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new oil boiler and sizing

We're getting a new oil boiler to replace what looks like a 40 yr old oil boiler. Just bought our first house, which was built in 1970. It's a 2000 sq ft colonial, 2 floors, 1/2 finished basement, 4BR, 1.5 bath. Original 19 single pane windows with storm windows, no sliding doors. Two entry doors both with new storm doors. Attic could use a bit more insulation, but it's not awful. I'd say the home has average insulation. I have not done a heat loss calculation, but if I rough out about 50 BTU per sq. foot, that's around 100,000 BTU. We'd want the option of adding an indirect water heater at a later date, but not yet. It's a chimney vent. House is in New England in the 6500 heating degree days zone.

I have about 5 quotes for boilers. None of them did a HLC and only a couple of them actually walked around the house to check the hot water baseboards and the rest.

The quotes I got include Buderus models G115/28 (98,000 BTU), G115/34 (120,000 BTU) and a G215/3 (134,000 BTU).

The G215/3 guy was recommended by neighbors & has the lowest quote, but I wonder about his boiler choice. He said he wasn't going to do a Heat Loss Calculation and he chose that boiler based on his 30 years experience and what was already there. (But who knows if the original boiler was sized correctly.) I pressed him about his choice concerned about it being oversized and he talked about how he can ratchet it down to 80% of the output anyway we'd need that size for future indirect water heater. I asked why his nobody else had quoted a G215 model and he said it was because the G115 models come put together already so they don't have to do assembly like he does with the G215. I sort of feel like I was getting the "don't you worry about that pretty little lady" treatment, but hey - what do I know? Any merit to his arguments?


Re: new oil boiler and sizing

You'll be hearing from Nashua Tech for sure, he's the Man, but my two cents says a HLC should all ways be done regardless of what is already there. Good Luck!!! :)

Re: new oil boiler and sizing


It's hard to imagine that the prospective installers you have talked to so far have not done a heat loss calculation----a HLC is the only way to accurately determine the appropriate size of the new boiler.

There are some rudimentary methods of estimating HLC, and if you Google "heat loss calculation" you can find an online HLC that may cost $50 or so & may take an hour or so to complete.

Basic estimates are usually based on 40 btu/sq.ft, instead of 50, thus in your case, 2000 X 40 = 80,000 btu/hr as the boiler size.

A more accurate, if still imprecise way is to calculate the total footage of all the baseboard in the house---each ft. of baseboard puts out approx. 560 btu/hr of heat---thus, if you have 125' of baseboard in the house: 125 x 560 = 70,000 btu/hr as the approx.appropriate new boiler size.

If the present boiler is as old as the house, then it should be replaced--there have been considerable design improvements in heating in the past 20 years that will have you see a 30% drop in fuel usage just by putting in even a basic cast iron boiler.

I assume natural gas is not available in your area.

It's not uncommon to test very old boilers & find that 1/2 the heat is actually going up the chimney as wasted heat---and the older boilers rely on much higher flue temperatures.

Buderus is an excellent boiler, but if the quotes are too high, there is always other excellent brands.

You should make a decision on your insulation update BEFORE you have the new boiler installed---this is very worthwhile & costs only a few hundred $$$---any money spent on more insulation will pay for itself in lower fuel bills and lower cooling bills in summer---R19 for exterior walls & R40 for the attic---they have a truck that blows the insulation into the walls from the outside & most jobs are done within one day---consult the Yellow Pages under "Insulation Contractors".

There are 3 basic types of boilers on the market (from lowest price to highest price):--standard cast iron, cast iron 3-pass boilers, and stainless steel/aluminum condensing with variable speed--all are rated by efficiency (the percentage of heat delivered for each gallon of oil or therm of natural gas---expressed in AFUE percentages---standard cast iron averages 82% to 85% AFUE efficiency; 3-pass approx. 87% AFUE & condensing 95% to 97% AFUE.

You will get a tax rebate if you buy an Energy Star boiler that has at least 85% AFUE efficiency (most boilers qualify for this).

The condensing units are relatively new to the market & are still getting some of the kinks out---they probably won't last as long as cast iron or 3-pass.

I would strongly recommend you consider a 3-pass boiler (87% AFUE) for reliability, high fuel efficiency and durability--I would recommend Biasi B10, Burnham MPO, Crown Freeport, Dunkirk EV or Empire, Energy Kinetics 2000, Peerless PRO/WBV, or Slant/Fin Eutectic---but even if THESE bring too high an estimate, a standard cast iron boiler by the same mfgrs would be fine.

Some simple HLCs are below.


The main strategy in replacing a boiler is to get at least 4-6 estimates---sources can include friends, neighbors & relatives who have recently had a new boiler installed---also check the Yellow Pages under "Heating Contractors" and "Fuel Oil Dealers", and "Heating Equipment-Parts"---the last one would require contacting (in person is preferable) the local wholesalers who sell the boilers & associated heating equipemnt---ask to talk to the counterman & request 2 or 3 referrals to local boiler installers.

Another resource is local real estate dealers---many of them own rental property & must have a tech to service the heating equipment----also, local home builders---who must have heating equipment installed on a regular basis.

I would recommend you consider telling the prospective installer that you don't have the money for an expensive boiler installation---perhaps your husband is out of work, etc.---you have to set the stage in the negotiations so that the installer will offer you an excellent boiler, at the right size, for the least amount of $$$---something like, "My husband is out of work now, can you give me a lower estimate on this?" or "Can you give me a quote for a basic boiler?"

The prospective boiler installer you eventually choose must be polite, courteous & helpful in your decision-making---willing to answer any questions you have and offering you alternatives if an item is too high---reject anyone who is rude, tries to "pressure" you to make up your mind "by the end of the week", or harbors any similar attitudes---you'll only have trouble with this type later on down the road---unfortunately, some installers & service people think they have total control over your heating equipment---which is not true, you can change oil dealers, service contracts and repair persons any time you want.

With oil heat, you're not tied to a single supplier (as with the gas co.); a number of people install 4 oil tanks in the cellar (room permitting & codes permitting) & buy all their oil in July when it's least expensive--there are now independent oil burner/boiler repair persons where you can pay an individual service fee plus parts instead of being bound by a service contract---Yellow Pages "Oil Burners--Repair & Service".

The indirect hot water heater should be seen as a companion to the boiler ($700); usually 40 gallon capacity, it is set up as a zone & the hot water is heated by using the boiler water---this is the most efficient way to heat hot water---best units have a stainless steel inner tank: Triangle Tube Phase 3, Weil-McLain Gold Plus, Lochinvar Squire, TFI Everhot.

The fact is, there are scores of boilers out there (even entry level boilers) that cost the installer $1200 to $1500, and $600 for the indirect hot water heater---naturally, the installer is entitled to labor costs, etc.---a basic cast iron boiler & IHWH will cost the installer $1500 + $600 + installation labor $1000 = $3100.

I can see paying $4k or $5k for an install, because often additional items like a chimney insert ($1k) may have to be installed & the cost creeps up--but I can't see paying considerably more than that.

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