Fixing ancient heater/furnace.

Tiras25 used Ask the Experts™
I got an old heater furnace.  Probably as old as my house.  Which is state "approx 1915" in city hall records.  Wondering if worth repairing or get a new furnace, that will be a pretty pricey project.

I attached a few pictures.  I can fire up the pilot.  However, when switching to the burner the pilot shuts off.  Also notices the pilot flares a lot larger than usual.  I replaced a thermocouple last year.  That didn't help.

Any suggestion or maybe someone knows another 'hvac' specific forum?

Thanks in advance!!
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Hello Tiras25,

Here is a great forum on HVAC
The biggest thing that has changed in heaters over the last 100 years is their efficiency. Older heaters put a lot of heat out the exhaust wasting a lot of energy. New heaters can go as high as 95% efficient. In fact, they are so efficient that the exhaust pipes now have to be plastic because they loose so little heat, you get moisture in the exhaust and plastic is necessary to avoid rusting. The motors are also much more efficient. You can even get variable speed motors to help hold the house at a constant temp, but they are a lot more expensive.

Looking at your pictures, that unit looks very similar to the unit in my house, from the mid 70's, and is probably 70 to 80 percent efficient. It can still be made to work.

Because we do not use our heater very often, we opted not to spend the $7K to $10K to update because the efficiency savings would take a LONG time to recover the cost. So, we had a heating company come in a do a through cleaning and "tune up" on the unit, the burners, the pilot, etc. You can add a pilotless ignition to save a few dollars by not running the pilot as well, but that is an option. They MAY need to replace the burners if they are too rusted, but that is cheaper than a new unit as well.

Also, be sure to change your filters on a regular basis if you use the heater a lot as that also improves efficiency.

If you do decide to replace, shop around, as prices vary a lot. We looked at Costco and their quote was fairly good. Some local companies also offered a lot of different options.

Lastly, if your system is that old, you might also have the company inspect and repair your heating ducts. They found a number of leaks in our system and repaired those as well.
It might be worth checking whether your state offers any financial incentives to offset the cost of replacing an old furnace with a new "greener" one.  It could well be that such incentives are only offered to people of a certain "status", for example having an elderly or incapacitated person in the household, but it would be worth asking the question because a subsidy might bring the cost of replacement into the realm of affordability.
Picture 3 it shows it's full of dirt and sand.
I wouldn't even think twice on replacing it. I believe that model has a 20-25 year life cycle.

Don't mess around faulty furnaces can be dangerous.
At first I thought the same while looking at the photos, but I have a feeling that what I thought was sand is actually fire cement.  I could be wrong of course.  Most debris could be vacuumed out, but I would worry about rust perforations and pin-holes in metal parts where carbon monoxide can leak back into the room, for example the flue where condensation can lie in bends and joins (as mentioned by Owen Rubin) or rust on the metal walls of the enclosed combustion chamber.

We have a different kind of central heating in the UK that uses a boiler to heat water that flows through pipes to radiators and also heats up our tap water at the same time, but the actual "burners" use te same principle.  Both kinds combust gas in an enclosed space and carry the same dangers of toxic exhaust gases and accumulation of unburned gas from a leaking pipe or a burner jet that isn't working.  I once had my boiler condemned at its annual maintenance and safety inspection due to pin holes in one of the walls of the combustion chamber.  I was told that it could potentially have leaked enough carbon monoxide into my home to have caused a danger to life.  I now have my boiler in an enclosed area in which there is a carbon monoxide detector with a very loud beeper.

One issue that others with intimate knowledge of the North American furnaces can comment on is that of the exhaust flue.  Old systems in the UK used air from the room to combust with the gas and expelled it through a single-walled flue.  Houses had to have air vents in the walls to allow fresh air to be replenished.  A lot of people blocked those vents and sealed teir doors and windows against draughts, but this resulted in valuable oxygen in the house being gradually used up.  Newer boilers have a "balanced flue" with concentric tubes.  Air from outside is pulled in through the outer tube and exhaust gas is expelled through the inner tube, so no air from inside the home is used for gas combustion.  These are fan assisted.  They are a lot safer, but still present a danger if blocked by debris of any kind or the exaust fan stops working.  I am not sure if newer American furnaces use balanced flues.

One issue that others with intimate knowledge of the North American furnaces can comment on is that of the exhaust flue.  Old systems in the UK used air from the room to combust with the gas and expelled it through a single-walled flue.  Houses had to have air vents in the walls to allow fresh air to be replenished.  A lot of people blocked those vents and sealed teir doors and windows against draughts, but this resulted in valuable oxygen in the house being gradually used up.

This has happened here in the US as well. Code requires adequate air flow to the unit, but when we bought our current house, many of the crawl space vents were indeed blocked. After an inspection, they said there was still plenty of air flow, but it was a good idea to check.  They did require a carbon dioxide detector to be installed in the room adjacent to the furnace to be sure the unit was not filling the house with CO2, which thankfully has never gone off.

As for the life of a furnace, I have done quite a bit of research on this. If you use your furnace quite often all year round, 25 years is about the right time to replace it.  But here in California we use it not very often. Our mid70s unit was just inspected (we do it yearly) by someone who sells new units. He told me that there was 10+ years life left, it was running at 80%+ efficiency, while a new unit in our price (4 to 5k) range would only be 85%+ efficient, so we might as well wait. ( The super efficient ones were $8000 to $10000!)

My suggestion is to disregard us all, as our OPINIONS are going to vary. Pay the money to have it inspected by a professional.  They can clean it at the same time to keep it running and tell you if it needs replacement. If it needs to be replaced, get multiple bids, and make them detail what is included. I suspect with a unit that old that duct work will also be needed, as well as bringing the space up to current code, which can add “surprise” costs at install time. Ask a lot of questions.  We noted that estimates varied all over the place, so some research into heater units might be worth while too.  

Good luck

BTW: This time of year many companies offer cleaning and inspection services.  Check them out online before taking one of those offers. Many are often a scam to tell you you need hundreds of dollars of unneeded work and do little cleaning or repair.

Check Yelp and your local Nectdoor for recommendations.


Thanks guys.   Did a bunch of a troubleshooting today.  Eliminated all the components.  Except the valve.  See attached.
Now the issue is to find these same valves is almost impossible.  Need to look for something compatible.  

Any ideas what could be the same vertical fit as this valve?

That valve is what kills the gas to the heater if the pilot goes out. It uses a thermocouple to detect that the pilot is lit, and keep the gas on as long as the copper tube going to the pilot stays hot. Otherwise, it will kill the gas to the heater to keep it from leaking into the house if the pilot gets blown out.  It can also be used to turn off the gas.

There should be a red knob on the top that has positions for OFF, ON, and LIGHT.

Any competent heater repair company can replace it with a newer compatible valve.  It will look something like this:

Hope that helps.


thanks again Owen.  i'm looking for a compatible valve that can replace mine.  I think orientation is important.  mine connects vertically to the input output gas.

Actually, orientation is not really important. When they replaced mine last time, the added one of those flexible hoses to the gas line to attach to the new valve.  This is what mine looks like now:



very similar valve to mine.   I was cautious and thought some valve can only designed to work vertically,  other horizontally.  I could be wrong tho.

I am not sure. I believe all the ones I have seen are mounted as I see mine. Again, you may wish to discuss this with a professional, or look at some specs on valves to see what they say.
Thank you Tiras25.


Thank you all!

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