Lochinvar WHN LP low fire flame flutter

delta T

Hello all, I have a Lochinvar WHN 110 (converted to LP in the field using the factory supplied orifice) and I have noticed that on low fire (less than 20%) the very bottom of the burner tends to flutter (best word I can come up with, only the bottom 1/2" or 1" of the burner and it is only at very low fire.) My first thought was gas pressure, monometer shows 13.4" static, and 11.9" on full fire. Combustion meter is broken, but I set it up a while ago to 10.8% CO2 at high fire was running great with 12 ppm CO. Did not check low fire when I set it up initially as it was a single day changeover and we are not done installing the new system (rads and TRVs) it is currently heating the house using the old existing baseboard. Any thoughts?

ced48

First question, how can the boiler be firing ay less than 20 percent, when that is it's minimum firing rate?

ced48

Also, what is the flame current reading at low fire?

Don_197

I have regularly seen the Knights display 19%........but NEVER lower.........that would be interesting.

delta T

Oh whoops, was doing three things while typing this meant to say less than 30% not less than 20%. boiler will not fire at less than 20%. sorry for the confusion. Have not checked the flame current and have not been back to the job yet.

Paul Rohrs_14

I have heard a "flutter" on modcons as you describe it but that trail always led back to the exhaust vent with slightly improper pitch so that the condensate would fill up the pipe and make the fan do bizarre things.

I don't know if it is related to the job you describe but I have "heard" this for myself on a job or two and that's the hydronic CSI cause I found.

Let me know what you find and I'll be glad to help further.

Best,

Paul

delta T

Sorry for the late response, have been swamped this week.

I too have had that happen, not my fault, though. Installed a TT and managed to vent it within the minimum developed length which was a real challenge on that job, but everything had fall, and all was supported well. six months later get angry call from homeowner stating that the POS that we sold him is not working.

I go out and start looking around in the boiler room, and realized that the venting connections where it went through the ceiling of the mech room looked different than I remember. started looking around and realized that the wall that we ran the vents through was no longer there. Another contractor who remodeled the upstairs decided he could just hack the vents apart and run them in a new location, no proper supports of any kind, and in the attic (which no longer had an access) found about ten feet of horizontal pipe on both the exhaust and intake that was pitched at aprox 1/2" per foot the wrong way.

Homeowner was a little sheepish after that and said the contractor was a friend of his, and was therefor cheap. Oh well.

Anyways, I have since been in contact with tech support from Lochinvar and it is looking like a small bias adjustment may be in order. Boiler is currently disconnected from system, (we are now installing the runtals and TRVs for the final system, before it was hooked up to the exsting baseboard temporarily) so once we get done with that and get the system back up and running, I will get back with tech support and perform the bias adjusment and hopefully it will just go away.

I will keep you all posted, thanks for the help.

Paul Rohrs_14

Was the 'flutter" causing a flame fail ignition, (not lighting off) or flame fail running fault?

This year, more than others, I have been noticing quite a few vent limiters sticking and causing some flame fail ignitions even while static gas pressure and wc drop checked out.

Glad to jump in if you want to discuss further.

Best,

Paul

ced48

Paul- What kind of flame current should this 110 be getting at low fire?

Paul Rohrs_14

It will vary based on how the combustion is set up and your earth ground but in general terms, I would expect it to be between 7 & 10 micro-amps on low fire.

bmwpowere36m3

Paul Rohrs said:

It will vary based on how the combustion is set up and your earth ground but in general terms, I would expect it to be between 7 & 10 micro-amps on low fire.

Is that based on personal expierence… as I recently purchased a WHN55, so I'm taking notes as I read these threads. The Lochinvar service manual states:

1. At high fire the flame signal shown on the display should be at least 10 microamps.
2. A lower flame signal may indicate a fouled or damaged flame sense electrode. If cleaning the flame sense electrode does not improve, ground wiring is in good condition, and ground continuity is satisfactory, replace the flame sense electrode.

Paul Rohrs_14

The manual is correct. On HIGH fire, it should be 10 micro amps or above. My experience with good combustion is usually between 12-15 micro-amps.

On LOW fire, I would expect, and have seen anywhere from 7-10.

delta T

The flame flutter does not cause any error codes at all, and disappears entirely at anything above 30%. It is only occuring at the very bottom (1" or 1 1/2") of the burner. The only reason I noticed it at all was that I was trying to show our new apprentice the works and showed him how the burner lit off, and how it modulated. "Is it supposed to do that?", "uhhhh, no. hmmmm"

RobG

bmwpowere36m3 said:

Paul Rohrs said:

It will vary based on how the combustion is set up and your earth ground but in general terms, I would expect it to be between 7 & 10 micro-amps on low fire.

Is that based on personal expierence… as I recently purchased a WHN55, so I'm taking notes as I read these threads. The Lochinvar service manual states:

Paul works for Lochnivar so I would take his word.

delta T

Hello everyone, just wanted to update this post seeing as how I left it without really saying what happened. I spent a good couple of hours on the phone with the very helpful people at Lochinvar's tech support trying various adjustment strategies and checking everything else that they could think of to try and get the flutter to stop and the combustion to even out, to no avail. At high fire I get great combustion numbers, however trying to adjust anything at low fire (< 35% either the flame will stop fluttering at a very high CO2 (>13%) and outrageously high and unsafe CO levels (>1000ppm), or I can get the CO2 to come down slightly and the CO down to somewhere around 200 ppm (still obviously unacceptable) and then the flame just falls apart and the flame sensor kicks the burner off. Verdict was the gas valve is not working correctly, installing a new one today. Thank you all for the help wallies, and a big thanks to Lochinvar tech support, very knowledgable helpful people down there!

delta T

Haven't been on in a while and I needed to close this out, turns out that there was no problem with the gas valve. put the new one in and everything was the same. After more tearing my hair out trying to find the obstruction in the combustion chain that had to be there to explain the problem, I finally noticed that there was a very very small amount of what appeared to be fine fiberglass insulation in the little slits in the burner. such a small amount that it was practically unnoticable. just brushed the inside of the burner out with a toothbrush cuz I was so exasperated, and started to see little bits of this fluff coming out. Problem solved!!

still have no idea how this happened as, the boiler was fully installed and fuctioning when the insulators were blowing into the attic, would have had to have airborn fluff travel about 150' from where the truck was parked outside to get this into the combustion air intake on the roof of the house. possible I suppose, seems unlikely, but can't come up with any other expanation.

Thanks again for the advice everyone!

L10ydchristmas

Hello delta T,

Thank you very much for your thorough account of this repair. I had a similar problem for months and your advice helped me fix my WHN 110.

Soon after cleaning the burner and heat exchanger according to factory videos, I began getting “flame fail ignition” and “flame fail running” lockouts. I ended up replacing the electrode harness, flame sensor and ignitor but the problem kept coming back. I could see the burner light but the flame would go out after about 15 seconds.

My gas line was upgraded to high pressure a few months after I started having the problem so Lochinvar suspected it may be a combustion issue and that the gas valve may need to be adjusted. I began to think the gas valve was the problem one way or another (i.e., it wasn’t opening properly) because tapping on it would typically get the machine to ignite and stay lit. I also removed and cleaned the gas valve assembly, checked the concentric vent for obstructions and cleaned the condensate trap. Initial success but no luck after a couple of days.

After reading your review I unbolted the heat exchanger door and realized there was a small amount of insulation from the refractory around the exterior of the burner. When I removed the burner, again a small amount of insulation in the slits of the burner. Factory instructions tell you to blow out the burner with compressed air or to vacuum it but your advice to use a toothbrush on the interior slits was key. After doing this I began to see daylight through the slits. I gently cleaned it for about 5 min, regularly blowing compressed air through it between brushing. I also blew off the refractory and the burner again after reinstalling it (there is no way to avoid getting insulation on the burner when reinstalling the refractory).

I am happy to say I have had zero faults since doing this 5 days ago.

Thank you again and Merry Christmas.

L10ydchristmas

I forgot to mention that the flame current is at 12.3uA on high fire, which thanks to Paul Rohrs_14, I know is in the ideal range. Therefore, it seems combustion is good. Thanks again.

delta T

@L10ydchristmas Glad this helped you! This is what this site is all about. Have a good Christmas and a happy new year!