Lochinvar Noble Boiler Cycling and Flame Failure

StudioXcel

Our house (built in 2017, purchased in 2020), located in Saskatoon, Saskatchewan, Canada, is a 2-storey plus basement, approx 720 sqft per floor (compact infill), well-insulated (R14 slab, R15 foundation walls, R40 above-grade walls, R60 roof), with Lochinvar Noble NKC199N combi boiler and radiant in concrete topping (and basement slab) throughout.
It's run well the last 3 years however recently started having "Flame Failure: Running" lockout messages. After looking into it a bit myself (admitting very limited hydronic system knowledge but working understanding from working in the architecture field), I found a tiny leak coming from a fitting off the HX, which was dripping down to the pump and onto a sensor.





After wiping this up and pushing the reset 1-2 times a day for a few days, we called in technician (from a recommended company) to look at the issue.

The tech noted a couple things:

• Ignitor wire jacket showed black marks where it contacted the front panel. Tech taped the wire (awaiting replacement)
  
• Replaced the ignitor (apparently wrong model installed)
  
• Tightened leaking fitting
  
• "Combustion fan" makes small screech at high rpm (noticeable during ignition)
  

They recommend a full cleaning (fan, burner, HX), new gaskets, replacement of ignition cable, and combustion analysis.
Also suggest replacement of fan may be required. An extra cost (but acknowledged this could be reduced a bit if done at the same time vs after if cleaning fan doesn't work.

We've okayed them to go ahead with the major service (expected to happen 5 days from now), mostly since we've never done anything in the last 3 years (and previous owner may not have in other 3 years), but also because we need heat as we enter the deep heating season. I should know better about regular maintenance as I preach that on vehicles and most other things...

I've noticed it's short cycling ("anti-cycling" lockout) then triggering the flame failure shortly after a few repeats.

Not sure exactly what advice I'm looking for from this community (I just joined today), but there seems to be a considerable amount of expertise and great advice around here. Maybe there's something one of you know or can offer guidance. I have more info about the system setup and settings, but don't want to overload the first post (even more than I have.

Couple overall photos for reference.



P.S. We have asked that they also perform the flue gasket recall work (assuming it hasn't been done yet). I also found a TSB regarding the venturi that suggests they know of issues in other Lochinvar models.

psb75

Welcome to the community. We don't discuss actual pricing amounts in our discussions.
Standard policy.

dko

Sounds like your are in good hands, but make sure they are actually cleaning the HX and give you combustion test results. Don't helicopter.. but ya know, make sure you're getting what you pay for.



You may require more thorough and deeper cleaning than what the manual says to do.

StudioXcel

@psb75 Thanks, that's fair. Edited my post to remove values.

@dko Yeah, I wasn't around the last two service calls (when they investigated the issue) as my wife works from home. I wouldn't mind being home this time to actually meet the tech and pick his brain (just a bit).

Bit more info...
Settings:
SH max set point 110F
Max rate limiting 70% (I've tried turning this down to 30% but makes not difference)
Warm day 85F @ outdoor 40F
Cold day 110F @ outdoor -20F
Warm weather shutdown 70F
Shift reset 0F

DHW max 140 - set point 125

ARHL 180
MRHL 190

During call for heat, pre-purge, ignition, then firing which ramps from high (60+%) down to 10% until it cuts out in less than 30 seconds, then post-purge followed by anti-cycling block. Outlet spikes to ~120F then inlet quickly climbs. Pump is Armstrong Compass running in auto mode (approx 17W at 4gpm), out to 3 zones (typically 1 or 2 constantly asking for heat currently). I did notice you can hear the water moving through the second floor zone piping and occasionally see what looks like an occasional bubble. I would have thought you shouldn't see any movement in the pex.

GroundUp

This is a common issue with Nobles when the combustion is out of whack. I'm betting that the CO2 is very low, and that the heat exchanger is filthy inside. It needs a good cleaning and a combustion tune.

StudioXcel

Figured I'd give an update...
Tech removed the piping to the inducer fan and found a leaf stuck (on the throttle valve? excuse the car mechanical term), blocking roughly half of the air flow. He feared additional bits likely have clogged the burner. After taking the rest of the top apart, he found it was extremely clean! Just a bit of condensate/particulates that he vacuumed away - much less than he expected for the age (at least 3.5 years since service, likely closer to 6.5).
Burner still looked great, so he just cleaned everything up, installed new main gasket (it was quite firm), and put it back together. Running well since!

Long story short... Make sure you have bird screen on the downward facing outdoor intake pipe.

hot_rod

Looks like at least 2 of the fiber washers are leaking, dripping onto the HX wiring?
Does the system have glycol in it?

EBEBRATT-Ed

@StudioXcel

Sound like you have a service company that knows the equipment. Your luckier than most.

StudioXcel

@hot_rod
Yes, I'm fairly sure it's a glycol mix (based on leak colour and red liquid in feeder). Is glycol an issue? I understand there are multiple types of glycol and not all are appropriate for hydronic systems.
Not sure which are the fiber washers... But it does kind of look like there was leaking at the fittings on top and bottom of the internal pump.

@EBEBRATT-Ed
Agreed. The company I worked with has two techs that are quite comfortable with hydronic systems, though neither have much experience with Lochinvar specifically (A.O.Smith and Navien are far more common here).

The tech is returning to run a combustion analysis/report (forgot his equipment...) and install the new ignitor wire (delayed arrival), so I have another opportunity to have them check anything else at the same time.