Another problem--Bill Clinton

Bill Clinton

I have a Utica boiler that has been in for 3 years. During the second winter, shut-down problems occurred, roll out switch trippin. Because of a previous falling out, the customer called someone else who decided it was insufficient gas pressure and adjusted same. The next winter the same thing happened and a parade of repairmen added air shutters, replaced roll-out switch several times, etc. Problem continued til they got someone who said the boiler was no damn good, the piping was no damn good and the zone valves were no damn good, and gave them a $7,000.00 proposal. They of course threaten to sue me.

Just went out there and checked the whole thing out. The heat exchanger is clean, there are no visible signs of roll-out. My Testo detects no co2 around the burner manifold, so all exhaust is going up the flue. CO2, CO, and 02 in the exhaust gas are all fine.

The problem has so far occurred only in December and January, when the boiler is on the most.

I repositioned the roll-out switch slightly so it wouldn't get quite as much radiant heat as it did before, but will get every bit as much heat from any "roll-out" that may occur. Beyond that, the only suspect is the flue and inadequate draft under unusual wind conditions. Troubles with that theory are that the problem happens with no wind, and I would think inadequate draft would lead to draft hood spillage and trip that switch, not the roll-out switch.

Any thoughts?

Bill

don_9

roll out

Bill, I had this problem on a gas furnace at one time.
After changing burner and rollout switches with higer
temp rollout, still did not help.But i got lucky after
running on a long cycle the gas valve would intermittently
over fired in trip out rollout.Oh happy days,never did find out why. I replace the valve and there been no problem since.But having a customer who understand is a big help also. Checked with the gas company they been known to mix the gas every now and again when its real cold outside
to keep up pressure,Been there with them also.don

Boilerpro

Just some thoughts

Have you ever been able to check and see if the vent is freezing up. I've seen one where in really cold weather the screen of the chimney cap would close up with frost. It would only happen in really cold weather... in more moderate weather it would stay open enough to vent. Also, in very cold weather, exfiltration from a heated structure excellerates dramatically. In typical winter weather, there may be an air change of .5 per hour, however in really cold weather, this may be 1.2 per hour ( take a look at the ASHRAE heat loss calc design charts). This stack effect tends to create negative pressure at the lowest level as air exits the highest level. The boiler is usually at this lowest level and if the chimney draft cannot overcome the draft in the structure, I bet you would get the problem you have. A sealed room for the boiler with a dedicated combustion air source should solve this problem. I recently was working on a 70 year old steam boiler where the oowner was tightening up the structure. If it is tightened up upstairs thats great, it reduces the negative pressure in the basement because not as much air is leaking out upstairs. However, if they tighten up the basement, you may not have enough air leadkage to feed the air leakage of the structure and the chimney. I put a little 6 inch round air intake in the boiler room window, just in case, to help provide additional air for this 400,000 input boiler(if this was the only air source for the boiler, it would need to be much bigger).

Boilerpro

Mark Eatherton1

Combustion zone testing...

Bill, something is happening when you're not standing there looking at it.

Is there a Jen Aire grill in the house? Are there any oversized bathroom exhaust fans in the house?

If it were me, I'd perform a combustion zone test whereby you fire the boiler with the house closed up as tight as it would be during the winter, then turn on all the exhaust fans in the home including the dryer and see if you are able to maintian draft action at the appliance. Eliminate all possibilites before condemning the appliance.

We've had 3 customers in the last three years that called us in a mass panic due to CO alarms going off, only to find that they had had a handyman install Jen-Aire grills in their kitchens that were causing the boilers to back draft from the hoods and spill products of cimbustion into the house.

Check out this link.

Let us know what you find.

ME

http://www.area51hvac.com/combtest.htm

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Paul Pollets

Draft

I'll put my money on draft conditions. Is the boiler vented into a chimney liner? If not, the appliance is attempting to heat up the brick, and lowering stack temps. Chimney liners are required in the state of WA. CA??

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Bill Clinton

So far nothing clicks

Thanks for the suggestions. The trouble is, everything on this installation looks ideal. The boiler is located in a shed like room attached to the house. It has plenty of ventilation directly to the outside, plus an open doorway into a wide open, very drafty basement and crawl space. It's too warm around here to ever have icing. The vent is type B and the exhaust gas is pretty hot (380 degrees before dilution).

Again, it seems unlikely to be a venting problem because the draft-hood spillage switch is not tripping, it's the roll-out switch. Still, I'm coming up dry otherwise. Should I try adding a few vertical feet of B-vent?

Thanks, Bill

don_9

Standing pilot

or electronic ignition ? If it a back draft I would think the pilot light would go out as well.Is it redundant gas valve? low fire then high.Two things come to mind,Lazy flame,short cycling of ignition.Intermitted problems
they can be a pain.Time to break out the marshmellows.

Mark Eatherton1

Something ain't right...

We're not talking rocket science here. You start a fire, it establishes a draft THROUGH the boiler, it reaches the vent pipe, excess draft is relieved thru the draft hood, and the whole process goes on. If you over drive the fire box, you'll get roll out. If the flue gas collector is partially blocked, you'll get roll out. If there's a negative back draft condition, you MAY get some roll out, but like you said, the vent switch should get it also.

Any chance of a bad pressure regulator somewhere letting too much fire into the combustion chamber un-noticed?

Maybe there's too much downward radiation coming from the burners, and it's being absorbed and or reflected back up to the thermal switches. Radiant energy is a POWERFUL energy. Look at it with your infrared thermometer before and after a long burner operating session and tell us what you see.

ME

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Paul Pollets

Vent height

Bill, how tall is the chimney? Is it all B-Vent? Is the B-vent exposed to the weather or enclosed? A 15 ft. high B-vent 6" in diameter should easily vent a 120KBTU boiler.

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Paul Pollets

Shed roof venting

If the shed roof installation only has a few feet of B-Vent, extend to the recommended height as shown on the B-Vent charts. Less than 10' rarely works. I'd check the ratings for height requirements.

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Unknown

Roll out switch problem

Some suggestions that may help from an old gas man;

1. Clock the burner and make sure the input is correct.

2. Check the rating plate to see what gas pressure should be. Test at the outlet of gas valve most natural gas systems run on 3.5" WC at the outlet.

3. What kind of burners on this boiler? cast iron, pressed metal, ribbon, gun type inshot.

4. Is this a sprk ignition, standing pilot, or HSI. If it is HSI make sure the correct igniter is on if incorrect warm up time it can cause a delay on ignition.

5. Do all the burners light in less than four seconds?

6. Remove the gas valve and check the sensing port for the servo regulator make sure it is not partially plugged. I assume this is a dual seated gas valve. While you have it out you may want to think about putting a step-opening gas valve which comes on at a lower pressure and then 10 seconds later smoothly goes to full fire. I have solved many a problem doing this.

7. Adjust the gas flame for a soft blue steady flame. Someone else suggested this and I would check to see if the utility mixes propane at any time during December or January
that will definitely cause flame roll out.

NOTE: It has been my experience on certain boilers that when they cycle frequently or are on for long periods of time they build up excessive temperatures which cause problems with ignition and in some cases burn out thermocouples more frequently. The boiler reps tell me that it does not make sense but I have taken temperatures during excessive long cold spells and they definitely get much hotter.The radiant energy then effects both primary air and secondary air to the burner causing flame roll out and in some cases delayed igntion. The step opening valves also have helped this problem.

Bill Clinton

Radiant energy is my best guess.

Thanks for all the responses. The flue is 15' high and is type B and our weather is mild enough that condensing is not a problem, plus the exhaust is well over 300 degrees, so it should have no trouble figuring out which way is up.

The thought that the propane company is changing the mix during the coldest months deserves a look.

I did observe, when servicing during cold months when the boiler runs a long time, that the sheet metal shrouding around the manifold end of the burner tubes was hot enough to burn my fingers real quick. Checking temperatures in the same area last week showed they were cool. Maybe during cold weather extended runs radiant builds up and causes the problem. If so, maybe the slight adjustment of roll-out switch position I made last week will make a difference. The change will reduce radiation and increase cooling done by incoming secondary air, but will not reduce roll-out gas contact, should there be any.

Verrry interesting.

Bill

D lux_2

welding shops sell temp sticks , you could try a couple dif. temp to see how hot switch gets could it be bad ? how bout fuseable link or to across the opening to see if they open on rollout or is it the radiant heat ?

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peter desens

Rollout switch

Bill,

You definitely seem to have a tough one. These are the hardest to solve, the intermitent ones that is.

If you would give me a call at 1-800-325-5479, I would be happy to assist in any way possible. I'm on the service side of the business now, but back in 92', I was in charge of the Rollout and Blocked Vent switch project. I'm sure we can put our heads together and come up w/the solution.

Pete Desens
Technical Services Mngr.
Utica Boilers

Dana

Had the same problem with a Utica. I moved the rollout switch about 6" up the boiler jacket and the problem went away. I checked on it several times during the winter when I was in the area and found no problems with scorching or anything like that so I left it. Been 2 winters now without any problems. It's the only Utica I installed, the thing gets dam hot down where they put the rollout switch. Could not find any other reason for the problem and I checked everything. The only other suggestion is to make sure they shipped it set up for the gas you are working with. I once had a manufacturer,s boiler come thru with tags and stickers everywhere that said propane gas. After about a month of problems, we finally measured the pilot and burner orrifices and they were for natural gas. The bad thing was the boilers were for domestic hot water. Very bad problem to have in a hotel.