The furnace for our 1st floor (we have 2: 1 for the 1st floor/a few vents in the basement and 1 for the 2nd floor) makes a strange buzzing when ever the burners stop firing. It's a Whirlpool NUGK075DG02 model. The furnace will start up normally and the burners shut off for about a minute or 2 after running for a while (happens everytime) and then will fire back up. When the burners are off, the furnace will begin to make a buzzing or humming noise and it will stop when the burners come back on. It doesn't make it every time but this is the first year I've noticed it. As far as I can tell it's original to the house (built in the 1980's) and the only major repair that I know of was getting the gas valve replaced in 2012 (we've been in the house since 2002).

For the 2nd part of my question, can anyone shed some light on this furnace? I know it's high efficiency as it has a PVC exhaust and condensate line on the flue pipe. I also found a sticker saying that it's a 75,000 BTU unit but around 68,000 BTU's after efficiency I'm assuming. It's natural gas, has 3 burners and the fan control is set to turn off at 90F and turn on at about 130F. That's about as much as I know about it. One more thing: there's this dirt all over everything (burner assembly, draft inducer motor, etc.) which I'm assuming is from the natural gas (at least I hope so. ).

 

That furnace was built for Whirlpool by ICP/Heil.

With it's age I'd highly recommend you get it professionally serviced and have the heat exchanger checked for any rust thru. The dirt all over everything sounds like rust.

You're going to have to determine the source of the humming or buzzing by being near the furnace when it happens. My guess is the draft inducer blower or main blower is having a problem.

The two manuals below have the specs for your furnace in them.


PART 1 /documents/NUGK SERVICE MANUAL.pdf
PART 2/documents/NUGK SERVICE MANUAL.pdf

 

That's a good idea although my dad will never have someone come in. The only time it will not work and he even hates that. I think it's because the last person to work on our furnaces told my dad the furnace control board was underwater at some point and he would have to replace it even though the basement has never flooded.

Sometimes the buzzing sounds like it's in the furnace and sometimes it sounds like it's coming from the outside. I'll try to pinpoint the sound when it happens. Thanks for the manual.

 

As for the dirt comment, I'd hope the furnace sees regular maintenance at a minimum of once per year. A furnace is an appliance that requires regular service

 

No. Both furnaces have not been serviced since at least 2012. My dad doesn't want to pay for someone to come out and clean them. I told him we need to clean the dirt out of the basement furnace but he has the idea we are going to dismantle the whole furnace. We did that a few months ago for the upstairs furnace after a bunch of insulation got stuck in the blower and the A-coil.

This summer I'll take off the cover and vacuum it out.

 

Dismantled? Why? You should be checking the heat exchanger but a complete tear down is a bit pointless.

 

We pulled the blower out of the upstairs furnace to get the insulation off of the A-Coil and blower. As for the downstairs furnace, I'm just going to pull off the front panel and vacuum it out. When I told my dad we needed to clean up the dirt in the downstairs furnace he had the impression I was going to dismantle the whole thing. I wouldn't really know how to get to the heat exchanger to check it.

 

A combustion analysis would give a decent idea of the condition of the heat exchanger. So would monitoring rollout.
You can purchase a decent analyzer for $500-$800.

 

Well, I'll look into it but I can't guarantee that it will happen.

 

I would suggest a furnace checkout by a contractor. A combustion test will not give you a yes or no answer. You'll have to take the readings it gives you, such as O2, CO, and such and interpret the data to determine the health of the furnace. A cracked or rotten heat exchanger can expose you to CO, which can quickly cause brain damage and death.
As I said before, a furnace is an appliance in need of regular maintenance. It's one of the most used pieces of equipment you own. It'll be used more then even got car. Checkouts are essential for the health and well being of not only the furnace but the occupants of the structure it serves.

 

Again, it's not up to me to get the furnace fixed. If the thing needs service, I'll suggest a combustion test be done.

 

Have you determined what exactly is buzzing? Is the heat currently running?

 

No to both questions. The noise comes and goes.

 

Many people are hesitant to call a contractor to work on their furnace due to the charlatans that don't deliver what they promise.

Call your gas provider. Most of them have highly trained techs and since they are bound by the gas company they are reliable and fair.

A furnace is NOT a "buy it and forget it" appliance.
If the heat exchanger leaks CO into the heated air.... people will die.

 

$$$ is the issue here.

However, I'll open the furnace up tonight and look around some more and see if I can find the source of the dirt.

 

There is no problem as to the source of the dirt. Cleaning is a requirement on a fuel burning appliance. The act of combustion, the fresh air needed to maintain combustion, and everything else going on create an environment that attracts and builds dirt. It needs regular maintenance.
So your house is currently without heat?

 

Post a picture of the furnace please

 

Here you go.













The dirt in the furnace stuck to a magnet.

 

I'm not sure why the forum flipped them. They're fine elsewhere.

Imgur: The most awesome images on the Internet

 

The "dirt" that stuck to the magnet is rust.

 

I figured that. The heat exchanger looks like it has rust in it.

 

Is this the model that had the horizontal inducer? There was a service bulletin out on that model. They'd give you a credit towards a new furnace. Horrible design.

 

I believe so.

Imgur: The most awesome images on the Internet

 

Buzzing is likely the inducer. That's one of the many design flaws that furnace suffered from. They were junk.

 

Maybe this thing will need service sometime soon and this thing can get overhauled or condemned.

 

It needs service now.
There is no overhaul. There was a service bulletin that would credit you some money towards a new furnace. It wasn't a recall and it didn't pay for the entire replacement or install.

 

It just started making the buzzing sound again. The draft inducer started up and when the burners started firing, the buzzing sound started. It then stopped when the burners shut off. This time I caught it on audio. https://youtu.be/pnpOane-qxE

You can really hear the buzzing at about 16 seconds.

 

I shall look into it.

Where was this service bulletin at exactly?

 

Didn't hear much buzzing.
Bulletin was via an ICP dealer. I got a replacement furnace for a friend of mine at cost with the discount from the bulletin. $300 seems to come to mind for the credit but that may be wrong.
You need to troubleshoot the furnace, have someone fix it or just turn it off. It's likely trying to tell you something's wrong that needs to be addressed. As has been said multiple times throughout this thread a furnace isn't something you just ignore. You need to maintain it before it fails, kills you or burns the house down.

 

I'm going to show my dad the rust from the heat exchanger. Hopefully that will convince him to do something.

 

Isn't that an intermittent ignition pilot light ?

When the furnace first starts up the spark igniter lights the pilot which lights the burner.
If I have that correct..... that sounds like the igniter coming back on. You could visually verify that.

 

You are right. So it's might be something with the igniter? I'm wondering if that's going bad. There's times where the furnace fires right up or it takes a few seconds (2-3) of clicking for it to start.

 

Well, I told my dad today about the furnace and rusted heat exchanger. He asked me if we could just get the heat exchanger replaced. I told him it might be the same price as a new furnace. I was looking on Heil website and I found a 92% efficent furnace that has a heating capacity options from 40,000 to 120,000 BTU. The closest model to the 75,000 BTUs is either 60,000 or 80,000 BTUs. I was figuring just to get the same size as we have now (looks like I'd have to get the 80,000 BTU mode). That size works fine right now. It's model number is N9MSB and it looks like it's compatible with a 2 inch PVC chimney (which we have now). Any thoughts on this or any other suggestions? It needs to be as cheap as possible but still use a 2 inch PVC vent.

 

You should do a heat loss calculation on your house to determine the size needed. It's very likely your home, like many others, has an oversized furnace installed.
Your dealing with gas and electric so you'll have to pull a permit and get an inspection per local code.
The furnace will not be plug and play. Changes to the gas line, high voltage and control wiring may be needed. Duct will need to be adapted. If you have air conditioning, it may be necessary to reclaim the refrigerant and remove the evaporator coil.
Afterward you'll have to perform startup which will include adjustment of gas pressure and airflow.
Equipment purchased online does not always have a warranty. Many manufacturers void the warranty for diy installs.
Exhaust size is based on length of the run. 2" is standard with increases to 3" if your over a length dictated by the manufacturer.
Trying to do the job for as cheap as possible may get you a mess. Furnaces are not plug and play. They require some technical skill to install and set up.
Read here-
https://www.angieslist.com/articles/...vac-brands.htm

 

I was thinking we could buy the furnace ourselves and have an HVAC company come in and install it.

 

I wouldn't suggest doing it that way as most of the companies willing to do that are ones you don't want working on the unit. An install is very easy to mess up. Plus if anything goes wrong the install company will hand you the bill. Same if the furnace comes in broken or has a failure. Your going to get billed from the installer as your the one holding the warranty, which may be void anyway if it's an internet sale.
If you asked me to do it, even on the side, I'd decline.

 

When it's time to replace it, I'm going to make it quite clear to the contractors to give us a basic system that fits the area it needs to heat and that will connect to the 2 inch PVC exhaust pipe. None of that modulating weather responsive blower and burners or useless things like that. Money is the big problem here.

 

The exhaust size is dictated by the length of the run. Yours could very well be wrong now, or it could be correct. Usually 2" is good for somewhere around 15-20' of length. Fittings have a bearing on this.
Purposely releasing refrigerant is not only illegal, but also screws over the consumer as it reduces the inventory of refrigerants no longer manufacturered and therefor drives the price up more. It's a supply and demand system. This is why R12 made it to around $2000 for a 30 lbs bottle (my cost). It has since reduced drastically as there's not much demand anymore.
My neighbor bought an eBay unit. Came in damaged and had to be repaired. He hired some cheap guy to do the install and the guy showed up in a battered pickup truck with few tools and took a week and a half to do the install. Equipment still doesn't run right. Condenser is overly loud and requires a sprinkler to be used on hot days. He actually had the nerve to come over and ask to borrow my tools.
The price you pay for a contractor includes permitting, licensing, warranties and skill. The internet has ruined the general publics perception of trade work.
In general you get what you pay for.
Many systems are already oversized. So this is especially bad if your converting from an 80% to a 90%+ as the output BTU is much different. A load calculation needs to be done. Or else you'll waste money on fuel and energy. Converting from R22 to R410A can cause humidity problems if not sized right.
There are still basic condensing furnaces available.

 

The Goodman brand is a trusted and respected brand. They are also one of the only brands that will sell to anyone. If it comes damaged the trucking company is responsible just like they would delivering to anyone else. I think it comes down to you know what you are doing or you don't, but if you do it yourself you can save you a ton of money(hence the name of the website DIY). The warranty is somewhat pointless since it still doesn't cover overpriced labor. It just covers parts. I could buy 3 units for the price that I was quoted by one "expert." In my case it is a very simple job.

 

Goodman is fine. They are now part of the largest manufacturer of HVAC equipment in the world with Diakin. They've just gotten a bad name because they sell to anyone, then when the equipment doesn't run right after a poor install the equipment gets blamed.
If the OP is up for it, diy is fine. However, they mentioned buying the equipment then having someone install it. I've never really seen a situation like that play out well for the owner.
As for the shipper or seller paying for damage, I went to a pizza shop years ago where the owner had purchased 2 walk ins off of eBay. Then hired us to put in the refrigeration systems. When I arrived over half the parts needed were not included in the purchase. So the owner paid for me to drive around for most of the day and gather what was needed. Then when the install was done, one compressor was locked up. Since I didn't own the warranty it was his problem to figure out. I think he sued the seller or something like that, not really sure. He had to pay out of his pocket for us to replace the compressor. He probably paid over three times what the job should have cost.
All my warranties cover labor between 1-5 years from the date of startup. Some specialized equipment does 10 years.