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80% vs. 90 Plus - Reliability?

Posted by harry_wild (My Page) on
Sat, Feb 4, 12 at 13:07

I read a couple of post on websites and they stated that the 80% gas furnaces will have less trouble then the 2 stage; variable speeds high efficiency models.

I guess, many who have switch from the old model pilot type to the circuit board; software state of the art gas furnaces close them a fortune in repair since the warranty only covers parts and you have to have it tuned up each year to keep the warranty current in either models. But in general; the 80% efficiency gas furnace were less complicate and easier to fix when broken and less labor cost too.

Any opinions?

Follow-Up Postings:

RE: 80% vs. 90 Plus - Reliability?


I do not know of any objective data that say the old non condensing 80% eff furnaces are more reliable than the high eff condensing models.

The high eff condensing models have been around for 20 plus years and have proven themselves to be a great product. Properly sized and installed with a decent ductwork system and they are a great product from a comfort, operating cost, and quieter standpoint.


RE: 80% vs. 90 Plus - Reliability?


Thanks for the reply. I guess after some length research; I concluded that it like buying a car; you get a lemon from time to time. But I looking to buy a Honda quality and not sure what brand that is in the HVAC world. I was going to go with Rheem but then my Rheem local contractor steerred me away from the Prestige model that I wanted to get and wanted to do a Trane instead. I went back and after his Trane and asked about the Prestige and he said that the Trane XV95 is the one!

Now, I made some calls and the one that has done 3 install of that Prestige model is located 20 miles from the Twin Cities; Minnesota area. LOL!

RE: 80% vs. 90 Plus - Reliability?

You can argue a more complicated machine is less reliable than the simple one. However the benefits of the a higher efficiency furnace in a location like Minnesota out weigh any small advantage in reliability. If you have any concerns about reliability then you should purchase a 10 year parts and labor warranty from the manufacturer. The savings from the higher efficiency furnace will offset the cost of the warranty.

Rheem and Trane both make good furnaces. You should be fine as long as you stay away from the builder grade versions. Consider the Carrier/Bryant products if you can't find a good contractor with the other brands. Look for a factory authorized dealer on the manufacturer's web site. These dealers usually work exclusively with one brand and are more knowledgeable about the product.

RE: 80% vs. 90 Plus - Reliability?

One important point to remember is that high condensing/high efficiency gas furnaces have to be vented out of the side of the house/structure. In addition a pump is also needed to pump out the condensed water from the unit. In addition if you are venting a hot water heater currently through your chimney and had been venting a lower non-condensing unit or an oil fired unit, you may very well need/do need a chimney liner if going with the high efficiency unit which will have to be vented through the side of your structure as mentioned.
The pump, potential liner costs and asthetics are all items to be considered.

Gregg E. Bullwinkel

RE: 80% vs. 90 Plus - Reliability?

While this Is an old thread, I want to reply to previous post. For most homeowners with reasonable access to an outside wall, the points raised about venting on the high eff condensing furnaces really are non issues. The cost of the venting usually is inconsequential.

And condensate pumps are cheap.


RE: 80% vs. 90 Plus - Reliability?

If the furnace is in an unconditioned space, like an attic - there is one more factor. The 90% furnaces have an issue with the condensate freezing, while there is no condensate to freeze in an 80% furnace. I just had a new furnace put in my attic and went with 80% for this reason. All the contractors said that they could use insulation, heat tape, etc to try to prevent freezing, but none of them really were confident that it was a total fix. Seems like the indistry is still trying to figure out a good solution to that issue.

RE: 80% vs. 90 Plus - Reliability?

There is a new Department of Energy rule taking effect on May 1, 2013. It mandates that furnaces installed after this date in northern states must be rated at least 90% AFUE. The industry has less than a year to figure out how to do an attic installation.

Here is a link that might be useful: DOE Finalizes New Energy Conservation Standards for Residential HVAC Appliances

RE: 80% vs. 90 Plus - Reliability?

"The industry has less than a year to figure out how to do an attic installation."

Build an enclosure around the unit with some minimal insulation.

More complicated things have a higher failure rate.

It is VERY expensive to make a device with more components have the same reliability as a device with fewer components.

Add to the cost of running, the increased maintenance and repair costs over the life of the unit and savings can become illusory.

You can save $500/tear in fuel but spend $1,000year in repairs.

At least some of the new hybrid cars are going to need to last 10-11 years to recover the cost in gasoline saved.

There is little data to indicate they will make it that long, and strong data to indicate the battery systems will NOT last that long.

RE: 80% vs. 90 Plus - Reliability?

its true 90%++ furnaces have more to go wrong than 80% furnaces, but that doesn't mean they are more problematic. 90%+ technology has been around for quite some time. The inducer motors and exhaust venting motors are built to last. If the 90%++ furnace is in a conditioned space there is no worries of freezing.

My 90% furnace is from the early 1990's. When I replaced the A/C with a heatpump I opted to keep the furnace because it had never given a problem and the installer said the inside's of this furnace looked like great and said why replace?

I"ve never had a problem at all with the furnace. I've been in the house for 6 years.

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