Boiler replacement sanity check

repleo

I would really appreciate some unbiased feedback from the contributors here on the type of system to replace my 25 year old oil boiler. (details below). We live on Cape Cod, MA and getting a contractor who will even return a call is a problem and finding one who is knowledgeable even tougher. I mention that because the reviews on most of the contractors in the area are full of cases where the technicians couldn't get even new installations to run properly. Simplicity is a significant factor, so I think I have decided on going with a standard gas boiler (cast iron ?) for the reasons below, but would really appreciate a sanity check and advise on cast iron vs any alternatives in regular boilers. Also thoughts on adding an indirect domestic hot water tank vs possible alternatives. Not sure how we currently get domestic hot water. There is no storage tank or separate heater, but we always seem to have sufficient hot water for our needs from the existing setup.

Reasons for wanting to change are : (a) want to change before the current boiler dies; (b) we may be selling the house next Spring and don't want to turn off buyers with a boiler that is visibly and functionally on its last legs; (c) if we don't sell in the Spring we will be settling in for the long haul and may as well get the benefit earlier than later; (d) I want to get rid of the oil tank in the basement. We will be converting part of the basement if we stay. I expect the change from oil to gas alone to reduce my fuel cost from about $2200 to under $1000 so additional small (+/- 5%) incremental efficiencies are not likely to be financially significant.

My question is, should we go with a high efficiency (>/= 95% AFUE) condensing boiler or a standard (probably cast iron) gas boiler. I know this is an often contested subject here but the difficulty in finding reliable service may alter the equation.

As I understand it, the higher efficiency of condensing boiler doesn't start to kick in until the return water temperature is below 130 degF. If the system is running that low, the output from my Slant-Fin baseboards will be cut by at least 40% or 65% at 110 degF, (the lowest rating for Slant Fins) so it is probably not going to be able to heat the house properly. The charts I have seen indicate that condensing boilers are only about 89% efficient at 110 degF or only about 4% - 5% better than a good non-condensing boiler running at 170 which would only translate into about $40 annual savings.

There are MA incentives plus Fed Tax credits that would amount to $2600 plus interest free loan for the high efficiency system but this seems to get eaten up by the premium the contractors charge for these systems plus they seem to require more maintenance. Draining the condensate during the winter could be a problem with icing up on the driveway. I am 70 years old but longevity of the system is still a concern.

Details
1144 sq ft Ranch over unheated full basement built to minimal 'Contractor' standards in 1973 on Cape Cod, MA. Currently heated with a 25 year old 100,000 BTU +/- Burnham cast iron boiler through 60' of Slant Fin baseboard. I have run heat loss calcs on Heatload.net and come up with heating load of 27,000 BTU so per Slant Fin these would need to run at at least 160 - 170 degF average to meet the heatload. I have had a MassSave energy audit and have done all of the recommended upgrades except the boiler. We have recently installed a gas fire insert and two split system AC/Heat pumps. We use the gas fire a lot and find it will keep the whole house comfortable on milder days but we turn up the boiler when needed. We expect our oil costs to be approx $2200 for the year plus a much needed service plan at over $600.

leonz

Novice homeowner here, a bit younger than you.

Have you compared the cost of changing the slant fin for
steel or cast iron radiators for more thermal mass?
You would have much more water for thermal mass and
you could operate your current boiler as is with just an
annual cleaning. Thermal mass is your friend.

Mad Dog_2

I strongly suggest you reach out to Charlie From Mass.  Charles Garrity out of Springfield.  He'll set you straight.  Mad Dog 🐕 

EBEBRATT-Ed

Not sure @Charlie from wmass would go to the Cape except for a needed vacation. 2 hours to the bridge from Springfield + another hours travel on the Cape depending on where you are.

@repelo to answer your question on mod con versus CI....there is no answer. This has and continues to be debated and probably will not be settled for a few more years if ever. They both have their good and bad points.

Most important is to find a quality installer.......that is the most difficult thing these days. Have you checked "find a contractor on this site"?

Good for you for doing your homework on the heat loss calculation. Your old boiler is horribly oversized.

Since you don't know where your domestic hot water comes from you oil boiler probably has a tankless coil built in. Gas boilers do not come with a tankless coil (they do in a mod Con Combi) but you don't want that in your application.

I would recommend with your small heat loss a CI gas fired boiler with an indirect water tank for DHW. A

40 or 50 gallon tank will be large enough in most cases.

also make sure the gas company can supply the needed gas. MASS in some locations is putting the stop on gas installations. You need a letter of availability from the gas company in any case in MA

Charlie from wmass

If you were going natural gas I would go with a condensing mod con boiler as even the cast iron boilers still have electronics and controls that seem to be becoming more problematic time. The days of sticking in a boiler and coming back in 40 years because it finally started to leak are gone. If you are going to install a high efficiency boiler look up the rebates as I have heard that they are going away in March.

Hot_water_fan

With that low of a heat loss and that much baseboard, you’ll be able to condense almost all the time! 

repleo

Thanks Ed. Yes I had the gas service sized for future boiler, stove, drier and generator so I should be OK. I was wondering about the boiler size. I infer from your response that a right-sized boiler would be more efficient as well as cheaper to install. I might add a bit to allow for a future partial basement conversion.

Charlie, I will definitely look into the rebate dates. I did see some that were only good until the end of 2023. All of the numerous problems I have had with my current boiler have been controls or burner related so I really would like to get something simple and reliable even if it at the expense of efficiency.

Leonz - I really don't want to go to the hassle of changing the radiators since the boiler needs to be replaced anyway but thanks for the suggestion.

Charlie from wmass

The highest deficiency would be with a boiler sized for your heat load that is a condensing modulating boiler and the use of a 40 to 60 gallon indirect water heater. If you did decide on a chimney vented cast iron boiler I would suggest the use of an indirect water heater. If you are not using a chimney vented natural gas boiler you really should just go with a modulating condensing boiler because it has all of the efficiency without any more complexity then having a side wall vented cast iron natural gas boiler.

WMno57

Another way to switch from oil to gas would be to have someone install a gas burner in your current oil boiler.

Charlie from wmass

@WMno57 the original poster of this thread has already indicated issues with the condition of the existing oil boiler.

WMno57

He didn't specify what those issues were.
My oil boiler had a gas burner installed. 50 years ago. It has outlived both the owner, and his son. His grandson sold the place to me. I was sure I was going to replace it before my first winter. That was five years ago and before I found HeatingHelp. The grandson's grandson was bow hunting my property this year. Maybe when I kick the bucket, the grandson's grandson will buy the place back from my estate.
Electronics and control boards, hah! I was watching a youtube today about the new cub cadet lawn tractor. No choke or throttle cable, just a dial on the dash that talks to the electronic brain, which talks to the electronic carburetor.

Charlie from wmass

@WMno57 I have no idea why people consider it such a badge of honor to have equipment like that running still. Just because it's old and still running doesn't mean it is well made. I hae a 104 year old boiler with the same conversion burner in my basement. I rent the property I live at from my mother-in-law. I have no honor or nostalgia related to having such an antiquated piece of equipment running. When the day arrives that my wife and I make the decisions regarding asbestos abatement it will be gone within a couple weeks. You see a long-lasting piece of equipment, I see a collosal of waste of fuel. But as the kids say "you do you boo"

WMno57

Charlie, you crack me up. My 75 year old boiler has proved it was well made. I see mod-cons (boiler in name only toys) as a colossal waste of money. I suppose its nice they are light weight when they have to go down and back up the basement steps every 10 years. I do feel bad for you pros that have to install and repair today's junk (assuming you can even get the proprietary parts from the supply chain). It must get old explaining all this to non technical customers who buy a new Honda or Prius every five years. My 20 year old Chevy V8 now has almost 10,000 hours (It has a Hobbs meter built into the powertrain control module).
This week there will be both new mod-cons and new 7 year life (chloride soluble cast iron?) Burnhams installed. Delivered to the jobsite by Fords that like to blow spark plugs out of the heads. Excellent chance my geriatric boiler and 2001 Chevy truck will outlive some of them.

WMno57

My boiler is almost as old as Biden

WMno57

and almost as old as Trump too

Hot_water_fan

It must get old explaining all this to non technical customers who buy a new Honda or Prius every five years.

HA! A Sunday evening laugh, thank you

WMno57

There is something to be said for new equipment that saves so much that it pays for itself. I like to make fun of the Prius (I grew up in Oldsmobileville, Michigan in the 1970's) but Toyota hit a home run with all their Hybrids and Atkinson cycle engines. If someone drives 50,000 miles a year, they are hard to beat. Very popular with ride share operators. By the time you have to replace the battery (red triangle of death), you might have saved enough in gas to buy a new one.

Maybe. Got to get out the pencil and crunch the numbers.
I don't see repair costs getting cheaper in our future. Lack of skilled labor. Supply chain problems. Proprietary parts. Inaccessible design. It takes 10 hours to R&R the heater core on my beloved Chevies. Sometimes you just want to buy a product that flat out works. Operating costs be damned. No drama.

Hot_water_fan

Ha if you think a Toyota or a Honda is unreliable and people sell them every 5 years, I want some of whatever you’re having. The hybrids are easy buys: for example, you pay about $1-2000 more for the RAV4 hybrid and save about 100 gallons per year at 12,000 miles a year. That’s cheaper than buying at the pump and they hold their value. 

WMno57

Hybrids and electric cars hold their value until the battery dies. Then they're e-waste.

clammy

Stepping on the other side ,unless your system is designed for operating in low temp at design temp and the type of heat emitter warrants it like cast iron rads or baseboard then possibly but if it’s wall convectors give up that ghost . Personally I would stick to a cast iron have your chimney lined if needed and have a hydro level electronic aquastsat which I believe has the capabilities to do outdoor reset and an indirect hot water heater built in just add a aguastat and a circulator . I ve said this before and I’ll say it again if the system was not designed to heat at design day at the most of 160 or lower I feel it’s a wash when yearly service and maintance are factored in and availability of parts as for cast boiler there parts are generic and even a oem type control can be replaced and re wired in a pinch ,while w a mod con it’s oem or nada no after market will work and your left hanging . Plus how much garbage parts are contractors suppose to hold on to for mod con it kinda never ends and besides from stocking basic stuff for them ,how much money should one have invested in parts stock for equipment that most after 2 yearly cleaning really are tried of paying for something most see no valve in until it’s doa and needs replacement . I kinda look to England and how often it’s stated there wall hung boiler are replaced ,I think people change there cars less ,it’s great for a turn around re cycle process to keep bussiness and the economy going and of course the land fills . The other possibility and thoughts are is the guy or company that’s installing it really care about what there doing or is it all just money ? You would be amazed to find the truth but it’s usually the money cause after a few years they usually don’t care and hate the bussiness but can’t get out cause of the money ( scar face ) remember money makes the world go around the world go around