Steam boiler ignition "looping" issue

jb_steam

I've had issues for the last couple of months with my steam boiler shutting down and immediately reigniting every few seconds. While I've made some progress in narrowing down a solution, I'm still seeking the root cause. Hoping you guys may be able to shed some new light.

Boiler in question is a Peerless 63-03, spark ignition, installed about 5 years ago. I also have a separate baseboard water system that heats an addition to the house. Often when the peerless has been running for about 10 minutes, if the baseboard boiler also gets a call for heat, the steam boiler will cut off and begin the ignition loop.

I took a video of the issue:
https://youtu.be/lb5yuTnqJgY

A couple weeks ago I had gotten a manometer and measured pressures at the gas valve. Input (household) pressure was around 2" h2o, dropping to 0.5" when the baseboard system kicks on, quite bad. I reached out to my gas utility and they came out within hours and swapped out my meter. New readings were 5.5", dropping to around 4.5" with both boilers running. My hopes that this resolved my problems vanished later that evening when the steam boiler began restarting again.

The flame sensor on the peerless is a single-rod type. I dropped in an ammeter between the ground lead and its connection on the boiler's controller. On startup, it reads about 0.6-0.7 microamps, dwindling to about 0.4 after about 15 minutes (boiler seldom needs to run more than 15-20 min at a time). With the boiler running and a reading of 0.4 uA, I flipped on the baseboard boiler and amp readings immediately fell, hovering between 0.1 and 0.0; and less than a minute later it would begin the ignition loop issue again.

I had tried cleaning the sensor probe with steel wool and tried a new grounding point on the probe mount itself, both to no affect. Flame coverage seems ok and gas valve output pressure is relatively steady at 3.5".

Checking power supplies, both steam and baseboard boiler transformers output 24VAC. Referencing the guide here: https://heatinghelp.com/assets/documents/Troubleshooting-Intermittent-Ignition-Systems-for-Gas-Furnaces-and-Boilers2.pdf I checked transformer phasing and found that the baseboard transformer is in-phase (a 96V reading) and the steam transformer is out-of-phase (150V). I don't see how one would affect the other but I tried wiring the baseboard supply to a different circuit in the house and got the same restart issue.

Is it usual for a flame sensor to reduce in current as it heats up over 10-15 mins? More importantly, why would my baseboard system have any impact on the flame sensor's current?

Many thanks.

-Jim

Steamhead

Could be several causes. But now that your gas pressure issues have hopefully been fixed, you need to have combustion tests done on your boilers (and other appliances as well). This is because the combustion parameters have changed with the increased gas pressure, which could cause an unsafe condition.

This will require a pro with combustion analysis equipment, who could also fix the original problem. Where are you located?

JUGHNE

Everything Steamhead said.......also if the FS is only in the pilot flame and that drops somewhat, it could lose signal.
Did you clean the pilot burner and is it adjusted high enough.
Too high may lift the flame off the pilot burner.

Is it possible to unwire the main gas valve and watch the pilot only?

jb_steam

Thanks guys, I'll take a look at pilot burner. I had only scrubbed the pilot hood with a wire brush to remove any buildup but I'll clean and check flame height.

I did have a plumber out (from the group that originally installed the boiler) a couple weeks back to help isolate the pressure issue. His initial impression was that it was an electrical problem, until he measured input pressure on the valve. Unfortunately it seems to have not gotten me anywhere. I since picked up a manometer to take measurements myself but I'm hesitant to call back because the service call wasn't cheap and didn't provide a whole lot of insight.

I'm in essex co in NJ - might see if there's another local steam pro that can dig deeper here. For now I'll check on pilot and report back.

Jamie Hall

Lots of good steam folks in your area. Check Find a Contractor, above. They are very busy and not cheap -- but good help never is.

Steamhead

jb_steam said:

Thanks guys, I'll take a look at pilot burner. I had only scrubbed the pilot hood with a wire brush to remove any buildup but I'll clean and check flame height.

I did have a plumber out (from the group that originally installed the boiler) a couple weeks back to help isolate the pressure issue. His initial impression was that it was an electrical problem, until he measured input pressure on the valve. Unfortunately it seems to have not gotten me anywhere. I since picked up a manometer to take measurements myself but I'm hesitant to call back because the service call wasn't cheap and didn't provide a whole lot of insight.

I'm in essex co in NJ - might see if there's another local steam pro that can dig deeper here. For now I'll check on pilot and report back.

Jamie Hall said:

Lots of good steam folks in your area. Check Find a Contractor, above. They are very busy and not cheap -- but good help never is.

@Dave0176
@EzzyT
@JStar
@JohnNY
@clammy

etc.

EBEBRATT-Ed

I suspect the ignition control or the flame sensor. The pilot looks good and from you video the flame doesn't look like it's failing do to gas pressure loss it looks like the control is shutting down the flame.

Are both boilers flued to the same chimney? That might be a clue.

Can you get the #s off the ignition control and do you know what the flame current reading should be??

HVACNUT

Another boiler was installed for an addition. Anything else added that's gas fired?

The meter was upgraded but what about the piping? Can it handle the volume?

JStar

Do both boilers have a dedicated ground back to the electrical panel?

jb_steam

Firstly, thanks for all the input! Really appreciate the insights on what some of the root causes may be.

I've had a couple of plumbers by to take a look at gas piping and both have said sizing in the house looks fine for the appliances we have installed. They include:

118k BTU steam boiler
70k BTU water boiler
40k BTU water heater
20k BTU gas dryer
gas oven/range (20k?)

When the meter was swapped I also inquired about BTU load and the utility man immediately said the meter can easily handle 350-400 BTU.

Both boilers and the water heater exhaust go into the same chimney. Last feb, a plumber was doing annual maintenance on the boiler and mentioned that draft looks poor on our setup. We had a chimney company come by and rework all of the ducts on both boilers and re-line our flue. Draft was improved but worth adding that this restart issue happened intermittently last season both before and after the chimney work. It seems these past few weeks it has been happening with more regularity/predictability.

I believe exhaust can be ruled out - while having both boilers running (they can run at the same time for a few minutes without problems) I started up the gas dryer in another room. As soon as its flame ignites, the steam boiler restarts. The gas dryer exhaust vents by its own duct.

There is not a dedicated ground wire back to the panel. All power for the boiler circuit is BX, so it's grounded by the metal shielding. There are some other outlets in the house (renovated) that do appear to have dedicated ground wire.

I don't actually know what the flame current should be for my controller, documentation seems to be hard to come by - Capable Controls model 527010000090003. According to the troubleshooting document linked above (hosted on heatinghelp) typical ranges are 0.4-0.7 uA, which mine falls within.. until it drops out to 0.1/0.0 and restarts.

I checked the pilot flame and while it's hard to get a good look at flame coverage, it seems to be ok. There is no apparent change in flame shape/intensity leading up to the boiler cutting off and restarting. I tried increasing and decreasing the pilot a quarter-turn to no affect on my issue.

I also tried running dryer+water heater+baseboard+steam systems at the same time and it took several minutes before the steam boiler began restarting. It only seems to happen when the steam boiler's pilot(?) FS(?) are really hot, 10 mins or so of continual heat.

JStar

The ceramic on the flame rod might be cracked and grounding after it heats up.

EBEBRATT-Ed

Something is causing the flame signal to deteriorate. What @JStar mentioned is certainly a possibility.

You could try running a wire from the pilot burner to the ignition control ground terminal.....one end on the pilot burner ...one end on the ground terminal on the control. Intermittant problems can be difficult to find. I would change the ignitor/sensor for sure

jb_steam

Yeah, that was my initial suspicion as well. Swapping sensor itself seems easy enough but looks like I'll need to order/fabricate a new pilot gas line as well.

I did try an alternate ground point on the mounting screw for the pilot/sensor bracket but it had no measurable affect vs original mounting point on the burner tube. Nonetheless, I'll order some high temp wire to ground to the pilot bracket for a more direct connection.

I'll follow up here with updates. Thanks again.

JStar

Change the ignition cable too. It acts as part of the flame sensor circuit after ignition and could have a small break in the wire.

jb_steam

Yup, looks like the replacement pilot/sensor assembly includes the ignition cable: http://www.partstoyourdoor.com/pilot-honeywell-q3481b1644-b-50996

Jamie Hall

On that ground via the BX cable. Ah... that is sort of OK (although not to code) for an ordinary wall outlet or something of the such. It may not be adequate for your burner to operate properly; the resistance of the cable sheath is pretty high, relatively speaking. Even if it doesn't turn out to be part of the problem, I'd recommend rewiring that circuit all the way from the burner back through the emergency switch(es) to the panel with new, 3 wire (hot, neutral, ground) BX. Also note that nothing else should be on that circuit -- no plugs, no lights, just the heating system (the 24 volt transformer, if you have one, can be on the circuit).

jb_steam

Do you think that both boilers can run off the same new circuit with proper ground wire? They currently share the same bx circuit (grounded via shield). I think I may indeed get a new line put in.

EBEBRATT-Ed

@jb_steam

It would be better to have each boiler on it's own circuit

B_Sloane

EBEBRATT-Ed said:

@jb_steam

It would be better to have each boiler on it's own circuit

why ..??

EBEBRATT-Ed

@B_Sloane
It just makes more sense to me and may even be code though I haven't looked it up

Jamie Hall

I think it is code, @EBEBRATT-Ed , but I've mislaid my code book. My recollection is that a fixed appliance -- such as a boiler -- must be on an independent circuit.

Steamhead

Jamie Hall said:

On that ground via the BX cable. Ah... that is sort of OK (although not to code) for an ordinary wall outlet or something of the such. It may not be adequate for your burner to operate properly; the resistance of the cable sheath is pretty high, relatively speaking. Even if it doesn't turn out to be part of the problem, I'd recommend rewiring that circuit all the way from the burner back through the emergency switch(es) to the panel with new, 3 wire (hot, neutral, ground) BX. Also note that nothing else should be on that circuit -- no plugs, no lights, just the heating system (the 24 volt transformer, if you have one, can be on the circuit).

One way to verify whether a ground is "good enough" is to connect a 150-watt incandescent (NOT CFL or LED) light bulb across the hot and ground (not the neutral) wires. If the bulb lights up all the way, the ground connection is good. If not, it's not- start looking for bad connections.

A real old-timer electrician taught me that one, decades ago. It has served me well, like his old GE snap-on ammeter that I bought when he became a Dead Man.

jb_steam

Update here: I dropped in a new flame sensor (+pilot single assembly) and so far things are looking good! Ammeter readings start at 0.7 uA, eventually move to 0.8 and stay there even when the baseboard boiler kicks on. I didn't see any obvious damage to the original FS probe though there is some discoloration/oxidation.

On Steamhead's advice, I bridged a 150W halogen work light between hot and ground (shielding) at both boilers' switch boxes and brightness looked good. Seems BX-as-ground is doing its job though I think I'll have an electrician give everything a look before long. I measured system draw a while back and both boilers together consume no more than 200W.

I'll continue monitoring it all but it's seeming the flame sensor was the culprit. Thanks all for your valuable input, it's a relief (so far) not having to hear the boiler restart every day.

EBEBRATT-Ed

@jb_steam
Glad you got it fixed. good job. Just some info

They at one time made 2 types of BX cable (code calls it AC (armor clad) cable).

The better stuff still made and used today has an aluminum strip inside the cable armor. It's not a ground wire but it is there simply to reduce the resistance of the cable armor to carry fault current.

Some older stuff (pre 1959) did not have the aluminum strip

I was told that in 59 is when the code changed to make 3 wire grounding type receptacles mandatory instead of the old two wire receptacles and that is when they changed so that after that date BX with the aluminum strip became mandatory. Prior to 1959 both types were in use

My house built in 1955 has bot types of BX.

I have also seen many houses of that vintage wired with romex

Must have been a time of change

JUGHNE

What seems common today is MC....metal clad cable.
It has no aluminum strip but has a green ground wire....12-2-G.
The aluminum sheathing does not qualify as grounding.
It requires the same protection that romex needs, for example anything below 6 1/2' above the floor needs guard strips etc.