Pilot sensor corrosion - chronic problem?

Hap_Hazzard

That's probably not sensitive enough, but you could give it a try at the lowest (200mA) range and see if it changes when the pilot comes on. If it doesn't show any change when the sensor is working properly then it isn't sensitive enough.

kenlmad

prwood said:

Hap_Hazzard said:

BTW, do you have a microammeter?

I have the cheapest multimeter from Harbor Freight. This is the DCA range: 200mA/2000mA/
20mA/ 10A. Not sure if that is sufficient for the required testing.

Maybe ... This may sound odd, but try the voltage setting to measure your very low current. The cheap/free HF CenTech has a 1 Megohm input impedance according to some online searches.

[EDIT] - Connect the meter in series as you normally would for measuring current with this meter.

If you use the 200mV VOLTAGE setting to measure the 0.1 microAmp (EDIT#2], you would hope to see 0.1 V or 100 mV on the display. This cheap meter isn't auto-ranging so you may get "100" on the display while in the low mV range setting.

Ohms law, Voltage = Current x Resistance, 0.1 V = 0.0000001 Amps x 1000000 ohms.

Hap_Hazzard

Connecting a voltmeter in series with the probe will make it stop working, and I'm not sure what the voltage drop would be, because we don't know the internal resistance to ground of the circuit. It might be close to infinite if it keeps the circuit from switching on. It would be more informative to leave the probe connected and check the voltage on the terminal.

kenlmad

My earlier MacGyvered idea with the cheap HF multimeter wasn't helpful, sorry about that. Part of why I prefaced it with "Maybe ".

Please check out the method for testing your flame sensor in this link, but you will need to acquire a better meter than the HF freebie. I hope this helps.

https://heatingcooling.fergusonhvac.com/wp-content/uploads/2017/03/21-FLAME-RECTIFICATION.pdf

Big Ed_4

With a problem sensor , I would replace the whole pilot assembly and run a ground wire from the assembley back to the control ., and ignition wire.. Normally its ether it's a weak pilot , bad sensor or bad ground .... What is left is the control ..

Shane_2

Has the gas pressure been checked?
With the burners on & off and with any other gas appliances on at the same time?
Seen some failed gas regulators do strange things to boiler safeties.

SteamingatMohawk

Like the others, I assumed you have a standing pilot. That's what I am familiar with.

Stainless steel wool won't rust like regular steel wool does.

prwood

Hi all, heating season is back again, and with it, this issue has come up yet again. Before I turned the heat on for the first time, I cleaned everything around the burners really well with air pressure and then with shop vac. I cleaned the ignition sensor electrode, and everything worked well for about a month. After a month, the electrode looked like this:



I cleaned it off again and things went back to normal for a couple more weeks, and today it failed to ignite again. Again the sensor looks like the above after having been cleaned. I cleaned it again and it started up again.

I haven't replaced the ignition assembly yet, or had the gas pressure checked.

We have a gas-fired hot water heater next to the boiler. It was installed new at the same time as the boiler. It has never had any issues.

Any suggestions on what to check next?

Hap_Hazzard

So, let's make sure I understand the issue. The pilot is lighting, but the boiler doesn't fire? And you're cleaning the sensor, not the spark electrode, and that makes it work again for a while?

Shane_2

I would replace the pilot/sensor assembly and check the gas pressure

Hap_Hazzard

Does your flame look like the picture shown in the manual? Is the sensor within the inner cone of the flame? Is the sensor glowing red-hot? Have you tried turning up the pilot flame?

EBEBRATT-Ed

Maybe @Tim McElwain will comment.

I can't think of anything else to try. I have herd that these sensors can have some protective coating on them and that they should be cleaned with a dollar bill. Don't know if steel wool can be too aggressive or not.

Maybe replace the sensor and try that.

mattmia2

maybe try loosening then tightening the bracket screws, maybe you are re-making the ground of the pilot burner when you clean the flame sensor rod, but look at the pilot flame too.

EBEBRATT-Ed

@mattmia2
good point

mattmia2

also make sure the burner itself is making good contact where it goes through the bracket

Tim McElwain

Replace the pilot and sensor and from now on do not use any abrasive to clean the sensor or spark rod. I dollar bill is sufficient. I would also check the microamps which should be somewhere between 2 to 10. There may also be some airborne particulant in your basement. Have an inspection doen to determine air quality in the basement.

Derheatmeister

prwood said:

Hi all, heating season is back again, and with it, this issue has come up yet again. Before I turned the heat on for the first time, I cleaned everything around the burners really well with air pressure and then with shop vac. I cleaned the ignition sensor electrode, and everything worked well for about a month. After a month, the electrode looked like this:



I cleaned it off again and things went back to normal for a couple more weeks, and today it failed to ignite again. Again the sensor looks like the above after having been cleaned. I cleaned it again and it started up again.

I haven't replaced the ignition assembly yet, or had the gas pressure checked.

We have a gas-fired hot water heater next to the boiler. It was installed new at the same time as the boiler. It has never had any issues.

Any suggestions on what to check next?

Do you have ANY Chemicals stored nearby..Contaminats such as Saw dust ?
If so they could be causing the deposits on your flame sensing rod.

prwood

Hi all, so last night the boiler wouldn't light again. I checked the sensor and it didn't have a coating, so I reasoned that that probably wasn't the issue. Therefore, I took another look at the troubleshooting flowchart, and went to the section that talked about checking for proper grounding. It listed the following items to check:

1. Check for good metal-to-metal contact between pilot burner bracket and main burner, and between main burner and burner rest.
2. Check ground lead from GND (Burner) terminal on ignition control to ignition control mounting screw, and from "C" on transformer to case ground. Make sure connections are clean and tight.

For #1, everything looked good and tight.

For #2, I found two issues:

1. The GND (Burner) lead was *not* going to the ignition control mounting screw. Rather, it was going to the C terminal on the transformer. The 24V (GND) lead was connected to the ignition control mounting screw. I swapped these into their proper positions based on the schematic diagram, so the GND (Burner) lead is going to the ignition control mounting screw, and the 24V (GND) lead is going to the C terminal on the transformer.


2. The lead from C on the transformer was *not* connected to the case ground - in fact it was not connected to anything, just dangling. I looked back in some of my earliest photos of the boiler from after it was installed, and it appears that it has always been this way. The schematic diagram shows that a ground wire is supposed to be connected to the transformer, but after disassembling the transformer case, I didn't see one. However, the metal conduit that the hot and neutral wires come through *is* connected to the transformer case, so I am wondering if this is meant to provide grounding for the transformer case. I don't know if there's a reason the installer didn't connect this (and also whether there's a reason he swapped the two ground connections I mentioned in #1 above). Maybe the equipment isn't properly grounded? Or maybe he just forgot or didn't check the schematics? It's possible he might have also just been using the old wiring from the oil boiler that was previously installed. Anyway, I connected the dangling ground lead to one of the screws on the transformer case which is what the troubleshooting check and the schematic diagram say is supposed to be done. Not sure if that's the right thing to do given that I don't know if it's properly grounded to begin with.

After taking the above steps, I turned everything back on and the boiler ignited. I would also say it was noticeably faster at igniting - previously, the spark would run for a few seconds before ignition, but this time it just clicked once and ignited right away. We'll keep an eye on it and see how it runs over the next few weeks. I also feel like I should do something to check the grounding of the transformer case, but I'm not sure how to do that.

mattmia2

If the conduit is connected to the box and the conduit is grounded somewhere along the line that is adequate grounding as long as all of the connections in the conduit are tight. Depending on jurisdiction and when it was installed that may or may not qualify as proper grounding under the electrical code, but as far as the laws of physics are concerned it counts if everything is tight back to where it connects to the grounding electrode system in the panelboard.

EBEBRATT-Ed

@prwood

There are a few different things at play here concerning grounding and it can be confusing.

1. Branch circuit "equipment ground". This is the 120 volt circuit coming from your panel. If this is run in NM cable (romex) it probably has a bare equipment ground in the cable. If BX (armored cable) the outer BX casing is the equipment ground. Conduit can also serve as the equipment ground. Somehow the "equipment ground" gets attached to the boiler. It's purpose is to trip the circuit breaker if a live wire shorts out to the boiler

Ground of the flame sensing circuit.

This is probably your issue. From your ignition control a wire goes to the flame sensor.When the pilot lights power goes through that wire from the ignition control through the flame sensor, through the gas flame (that's how it knows a flame is sensed) to the pilot burner and travels back to the ignition control through the metal of the boiler to the burner ground terminal on the ignition control.

Takes a complete circuit to make this work.

In addition the "common" connection on the transformer should be grounded to the boiler

HomerJSmith

When I clean the pilot assembly, I always clean the top hat (the pilot orifice). I don't understand why spiders are attracted to the pilot assembly, but I have found webs in them on more than one occasion.

You may have dirty gas in your area. Not all nat gas is equal, some are cleaner than others and BTU ratings vary. Talk to your gas suppler as to the quality and BTU per cubic foot of your nat gas.

prwood

EBEBRATT-Ed said:

@prwood

There are a few different things at play here concerning grounding and it can be confusing.

1. Branch circuit "equipment ground". This is the 120 volt circuit coming from your panel. If this is run in NM cable (romex) it probably has a bare equipment ground in the cable. If BX (armored cable) the outer BX casing is the equipment ground. Conduit can also serve as the equipment ground. Somehow the "equipment ground" gets attached to the boiler. It's purpose is to trip the circuit breaker if a live wire shorts out to the boiler

Ground of the flame sensing circuit.

This is probably your issue. From your ignition control a wire goes to the flame sensor.When the pilot lights power goes through that wire from the ignition control through the flame sensor, through the gas flame (that's how it knows a flame is sensed) to the pilot burner and travels back to the ignition control through the metal of the boiler to the burner ground terminal on the ignition control.

Takes a complete circuit to make this work.

In addition the "common" connection on the transformer should be grounded to the boiler

Thanks. I rechecked the wiring, and there is a BX cable connected to the boiler's transformer box. I traced the BX back to the electrical panel. I also connected the 'dangling' ground lead from the C terminal on the transformer to one of the screws on the transformer box. So I think the equipment is grounded properly, and the proper connections are made per the boiler's specs.

For the flame sensing circuit, I'm wondering if the two ground leads being swapped on the ignition control would have caused an issue with the circuit for the flame sensor. Or possibly the mating surfaces between the pilot assembly and the mounting plate on the burner need to be cleaned again. Or maybe there is a bad solder between the mounting plate and the burner tube.

That being said, even after making the fixes I mentioned earlier, we just hit a patch where the boiler took longer than expected to ignite. Normally the heat is active for about 20-30 minutes between the thermostat kicking it on, the boiler igniting and getting the radiators hot, and the heat kicking off. This time it had gotten to about 40 minutes since the thermostat called for heat and we hadn't heard the radiators kick on, but just as I was about to head to the basement, we started to hear them kick in. So, back to monitoring again...

Graph from our thermostat with problem areas circled in red. The thick orange bar at the top is when the thermostat is calling for heat. The thin orange line is the called for temperature. The breaks in the thin orange line are where I have manually instructed the thermostat to turn the heat off, prior to shutting the system off for maintenance. The white line is the actual temperature measured by the thermostat. You can see the issue when the white line keeps dipping down even though the top orange bar stays on - indicating the thermostat is calling for heat but the temperature hasn't changed. Normally our thermostat does not raise an alarm unless it has been calling for heat for 4 hours *and* the temperature has gone down by more than a few degrees. Normally we pick up on the cold sooner than that.

prwood

HomerJSmith said:

When I clean the pilot assembly, I always clean the top hat (the pilot orifice). I don't understand why spiders are attracted to the pilot assembly, but I have found webs in them on more than one occasion.

You may have dirty gas in your area. Not all nat gas is equal, some are cleaner than others and BTU ratings vary. Talk to your gas suppler as to the quality and BTU per cubic foot of your nat gas.

I'll look into it. I had assumed our gas was okay because we've never had issues with our gas hot water heater. But maybe the water heater is not as sensitive to gas quality? Or it just works better because it's running year-round?

prwood

Derheatmeister said:

Do you have ANY Chemicals stored nearby..Contaminats such as Saw dust ?
If so they could be causing the deposits on your flame sensing rod.

We have a fairly large basement space. It's a two-family house, and in addition to our gas-fired boiler and hot water heater, my in-laws' oil-fired boiler and oil tank are also in the basement, along with lots of cans of paint and finish, stuff like brake cleaner, degreaser, motor oil, alcohol, and plenty of sawdust from various woodworking projects my father-in-law has going on. As far as I know all of the containers are sealed, but I can't say for sure that they're airtight. There's also a bulkhead door which could be somewhat drafty about 8 feet from the boiler and water heater.

EBEBRATT-Ed

@prwood

If you can get your hands on a test meter that measures "micro amps" you can measure the flame signal from the flame sensor.. With the boiler off you disconnect the flame sensing wire from the ignition control and put the test meter in series with the flame sensing wire and the ignition control. As @Tim McElwain said your looking for 2-10 microamps. Then start the boiler and see what you get

Derheatmeister

prwood said:

Derheatmeister said:

Do you have ANY Chemicals stored nearby..Contaminats such as Saw dust ?
If so they could be causing the deposits on your flame sensing rod.

We have a fairly large basement space. It's a two-family house, and in addition to our gas-fired boiler and hot water heater, my in-laws' oil-fired boiler and oil tank are also in the basement, along with lots of cans of paint and finish, stuff like brake cleaner, degreaser, motor oil, alcohol, and plenty of sawdust from various woodworking projects my father-in-law has going on. As far as I know all of the containers are sealed, but I can't say for sure that they're airtight. There's also a bulkhead door which could be somewhat drafty about 8 feet from the boiler and water heater.

Even if the cans are sealed they offgas and cause problems such as you are experiencing...Saw dust is also a big problem, it will deposit on sensing rods and can also clogg up the Heat exchanger.
Most Boiler manufactures Installation instructions state this very clearly on the first pages..
Most manufactures will also rightfully void the warranty of the equipment if it is subject to all of the Chemicals you mentioned..
As far as i understand Chlorine turns into Hydrochloric acid when it goes thru the combustion chamber ! If you cleanup your combustion air these Issues most likely will disappear.

Hope this helps...
Richard.

prwood

Still chasing things down. There are a lot of different variables. I'm trying to figure which things we can check simply and inexpensively.

Air Quality:
There are indeed a lot of contaminants in the basement. The closest are about 8 feet from the boiler. Unfortunately it's a big open basement, there are a many things in many containers, we can't get rid of them, and there's nowhere else in the house to put them. If we eliminate any other possible issue, I guess we'd have to construct a wall around the boiler and provide it with fresh air ventilation. Just on a lark, I tried opening one the basement window that's closest to the boiler. It may make it too drafty, but it may also improve the air quality, if that's an issue.

Troubleshooting Flowchart Items:

Sense Wire:
I haven't tested the continuity of the sense wire as suggested in the troubleshooting flowchart. I'm assuming I would need to test this between the sense wire's spade terminal and the metal of the flame rod? My current multimeter should be able to do this. This step comes before testing the flame signal in the flowchart. If the sense wire is bad, then replacing the pilot assembly is recommended.

Flame Signal:
I don't have a microammeter and my multimeter doesn't test microamps, so I can't currently test the flame sensing circuit in series as described in this thread or in the troubleshooting flowchart. I found this Klein multimeter which can measure microamps for $45, don't know if it's good enough for this purpose: https://www.amazon.com/Multimeter-Auto-Ranging-Klein-Tools-MM400/dp/B018EXZO8M/ Testing the flame signal comes after verifying the sense wire is good. If the sense signal is bad, then replacing the ignition control is recommended. If the flame signal is good, testing gas pressure, cleaning pilot assembly, tightening connections, and checking grounding are all recommended. I've already done all of that except testing gas pressure.

Gas Pressure:
I don't have equipment to test gas pressure, which has been indicated several times in this thread and in the troubleshooting flowchart. I found this digital manometer for $40, but I don't know if it's suitable for this purpose: https://www.amazon.com/Manometer-RISEPRO-Digital-Pressure-Differential/dp/B01680C4C2/

Also, I'm not familiar with testing gas pressure, but did find this video:

https://www.youtube.com/watch?v=ugnizYBVH9o

The video covers checking inlet and outlet pressure on a furnace, not a boiler, but I imagine the principles of testing a gas valve would be similar either way. I can check the manual for the gas valve for specifics on where the test ports are located.

Spark Gap:
The flowchart mentions checking the spark gap. I know how to do this on a car's spark plug, but how do you measure the gap on the pilot assembly? Between the tip of the electrode and...? The gas stream? Would that essentially be indicated by the angle at which the spark plug is bent away from center?

Flame quality:
Here's a recent video of the pilot flame igniting and the the main burner igniting:

https://photos.app.goo.gl/x8q9fs1A4ragtD1YA

The boiler manual has specs on the pilot and main burner flames.

Proper Pilot Flame
1. Blue
2. Inner cone engulfing flame rod
3. Flame rod glowing cherry red

1 and 2 seem good. I can't see the entire flame rod, but the part I can see doesn't seem to be glowing, or at least not immediately upon pilot ignition. Should I be checking it after it's been in the flames for a while?

Improper pilot flame:
1. Overfired - large flame lifting or blowing past flame rod
2. Underfired - small flame. Inner cone not engulfing flame rod
3. Lack of primary air - yellow flame tip

I don't see any of those issues.

Proper main burner flame:
1. Transparent blue flame with a short inner flame and a taller outer flame
2. Yellow-orange streaks may appear (caused by dust).

Improper main burner flame:
1. Overfired would be indicated by large flames
2. Underfired indicated by small flames
3. Lack of primary air indicated by yellow tipping.

All of the above look good to me as well. The flame shapes also look good based on the diagrams in the manual.

Thanks for your continued suggestions and help!

Hap_Hazzard

prwood said:

Spark Gap:
The flowchart mentions checking the spark gap. I know how to do this on a car's spark plug, but how do you measure the gap on the pilot assembly? Between the tip of the electrode and...? The gas stream? Would that essentially be indicated by the angle at which the spark plug is bent away from center?

The spark will jump from the electrode to the nearest ground, which should be the pilot hood. The gap to measure would be between the points on those two things that are closest to each other.

It does look like the blue flame is wrapping around the sensor, but I don't see it glowing either. It looks like the main burners are kicking in before it gets hot enough to glow, and the light from the burners makes it hard to see if it's glowing or not. The discoloration in the picture looks like it's been red hot, but only on the side towards the flame. What happens if you tweak the flame a little higher?

HVACNUT

It needs a combustion analysis to see where everything is at. And adjust to within manufacturers specs. 

JK_Brown

A flame rod is just a stainless steel rod coated to withstand the flame without corroding. Your's looks like it could do with replacement. You could (with the power off) measure the resistance from the rod to the connector. Then maybe do the same before you clean it next time.

Flame rectification requires both bonding of the 24vac common to the equipment case and that the 24 vac is in phase with the 120v L1 feeding the equipment.

Search for a document: Transformer and Power Phasing - Reversed Polarity at Johnstone Supply Support. It is a clear explanation.

Look to see that there is a clean low resistance connection from the burner all the way back to where the common is bonded to the cabinet. Try a jumper if need be.

prwood

I got a hold of a multimeter that measures microamps so that I could do the flame signal testing. Here is the relevant section from the ignition control troubleshooting manual:



I had an issue with Step c - the MV terminal on the ignition control was connected along with the MV/PV and PV terminals in a single block, so I couldn't figure out a way to disconnect just the MV. I get leery of trying to hard to pull things apart, given that if I break something then I have no heat at all, rather than heat that just sometimes has trouble coming on. Anyway, I assume the purpose of this step is to prevent the main valve from opening and igniting the main burners which would interfere with the test reading. I hoped that I would be able to make the measurement quickly enough between the pilot ignition and main burner ignition.

My ignition control module is the United Technologies 1003-611A, which has a minimum signal of 0.1 microamp according to the above.

Here's a video of the flame signal ignition test: https://photos.app.goo.gl/VZS1KevBeFuRetns7

It appear that right after the spark, the reading starts at 0.1 microamp and hits 0.5 microamp just before the main valve kicks on, and then increases from 0.5 to 1.8 microamp after the main valve opens and the main burner flames up.

I ran through the test 5 times with the same results - good reading every time, and good ignition every time. It even worked ok when moving around the sense wire while testing.

Based on my interpretation of the chart above, the readings during my test, and the fact that the pilot and main burner did ignite, it seems that the system does have a proper flame signal, and that the flame sensor and ignition control are both working properly. The signal was able to reach the flame rod, travel through the sense wire to the multimeter, where it read the proper level of current, and into the ignition control, where it triggered the main valve and thus the main burner ignition.

I tried a continuity check between the flame rod and the sense wire connector, but got no continuity reading, which doesn't make sense given the results of the test above. So testing off of the flame rod itself must not be the way to do it.

This is difficult because the problem is highly intermittent - ignition works immediately nearly every time the thermostat calls for heat. On the occasions where it doesn't, it usually tries for 30-90 minutes and will often eventually succeed. If it doesn't succeed quickly enough for my liking, I go down, remove the pilot assembly, reinstall it, and it ignites immediately, every time. And this is regardless of whether I clean off the flame rod or not - just going through the motions of removing and reinstalling it is enough to kick it into working again.

I could getting a manometer and testing the gas pressure since that's the only diagnostic in the flowchart I haven't done.

I could try replacing the pilot assembly on the off chance that it has a flaky connection somewhere that is only occasionally manifesting.

Other than that, it seems like hiring a professional to analyze things would be the next step.

JK_Brown

The way flame rectification works is that the board puts 80-100 vac on the flame rod. When the flame is present, electrons can flow from the portion of the flame rod in the flame to the pilot flame hood in the flame. It flows more from the rod to the flame hood because of the greater area of the flame hood. This creates the rectification (DC). (if the board saw AC on the circuit it would know there was a dead short in the flame proving circuity). As you saw, for this it's tenth of milliamps so any added resistance from corrosion or loose connections can cause it to fail.

So the little burnt area on the rod and the pilot flame hood are your two critical points assuming the other wiring is good. Could the pilot flame hood not be tight in the end of the tube or could there be corrosion? You might test resistance from the pilot flame hood to the burner ground connection to verify it is as near zero as possible. When you go to clean the rod, you might be fixing something that has been moved by the heating and cooling as it operates.

JK_Brown

tenth of microamps instead of milliamps

JUGHNE

So this will work after you R & R pilot lite?
Perhaps each time you R & R you re-establish the ground connection from the pilot hood to the control.

If there is no actual ground wire from pilot to control then it relies upon the pilot tubing to the gas valve.

Sometimes gas valves have male 1/4 spades connected directly to the valve body.
IIWM, I would add a ground wire from mounting screws of pilot light back to the control module, maybe via the 1/4" spades if there.
Use good crimp terminals and stranded copper....should be bare or green....but doesn't matter as it is obvious.

It is surprising how long most flame sensors can be neglected and then recover with only a cleaning....maybe every few years. So you certainly have some other issue.

prwood

JK_Brown said:

The way flame rectification works is that the board puts 80-100 vac on the flame rod. When the flame is present, electrons can flow from the portion of the flame rod in the flame to the pilot flame hood in the flame. It flows more from the rod to the flame hood because of the greater area of the flame hood. This creates the rectification (DC). (if the board saw AC on the circuit it would know there was a dead short in the flame proving circuity). As you saw, for this it's tenth of milliamps so any added resistance from corrosion or loose connections can cause it to fail.

So the little burnt area on the rod and the pilot flame hood are your two critical points assuming the other wiring is good. Could the pilot flame hood not be tight in the end of the tube or could there be corrosion? You might test resistance from the pilot flame hood to the burner ground connection to verify it is as near zero as possible. When you go to clean the rod, you might be fixing something that has been moved by the heating and cooling as it operates.

Just to clarify, when you say 'burner ground connection,' are you referring to the plate attached to the main burner, onto which the pilot assembly is mounted?

I haven't paid much attention to the pilot flame hood, so I don't know if it's loose, dirty, or corroded. I have only been looking at the flame rod each time I remove and replace the assembly. I'll take a closer look at it next time.

prwood

JUGHNE said:

So this will work after you R & R pilot lite?
Perhaps each time you R & R you re-establish the ground connection from the pilot hood to the control.

If there is no actual ground wire from pilot to control then it relies upon the pilot tubing to the gas valve.

Sometimes gas valves have male 1/4 spades connected directly to the valve body.
IIWM, I would add a ground wire from mounting screws of pilot light back to the control module, maybe via the 1/4" spades if there.
Use good crimp terminals and stranded copper....should be bare or green....but doesn't matter as it is obvious.

It is surprising how long most flame sensors can be neglected and then recover with only a cleaning....maybe every few years. So you certainly have some other issue.

Correct, it does start working again every time I remove and replace the pilot assembly. Regardless of whether I do anything to clean it.

There is no ground wire from pilot to control. Just the pilot tubing to the gas valve. If this tubing was touching any metal surface, would that be enough to disrupt the ground signal? This is how it's routed right now. I think it may be resting on the main gas tube for the burners. However, if this was an issue, I'd think it would cause problems every time. Is there a best practice for how this tube should be routed?



I also noticed that there is a nick in the gas tubing close to the pilot assembly. Don't know if this would be enough to interfere with the ground signal:



When you say to run a ground wire from the mounting screws of the pilot light back to the control module, are you referring to the ignition control module, or the valve body? This is what the control module and gas valve look like:

JUGHNE

There is a green ground wire with a brass ring crimp end that is under a screw holding the module in place. Where does that wire go to?

There is also a green ground wire with a 1/4" female end connected to the module itself. Labeled "ground (burner)" where does that go to?
Then under that one another green wire labeled 24 volt (ground).
where does that one end up?

And then another ground wire not shown; it is the 120 vac power supply coming from your house power supply. It may be a bare wire inside Romex house cable or a green wire inside some sort of raceway.
It must be eventually connected to the boiler chassis.
The other end of the house ground wire must be solidly connected to the ground bar inside the circuit breaker panel.

All these ground wires must be bonded to each other by some fashion.
Often by sharing the sheet metal of the boiler.
For the pilot it used the pilot tubing or the burner sitting on the manifold orifice.
These pathways are not always 100%.

The actual wire ground to the pilot will exclude these possible unreliable connections.

You cannot "over ground" anything, the more the better as long as all connections are solid.
The flame sensor only needs a very small conductive path, however it must be a low resistance path, meaning all connections need to be clean and tight.

prwood

JUGHNE said:

There is a green ground wire with a brass ring crimp end that is under a screw holding the module in place. Where does that wire go to?

That goes to GND (Burner) on the module, as per the wiring diagram.

JUGHNE said:

There is also a green ground wire with a 1/4" female end connected to the module itself. Labeled "ground (burner)" where does that go to?

See previous.

JUGHNE said:

Then under that one another green wire labeled 24 volt (ground).
where does that one end up?

That goes to the C terminal on the transformer.

JUGHNE said:

And then another ground wire not shown; it is the 120 vac power supply coming from your house power supply. It may be a bare wire inside Romex house cable or a green wire inside some sort of raceway.
It must be eventually connected to the boiler chassis.
The other end of the house ground wire must be solidly connected to the ground bar inside the circuit breaker panel.

This boiler was installed using wiring from the old oil boiler, which was just a BX cable with hot and neutral wires, and no ground wire. In a previous message in the thread I had checked that this BX is connected to the boiler and then traced it back to the electrical panel. So the grounding to the panel is done through the BX shielding. The BX is pretty old, though, so I suppose the grounding quality may not be 100%.

Here is the wiring diagram for reference:

JK_Brown

Start at the green wire on the GND (burner) terminal. Trace it to where it connect to the body of the burner assembly somewhere. Is the screw tight even when cold. Is there a hint of corrosion. The follow from that connection point to most direct path to the pilot flame hood. Any junction of metals, look for looseness or corrosion. Could be through the bracket or via the pilot gas tube. The idea of the burner ground is to provide a wire from the control unit to the burner jumping over any sheet metal seams or such between the two. The burner ground will try to have the least resistance path from the burner ground screw and the pilot flame hood without running into the wire getting impacted by the burner flames.

The knick shouldn't cause an issue. We are dealing with microamps.

Just speculating but you said it would sometimes fail to prove the flame many times then work. This makes me think of something warming and expanding to then make adequate contact. So I would first look for something loose near the pilot flame.

JUGHNE

With the circuit breaker off, you might loosen the BX clamps a little on each end and rotate the metal BX to cut any corrosion, then the clamp must be tight and also the locknuts inside the boiler and also the CB panel must be hammered tight to cut thru the paint. You need to see a scratch on the enclosures.