is it important to replace a gravity (octopus) furnace for safety?

Question

BP furnace experts - do you consider it important to replace a gravity furnace (often referred to as an "octopus") for safety reasons?

A duplex I've had for eight years has one of these.   I do make certain to have a furnace company inspect and tune it up every fall.

I talked to the owner of the HVAC company I use and asked him what he thought of it.  He said that these types of furnaces, while they last a long time, when they do fail, the can fail spectacularly.  He also mentioned they don't have the modern safety features.

Jeremy Tillotson · Answer

Bill Gulley in regards to these furnaces (if you call it that) the burner can get clogged, and spill gas into this large chamber, It depends how much gas builds up until its either lights or goes boom. These can be dangerous, also if not cleaned they can cause carbon monoxide. Its not a scare tactic this is serious stuff that really does happen. I am a HVAC  guy and have seen these events in real life. As a side note the gas bill of your tenant would be cut in over half so they could actually afford to pay rent. They are not cheap to replace though, usually covered in asbestos, must be taking out in pieces and extensive if not all new ductwork installed.

Julie Sisnroy · Answer

Bill Gulley is spot on.  My bf is currently living in an older house with one of those, and we looked at the cost of replacing it - Not worth it for his 900 sq foot house. Asbestos being part of the issue and replacing it with a whole new HVAC system to put in its place.

It works pretty well, but there are no vents in the bedrooms and bathroom, so it gets cold.  Instead, we upgraded the insulation, which helps a little bit.  Replacing the windows will also help. You can also buy low watt wall mounted convection heaters.

It really depends on how much value you think it would add and how it would compare to other homes in your area.  We were quoted $10-15,000 for a house that is probably worth about $65,000.

Jean Bolger · Answer

That what my HVAC guy said about these too!

Unfortunately, he also said "If it is broke, I can't fix it" (because of code issues).

But (fortunately!) the furnace in question  just needed a cleaning of some contacts, so it did "miraculously" come back to life during his visit. As soon as a more serious problem develops it has to go though.

Apparently they have very few moving parts, therefore very few things to break. But considering how old they are I'd want to be sure of having good CO detectors in place - even if they aren't required by law in your area.

Tom Lane · Answer

I look for homes where the last guy did me a favor and stole the furnace and ductwork and if I'm real lucky they took the water pipes too! Its OFTEN easier to start with a clean canvas and at resale time its ALL new.

Dan C. · Answer

Thanks all.  The octopus furnace in question I did end up replacing last spring.  Often there are asbestos wrapped ducts that drive up the cost of removal, but fortunately in the case of mine there was not.

Bill Gulley · Answer

Not sure what if there was question, but yes, any gas furnace can go booom! :)

Bill Gulley · Answer

I don't think you can kill one of these, it's a gas line, to a valve, with a thermostat and a cast iron burner that will last 100 years easily. These burners make great BBQ pit burners BTW.  There are no moving parts really. Many are converted coal burners. As to repairs, that sounds strange to me that any existing equipment can't be repaired, granted, there can be a parts issue, it's not hard to replace a part. :)

Bill Gulley · Answer

Don't think that's what he's got, sounds like yours was a floor furnace and I'd yank those out in a heart beat! Good call on replacing it.  :)

Bill Gulley · Answer

They were and still are common here and I've never heard of one going boom or presenting any more of a hazard than any other furnace. A gas cut off regulator might be a good idea. There's always a bit of marketing in most everything playing on people's fears.

Yes, they made real furnaces in the old days, not as efficient as those today but not too bad. I think the great thing about them is that there is no forced air, no mechanicals to break down, they don't make noise, they don't blow dust or impurities through the house and when you get out of a shower and stand by a vent you're not blow dried.

I've converted a couple with a low pressure fan unit keeping the ducts in place using the large plentum, that way you don't get the blowing effects and it's still quiet.

Draw backs, asbestos wrapped ducts, those can be covered to meet code. They look wild and take up room. They can be costly to remove due to the size of the burner/furnace, usually put in before basements were framed in and you'd have asbestos removal.

If it ain't broke, don't fix it I'd say. :)

Jessica S. · Answer

We replaced one in a rental, primarily because the  floor grate that sat above it got so hot.  We thought it could be hazardous for little kids.