A Tale of Two Chimney Assessments
We moved into our 19th century townhouse last spring and, not having had occasion to use our heating system yet, just had our National Grid yearly check-up done. A tremendous amount of sand-like corrosion had collected on the ground under the burner tubes and the coils inside the boiler were caked with the same corrosion….
We moved into our 19th century townhouse last spring and, not having had occasion to use our heating system yet, just had our National Grid yearly check-up done. A tremendous amount of sand-like corrosion had collected on the ground under the burner tubes and the coils inside the boiler were caked with the same corrosion. A referred cleaning company came and scrubbed down the coils and explained that it was likely caused by improper ventilation – if the exhaust and vapor is not being pulled up the flue, it would linger around the coils and be re-burned or carbonized. Made sense to me. Chimney Company 1 came and inspected the boiler flue and told me the cement holding the clay flue liner sections together had eroded and the gaps and spaces would cause a lack of convection. They quoted $100 a foot to fit a stainless steel liner inside the clay liner (which everyone agrees is wider than necessary for the boiler output). Chimney Company 2 came and said hogwash – there are certainly some cracks and small gaps in the liner seams, but nothing that’s going to affect convection, certainly not given the diameter of the flue to the output of the boiler. If anything, there may have been some blockage at the bottom of the flue that the National Grid people would have removed (they didn’t mention whether they did) but there were no obstructions anymore. Given that CC2 was passing up a $3k+ job I’m apt to trust him, but I don’t want to risk re-carbonizing the boiler or worse, having exhaust back up into the basement or seeping through the clay flue liner seams if there is insufficient convection. Do I go for a third opinion? Any thoughts? Any idea what would cause that level of corrosion if the flue is okay and there wasn’t an obstruction? Just normal wear? Many many thanks for any tips or referrals.
Thanks to everyone for their thoughts! Very helpful. Rest assured, carbon monoxide detectors are installed throughout the house and the boiler itself has one (“spill switch”) right under the vent on the underside of the 45 degree duct from the boiler to the chimney flue.
As several of you speculated correctly, the boiler room certainly does have a ventilation problem and this could well be the cause of the corrosion. In fact we just had the door and drywall that separates it from the rest of the basement redone to address moisture problems, effectively sealing it off from the rest of the house! There is, however a metal double-door ceiling hatch in the boiler room that opens to the front yard. Would it be possible to install a vent in or next to these doors that would allow some fresh oxygenated air in while keeping moisture out? Any further thoughts or suggestions would be appreciated again!
When I had a similar dilemma, I had BUG (Keyspan/Nat’l Grid) come look at the set-up. They determined whether I needed more venting, greater intake, etc. I, too, had what I thought was an alarming amount of sand at the bottom of the flue – although I didn’t have the carbonizing you mention. Ultimately, I didn’t need a lot of work done but it was comforting to have the disinterested advice of the gas company people who know all the building codes for the City & can tell you if you’re in compliance &/or need any substantial work done. If the N.G. people didn’t say you needed “whatever”, you probably don’t.
OP, I have no idea who you called but here’s my two cents about chimney contractors:
There are generally three types of chimney companies in this world.
Type One: Doesn’t know anything about chimneys except that they can be lined with a metal tube as big as fits in the slot and connect the tube to a boiler and when they’re done someone will hand them a check for $3,000.
Tools: Ladder, long tube, tin snips
Type Two: Is more than willing and capable of doing same, but has the general good knowledge that a chimney has to be in pretty bad shape to actually create a problem and that in many cases, a thorough cleaning and inspection will buy you another 5-7 years before a liner becomes necessary.
Tools: Ladder, tin snips, full set of masonry equipment, ropes and pulleys, industrial cleaning equipment, lights, high heat furnace cement
Type Three: Same as Type Two, but understands the health, safety risks and warning signs of a chimney in a failing state, knows the properties of combustion gases and the dangers of carbon monoxide, understands how the size and height of a flue creates a desired ‘stack effect’ and draw, and puts pencil to paper to determine and install the proper materials to vent your particular fuel-burning appliances.
A Type Three chimney contractor will always take into account your need for intake, or make-up, air and include in his price something to make that right.
In other words, a *good* chimney guy not only knows what he’s looking at, he’s also educated to know what you really need and compare it to what you may already have.
Tools: Ladder, tin snips, full set of masonry equipment, ropes and pulleys, industrial cleaning equipment, high heat furnace cement, draft gauge, carbon monoxide monitoring equipment, mechanical venting tables including minimum and maximum flue lengths at specific pipe diameters, roof flashing equipment, finishing materials consistent with the construction of the building, appropriate terminal caps, NYC DOB Code book.
Type One guys are a dime a dozen.
There are very few Type Two and even fewer Type Three guys in our area.
And as you may have guessed, those are the ones with the big estimates.
What Chas said, additionally if you are getting incomplete combustion you are putting yourself at serious risk for carbon monoxide poisoning. I hope you have a detector. If the boiler is fairly recent why not contact the boiler company and see what the specs are for intake and venting and if your installation meets them. You also may want to contact a plumber who understands boilers (like some who post on this site) to advise you, rather than a chimney company.
I think you could take a chance on company no. 2’s advice, as long as you have a spill switch that shuts down the boiler if there should be a carbon monoxide back up. I’m sure National Grid will install one for a reasonable fee if it isn’t already there. I had one installed on my furnace about 20 years ago by Brooklyn Union Gas, NG’s predecessor. It might have saved my life when I REALLY needed a stainless steel chimney re-lining a few years ago.
Do you have fresh air to the boiler room? If boiler room is sealed you are getting improper ventilation for proper combustion and exhaust.
You do not need to reline flue.
I hate these predicaments. It makes you leary about trusting any “professional”. I would always go for a 3rd, and then maybe a 4th or 5th. I’ve had at least 5 people assess the condition of our foundation and concrete slabs, front and back. And I didn’t get the same answer from any of them.