Answered: Sharing some helpful HVAC advice/insight

[Matthew Banks]

People are getting ripped off with HVAC furnace replacements and repairs. I hope this helps others:

HVAC systems are treated like black boxes by most property owners, and that is a BIG MISTAKE. They are often quite simple, have few parts, and can be easy to troubleshoot and even do some routine maintenance and minor repairs yourself.

I've had to deal with a couple furnace issues in the last year, in both cases a bad logic board was the cause, and we only discovered this after having multiple HVAC companies come out and assess the problem, struggle to find the root cause, often replace other parts unnecessarily, and ultimately shrug their shoulders and recommend a full replacement at $5k+.

In one case, I went online, bought a logic board and installed it myself to fix a furnace that wasn't working consistently. Cost to me: $100. Lowest price for logic board from local OEM provider: $500. Lowest quote from HVAC to replace logic board: $1000+. Quote to replace furnace $5k+ (with a strong suggestion to do so by HVAC). In a second case, a trustworthy HVAC rep replaced the logic board for us at <$400 price, which is very reasonable.

Furnaces are very expensive to replace, and I'm finding that HVAC companies will often jump to recommend replacement when it is not necessary, because replacements make them a lot of money. You want to make sure that it is necessary. Have the HVAC company explain what is wrong with your furnace, specifically which parts must be replaced and what the cost of each part is. You can quickly go online to confirm for yourself. You also want them to explain which parts are working fine so that you know they checked all the sensors, blower capacitor, blower motor, exhaust motor, and burner. 

A typical mid-efficiency HVAC furnace has two motors, a logic board, a blower capacitor, and several sensors. It also has a burner and a heat exchanger. While there are other parts, those are the main parts that tend to fail on mid-efficiency furnaces for example.

The sensors are cheap (<$20). The capacitor is cheap (<$100). The logic board is reasonably inexpensive if still made (<$200). If it isn't made, you can find used boards or universal boards. I bought a couple used boards for $40-100 each, the first didn't work but the second did. The motors are more expensive. The burners are a little more expensive as well. But as you can see none of these justify buying new, even if you have to replace several of them at once.

Furnaces should have an indicator that will guide you to the source of the problem, but there are times where it doesn't give you enough of an answer. That's when you need to be able to visually inspect and even test some of the parts to identify an issue (like the flame sensor or the ignitor). Visual inspection can identify a broken sensor. Testing a part with an electrical meter can also help identify whether it is still good.

It is reasonable to learn how to to check the sensors, capacitor and motors yourself if you are handy. A good HVAC company will also be able to test them one by one as well and verify each.

What remains is the logic board, which is hard to test thoroughly, and I find most companies can't do more than test some of the connections.

If you are having furnace issues, before letting an HVAC company talk you into replacing a furnace, consider the following:

1. if you have an ancient octopus furnace, don't replace it, get it repaired. We have one that is over 110 years old. All modern furnaces have <20 year life span, and that is according to HVAC technicians I've spoken with. Yes, it won't be efficient, but you'll have to ask whether efficiency is worth a fat purchase price, unreliability and short life-span.

2. if you have a modern furnace, mid-efficiency and high-efficiency are two of the main types. High-efficiency has more parts and is more expensive and may have a shorter lifespan, according to HVACs.

3. If you are having furnace issues, you can go through a check list to determine where the issue is. If you have an HVAC expert come to troubleshoot the furnace, ask them to identify the exact source of the problem as well as which parts are working fine. Make sure they actually test the various parts, usually with a simple voltmeter.

4. HVAC techs can't always determine that a logic board is at fault. They can identify only a few cases, but the boards are too complex. They are the true black box of a modern furnace. If they tell you that they don't know what is causing the problem with your furnace, but they can confidently tell you that all the other parts are working fine and testing well, then consider replacing the logic board. Just make sure you aren't being gouged on the price.

*While you can make many repairs yourself and do some basic maintenance - which can save you considerable money - but you still should have a pro company come and inspect/test your furnace regularly.*