Loud Humming Noise - Napoleon HDX35 DV Gas Fireplace

https://napoleonproducts.com/downloads/fireplaces/manuals/W415-1434.pdf

Page 45, section 9.1 of the manual references a restriction kit for vertical vents. Do you know if one was used in your install ? Could try to find the manual for that kit to see what instructions are provided with the kit.

KeithO said:

https://napoleonproducts.com/downloads/fireplaces/manuals/W415-1434.pdf

Page 45, section 9.1 of the manual references a restriction kit for vertical vents. Do you know if one was used in your install ? Could try to find the manual for that kit to see what instructions are provided with the kit.

Click to expand...

My compliments to my friend Keith O, who looks like he has put his finger on a likely solution to the problem at hand.

The problem seems to be described in detail on page 16 of the installation manual in the graph showing acceptable and required horizontal and vertical vent runs for proper fireplace operation.

The maximum vertical rise recommended is twenty feet, but that requires a horizontal run of about six feet as I read the chart in the installation manual. Since John's installation apparently is all vertical, that suggests that the draft is excessive and is a likely cause of the problem described.


Just as an example, the illustration graph in the installation manual; prohibits the installation of a twenty foot vent rise unless the six foot horizontal run is included. The vent restrictor specifications might modify that, or might not. A manufacturer's tech rep would hopefully have the experience to know how to vent the system you have so that it will work properly.

I agree with Keith O that getting the manual on the vent restrictor to see what it has to say is a good idea and a good start. It might approve just what you need to do.

And you should be able to vastly impress the dealer from whom you bought the fireplace and the installer by coming up with what is likely a terrific solution to what was really a botched installation!


I think Keith O should be awarded ***** for his diagnosis and suggestions!

When I installed my Pacific Energy T5 wood stove with 8' of stove pipe followed by 10' of class A in the attic and poking out the roof, it had so much draft in cold weather that even after adding a flue damper in the stove pipe the stove intake would whistle when fully closed.

Gas stoves are probably more sensitive to high draft and usually lack any air intake control and draft is the only thing still active when you shut the stove off. It does not surprise me that you would have excessive draft with such a long vertical run. Some stoves have a built in damper that a tech can adjust but in your case you have to buy the restrictor kit to get that functionality. Getting the draft reduced will probably solve your issue.

KeithO said:

Gas stoves are probably more sensitive to high draft and usually lack any air intake control and draft is the only thing still active when you shut the stove off. It does not surprise me that you would have excessive draft with such a long vertical run. Some stoves have a built in damper that a tech can adjust but in your case you have to buy the restrictor kit to get that functionality. Getting the draft reduced will probably solve your issue.

Click to expand...

My guess is that Keith O will be proven to be correct, but you had you own theory of how to interpret the graph, and perhaps you are correct!

This suggests that someone who is an Xpert in installing these stoves needs to be consulted on the right way to do it. Stove manufacturers usually have tech reps who are those experienced experts with their own stoves. You dealer may be able to tell you how to contact a company tech rep or you can try calling the manufacturer directly.

Even though the flames aren't visibly disturbed, the noise you describe is likely to be caused by excessive draft. The graph supports that conclusion for me, and so does the availability of the restrictor. But that doesn't mean I'm correct!

If it was me I would remove a section of pipe above the stove and try to install a flue damper in just the inner pipe. The great thing with a flue damper is that you can open it to light the stove and close it after a few min. It would not be a standard damper install because no-one makes a damper for DV flue pipe.

I had a look for the vent restrictor and it seems to be an annulus which blocks flow on the fresh air side and not the flue side. It does not seem to be adjustable either.

<<If it was me I would remove a section of pipe above the stove and try to install a flue damper in just the inner pipe. >.

You don't want to butch u[p your equipment by doing modifications not approved by the manufacturer.. You void your warranty and create unknown hazards in the equipment.


<<I had a look for the vent restrictor and it seems to be an annulus which blocks flow on the fresh air side and not the flue side. It does not seem to be adjustable either.

Did it have information on how it might extend or modify the venting table in the installation manual?

I could not search for the restrictor on the manufacturers website, or else I may have found a manual for it. Looks like you need to be a dealer to get access. The listings were on Amazon and google, some selling at Walmart....

Check for heat shields and metal tags that vibrate as the firebox heats up. It's weird since there aren't really any moving parts but I've seen it just from the stove heating up.

I cant open the file attachment in your post where you installed the restrictor. Could you check that ? Did it go down by the fireplace or up on top of the flue ? Im personally sceptical of the effectiveness of a restriction on the intake air when the cause is too much draft caused by the flue section ????

Now just to be fair, I had a Morso wood burner, a beautiful cast stove with a built in cast iron grate with an ash tray below it. The ash tray had its own door with a latch. If you were having any difficulty with a new fire, you could crack the ash pan door and feed the fire with air from below the grate. If I opened the door, within about 30 seconds, air would be rushing in at such a rate that the whole chimney and stove would go into resonance and make a very loud "booming sound" something like a chimney fire. It was very scary.

I think you have a pretty big air leak somewhere. It could be between the fireplace and the first length of pipe, because that wiuld be a worst case for highest draft, but it could also be higher up in the system. Especially if it is with the inner pipe not overlapping properly, the internal draft of the inner could suck intake air which is coming down the outer annulus back out the central pipe, so it would not involve anything at the stove at that point. The little supports that space the inner from the outer are not very strong and could rattle a little. Especially if the inners are not overlapping in the first place....