Lochinvar Knight Boiler Flame Fail Ignition Errors - ready to pull my hair out

GroundUp

Again, adjust low fire first. Gas pressure needs to be tested and verified prior to making any adjustments, as Mattmia2 stated. If there is not enough adjustment in the high fire screw, it's either short on fuel or the low fire is way out of whack too- probably both in this case.

hot_rod

A manometer on the gas valve is the only way to know if you have sufficient gas pressure and flow

Static pressure and high fire pressure. The gas flex is a concern, it should have a btu/hr rating on it?

Why the regulator at the boiler? Is this a 2 psi system?

Ajmal

I don’t know why there’s a regulator, that’s how it was installed and has been working the last 3 years.

This is the only marking I see - there’s nothing in the pipe itself

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SuperTech

That regulator shouldn't be so close to the boiler and that crappy flex gas line should be replaced with threaded pipe. I bet that's part of the problem. You really need to be measuring gas pressure to the gas valve in the boiler and to the burner while performing combustion analysis. Having the analyzer is great but you need a manometer to do the job properly as well.

Try it again once you have a manometer and start with checking and adjusting it on low fire first. It's looking like you might have a gas supply problem due to that lame piping job but you can confirm that when you have a manometer.

Ajmal

I appreciate the feedback - I have a manometer and will test the gas pressure tomorrow morning.

the diagram in the manual wasn’t great so it was hard to decipher where to plug the manometer in but I’ll look again and figure it out

So if I’m understanding, I’d the gas pressure is low, the line from the regulator to the unit needs to be extended and with steel pipe? If that’s what it turns out to be, I’ll try to find someone to do that - I don’t want to mess around and have a gas leak but at least it would pinpoint the problem.

SuperTech

You need to make sure the gas pipe is large enough to supply enough gas to the boiler and the regulator should be adjusted properly as well. Check what the static pressure is to the boiler before you start testing, perhaps that regulator is not set properly. The installation manual should tell you what size gas line should be installed and what the maximum and minimum gas pressure to the boiler should be.

hot_rod

a gas flex can work and may be required in seismic areas. Usually a short, full 3/4” flex is adequate for that size boiler.

mattmia2

If it is propane that connector is probably adequate but there could be other problems. Ifs everything that needs to be set to convert it to propane set for propane?

JUGHNE

Around here LP installations have 2 gas regulators outside of the house.

A first stage reg at the tank that drops the pressure down to about 10 PSI.

The second reg is one the house and is set to 11-13" WC and handles all the load within the house.

You MAY not need the reg at the boiler if your second stage reg should be doing the job.

GGross

We know you have ignition issues, so the pressure drop at ignition is also very important. A short length of pipe like you have between the reg and the appliance can result is higher than desirable pressure drop on ignition, which can result in a failed ignition. That won't fix the problem you are having tuning the combustion on this unit though, that may be separate, but we need all the info, and incoming gas pressure comes first

proper way to measure is in a few steps, all recorded at the appliance incoming gas pressure test port located on the gas valve

1: static pressure, when the unit is off record this number

2: keep manometer on the unit, record pressure at ignition

3: run unit to high fire record the lowest pressure value

4: shut unit down, record the pressure after shutdown

4: if possible, with all gas appliances running, repeat the steps.

Ajmal

this is what I recorded - I don’t know if it makes sense, I may have tested wrong but I tried to follow the instructions in the service manual.

Off: - 5.89

Ignition: - 5.56

100% fire: - 5.53

Shutdown: - 5.89

I included some pictures of how I did it

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JUGHNE

Looking at a KBN 106 install manual, it states that any inline gas reg must be a minimum of 10' away from the boiler. I believe this applies to almost all negative pressure gas valves, which your boiler does have.

Also the CSST flex gas line you have will add to the pressure drop.

What size/type of pipe and length from the second stage regulator (which may be outside on the house) to the reg at the boiler?

Do you have 3 regulators in total? Pictures of all of them would be helpful. There is usually a small ID tag on them.

JUGHNE

I know I am not looking in the correct book for your boiler, but the specs I can see here are 14" max with no flow and 8" minimum with gas flowing.

What is the max/min for LP in your install book?

GGross

Yeah as far as I know that should be 8" -14" water column, 8" being the minimum. The reg distance would usually show a big drop on ignition as I said, but you are just under pressure all the way, I wonder if that regulator is just adjusted incorrectly.

Ajmal

the specs are the same

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this is the regulator at the boiler

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and this is the one outside - I think it’s just the two, I don’t see another

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and this is the pipe, I’m not sure about sizing but it’s about 50-60 ft from the utility room (assuming it’s run straight)

Ajmal

so I’ve never used a manometer, is it reading at 5 (so it’s under 8) or negative 5?

SuperTech

First test should be with nothing running. It should measure positive pressure unless your gas line is somehow in a vacuum.

JUGHNE

Need to be able to read the tag on the top of the outside regulator, also a picture of the reg showing pipes in and out of it. Not too close for that one.

There may be another reg at the tank under the big lid where the valves etc are, show that one also, not too close.

If you put your hose on the other barb on the top of the meter you should see plus numbers….they would be the same + or -.

mattmia2

I think plus or minus depends on which port you are using since I think it measures differential between the 2 ports.

Does the tag on the appliance regulator say what the factory setting is? That looks a lot like what you would set it for for natural gas.

hot_rod

are you using a slack tube manometer? You need to calibrate, or zero out the scale before you get a reading

On Lp systems the 1 stage reg is usually at the tank, the second stage just outside the building. If you have those two, you should not need a reg at the boiler

But the actual measurement will tell

The reg at the boiler should have a pressure tap also to check incoming pressure to it

The manual will tell you the acceptable pressure range for lp and nat. Gas

GroundUp

That outdoor reg should have an outlet pressure listed on it. It'll say either 2 PSI, or something like 9-13" WC (that's Rego's figure). If the latter, the reg at the boiler needs to go away. If 2 PSI, it stays but needs to be cranked up. I find the Loch prefers to have at least 10" WC for proper operation

Ajmal

thank so much everyone - I’m really grateful for everyone’s input and expertise.

So here are some pics and you are right, there are three regulators, one at the propane tank, one at the house and one at the boiler.

If I’m understanding and reading the tags right, the one outside the house is at 2 PSI, so I still need the rego at the boiler - based on the manometer readings, I need to crank that rego up to around 10 wc (since the manual says 8-14 max) and then once the gas supply issue is sorted - then to do the combustion analysis and tweaking starting with low fire and then high fire - did I get that right?

And one last question that’s been bothering me - if the supply has been so low, why would it be working (albeit with this flame ign error intermittently) for the last 3 years?

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GGross

I would first get the appliance regulator up to 10" water column, then check gas pressures the same way you just did, if all is good and you don't see wild pressure drops, then tune combustion.

The unit will work more or less because there isn't anything inside of it that knows how well it is or is not burning. more than likely the gas pressure is sometimes low enough that the flame sensor doesn't register that flame is present so you get the failed ignition error code.

That's why it always frustrates me when a tech sees failed ignition and changes sensors without ever checking gas pressures, if you have combustion issues the first step is checking out the gas, then check combustion, then look to see how damaged or not your sensors are. Poor combustion will leave a sensor/igniter in bad shape many times, but it is a symptom not a cause (usually anyway)

Ajmal

thanks for the information - so just to be sure, to get the regulator up to 10" wc, I would measure that the same way as when checking the gas pressures (plugging the manometer into the unit with the unit in standby and adjusting the regulator until reaching 10" wc)

I just wanted to be sure there wasn't another way to do it that I missed

mattmia2

Ideally there would be a pressure tap at the regulator before and after the regulator but a tap at the appliance itself before the internal regulator will also work, you will just not get the outlet of the regulator when there is flow, you will get the outlet of the regulator minus the pressure drop in the piping between the regulator and the appliance.

Ajmal

ok that makes sense bc you wouldn’t want the measurement to include the pressure drop of the piping.

that would be this tap here right?

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mattmia2

That is the vent for the regulator with a vent rate limiter installed in it.

Teemok

The gas supply and proper tuning advice above are regularly the primary suspects. In addition to it but secondarily: I have found a few Lochinvar boiler control boards bad due to excessive boiler cycling. The gas valve relay on the board fails. This is not a manufacturing flaw, it's a system design and installation problem. The symptom is intermittent ignition failure. I was able to test it and verify the fault with a meter. I repeatedly witnessed the gas valve not get opening current when it should. Replacing the board fixed the relay fault but did nothing to fix the root cause. Micro zone induced boiler short cycling.

mattmia2

Did you look at the board? A relay like that is rated for millions of operations, even like 10 cycles an hour is nothing for that type of relay. Usually problems with relays in that application are that the solder fatigues and cracks where it is soldered to the board.

Ajmal

hallelujah, I think I’m almost there, thanks to you guys.

So I turned up the regulator, but I realized that it’s a max 8 wc (it has an 8 stamped on it) so I could only get it up to 8, I left a little slack in the screw so it ended up being 7.9ish to the boiler. The manometer readings after were

off 7.84

Ignition 7.71

100% 7.48

Standby 7.8

Then I adjusted the low fire combustion to the below specs

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I then tried to adjust the high fire but again it wouldn’t go past 8.6ish (CO2) - I’m assuming it’s because there’s still not enough fuel - although the manual says minimum 8 “ wc and I am pretty close so that’s still a head scratcher.

I’ll try one more time to get the high fire adjusted but it is at least igniting now when needed

I’ll have to call someone to come replace the regulator with one that can push more volume out - that’s the right fix, correct?

One last question, when on high fire, how do you prevent it from stopping due to high limit reached? If I turn on my radiant heat, will that do it?

mattmia2

You might be able to change the spring in that regulator and make it a different range but replacement might be easier. If it was factory set to 5" wc and it is 8" wc max it almost certainly is for natural gas. What pressure range does the actual tag in/on the boiler say?

mattmia2

Since whoever installed it installed the wrong regulator, I would look at the section in the manual on propane conversion and double check that all the things in that section have been done, any menu settings, and settings or spring changes or similar on the gas valve and any regulator adjustments inside the boiler.

Ajmal

It says 8-14. I’m also thinking the propane conversion may not have been done properly.

Here’s the tag

GroundUp

Natural gas runs at a lower pressure than LP does so the regulators are different and you've got a NG regulator. I've had success swapping springs to get more pressure out of them, they're like $5-8 online. That appears to be a Maxitrol 325-3 reg. Your pressure drop looks good so once you get that spring taken care of, you should be in business. As for the hi limit, you're going to want to make sure there is a load on the unit. Depending how it's wired, you may need to run a circulator with a jumper or cord just to get it to move heat while in service mode.

Ajmal

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Teemok

@mattmia2 Nothing obvious on those failed boards. I checked wiring and connectors thoroughly. I agree with the millions of cycles relay life expectation. That said, I have found more than 10 old MCBA type Triangle Tube boards with nothing wrong but bad relays. I've seen the burnt contacts, in service at a fraction of the rated load. All older units. I carry the relays just in case of a well paying critical need situation. Two of the Lochinvar boards were 3-4 years old with extreme cycle rates. I know, correlation is not causation. I didn't open the relays to inspect. In modern technician terms: The fault was with the board and a new one resolved the problem. It certainly could have been non-relay related but that's not my best guess.

Ajmal

I checked the other components in the manual related to the LP conversion and it all seemed to check out - there’s also a sticker on the side with the company name and date that did the LP conversion.

In thinking back, I think my builder had his plumber do the install so that may explain the wrong regulator.

What really blows my mind is how in 3 years, and probably 7-8 techs, no one has thought to pull out a manometer and validate the pressure, I mean after doing it, it’s literally a 2 minute task and as you guys pointed out, seems like it would be step one in a combustion issue. I remember one guy using it but I guess he was just verifying gas was moving through and didn’t look at the values against the chart.

Everyone here seems to have expert level experience in their field, and I appreciate the help.

So sorry for the long post - I couldn’t find any videos on how to replace the regulator spring but looking at a diagram, it seems straightforward enough - turn off gas valve, unscrew the blue top plate, unscrew the white plastic screw all the way out, replace the spring and reverse the steps. Am I missing anything?

Also, I wanted to be sure this is the spring I needed:

https://www.supplyhouse.com/Maxitrol-R325C10-412-4-12-WC-Violet-Spring-for-325-3-Regulators?utm_source=google_ad&utm_medium=Shopping&utm_campaign=Shopping_X_Heating_X_SSC_ClassD/E/DI/NS&gad_source=1&gbraid=0AAAAAD_WAyuz3nJipf7U4xQnCy_39d_TV&gclid=CjwKCAjwgfm3BhBeEiwAFfxrG_iHKiGVv1EUfAYE4BUeqOYK_BhAS7QrIwnSJyaZWzd6UPLR1MYRFxoCR5EQAvD_BwE

SuperTech

Its sad but unfortunately the majority of techs are not properly trained on combustion analysis or equipped with a digital combustion analyzer.

I'm glad you are close to getting everything working properly. If it were up to me I would still get rid of the flex gas line and move the regulator at least ten feet from the boiler like the installation manual calls for.

Ajmal

I appreciate the feedback - I’ll look into it and see if I can get an HVAC guy out to make the changes to the flex pipe (add steel pipe 10 ft away)

I can't get the CO2 any higher on the high fire, so will leave it until I receive the above spring and a higher quality manometer so I'll check back in next week when everything arrives and installed —- keeping my fingers crossed!

Thanks once again everyone - I read back through the post a few times and I am amazed and impressed with the level of patience and knowledge everyone here displays. Knowing what I know now, the questions I was asking were so elementary for you all I'm sure, so I really appreciate you taking the time to break it down on a level that is easy to understand :)

Ajmal

so I replaced the spring and got the gas level up to the below:

off - 10.64

Ignition - 10.29

100% - 9.78

Standby - 10.68

i was able to adjust the low fire levels just fine but the high fire CO2 would not go past 7.13 no matter how many times I turned the adjustment screw?? It seems like it should be simple enough so I am not sure if there’s something else going on or what?? Anyone have any thoughts?

Combustion results are attached