Heating Vent Filter Question

[Pat K]

Okay, heating tech chiming in here...

Pre-filters are good.  Post-filters are bad.  That is, the return should be filtered, but the outlet should not.  The filter at the furnace (the 20x20x1) should be in the return duct, and I have no reason to doubt that it is, since it would be silly for someone to go to the trouble of changing that (anyone with the skill to do it would know better).  The filter at the return grate in the floor is also a good idea, as it will keep dirt and debris out of the ductwork.

In the case of each, keeping them clean is very important to maintain the equipment in safe and efficient operating condition.  Check the furnace filter monthly, and the filter at the return grate weekly.

As far as soot, if there is any, it is indicative of a cracked heat exchanger, and the furnace should be immediately replaced (heat exchangers can, technically, be replaced, but it is more expensive than replacing the whole furnace).

A draft test alone cannot reliably detect all cracked heat exchangers, and a full heat exchanger test is not typically done during a furnace inspection.  To fully test the integrity, a visual inspection (using mirrors, cameras, etc.) is necessary, and then a smoke bomb is used in the combustion chamber, while the fan is running, to provide a more-visible substance to check for in the ductwork.

If the furnace is circa 1989, then it is getting up there in age (15-20 years is the expected service life for a warm air furnace).

In any case, if you have any fuel-burning appliance in your home, you should have one or more carbon monoxide detectors, and maintain them in good operating condition.  CO isn't anything to joke around with; it can kill silently or, in lowed levels, cause permanent brain damage, or simply lingering illness, similar to a persistent cold.

IIRC, you're in Keene, right?  I expect to be down there in the near future, as my brother is running in the marathon on the 24th, if you'd like anything explained in-person...

Joe

Eggaxctly, thanks Joe, written as I should have.

[FTL_Ian]

About how much does a new furnace go for?

[Lloyd Danforth]

You usually buy them from the company that services them.  Unless some Keene person has some company they like, you should contact Dawn on this forum and ask her to ask her husband Bill about a good local company.

[mvpel]

I like Lennox furnaces - bought one for the first house we owned.  Every aspect of the design and construction of the unit reflected careful engineering and design consideration, right down to the door panels on the unit.

[FTL_Ian]

I like Lennox furnaces - bought one for the first house we owned.  Every aspect of the design and construction of the unit reflected careful engineering and design consideration, right down to the door panels on the unit.

Any idea what they cost these days? 

[MaineShark]

About how much does a new furnace go for?

It will vary depending on the size you need for your house, which is determined by a heat-loss analysis.  Most replacements jobs will simply match the existing size, but it's better to re-do the analysis, as the original installer may have just "winged it" instead of doing the work right.

Lennox is a decent name, as is Thermopride.

Pricing will depend on the installer, and may vary significantly... an installer who charges less for materials might charge a lot more for labor, so shop around based on the total price, not just the price of the furnace.

However, a good rule-of-thumb for a direct furnace repalcement (ie, the new furnace fits similarly to the old one, so little modification is needed) is between $3000 and $4000.

On another note, it may be worthwhile to consider a hybrid water/air system, depending on the specifics of the home.  In this, a hot-water boiler supplies the heat, and a water-to-air heat exchanger heats the air, while a water-to-water heat exchanger heats your domestic hot water.  This is a more expensive option, but if you have an electric water heater, this type of system can pay for itself pretty quickly, as it takes care of both the heat and hot water in a much more efficient manner.

Of course, we're putting the cart before the horse, here, because the existing furnace may be fine, and the "soot" you're seeing might just be dirt.  Get a carbon monoxide detector ASAP, and that may give you an answer.  If your oil tech has quality test equipment, he may have a "sniffer" that he can place near one of the discharge vents while the furnace is running, to check for the presence of carbon monoxide, directly.  I've saved quite a few people from replacing their furnaces without cause, by proving that there was not actually any leakage.  I don't mind making money, but I hate to see people throwing money out for no reason.

Joe

[slim]

Ian, the price range of $3,000 to $4,000 is probably pretty close for a new furnace and installed. If you do get a new furnace the contractor/installer should do a heat loss calculation because the current furnace may have been installed before some upgrades have been done to the house i.e. new windows, additional insulation, and other improvements. If the contractor does not do a heat loss calculation I would not use them. The furnace was manufactured by the company I work for and the heat exchanger should be covered (or at least partially) under the warranty if it is damaged.

As for what brand to buy you can usually get the exact same product (maybe different color or different label) under the original manufacturer's name and at a lower price.

[Recumbent ReCycler]

My twin brother is a HVAC tech in western MA, and he seems to prefer Buderus.  They make some high efficiency systems.

[MaineShark]

Slim: Will they cover labor?

My twin brother is a HVAC tech in western MA, and he seems to prefer Buderus.  They make some high efficiency systems.

They do, but they only make boilers, not furnaces.  If the system was being replaced by a hybrid water/air system, then a Buderus boiler could be used.  However, I'd generally recommend a Crown Freeport over the Buderus, simply because it is American-made versus imported.  Both are of similar quality and efficiency.

Joe

[slim]

Slim: Will they cover labor?

Joe

Labor is usually not covered under the warranty normally just heat exchangers, you would have to read the warranty. If there is a defect from manufacturing we would definitely cover parts and sometimes labor.

[mvpel]

...the current furnace may have been installed before some upgrades have been done to the house i.e. new windows, additional insulation, and other improvements.

Based on the performance of our own furnace/AC, it seems they did the heat loss calculation based on some upgrades that were never actually done until we bought the house.  The first winter here, during that vicious cold snap, the furnace ran basically continuously for about a week, because there were single-pane windows and R-19 in the attic.  Fried the flame sensor in short order.

[MaineShark]

Slim: Will they cover labor?

Labor is usually not covered under the warranty normally just heat exchangers, you would have to read the warranty. If there is a defect from manufacturing we would definitely cover parts and sometimes labor.

Hence, it probably isn't cost-effective to attempt a warranty claim.  The labor to strip the unit, replace the HX, and then re-assemble and test the unit generally puts it right up there with the cost of a total replacement, and the customer would have a brand-new furnace.  I've only seen a HX replacement be cost-effective on large commercial furnaces.

Joe

[Russell Kanning]

About how much does a new furnace go for?

Why do you think you need a new one?

[Lloyd Danforth]

They found soot, or, something that indicated a possible problem with their furnace.  It needs to be tested.