KHN 085 wont stay lit

keyote

I had this noise I thought it was air, sounded like a washing machine pumping out. Turned out to be combustion issue when modulating down. I then assumed I needed to do an annual maintenance and was about to order some gaskets and parts i heard often get damaged or might need replacing during cleaning/ inspection. But realized yesterday that my return water and flue temp were within a degree of each other, and manual says them being more than 50' apart is a sign needs a cleaning, so i doubt it needs cleaning also NYC water is not hard.The flame signal is another thing manual says to be sure is correct, but at even 40% mod its 10.6. so i dont think I have a problem there.

So I wondered about mixture, I did do an analysis when installed last fall and it came in at O2-8.5 and CO was .016
I think it was alaska rick who said back then he was finding 9.2 to be optimal, but since i was within the manuals range of 8-10.5 I thought I shouldn't mess with it. Now Im thinking that was the wrong call, and the trouble is mixture. The manual says 1/8 turn and retest, repeat as many as four times, if your analysis is off.. i borrowed the analyzer but figured since i was so low i could probably safely give it a 1/4 turn on the blind.

But i dont even know if given the above info I am even right about the likeliest cause of my issue. I had hoped to also do the annual maintenance for good measure even though I suspect its not needed since I have good NYC water and gas and its only run a season light duty. But I didnt get the gaskets ordered friday and now i tried to get the boiler restarted when i found the lockout but it made several attempts and locked out again,It wont stay lit, and I have tenants and dont think the apts will keep warm enough till the gaskets arrive. Id also consider calling someone but dont think the average brooklyn plumber is going to do well with this system. Any thoughts anyone in brooklyn

Jamie Hall

Oy. You do have a problem. Try @JohnNY or @EzzyT

JohnNY

First make sure you're not sucking exhaust back into your combustion air.

keyote

Thanks Jamie you think its serious huh? Do you think Im right that its the mix was on the low side and has since fallen a bit from use?
arent those guys steam heads?

Canucker

They both do more than just steam

keyote

Thanks Johny I followed the manual, they are about 18"-20'' apart and aimed away from each other, they're short runs only up two feet and out one foot. used cetrotherm. I was thinking in the morning Id take them apart to be sure theres no varmints in there i used the screen terminal pieces but its large enough some things could get in i suppose.

Zman

Your O2 is way high. It could be the CO2 should be 8-10.5.

keyote

Zman

Typo CO2 was 8.5 the o2 was .016

Jamie Hall

keyote said:

Thanks Jamie you think its serious huh? Do you think Im right that its the mix was on the low side and has since fallen a bit from use?
arent those guys steam heads?

I do think it's serious, and I do think you should get a pro. to look at it. And both the guys I mentioned are full range heating pros, and among the best.

Paul S_3

we service nyc.... you can give us a call... I work on Lochinvar a lot

NY_Rob

keyote said:

I followed the manual, they are about 18"-20'' apart and aimed away from each other, they're short runs only up two feet and out one foot.

FWIW- in addition to maximum intake/exhaust lengths, there's minimum lengths too.

On my mod-con boiler, the minimum length with 2" pipe is 10', the minimum was longer if you used 3" pipe.

Are you using 2" or 3" pipe?

MikeJ

What does it do when it goes to light, does huff puff and not light?

keyote

Rob
yes loch has a similar requirement although its not in the table with max length and diameter, its in a footnote, its 12' but they allow you to credit friction feet for fittings, and and so with fittings Im about 15' combustion air and probably a bit short at 10' on the flue unless i can count the factory installed internal portion. Also I used 2" so that probably helps since they dont change min length for the 2'' vs 3'' which are both allowed.

I watched the comb window when it was making the noise and it happened as it tried to mod low and sot of ocilated with the noise vibration then usually would sort of end with a little orange puff then mellow out. today though was the first time it actually ever faulted and when i reset it it tried several times to stay lit and couldn't and this time it was pretty much orange all the way through the struggle. seems like whatever's wrong has been getting worse and now it to clogged to push through

Jamie i tend to agree a pro would be best guess ill have to see if anyones taking plastic its of course the worst of times for this.
But youre right it should have a new comb analysis done if the mix is going to be adjusted, If thats even the right problem Im just a tinknocker what do I know. I think alaska tim was right though it should have been set higher than the fact default. . It wouldn't hurt to have my settings critiqued either I sort of slacked off on dialing in the controls once i got it heating the place. Im told you can really tune a boiler if you know what you're doing I didnt honestly it was the first time Id actually done an analysis myself seen them done on the job a couple times but really barely figured out how to work the thing it was borrowed.

keyote

Mike it lights but struggles and has orange in the flame and is un even, then it goes out and tries again until it triggers block out. It seems also to be starting to dirty the sight glass, not sooty more cloudy i think.
What I realized this morning is this blockout must time out and it tries to restart on its own. judging from the temps its been a little more successful. Also I found the hot water tank had been reheated. I think what happens is if it tries to restart when waters warm enough it wants to mod low it cant mod low. but if the water cools enough it can get going as i watched it do this morning until it had to mod down then it couldn't maintain a low flame, this would account for why it was able to heat the DHW at full mod.

MikeJ

Does it still make a washing machine noise when trying to light?
On the gas valve their is a hose goes up to the intake vent, try take that off see if it lights better. If it does that orifice could be plugged don't leave hose off just off for test purpose.

keyote

Thanks mike you mean the hose from combustion air ok Ill try that