A neighbor has an old oil fired boiler that’s giving up, and decided to go with a new natural gas boiler. Her chimney is brick with a clay tile flue in good condition. She had a local reputable company give her an estimate for replacement, and the tech said he couldn’t install a new boiler without also putting a stainless liner in her chimney; said it is a code requirement. Also said prices on all new heating systems are going up 7% as of January 1. The new boiler is an 82% efficient unit, nothing fancy. Does the liner requirement sound right? I can’t help thinking about the millions of houses out there with similar setups as hers getting along just fine, although maybe not at the optimum efficiency.
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Yes the liner requirement is correct. The newer furnaces are more efficient and therefore lose less heat up the chimney and need a proper sized liner to insure good draft.
If he's burning oil he does need a stainless liner cause the standard ones will corrode from the acid in the gas.
>>Yes the liner requirement is correct. The newer furnaces are more efficient and therefore lose less heat up the chimney and need a proper sized liner to insure good draft.Dang, somebody had better tell my campfire that.Size is important to keep the flue temps from getting too low leading to condensation and related problems.Also (although I'm not certain about this - we have very few oil appliances in my area) I believe the linerbis needed becasue of the change in fuels.
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Forgot about the condensation. Its been about four years since I sold those things.
But - (slow witted question following) - I didn't think that an 82% boiler (again, natural gas fired) was all that high tech or efficient. That's what makes me wonder about all the millions of older boilers at around 80% out there with clay liners. What am I missing?
I'm guess it may just be something that was learned over time by examining existing chimneys. Not really sure. I just know they are now required.
Except at extremes. the flue details won't affect efficiency.And efficiency calculations with a combustion analyzer are mainly "smoke"The formulas the analyzers use rely on invalid assumptions, and in some cases "higher" calculated efficiencies can actually lead to poorer actual efficiency (when measured by BTU input, BTU output in both the flue and the air/water being provided.A couple of reasons to reline:One, you can't discharge gases from different fuels into the same flue (at the same time) and I believe there are potentially bad chemical mixture issuesTwo, fuel oil fires are much hotter and thus have different flue sizing requirements.
The "War on Terrorism" has failed - in part by narrowing our options to only the option of last resort.
I propose we start a worldwide Partnership Against Terror, in which the reasonable people of the world work together to oppose terrorism and the conditions which lead people to that desperate condition.
"We hold these truths to be self-evident, that all people are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness."
National fuel gas code requires a new liner when you change fuels because of the possibility that soot residue from the oil-fired boiler will fall into the gas burner and clog up the works, causing CO, etc.
Don't ask me why, I just read the books!
I don't recall ever reading a code book that gives a REASON for the requirement. It only states what shall be done normally.There may be a small amt of truth behind what you say, but most clay flues would have a collection shelf at bottom for accumulation of soot so it would not fall into a gas burner anyway. The main REASON is that a flue too large will not draft properly allowing some dangerous exhaust gasses to accumulate in the living area of the house, putting the lives and health of occupants at risk. That is much more important than a little soot and efficiency.
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If a chimney doesn't draft properly, flue gases will condense, and that condensation is acidic.
The mortar joints get corroded by the condensate and the worst case is the flue gases enter the occupied space.
I've seen it bad enough that the space was filled with co.
Is the condensate acidic with gas too, or just oil? I'm more familiar with oil heat
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Gas too. Any CO2 reacts with moisture. Carbonic acid. Sulpher is bad too.
I see.
It's the sulphuric acid we hear about with oil burners
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while the liner is code it seems a good tech can get a oil furnace rated at 82.5% up to 85.5% which is another advantage a lot dont tell you about
Yes, needs to be sized for the waste exhaust of the unit being installed to prevent back drafts and condensation in the flue that can damage it.
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If it does turn out to be true, she migt be better off stepping up to one of the high efficieny units that vents through pvc pipe. Might be cheaper to get a more efficient boiler (there are some tax credits available too) than to pay for a chimney liner.
If the new appliance is natural draft, then it may be possible to vent it without a liner. Appliance btu input, height and size of the chimney need to be looked at on a vent table.
If the appliance has a draft inducer motor, then clay chimney venting is not possible per code. Anyone venting an induced draft appliance into an exterior masonry chimney without a liner is asking for huge problems. It *may* be allowed if the masonry chimney is interior.
Manufacturers are pretty specific with venting guidelines. Some techs may state it is *code* and it may just be manufacturers specs.
>>Anyone venting an induced draft appliance into an exterior masonry chimney without a liner is asking for huge problems. It *may* be allowed if the masonry chimney is interior.Remember that local codes vary - my area now requires a liner on all 80+ being ventede thru an exiating chimney
The "War on Terrorism" has failed - in part by narrowing our options to only the option of last resort.
I propose we start a worldwide Partnership Against Terror, in which the reasonable people of the world work together to oppose terrorism and the conditions which lead people to that desperate condition.
"We hold these truths to be self-evident, that all people are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness."
Yes, local codes vary.
However, *if* the bulk of the chimney is located in the interior space and attic (not entirely outdoors), and a special kit is used with all Type B vent pipe from the furnace to the chimney, Trane and Carrier will allow their 80% induced draft furnaces to be vented into a *clay tile lined* masonry chimney. Says so right in the installation instructions- even has part numbers and pictures.
The *special kit* is a B vent connector with an additional limit switch wired into the furnace in case of a downdraft. I have installed plenty of them.
Manufacturers instructions can trump an overzealous inspector if the situation is approached properly.
I know this is straying from the original boiler question, but there might be something of merit in the installation instructions. Believe me, plenty of equipment gets installed without looking at them.
Codes and inspections only do good if a permit is pulled and the municipality inspects the finished work. In my area, they just take the money.
Edited 12/25/2006 1:04 pm ET by danski0224
Thanks, interesting infoNow, if they'd just let the draft inducers run for a bit after flame shut down to purge the flue ....I personally believe that the flue liners aren't that good of an idea. I rarely see a 80+ installation into a chimney with a flue liner after a few years which doesn't have indications of condensate draining back towards and/or into the draft inducer and even, in some cases, into the heat exchanger >>Codes and inspections only do good if a permit is pulled and the municipality inspects the finished work. In my area, they just take the money.Even when they inspect, they have limited knowledge (in my area) of what to look for
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And a unlined chimney in the same situation wouldn't condense?????
Not everything the good doctor preaches is gospel.
Edited 12/26/2006 11:56 pm ET by rich1
Letting the draft inducer motor run for longer will change the efficiency rating of the appliance- no longer would it be 80% efficient without using a more efficient (expensive) motor to balance the additional energy sent up the chimney.