Anyone familiar with this type of furnace Carrier?

Is this 4 inch pipe the intake or exhaust?
I couldn’t get around to the back of the unit. Would the exhaust or intake come in there?
Sorry I don’t have an overall shot of the front with the cover off. I know that would be helpful.
I didn’t spend much time looking at this one. I noticed right away that the 4 inch pipe was open at one of the connections (thinking it was the exhaust) and it wasn’t b- vent. It was about an inch away from combustibles. I didn’t run the unit. Now I’m thinking I should have spent a little more time looking this over. I’m second guessing myself now thinking that the 4 inch pipe could be the intake…
Thank you for your help

That is exhaust. The draft induction fan is connected to it. These units are common in our area.

That is an 80% unit, don’t too many installed any more. Around here also we require the romex to be in conduit.

Good eye LeRoy. That is the same here or BX armored cable.

I found a diagram online last night which confirmed I called it right. I learned a lesson. I knew it had some major safety issues that needed to be taken care of by a professional so I didn’t spend much time looking things over. Once the report was finished I started thinking about the fresh air intake I noticed in the attic. The fresh air intake was in the attic next to the B-vent but I didn’t see it attached to the furnace anywhere. From my pic I couldn’t tell if the 4 inch pipe was attached to the induction fan or not. Next time I will look things over better even if I’m deferring it to a specialist.
Thank you for your answers
Have a great day!


I called out the fact that there was no service mans switch either.

Thank you

Quite frequently a room, closet or furnace needs more fresh air. The intake will NOT be attached to furnace BUT simply be in the room with the furnace (could be about 12" from ceiling - could be about 12"-24" from floor - could be both. The intake could then end outside; in the attic; in a crawlspace; or maybe in another room (like a family room above if configured right).

A 80% furnace with inducer fan is the norm today … 90% units show up about 1 in every 10-15 units.

60-% are obviously older units and no longer made.

In Wisconcin you’re licensed … When you went to home inspection school, did they not point out differences between units? Also some localities frown on installing under stairs … Does yours?

Hi Dan,
Here most of the newer furnaces are 90+. I’ve inspected mid efficiency furnaces before but this particular type was a first. Yes I have studied the different types of furnaces. As I said in a previous post I noticed the flue issues right away so I didn’t run the unit nor did I take any more time to inspect it. I defer it to a HVAC specialist for a full evaluation and repairs. While doing the report I started to second guess myself when going over what the owner said. She said the installer was a friend of the family and has been in the HVAC business for years (professionally installed). The question is they are the experts why am I calling out issues with the install. The flue was so poorly done (unsafe) I started thinking maybe it was an intake…
I did see the fresh air intake in the attic so I assume it is piped into this “open closet”. Never saw a furnace installed under stairs before.

Don’t know about other countries but this flue is illegal as hel in Texas and US. It is single wall DUCT PIPE. Too close to touch by humans, too close to combustionables, joints not sealed and will leak CO into living area. I see no door on closet area. Because of this there may not be a requirement for combustion make-up air as the “room” is considered this whole combustion air supply area. As said, no on the romex. That was no professional installation, it was a “jack leg” job! Old saying seen here: You have to “get” to your friends since your enemies won’t let you. God help those customers who were not his buddies. I assume you had the front cover off for photo purposes. The inlet of a fan like this comes into the side, the outlet is on there circumference of the fan.

and where is the unit vented to?
New Construction?
Replacement Unit?

This unit is vented out the roof.
It was a replacement unit.

some general advice…

That type Carrier unit has one 6-7 inch screw to hold the cover on. Due to the exhaust pipe the cover fits poorly and the screw is often secured by 1/2 to 1 thread at the end of the long bolt/screw. Sometimes its evident the installer had to bang the thing in place in order to get that elusive 1/2 thread to start so good luck with removing and installing those. Also good luck with the cover not falling off the next day.

Richard -

For conversation … The Single Wall Flue itself is NOT a defect in a heated area, not concealed and especially not in same conditioned room with furnace. Where it does get BAD is if less than 6" to combustibles or when it leaves the room thru ceilings or walls (w/out Type “B”) or in the unconditioned attic type areas.

That is correct. :slight_smile: