Home>Discussions>PLUMBING>Oil to Gas Conversion Questions
3 posts / 0 new
Last post
Oil to Gas Conversion Questions

We bought a historic home in MA about a year ago and just went through our first winter. It's a 2,600sf house and the oil bill is about $800/month, which is extremely high compared to everyone we know. The oil boiler has problems and was supposedly fixed before we bought the house, but we feel that it's time to make a drastic change and convert to gas. The gas line is already brought right next to the house.

We've been getting quotes from 4-5 plumbers and it's been a frustrating experience, because it's almost impossible to make an apples to apples comparison. Some plumbers provide broken out pricing, some don't. None of them discussed equipment brands with us. Can you provide your input on the following issues:

-90% and higher efficiency gas boilers are supposedly more prone to breaking down and more difficult to fix due to electronic parts. Is this true?
-Indirect heater vs. direct? One plumber recommended direct so that we don't fire up the boiler to get hot water during the summer. Others recommended indirect.
-National Grid's "value plus" installers and discounted equipment program. Has anyone done these before?
-We are planning to apply for the Mass Heat Loan program (already had the energy audit done). Anyone with experience with that? The application required heat calculations which no plumber has given to us yet.

Thanks in advance for your input...

Re: Oil to Gas Conversion Questions


I'm not completely convinced that you should yet switch to gas heat without exploring things a little more.

How many gallons of oil are you burning during a heating season (Nov. to March)???

It would depend on 1) how old the oil-fired boiler is; 2) if it's still efficient, is tuned up, has annually been serviced; 3) that the exterior walls have insulation; 4) that the windows have storms or double panes; 5) that the attic has R30 or R40 insulation.

It's a waste of money to buy a new boiler if the main problem, for example is inadequate insulation, or an inadequately tuned oil burner (especially the size of the nozzle and having a combustion adjustment done with a combustion analyzer)---an analyzer measures the flue gases while the boiler is firing & the tech precisely adjusts the amount of air/fuel mixture; a smoke test is also done to reduce the amount of soot buildup to near zero so the boiler burns cleanly throughout the heating season; several oil burner nozzles are tried to get the most efficient one.

A very rough aproximation of how much heat is required to heat the house is done by multiplying the total square footage by a multiplier (between 30 and 60--30 being a very tight house, 60 being a very loose house with a lot of air leaks & no insulation)

Thus 2600 X 40 = approx. 100,000 btu/hour needed to heat the average house that has good windows/storms but may need some insulation blown into the walls.

Such a house is a good candidate for more insulation, newer windows & attic insulation that reduces the heat load down to 80,000 btu/hr and the oil usage down to 800 gallons or less for a heating season---800 X $3/gal for oil = $2400 per heating season.

Can you indicate how old you think the boiler is, or post its make and model number---what are the oil techs saying when you ask them about boiler performance???

What was the result of the energy audit???

If you Google "heat loss calculation" you will get several free HLC's on the internet that will give you a more accurate estimate of the btu/hour you need to heat the home.

Don't forget to get several estimates from oil dealers if you decide to switch to a gas-fired boiler--oil dealers often charge less & are licensed to install gas equipment; also check the Yellow Pages under "Heating Contractors" to get additional names--a qualified prospective installer should always do a heat loss calculation (Manual J) while in your home, & be able to tell you whether your present boiler is efficient, and properly sized for the house.

Gas-fired high efficiency boilers operate on a condensing principle, where they have an additional combustion chamber that converts the high hydrogen content of the burned natural gas to water vapor (condensation) during the combustion process which releases additional heat that is lost in conventional cast iron-type boilers.

These "condensing boilers" are made of stainless steel innards, instead of cast iron, & can be problematic during the first few months of ownership, until the bugs are ironed out--but the savings at 95% AFUE over the conventional 85% AFUE of normal boilers is worth the expense if you intend to stay in the house for the forseeable future ($8k to $10k); it will take 5 years or so for you to recoup your investment at these prices.

Some condensing boilers have an aluminum combustion chamber---if you happen to have hard water in your area, go with the stainless steel version to avoid the corrosion which often occurs in aluminum units.

On the other hand, a conventional gas boiler would cost approx. $5k for an install (85% AFUE), but unless your present boiler is considerably inefficient due to age or other issue, the only advantage would be less maintenance, since gas burns cleaner than oil & the boiler requires much less routine cleaning services.

I would recommend an indirect HWH over a direct, the amount of fuel burned during the summer is minimal & these units are highly insulated--they use the hot water from the boiler as a heat exchanger to heat the domestic HW--this is considered a very efficient way to heat domestic hot water-- a 40 gal unit is considered for most cases.

I would be careful of any "value plus program"--they often offer you the least efficient unit they have--try to get them to go to the next step higher in quality for the same deal as to the brand name of each boiler offered.

I like Triangle Tube Prestige and their companion TT Phase 3 indirect; I also like boilers by Crown, Dunkirk,Hydrotherm,Peerless, Slant/Fin,Utica,Viessmann (expensive), Biasi and Weil-Mclain.

Other indirects: by HTP super stor,weil Mclain Gold Plus,Lochinvar Squire,Viessmann Verticell (expensive).

Google "boilers product list" for a list of hundreds of Energy Star boilers that give their AFUE and model numbers---try to download the March 15 2010 updated version using the "download as HTML" version if your system doesn't support the XLS version.


Re: Oil to Gas Conversion Questions

Thank you very much for the reply. I will definitely consider your recommendations. During our home inspection, we observed water actively leaking out of the boiler and there was little evidence of recent maintenance, since the previous owners did not live in the house for a few years. The inspector said that the boiler was gone and had to be replaced. This became a problem during closing negotiations, and the sellers agreed to "fix" the boiler. We do know that the tankless plate was replaced and it doesn't leak water anymore, it also appears that they spray painted it, so I can't read a brand name/model. The oil tank is also dripping at its pipe outlet and the oil company refuses to cover the tank in their service agreement. With the gas being right outside, the incentives and interest-free loan, it seems that getting a new gas boiler is the way to go.

The energy audit determined that the house was decent in terms of thermal insulation and windows. The windows are old, but they do have storms. The auditor recommended further attic insulation and filling in cracks in basement ceiling with spray insulation, in addition to getting a new heating system. Another problem is that the entire house is a single zone and we will split it up into multiple zones as part of this work.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.