Knight Locking Out

Doug_7

Flame signal at high fire should be at least 10 microamps.

Low flame signal may indicate a fouled or damaged flame sense electrode.

See page 26/27 of Service Manual.

Darin(in Michigan)_3

Knight Locking Out

HI ALL!! I'm working on a Knight boiler that we installed a year ago. It has been running on LP since last fall. I converted it to natural and can't keep the bloomin thing running. At 100% it is reading 2.5 microamps. As the fan ramps down, the signal drops and eventually fails. After that, the unit goes into retry, burner lights and then goes out. Flame signal is zippo. All the wires are good, there is continuity between the ground an nuetral, I've pulled the burner, venturi,intake, exhaust piping, cleanded the spark rod and sensor....

Their sales rep is going to drive 3 hrs to bring a combustion analyzer to check settings. Anyone have any ideas? I feel that this should be a "Flame Rectification 101" question. It shouldn't be this tricky...

Darin

lee_7

Where is your combustion Analysor? If you do not have one, make that THE next tool added to your truck. Each and every unit should be tested. We test all units worked on, even for non combustion issues. As the good lawyers say " You touched last, what did you do to it?"

Doug_7

Low flame signal ?

Flame signal at high fire should be at least 10 microamps.

Low flame signal may indicate a fouled or damaged flame sense electrode.

See page 26/27 of Service Manual and Section 3 of Troubleshooting.

May need to replace flame sense electrode.

Doug

black_gold

whooaaa Nellie....

I work on mostly oil stuff...but lately I've put some mod-con boilers in to. I am going to assume you did not use a combustion analyzer to se this puppy up. The golden rule is to use a analyzer. You cant set these things up without them - period. No way, no how - read the book if you don't believe me.
If you rep is driving 3 hours to dial this thing in because you didn't set it up w/analyzer...you owe this guy biiiig.
Big.
Not a slam, but it's part of the job man.
You really should hook this guy up...he's doing part of your job for you.
You sound like a technical guy, I'd bet you can handle this... spend the coin & get the tool to do the job right.
Best 'O luck to you.

tim smith

I'd bet that combustion is off on unit, get an analyzer soon.

Then you will be able to identify what's up. Also could be fouled flame rod but this would be caused by poor combustion also. Again, analyzer.

hot_rod

take a sensor and

the wire for it. Usually it is one of the two that causes that.
I agree with the combustion analyzer. Buy one with a printer to leave behind a copy of the results and date of test, for the next serviceman to refer to.

hr

[Deleted User]

I'm betting its a lean mixture...

because I have pulled one of the two flame rectification rods and never seen it drop below 9 micro amps. In other words, with only half the flame rectification, it reads higher than he is seeing. That is the ONE feature that causes the Knight to shine above its competition.

I'm guessing that once he sees whats going on in the combustion chamber, his adjustments will make the problem go away.

If you work on the beauties, an analyzer is not an option, its a MUST HAVE.

ME

Rexford_2

pressure

I agree analyze, also check the gas pressure at 100% fire rate should be no less than 4" water column. if everything is within the specified parameters then go for the probe.

Darin(in Michigan)_3

And the winner is........

A bad control board!!!! I put a new control on it today and the microamp signal went well above 15 and stayed there even through low fire. Incidently, a combustion analyzer would be a wonderful tool to have on the truck(we still use the bacharach fyrites on f/o) but I understand the ones we should use are around $1500. I'm not an owner, just an hourly joe who brings home enough to put food on the table, pay for the mortgage and bills and pray the truck lasts another month on the old tires. You all are right about proper trouble shooting technique and tools, but sometimes the need may not justify the cost. Realistically, the rep didn't even have one himself and he is supposed to deal with this stuff constantly. We are putting more knights in but certainly not saturating the market, so that kind of cost outlay may be justified but it may have to wait until money loosens up.

k