Drolet tundra sides shaking?

[Bwfried1]

Hello everyone,
My name is Brian I'm new here to the forum. I've been reading/watching for quite some time now. I installed a drolet tundra about 2 months ago in my basement. I've been using it for about 3 weeks now and noticed something odd tonight. About an hour into the burn the sides of the tundra start shaking/wobbling and it sounds like thunder coming through the vents. I'm going to call SBI tomorrow, I just wanted to see if this is normal or if anyone else has encountered this? Thanks for the input guys.

I'll try to get a video of this happening

House info:
2400 sqft
Forced hot air duct work
Seasoned wood being used

Thanks Brian !

 

[Bwfried1]

 

[DoubleB]

Hi Brian,
Welcome to Hearth!

No, not normal, and no, I haven't heard anyone report that problem. Sounds like your blower must be involved, it's about the only thing that is energized and could make noise.

I notice in your picture that you have reducers right away on your ducts, which then travel some distance with elbows too. I worry you're inviting trouble. You want to keep ducts big and short enough for the blower to breathe, and it looks like you're already down to a couple 7" ducts max (I can't tell if they're 6", which would be even worse.) My foggy memory is pretty sure that's contrary to SBI's instructions, and there's a reason for their instructions.

Let us know what they say. Good luck!

 

[DoubleB]

And of course you're at liberty to take off the covers to the blower box to get a better peek if anything that got boogered up with the blower. (Best to unplug to the blower doesn't come on with your fingers in it). Removing the covers might also help see if the noise is coming from the blower, because if not, then maybe some material got into the air jacket of the furnace and is flapping in the breeze?

Also, looking at your picture, be sure to close that door handle all but the first few minutes from a cold start. Looks like a smallish fire, but even those can overheat in a hurry if the door is open. I'd hate to see you get overheat cracks around your door. A lot of us got cracking even without egregious overheating.

Do you know if you have an older Tundra without firebrick on the inside of the front (door area), or a newer one that does have firebrick lining the inside of the door to try to mitigate hot temperatures?

 

[brenndatomu]

I hafta agree with @DoubleB , you have the blower restricted too much. When the flow through a blower drops below a certain point, it will actually loose momentum and reverse, causing a surge...lather, rinse, repeat, you end up with what you saw tonight. That is why SBI recommends 8" ducts and static pressure set at +.2"WC.
We have very large industrial blowers at work, they have a minimum set point based on motor amperage, they are to never fall below the factory designated "surge point", if they do, you can have a VERY expensive BOOM!
The Tundra only has a 1/2 HP motor (IIRC) and made all that ruckus that you heard, imagine what that would sound like with much larger blower driven by a 75 HP motor.
I'm pretty sure SBI will tell you to fix the ductwork...
Edit: do you have the factory air filter on the blower box? A more restrictive filter would contribute to the problem too. It doesn't matter if you restrict the intake or the discharge side, or both, either can result in surge

Not sure whats up with the font size change, I can make it bigger, or much smaller, but not std (4) !?!?
Oh, and welcome to Hearth Brian!

 

[brenndatomu]

Test post...for font size
Edit, weird. Oh well, movin on

 

[DoubleB]

If you temporarily take off 1 or both covers on the front/back of the top of the furnace, you'll get much more airflow through the furnace, and that may help you confirm that inadequate airflow is the problem. Of course, don't leave it that way, but it may help you quickly notice if anything changes, and then you'll know why. And of course make sure you have plenty of unrestricted return air as @brenndatomu indicates.

 

[maple1]

I'm not a furnace guy, but it sounds like restrictive ducting to me also, especially seeing the reducers right at the take-offs.

But if you've been burning for 3 weeks now & it just started doing it - that is a curiosity. Unless maybe it was borderline 3 weeks ago & a filter got just dirty enough that it just made it cross the borderline. Or a duct damper got closed some or something.

Should be able to do some trouble shooting but not sure how easy it would be seeing all the tape there - pull one of the ducts off the top & see if that makes a difference. Or maybe try pulling filter out first & see what that does. We also can't see how restrictive things might be downstream.

 

[Bwfried1]

Hey guys thanks for the replies, the ductwork has been an on going experiment. I've been playing with blower speeds and duct size to try to get heat to the far end upstairs bedrooms. I do have a newer tundra with the front fire brick. I took a look this morning and the filter is filthy which I guess is a good thing. I'll grab a case of good filters from work today (fastenal). Haven't had a chance to call sbi yet

 

[Bwfried1]

So last night I changed the filter and problem no longer exists. Thank you for the help guys greatly appreciated!

 

[DoubleB]

I changed the filter and problem no longer exists.

Glad to hear. If you used a pleated filter (like I do), it doesn't take long for them to collect all the gunk flying around, especially without a return air duct so that you suck in the basement air that just got filled with ash from cleaning out the firebox.

Even if the problem seems to have gone away, I suspect you still have a developing, long-term problem. If all it took was 3 weeks of shoulder season use on the air filter to cause thunder in your ducts, then I'd worry your system is so marginal on its best day that you're going to keep having problems starting with poor performance and ending with something overheating and/or breaking.

I think you will serve yourself well to increase those ducts to proper sizes and make sure you're getting enough airflow.

Glad you're making quick headway. Happy Heating!