Knight / Lochinvar WBN080 Natural Gas Repeated "Lock Out No Flame IGN"

boilingover

I bought a home with a Knight WBN080 that has had a couple of "Lock Out No Flame IGN" errors each year for the past 3 years. I have tried 3 different companies ( the original install company is out of biz), checking Lochinvar recommended techs and I even found the original tech / installer via Linkedin.

He was the most helpful, pulled code history, did combustion analysis, drained, cleaned and checked everything . We replaced flame sensor and igniter. He had an extra control board on his truck but that made no difference. We would get initial flame, but it would not fire up. One last thing he tried was a new ignition cord, and then it fired up. He has since retired:(

The "Lockouts" have continued. Only a couple of times a year. In warmer months the error code usually clears and it fires up. However after very cold winter stretches it can lock out and won't clear or fire up. The new service company is stumped as well. They contacted Lochinvar who said we should install new flame sensor and Motherboard.. which I have already tried once…

Any other ideas or suggestions? Thanks!

Ironman

What are the numbers from the combustion analysis?

jesmed1

Have you checked dynamic gas pressure and verified it's in spec? (Static pressure can be OK, but dynamic pressure may be lower.) Also make sure you have the correct size gas line. In cold weather, high demand on the natural gas distribution system and/or incorrect gas line size can drop the dynamic gas pressure below spec.

This is more likely to happen in cold weather, which fits your pattern.

GGross

Yes someone needs to check the gas pressure

static pressure before ignition

light the boiler and record the lowest value at ignition

run to high fire, record this value

shut off boiler record this value

Ideally these are all performed with your gas supply at full load, meaning all gas appliances are running at maximum

Once gas pressure is recorded and can be fully verified within allowable range, and not greater than or equal to a 1" wc pressure drop from static, then a combustion analysis needs to be done, adjust until within spec on low and high fire

If damage is already done to the igniter and flame sensor they should be replaced before tuning combustion. Igniter and flame sensor are wear and tear parts however their failure is also generally a symptom of poor combustion, especially when they are failing within a couple of years.

GroundUp

This is almost always a gas supply or a venting issue. Whether that be undersized gas line, undersized regulator, faulty regulator, faulty gas valve, plugged intake/exhaust, oversized exhaust, poor vent terminations, or one of the other dozen possibilities we can't diagnose from here… We can't answer definitively from here. If the ignition cable solved the problem last time, it's possible that it's got a poor connection again. They use a spade type connection and I've found a few of them that were loose and needed to be re-crimped. I also recently found one that had been bent and broken inside the heat-shrink so it only wouldn't make connection when the front panel was installed (that was a real head scratcher). If the venting is arranged in a way that it can draw exhaust back in the intake under certain circumstances, the burner and venturi are probably filthy and require cleaning. If the technicians have never opened the heat exchanger up for cleaning, I'd start looking for a new one before spending any more money on them. They also should have left two printouts on site of the combustion numbers at both high and low fire, which would be helpful in determining what exactly we're looking at here. Do you have those?

boilingover

Thanks everyone, confirming that all the techs visiting.. have been cleaning heat exchanger. The last analysis I saw was done on laptop no print out. but I'll be sure to get screen grab / print out next time. We have a gas range, indirect water tank, and no other gas appliances.

The sensor, cord, igniter replacements were always done along with that cleaning as we tried to rule out most common failures / potential quick fixes..

Far from a boiler guy, but reminds me of engine repair fundamentals.. we need spark, and the right mix of fuel and air.. Where the sputters and backfires of an 82 Buick used to be a guide… combustion analysis and gas pressure sound much safer:)

I'm also realizing that at 15 year mark I'm probably reaching /exceeding the life expectancy of this unit. Former owner was an engineer, very involved in design and everything else works great. Should I look to replace, are there brands / units that do better with potential fluctuations in gas pressure?

I greatly appreciate everyone's advice and help. Thanks!