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Warning on furnace cleaning

Posted by doug_gb (My Page) on
Sun, Feb 3, 13 at 17:12

Our home was built in 1950. It's a large home, with 4 zones, and a 250k btu hydronic heating system - natural gas - it's the original furnance.

About 5 years ago we began to smell a 'chimney odor' - I paid to have the fules inspected - all was good. Since the home has two fireplaces, it was suggested that since we don't burn wood - it's what was left from before.

Three years ago, I paid $300 to have the furnance cleaned.

Several months ago I noticed that there was soot around the the cover in the boiler vents. Also, my wife complained about a 'combustion smell'. CO / draft checks ok.

Last week, the pressure/temp gauge began to leak. I decided to fix it on the weekend. I took the cover off the side of the furnance - it really wasn't meant to be taken off - about a dozen screws.

The boiler consists of 8 segments - like a squared off radiator - between each segment there was a cast iron cover that covered the opening between boiler segments. One of these covers fell off, while I was removing the side of the furnance.

What I saw: The boiler was completely 'impacted' with scale and soot! I removed over 20 lbs of material from the boiler flues.

After a week, all is well, and the odor is gone. Apperently nobody ever cleaned the boiler after 60 years! I looked at my boiler cleaning bill - it doesn't say what they did.

I was lucky - I think the whole thing could have overheated in a much more serious way.


Follow-Up Postings:

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RE: Warning on furnace cleaning

Apparently nobody ever thought of replacing the boiler after 60 years!


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RE: Warning on furnace cleaning

@snidely: "Apparently nobody ever thought of replacing the boiler after 60 years! "

I works perfectly well. No control boards, no nothing, just a standing pilot and a MH gas valve. Keeps this home in Minnesoata warm, and is dependable - for the 20 years I've owned the home.


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RE: Warning on furnace cleaning

I'm just another fellow homeowner, doug, but I wouldn't think that finding 20 pounds of scale and soot suggests that it's working perfectly well. I didn't think a natural gas flame produces soot at all.


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RE: Warning on furnace cleaning

@snidley: "I'm just another fellow homeowner "

Well then you don't really know anything. Except you like to give an uneducated opinion.

I'm an engineer, and a grandson of an HVAC engineer. I posted this to warn other people, that even thought they pay for a service, they may not get the service they might imagine.

And yes, when cast iron is heated, it produces scale, and after 60 years, the scale builds up, and with the lack of air flow, then soot builds up.

Please don't respond again.


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RE: Warning on furnace cleaning

"I'm an engineer, and a grandson of an HVAC engineer"

Thanks for the clarification.


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RE: Warning on furnace cleaning

amazing that no one ever noticed it!
makes you wonder when the last time it was cleaned...
or if it ever was.

did your grandfather do the install?

best of luck.


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RE: Warning on furnace cleaning

doug_gb: for those of us who aren't engineers or grandchildren of HVAC installers :), what should we look for to be done when we hire someone to clean the furnace?


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RE: Warning on furnace cleaning

Doug, I'm happy to see that there are others who understand that there is no need to replace older, functioning hvac simply because of its age or need of a good cleaning. Especially boilers which last almost indefinitely if they're not leaking (and having make-up water constantly introduced). Far too often people (especially laypeople and even some hvac techs who's lies have fooled themselves) believe that after 20 years their equipment is on death's door and needs to be replaced.

With modern gas heating equipment this is often true - especially with forced air gas/propane equipment - burn through and cracking of heat exchangers causing roll out is very common in equipment around 20yrs old. The older stuff lasts MUCH longer. I have a few rental properties and some use oil, some use gas. The newer gas furnaces are nothing but trouble. My own home has a large 1940's gas furnace made with heavy 10 gauge steel - still in solid shape; Standing pilot and electrical controls that have NEVER needed replacing. With a thorough cleaning and speeding up of the blower speed (thus dropping stack temps) and a smaller pilot light, and adjustment of the atmospheric burners and breach draft (draft hood and barometric damper) The combustion efficiency and overall efficiency was analyzed and calculated - just over 82% fuel utilization (overall appliance) efficiency. Very respectable for a 65 year old appliance in excellent shape that should require little maintenance or replacement of components for the next 50 years.


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RE: Warning on furnace cleaning

@Artichokey: "what should we look for to be done when we hire someone to clean the furnace?"

I think you have to be explicit that you want the boiler flue cleaned with a brush. Be there, and make sure it's being cleaned.


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RE: Warning on furnace cleaning

@berlin:"I'm happy to see that there are others who understand that there is no need to replace older, functioning hvac "

Exactly. In twenty years all I've replaced is the thermocouple. No circuit boards, no igniters, no maintenance.

About five years ago I replaced all four B&G zone pumps. If your furnance has these large, red pumps - don't replace them with the cheap, tiny wet rotor kind - they have a high pitched whine that travels through the heating system


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RE: Warning on furnace cleaning

Even gas boilers get surface rust that then collects more stuff by disturbing the combustion process.

When I replaced my dad's boiler years ago the efficiency improvement was very noticeable.

The 10 inch flue had an electric damper (and a 'proving' switch to ensure it opened), flame roll out sensors, and the 'knobs' on the boiler segments in the flue gas where so long they nearly touched the next section.

Still nothing electronic though.

Just relays and switches.

It is now over 30 years old and still going strong.


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RE: Warning on furnace cleaning

doug_gb: Thanks!


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