New Oil Furnace Smell Exhaust/Flue Size Question

Will_L_17

I had a brand new Carrier OBMAAB060154 furnace with a Beckett NX burner installed 5 months ago and I smell exhaust each time it fires on, both in the furnace room and out of the air ducts when the blower starts. The smell dissipates quickly with the blower running but it seems odd to me that I'd get any smell with a brand new unit. The installer said that this issue is likely due to the 6 inch furnace exhaust flue being reduced to a 5 inch chimney flue and that the flue sizes should match. Is that true? The unit's input BTU is 126k, the chimney is at least 25 feet high (runs from the basement up three floors in height), and the chimney flue is a 5 inch circular stainless steel liner. Looking for a second opinion before considering a new, larger liner installed. I'd also add that the exhaust roar is substantially louder with the new unit both in the house and outside. Would a larger chimney flue help reduce the sound as well? Thanks.

pecmsg

If this is a new install and the installer says the reason is the reduced flue, that has to be addressed by them!

Im guessing NO combustion Analyses was performed! Wonder what else was skippped?

Will_L_17

I no longer trust the furnace installer which is why I’ve reached out to this forum for guidance. Any idea why there’s an exhaust smell? Bad draft? Is a larger chimney flue liner needed for this unit?

pecmsg

Unfortunately without being there I can only guess. Get a different contractor on site to review the entire install.

How was 126K Input decided?

Will_L_17

I had three contractors quote and 2 suggested the 126k unit. Not sure what they based it on. 

pecmsg

Will_L_17 said:

I had three contractors quote and 2 suggested the 126k unit. Not sure what they based it on. 

Guessing!

What was there, Did it cycle on the coldest day, if yes then it was oversized!

Will_L_17

A 34 year old York oil furnace with 125k bonnet btu was there before. 

STEVEusaPA

It's possible the chimney liner is the correct size, although it seems like 6" is better for that size. Only a complete combustion test and checking for draft would confirm.
The liner manufacturer have instructions that base the liner diameter on the length of the chimney connector, and height of the chimney.
They should've sized the furnace based on a calculated heat loss.
Now as far as the smell, it could also be related to improper burner set up, lack of combustion air, or something actually wrong with the furnace.
If it is the furnace, it could simply be the cleanouts bolts, or heat exchanger bolts not tightened properly or loose/damaged/missing gaskets. Many times with any new equipment, you have to go around and tighten all the nuts and bolts.
I'd try to find a competent oil burner tech to go over everything, proper combustion testing, etc.

Will_L_17

STEVEusaPA, thanks. Sounds like I need a trustworthy and thorough technician to come out. I’m open to suggestions if you or anyone else knows of one in the Philadelphia area.

EBEBRATT-Ed

@Will_L_17

Check "find a contractor" on this site

Some of the newer burners can be quite noisy.

It is possible that the liner being smaller that the furnace outlet could be correct with the flue being 3 stories tall.

I would suggest a compitent chimney sweep to check the liner and the sizing. The average oil burner tech won't have a clue.

If the liner is ok then get the burner set up properly


If your smelling fumes upstairs make sure you have some carbon monoxide detectors and use caution

STEVEusaPA

OP, Where are you located?

EdTheHeaterMan

My first impression is the burner is not properly set up. That furnace with that burner should not be real loud. and the odor should not be there at all. Although not a fan of the Carrier furnace with the NX burner, A competent pro should be able to get it right. could be the wrong nozzle, A few years ago I had a Carrier furnace with that burner and the factory instructions specified the wrong nozzle specification and I was unable to keep the burner operating. If course it was a Friday night of a holiday weekend and no one was available for Tech Support for several days.

To get the furnace to operate, I needed to replace the Beckett with a Riello burner I had in the shop. Once I got to tech support, they said it was a matter of using a different nozzle. There was Technical Bulletin on the problem, but not being a "Carrier Dealer" I did not have access to that info.

I left the Riello burner there and returned the Beckett burner to the distributor and got a Riello warranty replacement. The only reason I have an open account with that distributer is to be able to solve warranty issues on Bryant and Carrier products. Hardly ever used it for other stuff.

EBEBRATT-Ed

I have had the same issue where the "factory nozzle" wouldn't work.


At that point you toss the instructions and do what you want. If anyone think these manufacturers do adequate testing I can answer that. They don't

I always start with what the factory wants.

I have had Carlin out on two jobs where the spec nozzle didn't and had the problem with Powerflame as well.

The answer you get from the as to why is always the same, basically "In this boiler with this fuel etc.the spec nozzle isn't the best choice"

This is far from the exact science that many believe it is

426hemi

There’s more then one issue here #1 a properly set up burner shouldn’t have any smell even if the exhaust vented inside the house #2 there shouldn’t be any positive pressure in the stack ever get someone to look at it and set the burner up correctly and check the draft both over the fire and in the stack if anyone tells you they can setup a NX burner without a combustion analyzer find someone else this isn’t a Beckett AF best case scenario your sending money up the chimney or clogging the thing up with soot both will cost you more money in the end then getting someone to set it up correctly 

SuperTech

I'm also not a fan of the NX burner on Carrier furnaces.  They can be a bit finicky.  That furnace should have a cover over the burner to reduce the noise. These furnaces absolutely need to be tuned using a digital combustion analyzer.  Proper draft and true zero smoke are essential.  Was a barometric damper installed? Post some pictures of the furnace,  that would be helpful.  

Ctoilman

Like many have posted already, there needs to be a combustion analysis done, ESPECIALLY with the NX burner.  My suspicion is a poor start/ignition issue is giving off the smell.  You need a good burner tech.  

Will_L_17

Thanks all! Definitely going to have another tech come out and take a look. 

Bob Harper

Can you provide pics or a description of the chimney connector pipe configuration? Also, what area of Philly. Yes, need combustion analysis. Gross stack temp must land btw 400-575F pmi. If connector undersized or too tortuous, as many front outlets are, the backpressure can result in odors and noise. Connector must equal vent collar even if the liner is downsized. At 3 stories, a corrugated ss liner probably ok at 0.9 gph/ 126mbh input BUT may behave better with a smoothwall 5.5"ss liner and 6" connectors. Set primary for pre-purge and post-purge if not already.
I'm a venting specialist in Eastern Delco but do go into parts of the city.

Will_L_17

@Bob Harper

Will_L_17

@BobHarper here are pics of the flue set up. I also posted a print out of the combustion analysis that I had to ask the installer to do a couple weeks after install when I found soot all over the floor and spitting out the barometric damper. They clearly didn't do it at install. I'm still getting soot on the floor so not sure if these specs are good. I'm contacting other technicians who service the Cheltenham/Abington Township area (I'm near the Township line). 

Bob Harper

Unfortunately you're out of my service area. Your combustion numbers suggest it's under fired a little. If the stack temp is driven towards 575F while reducing O2 and keeping CO as read below about 50ppm would be better. However, for that unit you're probably going to need a 5.5" smoothwall liner min. for it to breathe properly. A 6" SW would be even better. Also, there is no cleanout. While not clearly required on listed liners, a cleanout can provide a sump to collect soot, provide a suitable means of inspection and sweeping. A wye fitting below the breaching would be advised. There should be a hole in the connector where they took the stack draft reading. If not, that draft number is bogus. Keep in mind draft is a pressure measurement and does not equate to mass flow.

EdTheHeaterMan

I'm not sure where in PA @STEVEusaPA is from but he might be close enough. An oil guy I know that does service that area is https://www.ftyoung.com/wp/wp-content/cache/page_enhanced/www.ftyoung.com/_index.html_gzip. He lives in Richborough PA. I don't talk to him much anymore but he is almost as good as me.

STEVEusaPA

@EdTheHeaterMan maybe he doesn't talk to you anymore because you think he's almost as good as you...lol
Yes the OP is out of my service area.

Will_L_17

@Bob Harper I found the paperwork from when we had the chimney liner installed and it says that a "6 inch round stainless steel flue pipe system" would be installed. I'm now realizing they didn't install what I agreed to and paid for. Do you think I should hold them to the contract and have them replace the 5 inch with a 6 inch? The agreement says they insulated it with Chim-mix. Does the Chim-mix now prevent a larger liner from being installed?

@EdTheHeaterMan I connected with Frank earlier this week. Thanks for the referral!

Bob Harper

It's your home. If he didn't perform to the contract you can force him to make it right at his cost. Pulling an insulated liner is his problem. It can be done. If the chimney has to be demo'd then rebuilt its on him. If he doesn't make it right and things go bad, the cost through litigation would be a few decimal places more than the cost to make it right. Why wait for someone or something to get hurt? If it ain't right, it ain't right. Hey you gotta' live on that house and breathe that air.

Good luck!