Should I replace ~70-year-old boiler?

[gadolphus32]

I recently bought an old house. It has a gas-fired hot-water boiler that was installed in 1949. So far, the boiler appears to run without issue. It has averaged 6-8 hours of running time per day during the winter months.

My question is whether we should replace the boiler just because it is so old. Part of me thinks that I can't count on something installed almost 70 years ago to keep working reliably. And if it's going to break at some point, I'd rather replace it this summer than wait and have it inevitably break down on the coldest day of an upcoming winter and force us to do an emergency replacement. It's also not clear to me how easy it would be to find parts to repair this boiler if just one part of it broke at some point.

However, the other part of me thinks it would be dumb to pay to replace something that's not broken, and that a boiler manufactured in 1949 -- before the age of planned obsolescence -- might have significant life left in it yet, even though the lifespan of modern boilers seems to be more like 30 years.

So I'm wondering how much you guys with lots of boiler experience would bet on an old boiler like this one continuing to work for a long time to come -- and if there is anything in particular I should do to keep it working.

A few other considerations:
-We plan to stay in this house for a long time -- decades, hopefully -- so I'm looking to make whatever choice is wisest for the long run. I'm not just looking to get another few years out of it and then make it the next homeowner's worry.
-For what it's worth, I've had a couple of guys from the local heating company take a look at it. Neither found anything obviously wrong, but I'm also not highly confident in their level of experience with such an old system.
-We have a 2500+ square foot house with almost no insulation and the original windows. While we could afford to put in a new boiler right now, I wonder if spending that money on insulation and tighter windows would be a better investment over the long term.
-The boiler appears to have asbestos inside it, so that is a point in favor of just leaving the thing alone for now and hoping for the best. (That said, I think it would be possible to install a new boiler alongside it and keep the current one in place in order to avoid having to deal with the asbestos.)
-A chimney guy who inspected the flue that the boiler vents into told me the chimney needs a new liner, which would cost $4k or so. I don't trust the guy because he wouldn't actually show me the pictures that he took purportedly showing the damage inside the flue. But I gather that if this really is an issue, installing a new boiler would allow me to obviate it, because I could (I think) have the new boiler vent out a pipe that goes out of the basement wall or something instead of the chimney. (The chimney is not used for anything other than the boiler venting, so there'd be no need to repair it if not for the boiler.)
-I don't have a good sense of what kind of risks come with a boiler from the 1940s. I assume it lacks important safety features (like something to shut itself off before overheating and burning my house down), which would be a point in favor of replacing it, but maybe I am wrong. I just don't know much about how far boiler technology has come in the past half-century.

 

[Sylvan]

I just replaced a boiler installed in 1921 (HB Smith) . The only reason I had to replace it was the people shut the heat while they were away and the building had a total freeze up

Generally hot water boilers last a lot longer then steam, less thermo stress for one thing and a closed system does not allow oxidation to kill the system

Also a boiler is a pressure vessel so adding additional safeties such as a LWCO with manual reset, high limit safety ,flame roll out are an option

The only problem is the lack of efficiency the older boilers have as fuel was cheap in those days.

My own boiler another HB Smith was installed in 1921 went from coal to oil and I replaced it with two small gas fired boilers as I like redundancy in heating when possible


My home has 11 rooms over 10 (2 story plus huge basement) so I opted to have the floors isolated (with piped in by pass) and installed nonelectric zone valves on each CI rad

 

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[Kebo147]

I have one high pressure steam boiler still in service from 1896. I rebuilt the unit about 10 years ago to meet all modern day safety standards. Some pics would be most helpful, but there weren't many parts from back in the day that cannot be replaced with a modern equivalent. The boiler you have now was also sized for a house with no insulation and single pane windows. At this point you are throwing away BTUs 2 fold, up and out the vent for an old boiler and out the walls, windows, etc. I would insulate and take care of the windows. Then you will need a smaller boiler when it's time to replace...possibly half the size! Also keep in mind modern boilers are vented in PVC, typically having an exhaust and an intake of 3". There are lots of options for how to vent new boilers.

 

[rjbphd]

Whatever you do, hire company that have extensive experience with hydronic heating system. . Not just any hvac company because it's heating nor plumber because it's contains piping. I'm in middle of project, redoing the boiler and near piping due to butchered by forced air company, resulting uneven heating and high fuel consumption.

 

[gadolphus32]

Thanks all of the responses. These are helpful indeed. It sounds like as far as maintenance and reliability go, I do not have anything in particular to worry about, so that is a relief. But maybe it would save money in the long run to install a more efficient boiler.

I think we'll keep that thought on the horizon, but move forward now with better insulation and windows and see how much of a difference they make in the heating bill -- which is actually not as bad as I expected for an uninsulated house in upstate New York. They built this thing with really thick walls, so I think that helps. But I'm sure insulation and updated windows would help much more.

When we do upgrade the boiler I'll certainly make sure we hire someone who actually knows these systems. I already wasted money once getting a "pre-winter inspection" of the boiler by a local HVAC company. They sent over a guy who basically turned it on at the thermostat, told me "it works" and charged me 100 dollars. He then asked, while standing next to a radiator, whether my radiators were steam or hydronic. Clearly, he didn't actually know a thing about the heating system.

 

[Dana]

Spending the money on tightening up & insulating the place is definitely a better long term investment. If the house leaks a ton of air and has almost no insulation you should be able to reduce fuel use by more than 25% with selective upgrades, starting with blower-door directed air sealing prior to (or as part of) insulating. Don't insulate without air sealing first, or you'll risk creating moisture problems along exfiltration paths.

If you have wood sashed windows that are still in decent shape, fixing up any weatherstripping then installing tight low-E storm windows is a better investment than replacement windows. Harvey Tru-Channels are the tightest in the industry, and they have a hard-coat low-E glazing options, but the better grade Larson's (sold through box store distributors) don't suck either if you avoid their absolute cheapest models.

You can use the existing boiler to establish an upper bound on the actual heat load using the boiler as the measuring instrument. A 70 year old gas-burner might have had a steady state combustion efficiency of 80% when new (figure it out from the nameplate BTU numbers), but being oversized by more than 3x and having 7 decades of erosion on both the fire & water side of the heat exchanger plates don't assume it's any better than 70%. If it's a steam boiler it's likely that you're only in the 60% efficiency range. (But yours is pumped hot water, right?)

 

[gadolphus32]

If you have wood sashed windows that are still in decent shape, fixing up any weatherstripping then installing tight low-E storm windows is a better investment than replacement windows. Harvey Tru-Channels are the tightest in the industry, and they have a hard-coat low-E glazing options, but the better grade Larson's (sold through box store distributors) don't suck either if you avoid their absolute cheapest models

That's good to know. I actually am not very keen on replacing the original windows as I like the look of the old wood frames, which are stained to match all the the other ornate woodwork in the house. We already have storm windows, but they're not in good shape at all. The window company guys tell me just to replace the entire window with a new one and then there's no need for storms at all, but that's clearly not unbiased advice. If I can invest in really good storm windows, I'd much rather do that.

You can use the existing boiler to establish an upper bound on the actual heat load using the boiler as the measuring instrument. A 70 year old gas-burner might have had a steady state combustion efficiency of 80% when new (figure it out from the nameplate BTU numbers), but being oversized by more than 3x and having 7 decades of erosion on both the fire & water side of the heat exchanger plates don't assume it's any better than 70%. If it's a steam boiler it's likely that you're only in the 60% efficiency range. (But yours is pumped hot water, right?)

Yep, it's hot water. I actually was disappointed at first that it was not steam, since I once lived in an apartment with a steam system and loved the moist heat it put out (and also the faster recovery time -- with hot water it can take hours on a cold winter morning to get the house comfortable, though the Nest that I installed does a good job of figuring out how early to start the system so that it's warm by the time we wake up), but I'm gathering that when it comes to maintenance and longevity, hot water is better.

 

[Dana]

Being in NY you probably have Harvey contractors near you for help figuring out the storm windows. The hard coat low-E glazing needs to be called out- it's more expensive, but it also has quicker "payback" than clear glass storms. Theirs are hands-down the best-in-class for air tightness, and it'll be less than half the cost of a code-min replacement window.

Air sealing and insulating sash weight pockets might be in order too, which could be done from the exterior if you don't want to mess up the antique interior trim.

When assessing the insulation issues don't neglect the foundation/basement. Current IRC code-min for basement walls in most of NY is R15 continuous insulation (R10 in US climate zone 4= Westchester, NYC, & L.I.) The expensive way to do it in a low mold-risk way would be 3" of closed cell spray polyurethane, but you can also get there on the cheap with reclaimed rigid foam board, assuming it's a poured concrete or CMU/cinder-block foundation. Field stone foundations may need a combination of spray foam + insulated studwall to do it both economically and without creating a mold farm.

Even if you never plan to fully condition the space and turn it into living space, an uninsulated foundation is a very LARGE heat leak, especially when you have an oversized high-mass boiler down there along with large diameter heating system plumbing. I've seen houses where insulating & air sealing the basement walls reduced the fuel use by more than 25%. (In my own house it was something like 15-18%, but I don't have a beastie-boiler with large diameter distribution plumbing keeping the basement hot during cold spells.)

If you keep tabs on the heat load with fuel-use calculations you can track the amount of improvement you get out of different building envelope upgrades, and when it's finally time to scrap the beast you'll have a solid sense of what the true heat load is (or at least a solid upper bound), to avoid oversizing the replacement. With a modulating-condensing boiler and high-mass radiation you'll get more out of tweaking the outdoor reset curve than you would get out of deep setback strategies, but you'll want to size it so that it can modulate nearly continuous burns through the heating season, with very little on/off cycling. When the time comes there are some fairly inexpensive and effective fire-tube mod-cons with high turn-down ratios out there suitable for replacing a high-mass boiler in a high-mass radiation system, cheaper than replacing it with another cast iron beast.

I haven't kept track of what's available, but in the past NYSERDA has sometimes offered fairly substantial rebate subsidies for both insulation and HVAC equipment upgrades, which may alter the order in which you tackle things.