Is Serious Furnace Cleaning Necessary?
January 21, 2014 1:49 PM   Subscribe

I have an old style furnace that has been cleaned (by vacuuming) on a mostly annual basis for about 20 years. Should I pay the big bucks to get it scraped out by a professional?

Our furnace was installed in the early 90's (not sure when exactly, but it's about 20-25 years old) and is not a modern high efficiency type. Most years we got a furnace cleaning company to come and vacuum out the ducts, but this hasn't been done for at least 4 years. The furnace is definitely showing its age, and parts are beginning to fail. (The humidifier rusted off and is long gone, and two years ago I had to replace a burned out thermocouple.) But new furnaces are $100 000+, which is way out of my price range. So I want to keep this one running as long as possible.

A guy from a local furnace cleaning company (Sears) gave the furnace a free inspection today, and tried to sell me on his company's services. He said that vacuuming doesn't remove all the dust, so it builds up over the years. His company does an extremely thorough job because they actually cut into the main duct, get in there and scrape out the dust inside. (Heart surgery for the furnace, basically.) Then they'd have to weld the access plate back in place, in a much more complicated and expensive process than anything we've done before.

I'm not sure what to do. One one hand I'd rather not pay $500+ and have someone welding in the basement, but on the other hand I really don't want a furnace that's approaching the end of it's life to fail and stick me with the cost of buying a new one. That would be orders of magnitude more expensive.

Does this kind of furnace surgery sound like a good idea? Or can I just call the guys with the vacuum again?
posted by Kevin Street to Home & Garden (9 answers total) 1 user marked this as a favorite
With the caveat that I can't ask the guy to clarify exactly what he was talking about, this sounds like a total ripoff to me. There is (or should be) a filter that removes the vast majority of dust from the air before it ever enters the furnace's inner workings. Furthermore there is nothing inside the "main duct" that needs to be cleaned to preserve the health of your furnace. Having cut into a duct for access, there would be no need to weld the plate back on. This is silly all the way around.
posted by jon1270 at 2:23 PM on January 21, 2014 [1 favorite]

When we had our furnace replaced, I was shocked by how much crud had built up on the heat exchanger, even though we replaced or filters regularly. A real furnace cleaning (not just the duct cleaning) may very well extend the life of the furnace.
posted by markblasco at 2:26 PM on January 21, 2014

If you are going to get this service done, I wouldn't have Sears do it. I've found them to be very expensive compared to other HVAC companies.

Having the ducts vacuumed won't keep the furnace itself working longer. The air in the ducts has already left the furnace.

But new furnaces are $100 000+

Unless you have a gigantic mansion, that's ridiculous. Light years beyond ridiculous.

Get several quotes from different HVAC companies. You may feel that you don't have time to do this, but they probably won't make you sit through the long sales pitch Sears does.
posted by yohko at 2:28 PM on January 21, 2014 [3 favorites]

I'm sorry, you typed $100,000. Is this USD? Maybe this furnace is made with a rare piece of artwork/black truffles/unicorn hair?

But seriously, this is a typical single family home? I can't see why it would cost so much. Maybe more in the $10,000 range. Unless your furnace is seriously not-to-code today and would involve redoing flue/chimney/all ductwork/then maybe some roofing/flooring. And you lived in a super-expensive area. Even still, I can't see getting to $50k.

Having said all that, how many more years can you really expect to get out of your furnace? If it's pushing 30, there is likely not all the crud-scraping in the world that will keep it running.
posted by fontophilic at 2:30 PM on January 21, 2014 [1 favorite]

We paid just under $1000 last autumn to get our 1970s furnace back into service, because a full replacement would probably involve the additional expense of major construction work. That included crud-scraping, a new heat exchanger to replace one that looked like a bit of an exploded bomb, and a fair bit of labour, which made up the bulk of the bill.

Your estimates on the cost of a new furnace are way out; you also need to get at least another couple of estimates from dedicated HVAC firms, and be explicit with your conversations with them about the life expectancy of the current furnace and the cost required to get X years of decent additional life out of it.
posted by holgate at 2:50 PM on January 21, 2014

What kind of furnace? Are you talking about cleaning the furnace itself, or cleaning the inside of the duct work? They are different issues. Cleaning the ductwork is usually not really necessary, unless you have a specific problem like mold. Having the furnace itself cleaned (depending on the type of furnace) is an essential element of regular maintenance, kind of like changing the oil in your car. Neglecting it can lead to a world of $regret.

If it's an oil furnace, it is indeed a very good idea to have the FURNACE cleaned annually. The inner works of an oil furnace can get clogged with a build-up of oil and soot. This can cause the furnace to fail in a way that will fill your home with stinky black soot. It wouldn't be a matter of just replacing the furnace, but also of extensive cleaning, re-painting walls, replacing ruined possessions, and probably moving out for as long as it takes to do all that cleaning. Neglecting to clean an oil furnace can lead to a very, very nasty outcome.
posted by Corvid at 2:58 PM on January 21, 2014

Get an actual HVAC company come out to do a furnace maintenance visit. And, unless you know for sure that the ducts are filthy for some reason, I'd skip that part. The HVAC tech will be able to give you a good assessment of the condition of your furnace and ducting and should be able to estimate how many years left you may have before having to consider replacement. Don't trust the Sears guy.

About 6 years ago I replaced my home's furnace and all of the ducting. The old ducting wasn't filthy at all save for some larger items like bobby pins and what-not that had fallen through the registers over the years. No major crud or dust. And, it was a very, very old furnace - like 40+ years old.

The replacement high-efficiency furnace plus new insulated ducting was around 6K if I remember correctly? The house is ~1500 sq ft, so not large by any stretch, but 100K sounds like an incredible price. Even 10K sounds a bit high to me.
posted by quince at 2:59 PM on January 21, 2014

Best answer: For comparison, we had a positively ancient oil fired boiler (which started its life as a coal-fired boiler, later converted to oil), replaced with a high efficiency gas boiler. The total bill was $15K in Massachusetts, which included safe removal of asbestos insulation on pipes, installation of a new chimney liner, running a gas line, installation of a new furnace and hot water heater, removal of the old oil tank, disposal of the oil.

So if I were you, I would bring in at least two other HVAC people and get estimates for what needs to be done and how much it costs. Unless you're planning on staying in the place for at least another 10 years, it would probably be a net loss to install a totally new system as opposed to repair/rebuilding the old system (if it needs it).

In our case, parts of the old system were close to the age of the house and we anticipated owning the house for longer than we actually did (but that's another story).
posted by plinth at 3:16 PM on January 21, 2014

If we're talking $USD, $100,000 is absolutely outrageous. Even a 120,000 BTU natural gas furnace (which is extremely overkill for your average 4 bedroom house) is only $2,500.00; even doubling that for installation (which is way too much) only brings you to $5,000.00.

You need to get a good HVAC company to give you an estimate. It sounds like you've already got a forced-air furnace and all the ductwork in place; there is no reason they cannot (or should not!) reuse that ducting and just replace the old furnace unit by itself. For $100,000 they better be building a house around that furnace!
posted by xedrik at 6:17 PM on January 21, 2014

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