1950s Janitrol Gas Furnace won't auto turn off

cmg80

Hi there,
I bought a house about 5 months ago that was built in 1953 and has a pretty serious hvac system. I know its an antique and needs to be replaced, but since it still works rather well, I've decided to wait until next spring. Its a forced air furnace by Janitrol; model: FEC 180-84k; Input: 180,000 Btu. / Output: 144,000 Btu.; Type D; S#: 0451f0814. The a/c doesn't cool as well as i'd like but at least it does (sort of) communicate with the thermostat. When i want to switch the system from a/c to heat i have to flip a lever on the unit (i believe it used to have a motor that made the switch but has burned out). i turned the t.stat to off, switched the lever and turned the gas to on. the giant burners sparked a little but lit right up. within 5-7 minutes my 3200+ sqft house was nursing home hot--from 65 degrees to 80. i tried lowering the t.stat to the lowest temp and it didn't turn off, then i turned the t.stat off and still nothing happened. after 45 min i had to go back to the unit and turn the gas off to get it to stop blowing. Also, it seems like the t.stat thermometer is innacurate. i noticed this summer that the thermostat and i had wildly different opinions about what 70-73 feels like. It would read 67-70 but felt like high 70s in the house. i often had to turn it down to 60 just to get it to kick on. I haven't had the best luck finding a professional that knows much at all about the system. A few months ago, I met with a previous owner of the house and he came over and showed me how to work everything, but since it was 110 outside i wasn't terribly concerned about the heater. he showed me how to switch the system over to heat from a/c and showed me the "pilot cock" but other than that i don't recall anything else. Should i have kept the thermostat on and set to heat before switching the unit over, instead of turning it off? Any info./suggestions or leads on a manual would be much appreciated.

Thanks.

Ironman

That sounds like an extremely dangerous situation. I would recommend that you get a COMPETENT tech out their right away.
To be honest, that system is extremely inefficient and at least 30 years over-due for replacement. A new 95%+ furnace would probably cut at least 40% off of your fuel bill.

It also sounds like its way over-sized. Have whoever bids replacing it do a manual J heat loss calculation and size the furnace to that.

Personally, I wouldn't invest a dime in something that antiquated. You wouldn't expect a car to last over 60 years. Furnaces are 20 year appliances.

Tim McElwain

It sounds like you have a gas valve that will not shut off. That is very dangerous. As was already stated get a pro to look at it. Have them get it running then shut it off, if it keeps running disconnect the wires on the gas valve if it shuts off then the valve is okay and something else electrically is wrong. If it doesn't shut off then the gas valve is passing and needs replaced. Based on the age of the system a new gas valve plus labor would be better invested in a new modern high efficiency furnace and AC system.

cmg80

Thank you both for your input. Before I purchased the home, I did get an estimate to replace the entire system. It was $11500 and included 2 units- one for each side of the house. Does that seem accurate? The company as a whole is well respected but the 2 men seemed to be in awe of the design. For instance, about a 2nd unit of some type that was added at a later date to include for the sunroom that was originally outside. The 2nd unit was installed in a bedrm closet that backs up to the sunroom wall. It seems to only serve as an end point for the newer duct. It has a t. Stat but no brain and only blows if the main unit is running. There's no attic to run duct bc all ceilings are vaulted cedar plank so the original duct runs under ground and inside the walls. The sunroom being the exception - duct runs along the ceiling built out for it. I can send pics if you'd like. My description probably make no sense.

Techman

Before you replace the furnace with a "properly sized" unit( I agree w/ Ironman about the existing furnace being way oversized) have the size of the duct's checked out. If the ducts are sized for the oversized furnace , then the ducts will be oversized for the new smaller ( less airflow CFM) unit. You will have lots of problems if you don't. Under ground ducting is a breed all to it self, requiring special application.