Cannot find draft test tube on Harman P35i

[jeffreybcox]

I have a Harman P35i insert that has been giving us smoke/CO trouble from the first day it was installed, brand new and by the Harman dealer. Eventually they gave up trying to find the problem and swapped it out for their floor model. Since then we have still struggled with smoke but at least the CO hasn't been a problem.

I'm trying to go back to square one and make sure they didn't mess up the original installation. I wasn't home when they installed, so I don't know for sure they didn't do a draft test either on the first or second insert. But the places in the installation manual where they were supposed to record the readings are blank, so I'm skeptical. I have a Magnehelic from work and am ready to test.

But there isn't a draft test tube where the manual says it should be. There is a single tube running from the back of the burn pot housing to the vacuum switch, but that's it. Am I supposed to pull it from the switch and test there? Or am I missing something?

 

[jeffreybcox]

In case anyone else has this difficulty, here's what we eventually figured out. Basically, the floor model they swapped in was enough older that the manual was a mismatch. I had found other versions of manual, but apparently not the right version. In the right version, it tells you that the draft test port is just a hole plugged from the inside with a bolt. The bolt is inside the firebox, pointing down from the left-side shelf area. Then you put the test hose up into the port from the outside, which is located above the ash pan spring latch.

 

[Don2222]

In case anyone else has this difficulty, here's what we eventually figured out. Basically, the floor model they swapped in was enough older that the manual was a mismatch. I had found other versions of manual, but apparently not the right version. In the right version, it tells you that the draft test port is just a hole plugged from the inside with a bolt. The bolt is inside the firebox, pointing down from the left-side shelf area. Then you put the test hose up into the port from the outside, which is located above the ash pan spring latch.

Hello
The place in the back of the unit that usually can leak smoke is the exhaust flange that that slides into the frame where the liner is attached. Harman has a very good foam gasket that keeps it from leaking smoke. I have replaced that gasket on an old invincible model where the foam gasket was very old and coming apart. Anyway that is what you should check to see if the gasket is good and also compressing against the frame to make a good seal.
Also I have seen poor installs where the stainless steel liner is not properly sealed with high temperature silicone before inserting and bolted into the frame collar with self tapping screws and then additional silicone added on the top edge of the collar against the ribbed SS liner. You can also add high temperature HVAC foil tape from Home Depot around the the same seam between the frame exhaust collar where the stainless steel liner is inserted,
That is where you can get the smoke also.

 

[jeffreybcox]

Thanks, Don. I've changed that gasket out a couple times. I have never been convinced that it was the real source of the problem, though it does make it worse if I let it get worn out. Checking things like the liner joints, top and bottom, is high on my list after the draft test.

 

[Ranckie]

I've had the Harmon Accentra Insert since 2007 and I'm getting ready to do a draft test on mine. There are many things that can affect the draft in each stove installation including line voltage in the home as well as the height and location of the chimney. I'm sure that's why Harmon wants a draft test done on each installation. My draft test hole is located under the ash pan, near the left front side of the stove, and is plugged with a short bolt, and came from the factory that way. I just found the actual test procedure (link shown below) while looking for the fitting that goes into the test hole to connect a tube to. The Harmon part # for the Draft Meter Bolt & Tube is 1-00-04004 and can be purchased at Mountain View Hearth Products for $19.00. In actuality, it appears to be nothing more than a bolt with a hole through the center, but the tube looks to be rigid metal and I can't figure out how the tube is used. Here is the link for the actual procedure; https://www.manualslib.com/manual/1579469/Harman-Stove-Company-Accentra.html?page=21#manual (That's not a hyperlink, I just colored the text blue to show you the entire link; just do a copy and paste on your search bar using the blue text above. Your manual should give you the ideal Hi and Lo draft settings. Good luck with your test.

 

[jeffreybcox]

When I tested mine, I used a conical rubber air gun nozzle to seal the bolt hole. It didn't have to be a perfect fit to get the reading to stabilize.

My low-speed fan setting was set way, way too high. I had to turn the adjustment all the way down to even get close to the vacuum range specified in the manual. It has already improved the situation, though I can't tell yet whether it's the entirety of the cause of the smoke.

I suspect that if the stove is cold and there's no natural draft, the combustion blower is trying to push the stove air up through the flue without any draft help. When the fan speed is too high, two things are happening:

1. The igniter has a much harder time starting the fire, since the blower is pulling too much cold air over the pellets. Therefore, the fire takes a long time to start, and spends a lot more time in smoldering combustion, making a lot of nasty smoke inside the firebox. I've certainly noticed that on particularly slow starts, it gets outrageously smoky in there.
2. At the same time, the blower is pushing hard up the flue. The firebox is negatively pressurized, but the flue is positively pressurized. Even if there isn't an egregious leak anywhere downstream of the fan, any seal that's positively pressurized has a greater chance of leaking. I suspect that one of them (docking gasket, some joint in the liner, etc.) leaks in this situation.

Turning the fan down allows the fire to start faster, make less smoldering startup smoke, and reduces the positive pressure in the flue when there's no natural draft. All this together makes the stove less likely to smoke during startup or up/down rate setting changes.