Please why combustion fumes??

Snowden

I’m trying to research this as I’m waiting for our furnace installer to come someday soon.

We have a 2-year old power vent connected to a brand new oil furnace, tank and lines. The power vent let fumes upstairs since it was installed. Now with a new furnace we still have the fumes.

I fear no one can figure it out. I’ve heard some say there is a pressure problem where there’s negative in the house and it makes it up somewhere.

If that’s the case, what can be done? Any help is appreciated. Thank you.

Jamie Hall

We'll need a lot more detail -- make and model of furnace, ditto for power venting, detailed description of vent piping, detailed description of intake air, location of exhaust and intake relative to windows or doors... at the very least.

Also, do you have any exhaust fans or heat recovery units operating? Kitchen? Bathroom? Attic?

Leon82

Do you have a carbon monoxide detector in a room near the vent? Two years is a long time to tolerate combustion fumes coming into the house.

Snowden

I do have a monitor in the room where the fumes reach but it has not ever gone off. Yes, two years is a long time. The co that put that power vent in blamed the fumes on the 25 year old furnace that was never maintained. That did make sense, but we have a new system now and the smell is exactly as strong.

Jamie-I’d have to get all the information together. I know it’s just a basic AirTemp oil furnace highboy. The vent pipes were enlarged by the furnace installer because they must’ve been too small from the original installation. The fan unit is a FASCO and it has a control board UC1 universal 3/4 HP Max Tjernlund. He replaced that entire control board and put a new pressure switch in the fan part. The fan is a FASCO 71214989. The distance from the new furnace to the vent kit is probably 15ft. The installer 2 years ago cut half of a basement window out and fit the fan kit into the other half.

Basically the strong smell is most strong when the furnace has stopped running between cycles. Then it gets worse.

There’s got to be a fix IMO. Find how the fumes are not staying outside and find a fix for it. I don’t like to question the expertise of our installer, but there’s got to be a way to do this, even if I need to help him figure it out.

STEVEusaPA

Based on your post in the other forum, I recommend a 4 minute minimum post purge. The 20 second post purge you are currently set at is way too short.

Snowden

Hi Steve. Lol. You’re in both forums. Just in case you have any thoughts or opinions on the vent setup.

STEVEusaPA

That's a long way to go for a power venter.
Brand/model #?
Length of run?
How many elbows (looks like 2)?
You might be exceeding the maximum allowed distance, based on feet of run and 2 elbows.
You still need the post purge, 4 minutes, min.

SuperTech

I don't see many Tjerlund power venters like that one. The last one I saw had a time delay relay in it, that took care of the post purge. If possible try to open it up and take pictures of the wiring diagram.

That vent pipe does look way too long for my liking. Why such a long run?

Snowden

I did a measure. It’s hard because yes, the vent pipe goes like 3ft then takes a 90 degree turn and then like about 18 ft and then another bend and then like 3ft to the fan by the window. So it looked to me like total of like 23-25 ft. I don’t really know why two years ago this company wanted to take it that far-probably cause it was an easy path? Idk. There’s a few pictures I took also of that control box.

When I spoke to the installer last weekend he mentioned maybe it could be vented in a different area. I really feel like and hope that he can help.

Anyway, thanks again.

Leon82

the elbows are counted as additional length , so a 90 can equal 5 feet of pipe length

SuperTech

I'm glad to see that your power venter is a new one with a circuit board in it. The old sequencer relays in the old models have a high rate of failure. I would set the little dip switches on the board for a long post purge, that should definitely help.Try four minutes first and if that doesn't work bump it up to eight minutes. If I were you I would try to shorten the length of the flue pipe. I can't imagine that it's current point of termination is the only location that is suitable. With a shorter length of pipe you may be able run a shorter post purge and that should help efficiency a bit.

Keep us updated on any progress! I hope this helps.

Snowden

Thank you very much

captainco

I have never seen a power vented oil appliance that didn't need at least 8 minutes of post purge to keep smells out of the house.

Sold a 90% oil furnace with 5 minutes of post-purge and we still had smells. Increased it to 8-10 minutes and it was fine. That is why the Field Oil power venters come with a post-purge up to 10 minutes. This is the answer and the only answer!

Snowden

I may be speculating too much, but what if the furnace goes off, the fan runs for 4 or 8 minutes, but the house can’t stay warm and calls for heat again before the last cycle ended? Especially on be very cold day when it gets down to zero. Would that cause a problem the way it works? The exhaust fan would be running about continuously then I would assume.

SuperTech

No I don't think that would be a problem. A friend of mine has a boiler with a power venter, in January between the four zones and lousy tankless coil the power vent motor runs an awful lot. I'm not sure about the Tjerlund units, but the Field Controls models require oiling the motor. Make sure to follow the manufacturer's maintenance instructions and you should be fine.

Snowden

Gotcha thanks

captainco

This is only a problem on equipment that has built in inducers but then there is a correction for that.

I wonder if the burner motor or the circulator pump motors need oiling??

Snowden

Anything on the furnace should be ok cause it’s brand new only 1 month old. The power vent is actually almost 3 years old now.

Snowden

I read how there are inducers on newer furnaces. I could only imagine that our installer would know a correction for what you are talking about. I’m learning as I go.

GBart

I seriously don't think where the flue goes under the stairs is cool or remotely meets code.

Leonard

Is that long vent pipe an EXHAUST pipe ?

Any fans pulling air out of building, bathroom, cooking, radon abatment?

In a restaurant cooking exhaust fans pulled so much air out of building even with makeup air that building was at a slight vacuum relative to outside, ........and air flowed DOWN the chimney.... into building . So tenant put a power vent on hot water heaters to FORCE it up chimney. ( HVAC was on roof)

When crack open a window is air blowing into house when it's not windy outside, and that power vent is off ?

GBart

It's illegal and too long.

Intplm.

GBart said:

It's illegal and too long.

ron said:

that's what she said

Agreed this is too too long. Dangerouse. Alternate venting needed. Build a SS chimney close to the boiler. A shame this is like this.

invermont

ron said:

that's what she said

Made my day

GBart

and once again we have no input as to the outcome