ir receiver that plugs into the front grumble grumble grumble...the fan wont turn on grumble grumble grumble grrr...think positive...this is the brand new super delux blah blah blah model i feel like what happens to the pieces after they are delivered is that they are picked up by trolls and hocked in the troll hoc shop the led light doesn't come on the electricians have a hatred for any two switches side by side to turn off or on in the same direction ....sorry er...it is just a matter of Time before i have discovered everything that could go wrong and get it out of the way of actually getting anything accomplished in a day.


the place has 6 switches on the left of the fireplace and 4 on the right )) Man **** )) its like a fricking rubic cube problem ) thank god i am nuts or this stuff would be getting to me:)

Jim M

fireplace

I had one doing the same thing. what I found was the thermopile slowly lost power and eventually shut everything down. Replaced the pile and unit has been ok since.