ignition problem?

bill clinton_3

Looking for some help on this one: I have an installation about twelve years old, Lochinvar copper boiler on fair sized radiator system. From cold start, boiler operates fine for about 20 minutes: runs up to about 140 degrees; aquastat set at 200 degrees, outdoor reset supposed to control. Then it starts to cycle: Burner shuts off and instantly relights; runs a minute or two, then repeats. This goes on for a couple of hours, then something stabilizes and it runs fine. Next morning, same thing.

We have:
1. taken reset out of circuit
2. cleaned pilot and flame sensor
3. replaced ignition module (twice with no change in behavior)

Any ideas?

Bill Clinton

Steve Thomas (Foley Mechanical)

Try this

Had the same problem with a Burnham that had spark ignition. Try changing the entire pilot assembly. Worked for me.

Mad Dog

Flag is right

Have some jobs out there that I still never pinpointed, but at a certain point you had to bite the bullet and change everything. You can't sit there for 3 days straight, you know. Ask Timmie - he's the best with this stuff. Mad Dog

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masterplumb

Try

cleaning the ignition ground. It sounds like the ground may not be making good contact. Chris

bill clinton_3

Thanks, guys nm

Jeff_12

I have seen pressure switches causeing this same behavior on weil-mclain boilers that are fan assisted. I've never worked on that boiler, but, if it has a pressure switch you may want to investigate that.

Bruce_6

I am not

a huge fan of copper boilers. air can be a huge issue and create the cycling effects you describe. make sure there is an air scrubber, not just an air vent. have seen lots of installs with only air vents instead of the scrubber installed, creating an air issue and cycling was every couple of minutes as you describe.

I have seen bad grounds cause this, you might want to check the house ground also.

Mark Eatherton1

Improper draft conditions...

I had one last week where I think the CO2 from the combustion process was pooling in the combustion chamber and snuffing the flame. There was NO negative pressure in the flue breaching before the draft diverter, but there was -.04"WC available down stream of the relief/diverter hood. When I wrapped the relief hood with aluminum, my CO dropped like a rock.

Just when you think you've seen it all, something like this raises its ugly head and yells "YOU AIN"T SEEN NOTHIN" YET!!!"

Just for grins, you might try doing a combusion test and see what the blocking or partially blocking of the relief vent does for you...

Jim Davis taught me to think outside of the fixed box...

ME

Ray_7

I just ran into a fan assisted furnace that did the same thing. Found out the inducer would slow down after a few minutes of heating, tripping the pressure swith. The furnace would re-ignite in approx.10 seconds. Just a little FYI.

Ray

tim smith_2

short cycling

Sounds like to me it may be cycling on aquastat. Get your meter out and put it across aquastat terminals while running. You may just have a lack of flow and the temp rise through boiler is too high. Other thing I have found is after the ignition module has been under load for awhile the hold relay will drop out, I think due to a weak coil or something. My first impression is the flow issue or a defective aquastat.

Unknown

Mark, give us a little more

information as to cause, effect and final results. Thinking outside th box may not make sense to the newbies here on the Wall.

What readings did you get? What do you think was causing this? Did you leave the diverter with aluminum wrapped around it.? Sounds to me like other things may have been happening. I am also curious what kind of boiler or furnace was this and is this typical of this system. Is the manufacturer permitting this alteration to their equipment? What happens if there is a downdraft and the diverter is sealed? I would think the back pressure would now go into the combustion chamber and cause a possible delayed ignition or explosion. There are three purposes for a draft hood only one of them to neutralize the effect of stack action is being addressed when you block off the diverter.

By wrapping metal around the diverter you cut off dilution air which was cooling flue gases at that point. The stack temperature should now increase which means flow velocity through the package increases. This brings in more excess air across the burner which accounts for reduced CO. What was the CO with the diverter open? What was overfire draft before and after?

I have a hundred more questions but that is enough for now.

Mark Eatherton1

Timmie...

I don't want to mention the manufacturer by name because it may un-neccessairily taint their good name.

I understand that things like this happen in the field, and it's generally a field condition that brings it about, and those conditions are impossible to create under labratory conditions. Besides, the manufacturers reps are good people and are doing everything in their power to rectify the situation. They've even brought in outside help at their expense trying to figure it out. As the owner of the rep agency told me, "We WILL get this situation rectified" and I know they will.

Here's the scenario. The boiler is in a basement. The room has more than adequate outside combustion air. The boiler is 600K @ sealevel. We're operating @ ~ 9,000' ASL. The input to the appliance has been clocked and is dead nuts on. THe boiler is atmospheric with a bell shaped draft hood on top of the unit. The flue pipe is 10" diameter, and is ~ 20 feet tall. It has minimal offsets in it. The boiler room has an automatic closer on the door and the door is kept closed.

We did catch them trying to operate it with the boiler room door open, and there is a large kitchen exhaust fan that was causing problems. That has been corrected.

The last test we did was with the exh. fan off (which it usually is except for rare occasions) and the boiler room door closed. With the system normal, the CO was around 400 PPM. Draft at breaching before the hood was 0" W.C. Draft in the flue pipe downstream of the diverter was -.04" WC as tested with an incline manometer.

Although it didn't do it in the relatively short time frame we were there, the maintenance director at the facility said the boiler shuts down and locks out during sustained call for ignition. This has been confirmed by the lockout code on the ignition controller. (Loss of flame signal duriing full burner operation) THe gas train is CSD1, hence the lockout as opposed to retry. This situation generally happens in the afternoon, which means it is happening when the boiler is probably in LOW fire.

We tried raising and lowering the manifold pressure. It had a minimal effect on the CO. As soon as I blocked the hood with the foil, the CO dropped to around 50 PPM.

My thought is to install a barometric damper on the boiler, thereby elimnating the fixed draft diverter/relief hood. Jim Davis has done this on thousands of boilers and overcome the problems associated with incorrect draft through the fire box. It's not really something I want to do, but nothing else has worked. So far we've replaced the ignition control module, pilot/flame sensor and added an additional ground from the burner frame up to the common ground, and the problem persists.

There was a roll out shield that blocked secondary air at the face of the burner that we pulled out this last round. We're getting desperate for solutions. If in fact that works, we will have to go back and install roll out flame detection around the face of the burners, because there are none required for this size of boiler. Removing the air dam below didn't make any difference in the draft conditions, although it did lower the CO, but to how low I don't recall. We did not leave the foil on the hood.

I don't know how, nor why, but the fact that I have ZERO draft at the boiler breaching tells me something is not right. There's no incentive for the flue gases to leave the combustion chamber in an orderly manner.

I would love for the manufacturer to come out and take a look at it to confirm that everything is correct, and it's still not working right.

I have my theories on what is occuring in the field that doesn't occur in the lab.

The appliance has been derated using the typical 4% per thousand feet. This means that at high fire, the appliance is only seeing roughly 1/2 of its' nominal fire box capacity. The appliance is two stage. When on low fire, it's running at 1/4 its nominal capacity. Under these less than ideal conditions, the appliance can not maintain adequate flue gas movement within the combustion zone to adequatley get rid of the products of combustion.

They accumulate, smother the fire and cause the controller to lock out.

The only correct solution I can see is to elimnate the fixed draft hood and replace it with a properly adjusted barometric damper. Even at that, it may become necessary to install a Guillotine in the breaching if we create too much draft.

Oh, by the way, with the foil on the hood, excess air was at 68%.

Your thoughts are welcome, and I'm sure the rep agency is reading this. They never miss a thing on The Wall:-)

Thanks for all your help guys.

ME

Unknown

Mark a lot to digest

I am going to look over what you have posted and get back to you tomorrow. I have a couple of thoughts but want to run it all through my head before I post.

Unknown

Bill have you done a

combustion test on this unit? Is it developing any kind of stack temperature when it kicks off at 140 degrees?

Unknown

Mark on your situation....

I think this boiler is reacting to derating due to your altitude situation. There is not enough pressure difference in the combustion chamber to create any kind of over fire draft. The vent however is drafting due to height and delta "T". What I would do before putting in a barometric is to cut in a Guillotine after the existing draft hood as close to the common vent as possible. Adjust it until you can see a change in combustion condition and air change at the fire box. I definetly would look at increasing some input even though you have followed proper altitude perimeters (they are not working). Start with orifice changes with recommended pressure to increase and then for fine tuning use the regulator adjustment.

Your vent is also reacting to the altitude condition so by deceasing the -.04 at the chimney less dilution air will be brought in and the total vent gas package will decrease (68% excess air is a lot of flue gas and excess air for the package to handle), it sometimes does not make sense to think about how much the flue is actually handling but we have to think of it in terms of products of combustion, primary and secondary air and then the real culprit most of the time "excess air" too much excess air reduces efficiency and affects the entire package.

So in summation I would give it some more gas and cut in an adjuster between the bell shaped draft hood and common vent this will allow you to control total draft. Make sure when you finish and have it working to lock up the adjuster with sheet metal screws (code allows that just no manual dampers). If that does not work then try the barometeric damper,the reason I do not use a barometric right away is I have had problems even after doing that and found it did not always work, the adjuster really allows me to reduce the cross sectional area of the flue as close to chimney draft as I can get,it seems to work everytime. The fact that factory folks are on board gives you a lot of flexibility to make adjustments. The real test lab my friend is always in the field.

Unknown

Bill

Just a thought only because I have seen this happen in the past. Is this unit equipped with a flow switch such as a McDonnell Miller FS-4 Flow Switch in the system piping to prove flow through the boiler? This could be causing the problem if there is. Check to see if the current to the ignition system is being interrupted when it starts to flutter. If it is then the cause is from somewhere in between the high limit and the ignition module and that would probably be the flow switch. Hope this helps.

Glenn Stanton

Burnham Hydronics

Duncan_9

Maybe gas, maybe electric, definitely cleaning time.

What is the gas pressure IN and OUT of the control doing when the problem occurs?

Just this weekend I ran out of propane, so I hooked up to a small bottle. I marveled how the boiler burners would ignite and run smoothly. Until the -5°F temperatures (combined with the evaporating propane vapor in that little bottle and maybe vapor turning back into liquid) dropped the inlet pressure to a point where the low pressure was too low to force fuel through that tiny little pilot orifice. Then everything would drop out.

In your case it could also be be a case of undersized piping in combination with a different, intermittent large gas load. When the other large load comes on line, the pressure to your boiler may be dropping.

Hmm... maybe an electrical problem interrupting the gas valve circuit?

What model Lochinvar?

How's the spark ignition is wired in?

*Is the pump relay cutting out too?*

If it's only the gas valve shutting down, but the pump relay stays pulled in, it would be in the series of safeties before the gas valve: aquastat, high limit, aux limit, flow switch, rollout fuse (not likely), or vent spillage switch or... vent damper problem. Or loose connections to any of those.

If the pump relay is also cutting out when it happens, I'd look at the vent damper. Maybe if a service truck is passing by and has a minut, the vent damper could be temporarily overridden (per manufacturer's instructions!) and see if that cures the problem.

Guess I'd try the easy stuff mentioned above first like grounds and pilot assembly. Personally, I don't like the shotgun approach (replace everything!), prefer to pinpoint the problem. But it depends on the severity of the problem and the customer's patience. Sometimes you need to get out the shotgun.

When approached correctly, the burner tray of the Lochinvar slides out easily with removal of half a dozen screws or so. So replacing the pilot assembly is not necessarily a pain.

Twelve years old. If it's been short cycling like you describe for an extended period of time, I DEFINITELY would do a CO test. Then get out the respirator, shop vac and metal brushes and pull the burners and lid on that boiler and give the heat exchanger a top-to-bottom cleaning. Then CO test again. Twelve years old = dirty fin tubes. Maybe part of your problem, maybe not - but it needs doing.

Duncan_9

Gas, electric, definitely cleaning

What is the gas pressure IN and OUT of the control doing when the problem occurs?

Just this weekend I ran out of propane, so I hooked up to a small bottle. I marveled how the boiler burners would ignite and run smoothly. Until the -5°F temperatures (combined with the evaporating propane vapor in that little bottle and maybe vapor turning back into liquid) dropped the inlet pressure to a point where the low pressure was too low to force fuel through that tiny little pilot orifice. Then everything would drop out.

In your case it could also be be a case of undersized piping in combination with a different, intermittent large gas load. When the other large load comes on line, the pressure to your boiler may be dropping.

Hmm... maybe an electrical problem interrupting the gas valve circuit?

What's the boiler temperature doing when the problem occurs?

What model Lochinvar?

How's the spark (or HSI?) ignition wired in?

*Is the pump relay cutting out too?*

If it's only the gas valve shutting down, but the pump relay stays pulled in, it would be in the series of safeties before the gas valve: aquastat, high limit, aux limit, flow switch, rollout fuse (not likely), or vent spillage switch or...possible connector problem at the vent damper. Or loose connections to any of those.

If the pump relay is also cutting out when it happens, I'd look at the vent damper. Maybe if a service truck is passing by and has half an hour to kill, the vent damper could be temporarily overridden (per manufacturer's instructions!) and see if that cures the problem.

Possibility of negative pressures in the boiler room?

Guess I'd try the easy good ideas the guys mentioned above first, like grounds and pilot assembly. The pilot assembly hasn't been changed yet, right? Personally, I don't like the shotgun approach (replace everything!), prefer to pinpoint the problem. But it depends on the severity of the problem and the customer's patience. Sometimes you need to get out the shotgun like Mad Dog says.

When approached correctly, the burner tray of the Lochinvar slides out easily with removal of half a dozen screws or so. So replacing the pilot assembly is not necessarily a pain.

Twelve years old. If it's been short cycling like you describe for an extended period of time, I DEFINITELY would do a CO test. Then get out the respirator, shop vac and metal brushes and pull the burners and lid on that boiler and give the heat exchanger a top-to-bottom cleaning. Then CO test again. Twelve years old = dirty fin tubes. Maybe part of your problem, maybe not - but it needs doing.

bill clinton_3

still struggling

We were out there today for the fourth time. Checked voltage to module while cycling is happening: Voltage remains steady indicating problem has to be in module or flame sensing. Replaced pilot assembly; cleaned and checked continuity of burner ground and 24 volt ground; checked all wires for good contact; replaced module (again)--no change. It still starts up fine, runs up into the 140 degree range, then starts cycling--pilot goes out, burner to at same time, instant relight; does it again in 30 seconds or so (variable time lag here).

My tech is coming back to the shop right now having spent four more hours playing around to no effect. Pretty desparate.

Bill

Mad Dog

I feel for ya Bill...been there before

You'll figue it out soon. Mad Dog

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Bruce_6

I just replaced

a gas control valve on a slant fin, that was doing the EXACT same thing as yours is doing. Slant fin is about 7 years old, everything seemed OK, and all current (110 and 12v), and gas pressures were fine, but when run for a period of time, it shut everything down, including pilot. after replacing the gas control valve, the problem went away.

I wonder if that lochinvar is having the same problem???

just a thought, but thought I would thow it out there!!

Mark Eatherton1

Thanks for the advice Tim...

But I am somewhat perplexed. First off, the vent is an individual vent serving only this appliance. If I cut down on the potential negative stack pressure, it would seem to me that it would have a tendency to compound my problem of zero draft over the fire. In all my years of working on this stuff, I've only cut a guillotine into the breaching between the applaince and the appliance relief/draft hood. Never down stream of the hood. I can't say as I've ever seen a recommendation to cut one in down stream of the relief hood.

Am I missing something real obvious here, or am I missing the forest because of the trees.

Confused, dazed, but not down and out in Denver:-)

PS, The maintenance guy said it made it through the weekend without any lockouts. The factory is going to do some testing and give us a letter acknowledging the field modification.

Thanks for your help Tim.

ME

Unknown

Mark I also encourage people

to think outside the box. I learned about putting the Guillotine after the draft hood from an old engineer I used to work with from Midco.

Here is the thinkng on this: when it is cut in ahead then you only control overfire draft. When it is cut in after the draft hood you control all of the draft. You have excessive draft after the draft hood by reducing that draft less dilution air there fore flue gas temp will increase ahed of the draft hood which is increasing temp inside the package and will draw in more air over fire.

Believe me this works. I know all of the books show it ahead of the draft hood, they also show it cut in at the top and I cut it in at the bottom of flue pipe that way any build up of scale will stack against the damper and not block the flue. It is also safer if the damper corrodes and rots it will fall out of the flue not down inside and block the flue.

Unknown

Bill try disconnecting the

external circuits to the electronics and feed it direct from the transformer. Just be careful as all the safeties are out of the picture and you are running on just the module. That way you can eleiminate any flow controls or other limits that may be reacting to cause this. This is obviously a temporary measure to eliminate possible sources. I find when all fails this technique of one by one eliminating components will often find the problem.

If it still fails then something may be going on with the combustion side of things. Put a combustion tester on it and monitor behavior at the time when this oocurs.

Dan Foley

Ignition Problem

Hi Bill,

Hang in there! We have all been in your postion. You have tried everything (twice, even) and you still can't find the problem and you are ready to pull your hair out!.

I had one a few weeks ago with a similar problem. It had a Honeywell S8600 spark ignition system on a cast iron steam boiler. It would ignite and run fine up until the boiler got hot enough to steam, then cut off. The burners would then cycle on and off every five to ten seconds.

First I replaced the spark module with a new S8610 - same results. I eliminated the gas valve as a problem by jumping out the control. The burners would run fine with the control jumped out.

I suspected a weak ground. To test it out, I ran a temporary ground from the boiler to the ground rod for the main panel - same results.

After several trips, an angry customer, and much distress, I found the problem to be a weak spark wire (the orange high voltage spark wire that runs from the module to the pilot). When it got hot, it affected the current flow in the flame detection circuit. I changed it out and have had no problems since early December. Good Luck! -DF

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Jim Davis

Having sold Lochinvar as a wholesaler for many years, one of the main problems I encounted was getting them to vent. Many times the roll-out switches would trip or the controls would melt. Normally roll-out switches are manual reset but for whatever reason (I can guess)they might have been change to automatic. Lochinvar boilers can run with a very low flue temperature which makes it hard to establish good draft. After several hours of operation the flue finally may be getting hot. On most Lochivar boilers I have had to get my contractors to elevate the rear of the boiler to get the heat away from the front. And in most cases to keep the chimney from condensing and the copper fins from falling apart a modification to the drafthood was also necessary. Lochivar is one of the few manufacturers that I have a letter from, stating modification is okay to solve venting issues. Only a trained & certified NCI contractor is totally familiar with these corrections.

bill clinton_3

Thanks again guys

gonna try some of these suggestions.

Bill