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Oil to Gas Conversion with added chimney problem

We live in a 65 –yr-old home in Arlington, VA that has wonderful radiator heat. The old oil boiler needs replacing, and we consequently found a 2-ft chimney tile had fallen within the flue, which prompted us to consider switching to a high efficiency natural gas boiler for side venting, thus saving on the repair of the (boiler) chimney flue. Our concern with side venting is exactly how much exhaust is created with a direct venting system? Or, should we bite the bullet and install a standard efficiency gas boiler along with a stainless steel liner for the flue? Since we’ve been quoted a range of $1,500 to $3,000 for the flue liner, should we just simply put that money into a high efficiency system? Has anyone had similar issues with replacing a boiler? By the way, we are getting boiler estimates, but the high efficiency quotes seem sky high to the gas boilers ranging from 82-85 percent efficient. Help, and thanks in advance! By the way, I've learned a lot from all all the previous posts...what a gold mine of information!

Re: Oil to Gas Conversion with added chimney problem


My preferance has always been to use the chimney before going into a side vent.

I would recommend you get a few more estimates for an aluminum coil to be run up the chimney--it seems to me it should be a lot less than $1.5k to do this.

If it DOES come to a side vent---try to get it as high as possible on the house to avoid any exhaust odors wafting thru open windows or down to the yard in milder months---some staining of the siding is always a possibility with a side vent, thus the chimney is preferable.

Don't ignore fuel oil dealers in your search for bids---they usually charge less & are licensed to install gas heating equipment---it's in your interest to get at least 6 bids on this deal---you'll get a better price the more bids you take.

Click onto my name to get past posts that list a wide selection of good gas-fired boilers.

The efficiency you quote of 85% AFUE is "good, but adequate" in today's gas-fired boilers---this would be for an entry level pin-type boiler ---the next step up is a 3-pass boiler, where the heated gases are circulated longer in the combustion chamber--88%-90% AFUE--the highest step is a condensing, variable output boiler @ 95%-97% AFUE efficiency.

Any one of these boilers should produce a 30% drop in your fuel usage (if not more), so the top shelf boiler is not really essential---in fact the top shelf boilers need more adjustment & thus more service, & cost a lot more because their combustion chamber is made of stainless steel or aluminum, instead of cast iron.

Home Depot is selling a good cast iron Slant/Fin boiler (Liberty/pin-type) for $1300---use that as a starting point in your negotiations.

A 40 gallon indirect hot water heater as a companion to the boiler is strongly recommended for about $700.

Besides Slant/fin I like Buderus, Burnham, Crown, Dunkirk, Munchkin,Lochinvar, NTI, Peerless, Smith, Triangle Tube, Utica & Weil-Mclain.

Each one of these mfgrs sells all 3 levels of boiler--adequate range, mid-range & top shelf (condensing) range.

Re: Oil to Gas Conversion with added chimney problem

Thanks so much. Since you first recommend using the chimney, what do you recommend for the stainless steel liner: insulation added between the liner and the old chimney flue tiles, or no insulation between the liner and the flue tiles? I need to add that a 2-ft piece of tile fell (within the flue) last year. I'm told that the oil exhause is extremely corrosive and will do that to tiles. Anyway, one of the chimney specialists recommended the insulation "to keep the temperture warmer in the higher part of the chimney to better allow the gas exhaust to properly vent up the remainder of the chimney." Our home is a 2-story colinial and the chimney extends above the roof line. By the way, I'm glad you recommend an indrect hot water heater, as we were considering a hot water heater as well. However, our existing water heater is across the basement from the boiler. Do you think that is a problem for the existing plumbing work?
Thank you again for your expertise. It's greately appreciated.

Re: Oil to Gas Conversion with added chimney problem


I guess I'll leave it up to the installer to determine the LABOR charge for installing the flex vent thru the chimney, but my catalogs list this 2-ply 6" dia. aluminum double wall insulated Z-flex coil for $125 for 12'---if your flue diameter is 8", that would cost a little more.

The typical chimney is 25' & if there are any bends, it may require a little more labor & coil length--also chimney caps & connectors will probably bring the total coil equipment cost to <$400--that's why the estimate sounds way out of line---check patriot-supply.com for another quote---or Google Z-Flex insulated flue liner.

Aluminum flue liners are used for gas-fired equipment & stainless steel for oil-fired equipment---and get some more estimates from other installers.

Even though you've had a piece of chimney tile fall & the masonry chimney is old, once the aluminum coil is installed, the internal condition of the masonry doesn't really matter---the aluminum coil is sealed & no noxious gases will enter the home once it's installed---the draft up the chimney should be greatly improved.

The indirect hot water heater can be placed anywhere in the celler (or 1st floor for that matter)---it's always best to position the indirect HWH in the basement directly under the water piping supplies for the tub/shower/bath sink & kitchen sink/dishwasher/clothes washer---these fixtures are often clumped together in most homes, even for the 1st & 2nd floor (one on top of the other)---the idea is to avoid long runs of supply piping between the HWH & the taps that will make you wait for the hot water to arrive at your sink or shower & thus waste water waiting for the hw to arrive---a wise placement of the indirect will cut down on hot tap water heating bills considerably.


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