Help: Very Old (c. 1970 or earlier) Williamson Gas Furnace

matt_v_824 · March 28

My wife and I are under contract to buy a house with the Williamson furnace pictured below. As best I can figure, this beast was manufactured no later than the early 1970s. It still runs well, from what I can tell. I am just trying to get a feel for what we are buying into here. My understanding is that furnaces this old were "overbuilt" but simple in design and easy to maintain.

Model #: 72415.

Serial #: 171 (not a typo, lol)

mattmia2 · March 28

that's probably 50's. 20's or 30's would be very old.

it is good until the heat exchanger rusts out. sometimes they have asbestos paper or corrugated asbestos paper insulation inside the jacket so that is something to look out for.

that register on the plenum that close to the burner isn't allowed but closing that off isn't a big deal.

i can't tell what sort of gas valve it has, if it has an integrated pilot or not. i see something connected to the pilot tap on the manual valve but that might just be a pilot lighter.

in general if the heat exchanger is in good shape it could last 6 months or 40 years.

what you don't want to do is change the burner. if you change the pattern that heats the heat exchanger from what it has been used to for the past 70 years it will crack.

EBEBRATT-Ed · March 28

If you buying a house get some budget figure quotes from a couple of contractors and have them knock some $$$ off the price. Just give them the furnace BTUs and the house square footage. If you have a decent home inspector he should be telling you that.

That furnace may be 100% ok but nothing lasts forever.

Warm air furnace usually last 20 years.

I agree with @mattmia2 maybe mid 50s-mid 60s.

How old is the house?

Doesn't look like the ductwork/plenums have ever been changed. I would bet that is the original furnace.

AndythePlumber · March 28

I would get yourself some quotes on replacement in your area. You’ll know where you stand. That holds weight on its own. If it’s in the budget, do it and be done with it. I’d recommend a local company who isn’t trying to sell you everything under the sun, and get the guy you trust in your heart. Don’t get the cheapest, and not necessarily the most expensive either. Take your time and shop, that ol girl ain’t going anywhere too soon. There will be someone in your area who’s down to earth and stands by quality and customer satisfaction. If they send in a salesman and goes on and on about UV lights and 10 year parts and labor warranties….well buyer beware.

If you do nothing and just run the Williamson you’ll always have that damn furnace in the back of your mind nagging at you. It may in fact run for your entire tenure at the property, with or without a heat exchanger issue, or may break down closing night. Good luck sir!

mattmia2 · March 28

i would take the opposite view, i would get a good low level co monitor and inspect and clean it yearly and keep the blower oiled and run it until it dies, which may be the lifetime of several new furnaces. as long as it isn't flaking off pieces of asbestos from inside the jacket. it wasn't super common but it is something to check.

unless you want ac, then replace it.

EdTheHeaterMan · March 28

I don't care how old that furnace is or what condition it is in. If you like the home and want to buy it, then offer a price that reflects the need to replace the furnace. Furnaces don't last forever, You will be replacing it within the first 2 to 3 years. Guaranteed.

If it is Natural Gas, check with your gas supplier to see what rebates are available and what low interest or zero interest financing there is on a replacement furnace. You may find that there is money available to help you upgrade. Many utility companies are required to charge a small percentage to every customer to pay for these rebates and other incentives. By not using those programs, you are leaving your money on the table for someone else to use. That's just the way I remember it in New Jersey when I was in business.

retiredguy · March 28

Just for your information, a lot of the older Williamson "low boy furnaces" that yours is came with cast iron heat exchangers that lasted almost forever. I can't say that the furnace you show has a cast iron heat exchanger but many of them did. You would need a furnace tech to se if that one does have a cast iron heat x

HVACNUT · March 28

If I was looking at that house to be my home and that furnace was there, it would be a bargaining chip, or be put on top of the "replace" list. Lack of safeties, obsolete gas valve, belt drive shaded pole blower motor. Its going to the scrap yard.

Is the heated space about 5,000 sq ft? Because thats what the furnace is sized for.

pecmsg · March 28

There is no way of knowing how long that furnace will last. 1 day, 1 week, 1 month, 1 year, several more years.

Bottom line

Do you and more importantly does your Wife like the house?

Does the sale price reflect an old furnace?

When we bought this house, I knew the 1920 Thatcher boiler had to go. The 60-amp service had to go. The price reflected the house. For the record we spent more than we wanted but 25 years later we don't regret a thing.

Help: Very Old (c. 1970 or earlier) Williamson Gas Furnace

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