Most conservative setting for barometric damper without a draft gauge?
I've struggled to find an oil heating technician in the greater Boston area who utilizes a combustion analyzer and measures draft with a draft gauge. Most oil companies around here require you utilize their service for oil delivery, so the process has been very difficult. Oil technicians who are not part of a larger oil delivery company seem to be rare. But, I digress.
I've continued to find small amounts of soot behind our 1995 Vaillant boiler (see photos). The most recent technician to visit made adjustments to our burner and barometric damper which included moving the damper weight from the rightmost position to the leftmost position, which appears to make the damper open every single time the boiler runs, and afterwards. It's rarely shut unless the boiler hasn't ran in quite a while. Neither solved either issue, but in the interim I want to make sure we aren't at risk for having any draft issues.
Is there a recommended setting for these dampers that is considered the most "conservative" or "safest" until I can find someone that will measure the proper draft with a gauge? (i.e. far right, or far left as it is now).
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Are you saying that the most recent guy did not use a combustion analyzer and did not measure draft pressure? And what "adjustment" did he make to the burner? How did he know what effect the burner adjustments had on combustion and draft if he didn't have the equipment to measure those?
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Yes. I don't know what he did exactly, but I walked down and didn't see any instruments. He only performed a smoke test. No draft gauge as he did that last while I was down there. Very frustrating.
This is a relatively new home to us, so for all I know that damper had been set that way for 30 years. At the very least, I figured I should keep it at the most conservative setting until I can find someone who will actually measure it.
I was told the soot around the boiler was the result of the boiler's age. Although, I grew up with an old oil boiler from the early 90's, and never saw a speck of soot.
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Unless they've changed, the Valiant HX clean out cover plates on top of the boiler are held in place with tension rods. If the cover plates are not positioned correctly, then it's not a good seal. Poor design IMO. If you lift off the top cover of the boiler jacket, you'll likely see the soot colored insulation wrap. Under the insulation are the access plates.
As far as the draft regulator, the flue is kind of on a 45°, so whether or not the weight goes in the vertical or horizontal side is field set using a draft gauge. The Valiant is a 3 pass boiler, so a -.02 draft in the breach is fine as long as it's 0 to slightly positive over fire. Also, if the seam in the foundation wall in the first picture is level, then the draft regulator is not level. It must also be plumb… or violet at the very least.
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@HVACNUT you’re correct, the top plate is a tension rod (and not a very tight one). I’ve never removed it for fear of reassembling it incorrectly. Would this be a point where soot and/or combustion gasses could escape? (I would assume whatever access panel is below would be the actual seal). Looking closely, I can see some of the insulation poking out around the sides. Is this something worth removing and reinstalling?
The flue is just below 45 degrees (40ish) so my understanding is that’s considered horizontal.
The weight was previously at the leftmost position and didn’t open nearly as often. It would slam open when the boiler shutoff. Now it’s open nearly constantly. The most recent adjustment was without a gauge and I’m hesitant to keep it that way, unless more cold air can’t hurt until I can find someone that does it properly.
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So long as the axle of the baro is horizontal, that's good.
But… there is no way that the burner and draught can be adjusted without the necessary gauges and measuring devices. Decades ago perhaps, but never well. Nowadays, not a hope.
You may have considerable difficulty finding a tech. who is independent of an oil company or an HVAC company. Not much call for that as a trade all by itself.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Normally the barometric weight goes in one slot for a vertical flue and the other slot for horizontal flue. I am not sure what Field recommends for a 45 degree flue.
IMHO running the boiler with less draft is worse than running it with too much draft. The overfire draft must be in the range the boiler MFG wants.
As a rough test get a candle or a Lucky Strike and let the smoke go in over the fire. If the smoke blows out you need more draft so you would close the barometric. Adjust the weight. Close the barometric for more draft and open it for less draft.
When the smoke suck in at a slow stead rate you should be close. Move the weight to adjust. If one slot does not work try the other
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thank you. By over the fire, do you mean hold the candle/smoke at the damper? (You’ll have to excuse my lack of mechanical knowledge)
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From the field controls installation sheet;
Adjusting the control.
The burner must be running when the adjustment of the control is made.
The use of a draft gauge is required to set the overfire draft.
Set the over fire draft according to the appliance manufacturers instructions.
Set the control to maintain as low a draft as will give good combustion and meet the requirements for heat.
Turn the adjustment weight counter-clockwise too loosen, then slide in slot to the proper position and tighten.
The bracket is marked 2, 4, 6 and 8, which indicates draft settings of .02", .04", etc. (These are drafts adjacent to the control, Not overfire drafts)
Oil Burner Combustion Air And Overfire Draft Setting (inches of W.C.)
After the burner has operated for at least 5 to 10 minutes, take draft readings over the fire. For a domestic burner the over-fire draft should be .02-.03, although there are some makes of burners which require higher drafts. Follow the burner manufacturer installation instructions for proper settings. Ther must always be enough draft so that the burner does not puff back into the room at the moment it starts, and there should be no objectional smoke. CO2 and smoke readings must be taken to determine the proper adjustments.
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If you really want to ride herd on this you can purchase a Dwyer Mark II Manometer and a probe from Dwyer to monitor the draft on your oil boiler.
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I thought Massachusetts had strict requirements on the knowledge of their techs. Maybe a call to the Service Manager to ask why no combustion analysis. If something bad were to happen with the boiler, wouldn't the company want proof it was running at peak efficiency and cleanliness when they left? Do the techs have a quota and limited time. Dialing in combustion and draft while the boiler is at steady state can take anywhere from 20 minutes to an hour. Run all heat zones. Run the hot in the bathtub if needed. Just keep that burner running. The first thing I do on a heat maintenance is raise all the thermostats, then test the burner safety. This way the boiler will cool off while I'm working. By test time, I know I'll get good run time from the burner because the boiler went cold.
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MA requires oil techs to be licensed. I am sure that there are many HVAC techs and plumbers fooling with oil that are non-licensed.
Had mine since 73" first license I ever got. Have no clue why I keep it. #2,4, & 6 oil.
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Over Fire Draft on a Vaillant boiler is measured directly over the fire, by removing the sight glass from the view port.
The round glass is held in by a snap ring that needs a snap ring tool to remove it. If you have a pair of old needle nose pliers that you can grind the tips into 2 small round points you can make one, or purchase one at an auto parts store.
This is when you will clean the soot off of the glass and get a new gasket for the glass to seal it to the cast iron of the boiler. Come to think of it, If that gasket is missing, that could be the source of the odor.
The view port is directly over the oil burner where it enters the boiler. look closely in the area of the Red Arrow on the photograph below. When @EBEBRATT-Ed indicated that you use a cigarette smoke or smoke from a candle, and see if the smoke gets sucked in or if the smoke gets blown away from the opening, he was talking about that over fire view port. That is also where you would measure Over Fire Draft if you had a Draft Gauge or manometer.
There are 3 places that need to be accessed on Valiant boilers when vacuum cleaning to remove the soot. The first area is the top, just under the green cover. remove the cover and the insulation to reveal the plates that cover clean-out ports and are held in by tension clips. You may want to purchase some fire proof insulation from the local supply house or wood stove dealer. The trade name for this insulation is Kaowool or ceramic fiber blanket.
The second place to open up is behind one of the front green panels. Just above the Red arrow in the photo. You may need to remove the Aquastat relay to access that second opening or it may be behind a different green panel depending on the model number of the Boiler. Manu mechanics do not know this but the pressure temperature gauge (if it is original) can be removed without draining the boiler. Just spin it out of the well that it is connected to. There is an O ring that seals the pressure portion when removed. The third thing to open is the actual burner door. That gives you access to the combustion chamber and some hard to reach sections of the heat exchanger. There may also be a removable panel behind the bottom green panel. all these panels have steel plates that cover the clean-out access and will need to be sealed with the Kaowool gasket material.
Here is a close up of that view port and what the snap ring might look like
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I have the RC 6 inch barometric with the sliding weight for my coal stoker boiler which is just like his barometric damper
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@leonz My bad mis read your post
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Not a problem Ed,
I am more concerned with the bent sheet metal on the right side slide for the weight. Whoever adjusted it did not bring the metal strip back to even it and this would of course cause a weight imbalance on the damper door.
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