Lochinvar Burners Intermittently go Off and On

BrianCNY

Hello Everyone

I'm having an intermittent problem with
my boiler and I a hoping, really hoping,
someone can help me or point me in the
right direction.

I'll try to give you as much info. up-front
as I can.

The Boiler is a Lochinvar Solution CB090
and is 7 years old. There are no options
(like Outdoor Air Reset), but I do have a
power vent and a GuardDog RB24E low
water cutoff and I am pumping away and
have followed all of Dan's advice.

The boiler is disassembled and meticulously
cleaned each season.

This season, after cleaning, the power-up
went as usual, except I noticed after a
time (maybe 10 minutes), the main burners
stopped, restarted, immediately stopped
again and restarted, but then stayed lit.

I would not have even noticed this, if I hadn't
been right there watching it. During the first
season start-up, I stay with it through a full
cycle to make sure everything is working ok.

I don't make a habit of willy-nilly replacing parts,
but I have spares of some things, so why not?
I have replaced the ignition module and the electronics
part of the power vent (the relay and vacuum
switch).

This made no difference.

As I was watching this afternoon, the boiler
came on normally and stayed that way for about
8 - 10 minutes (water temp was up to 140 if it
matters), then burners off, immediate restart,
burners off again and another immediate restart.
After the second restart, it stayed started.

When this happens, I can hear a "click" like a
relay sound, right after the burners shut-off,
but I'm not not sure exactly where it's coming
from. Also, the power vent motor stays on the
entire time, whether the burners are off or on.
Not sure about the pump though? Could the
"click" sound be the pump relay? Maybe I have
a weak pump relay?

Things worked as normal for about another 8 - 10
minutes and the same thing again. Off-on, off-on.
Water temp was 170 now.

Everything fine again for about 20 more minutes,
then the same thing again, but this time, the off-on was
three times instead of two.

Not long after this, the thermostat was satisfied
and the boiler shut-down. The off-on will repeat itself
every cycle.

If this was a solid failure, I could troubleshoot it.

Being intermittent, I have no idea how what to do.

Any ideas how I should proceed?


Thanks for all your help . . . . . Brian

EBEBRATT-Ed

Not famalir with that boiler. sounds like it could be an air flow or pressure switch of some type. I suspect the ignition circuit and flame proving is working because it stays on for a decent time.

Retrace everything you did for the annual service and see if you can find any loose connections.

Do you have a test meter and a wiring diagram to troubleshoot with??

As your finding out intermittent problems are difficult to find

JUGHNE

You say it is power vented. Could the vent terminal be partially plugged. Are there any condensation drains on the boiler?

BrianCNY

Thanks EBEBRATT-Ed. I've looked at everything I disassembled for cleaning several times and found nothing. I have a wiring diagram and test meter. Have no idea what to test, when everything would probably test ok, except when the failure occurs.

Thanks JUGHNE. I have checked the venting as it is all clear. There is a vacuum proving switch in the power vent that I just replaced. I suppose I could jump that switch, to keep it on constantly to rule that out. But I don't think that's it. I do have a condensate drain and it's not blocked and seems to be draining normally.

I appreciate your replies . . . . Brian

Jamie Hall

Check the low water cutoff? Clean? Properly seated? etc.

BrianCNY

Thanks Jamie Hall. The low water cut-off is two years old, because my first one failed. When they fail, or if I press the test button, the entire boiler shuts down, power vent, everything. So I think if there was a fault in the low water cut-off, it wouldn't just momentarily shut the burners off (but . . . I could be wrong). I just pressed the test button and the boiler shut off. It may be low water cut-off, but I think it's way down the list. I appreciate your comments though.

BrianCNY

Does anyone know if a failing gas valve would have these symptoms?

BrianCNY

Also, I have a spare Thermostat control board and I was thinking of swapping that out, but I am just grasping at straws, which is not the proper way to diagnose a problem.

HVACNUT

Seems that if everything was fine before the maintenance, it's usually something to do with the maintenance.
Go over everything again.
Is the igniter also the flame rectifier? It's positioned correctly? I not sure about Lochinvar, but most have an asymmetrical insertion so it can only be installed one way. Is it the same on yours?
Pretty weird running for 10 minutes, interruption before limit, then no flame rectification for 3 ignition trials until it finally sences.
No lockout?
This boiler is atmospheric or mod con?
Do you have an analyzer?

BrianCNY

Thanks HVACNUT. I'm not sure everything was ok before maintenance. I wasn't monitoring it at the end of last season and it may very well have been doing this, or not. I have no way of knowing. The igniter is a single wire that also serves as the thermocouple. It does only go on one way. I have noticed that it is not centered between the two burners (slightly off center towards the right burner), but that is not new. Also how would the off-center allow it to work for 10 minutes then suddenly stop, but be ok to restart? It would seem that if the pilot is proven and can run for 10 minutes, then that's not the problem? But . . . . So far I am not able to diagnose this, so my knowledge is lacking somewhere.

It's not a condensing boiler and I don't have a gas analyser.

Just to clarify, when it shuts down, it restarts, including the main burners, shuts down again and restarts, including the main burners. So each time the pilot lights, and is proven for the burners to come on. That's why I am thinking it isn't the thermocouple/igniter. But . . . it would be a relatively inexpensive thing to replace. This is the 2nd one in 7 seasons.

I attached a picture of the igniter.

Thanks for your help.

MilanD

Try jumping the tstat. It may be faulty.

BrianCNY

Great idea MilanD.

Tried it and didn't make a difference.

Thanks for your input.

MilanD

Do you have outdoor reset? Does it operate in 2-stage? Could the valve try to do low stage and fail??

JUGHNE

The pilot assembly must be grounded back to the electric module. The service work may have compromised it's ground path creating an intermittent problem. It relies upon chassis grounding. You can insure a good path with a solid ground wire from pilot to module.
Also all the 1/4" push on terminals should be pulled and reseated to cut a good connection.

How about the gas supply? If utility pressure is not constant you could lose flame during operation. If their regulator is faulty and inconsistent it may recover during flame out and seem normal after retries.
The best check is to observe gas pressure on each side of the gas valve.

BrianCNY

I don't have an outdoor reset, but the gas valve is 2-stage. There is a "High Fire Offset" which is the number of degrees before the set-point (mine is 180) that the valve goes to the low stage. I had it set at 5 degrees, but I now set it at zero, which means there will be no 2nd, or low fire stage. When I noted the water temperatures in my original post, I have been no where near the temp required for the second stage (180 minus offset of 5 degrees = 175 degrees), and there is still a problem. So I don't think this is the issue. A good thought though and changing the offset to zero should eliminate that as a problem.

delta T

I am leaning towards a low fire problem. I have installed quite few of these boilers, they are two stage, and if you do not check the low fire settings (manifold pressure and proper combustion) I have seen this problem on occasion, though it is rare. Do you have a manometer? check the manifold pressure on high fire and on low fire (they each have their own adjustment screws on the gas valve) to make sure they are set according to the manual. If you have a combustion analyzer you can fine tune those settings, but I have found it very difficult to get a good reading with a combustion analyzer on these boilers given the draft inducer design. I typically have good luck using the manifold pressure settings according to the manual. As JUGHNE says, the utility's gas regulator could be faulty. What is the high fire offset knob set at?

BrianCNY

One thing I just noticed is the transformer is hot to the touch. I can touch it for a moment, but would burn myself if I kept touching it. I've never touched it before, so I don't know if it's supposed to be that hot? Warm I would expect, but not hot. And, it's not hot because the boiler is hot. I do have a new transformer I could try? I read one post where someone had all sorts of strange problems with a failing transformer.

JUGHNE

Usually whenever I change a failed transformer, I install a 3 amp fuse in the secondary. Most FAF's have them, just an automotive type with insulated 1/4" spade connections that can float on the wires.......saves the new one if there is any problems downstream.

BrianCNY

If I have a transformer that's hot to the touch, should I replace it?

BobC

Transformers should run warm not hot, is there a chance it's not big enough for the load? Can you measure how many amps it's delivering?

Bob

BrianCNY

It's the oem transformer and it's hot with no load. Whether this is the problem or not, I have another one, so I'm just going to put it in. I'm not encouraged this is the problem, but it's a problem anyhow. Thanks BobC.

Jamie Hall

How hot is hot? as @BobC said, a transformer may run warm -- particularly under load -- but should not run any warmer than moderately cosily warm. You certainly should be able to hold your hand on it for a short time, anyway -- particularly if there is no load on it.

gennady

you might have internal short in transformer or gas valve.
check voltage on gas valve and see if it drops to lower than 24v value when problem occurs.
Also check flow switch operation
BTW, these come with outdoor reset if i recall correctly.
Check intermittent ignition control module S86 or what ever is there as well.

EBEBRATT-Ed

Change the transformer. It should be warm but not so you will get burned on it as you have said. If the new one gets hot you likely have some sort of short.

Check the voltage in and out of the transformer

BrianCNY

I think I may have found the problem.

I've been watching the igniter, never taking my
eyes off it, and here's what I noticed.

On start-up, the igniter makes its electric spark
and ignites the pilot. There are 3 pilot streams
of gas. One left and one right to each burner and one in
the middle for the flame rod.

The left and right ones look strong, but the one
in the middle is smaller, but I think it should be
that way. What seems to happen is the middle
stream to the flame rod, fluctuates and almost
goes out. This seems to be when the burners
shut-off, which makes sense if the flame rod
thinks there's no pilot.

During the momentary burner shut-off, the
pilot still stays lit and the left and right streams
are strong and unchanged. The middle one though
seems very weak, off to one side, or non existant.

I don't have an explanation for why the middle
stream would be ok, or enough for the flame rod,
for 10 minutes, then suddenly not be enough?
But then after one or two restarts, it's ok again
for a while? It would seem the flame should
stay the same the entire time, like the streams
for the burners do.

So I'm thinking, even though I can't explain it,
somehow the center stream for the igniter is
partially blocked. I ordered a new igniter and
will put that on and let everyone know what
happens.

The tip of the flame rod sometimes glows red,
and other times doesn't. Also seems like it should
be one way or the other. The problem never occurs
if the flame rod is glowing.

Lastly for now, I want to say how much I appreciate
what everyone has done for me. It's wonderful that
all of you are so helpful.

aviation421

I am having the same problem with my Lochinvar CB75 boiler. Any solutions? Please help
Thanks

BrianCNY

After re-reading my post I noticed I didn't mention what happened with the new igniter. I installed it and it didn't change a thing. I have spares for every component and swapped parts out, even though I knew there was no way they could cause this problem. Nothing has changed, same problem. I put in a new gas valve, measured and adjusted the pressures (in and out) and adjusted the pilot flame. Made no difference.

I've noticed that when the two-stage gas valve is on the lower stage, it doesn't happen. It only happens on high fire.

I've just learned to live with it, but it does bother me, because there is a reason why this is happening and I should be able to figure it out.

Here's a theory I have. On high fire, pressure builds-up after a time and the pressure is enough to "squish" (yes, that's a technical word) the pilot to the flame rod, down. When it gets down to a certain level, the flame rod no longer has a voltage and we have a restart. The pause in firing is enough for the pressure to go down and the whole cycle starts again. It doesn't happen when it's cold, because no pressure has built-up and it doesn't happen on low-fire because there is less pressure (not enough to squish the the pilot). I have watched the pilot get squished on high-fire, and watched it not-happen ever, on low-fire. So this is an important clue.

I have a power vent and there are no restrictions anywhere in the system that would cause a pressure build-up.

On the top of the heat exchanger, there is a series of V-Baffles, as Lochinvar calls them (part# JKR2060 for my model). I wonder if there is a design problem and these are too restrictive? This would not explain why the problem suddenly got worse though. It has always happened, but to a small degree. I would be near the boiler, which makes a lot of noise due to the power vent, and I'd say to myself "did I just hear that?", when everything shut down and restarted.

Sorry I can't be of more help, but I have given this countless hours of thought, to no avail. I even had a tech come out once and he asked if he could spend come time with me to learn about this boiler (of course I said yes). He thought, the only thing it could possibly be is a fault in the pilot circuit of the gas valve. I thought the same thing, so that's why I replaced the gas valve. He watched with me as the pilot got squished.

If anyone has any ideas, I'd love to hear them.

Brian

delta T

There should be a pilot adjustment, maybe it is too low by just a smidgen? Is the power vent the one that lochinvar sells? Also, is there enough combustion air in the room?

BrianCNY

One more thing . . . .

When I say I have replaced everything,
I really mean everything, except for things
like roll-out switches.

Parts replaced:

Gas valve and new pilot tubing
Igniter (flame rod)
Burners
Ignition Module
Thermostat Board
Transformer
Pump Relay

(and more that I can't think of . . . . )

Also, I do not have a outdoor air reset.

aviation421

Thank you very much for the response.
I have already spent $900 on this thing and still does the same thing...I guess I will have to live with it as well
The guy that worked on it says that maybe it needs to be clean since there is quite a bit of soot in it. He says that should fix it...

JohnNY

The Solution is an odd boiler. I put about 6 or 7 of them in to replace cast iron boilers several years ago and have been happy with their performance. The truth is I felt they were a bit too techy considering they were basically standard-efficiency units. As far as this issue is concerned, I have to agree that the problem (if you must call it one) lies in the ignition system and I would monitor the ignition module for this persistent, momentary glitch in holding flame. Also, your power venter. It's imperative you match your fan speed (CFM) to your BTU delivery or you'll lift your flame off your burner and cause exactly what you're describing.

icy78

@BrianCNY
Has anyone ever performed a combustion analysis?
Combined with what @JohnNY said , and what you said about it firing fine on 1st stage only, I'm thinking it's possible that you're overfired on stage 2, regardless that the gas pressure may be set per the manufacturer.
    The soot that @aviation421 refered to could also be from 2nd stage overfiring.

By overfiring, I mean that it feeds too much fuel for the available oxygen and/or venting.

Larry Weingarten

Hello, This may be too simple, but Isn't there a pilot orifice that could have gotten dirty?

Yours, Larry