Combustion Analysis and B-Vent

[swamp rat]

I have been slowly growing my business for about 4 years and am just now buying a combustion analyzer. I know that you guys are probably going to tear me up and call me a hack for not owning one yet, but I've been accumulating other tools and figured I could get by with timing the meter and some other measurements. So, when you're done with any insults you want to toss out there could you tell me how you are getting flue gas analysis on systems with B-Vent? Or for that matter, how about the 90 plus systems? I don't want to breach the integrity of the vents.

[targetman]

http://www.bacharach-inc.com/

[Rudy]

Drilling holes in B-vent is no problem. If you need, we have letters on file from several B-vent manufacturers stating there is no problem.

I've always drilled the plastic pipe on 90+ equipment (and sealed the hole after testing) - if you don't want to drill it and it is sidewall vented, just take the sample from outside.

There is alot of info regarding combustion testing on our application website - http://www.bacharach-training.com .

If you have any specific questions regarding instruments or applications, don't hesitate to give me a call (412-576-1350).

Good luck, rudy

[MikeJ]

Good foil tape seems to work on both applications, at least it is still there a year or two later.

[wormy]

Rudy,

I didn't know it was ok to make a test hole in a flue.
I'm sure my boss would like to have info on this
(knowing him, he already knows it..... its hard for me to teach him anything. He's a freakin walking encylopedia)
Can you have bacharach post info on this on their website.
Unless its there already and I haven't seen it.
If its there, then give me a link.

Also, you got any suggestions on how to seal the holes?

Being a tech, I'll need something that sets up 'really fast'. Actually I need something that can be removed for
future testing. We do a flue gas analysis on all our safety and effeciency contracts. Do you know of any products that are UL listed for this?

Hmmmm
Is a hole in B vent considered a B hole?

[wormy]

Wow....

after reading the Application Information link....
I found out I didn't know half as much as I thought I did.

Definatly gonna have to study that one.

Great read.
Thanks for the link.

Thought I've already read all the stuff on that web site.
Guess I didn't.

[hearthman]

I wouldn't seal holes in PVC with foil tape. It may stick now but over time the acrylic adhesive will break down and it will lose its grip. Since this pipe is under positive pressure, you have something trying to poke its way out or pry it off. Also, the very acidic condensate will eat right through that foil.

If you're gonna drill it, seal it with something that's air tight, liquid tight, and acid resistant. Then test it for leaks using a chemical smoke puffer, soap bubble soln., and a CO meter. The smoke will show you pin hole leaks. You can try soap bubbles but generally the high pressure will simply blow it away without forming a bubble. The CO should be self explanatory.

One tip, don't drill where condensate will probably drain to the hole.

Second tip: permanently mount a fitting with a cap. Record the vent pressure as a benchmark.On B-vent, you can get a draft reading. Should anything go wrong with the pipe joints or the blower, the pressure will change. With PVC, a blocked vent will usually read high. Here you'r looking for a change and not so much one specific number. Before cementing the PVC to the appliance collar it is always a good idea to run a quick pressure test. Seal the end towards the appliance with a cap cemented on that will be cut off later. Install a test plug with a Schraeder valve at the discahrge and put a few pounds of air in it. Read your pressure off the test plug. You can puff the joints if the gauge starts dropping.

When sealing B-vent, make sure you work some silicone in btw the inner and outer walls so you don't lose the seal. OF course, since most vent connectors are single walled galv. you can drill this and seal with a button plug for easy removal. Since this pipe should be under negative pressure, any micro leaks should act as a venturi and entrain room air. However, with Cat. IV fan assisted furnaces, you'll want a tighter plug so it doesn't blow by.

HTH,

[Rudy]

Good suggestions HTH.

I've scanned the letters from the B-vent manufacturers but I'll be damned if I can find them this eve. I just emailed one of the other trainers I work with asking him to email them to me (again). As soon as he does I'll put them up on the training website and post the link.

I've always used silicone to seal the holes.

OK, halftime is over, go UNC!!

[MechAcc]

3M has a +600 degree rated aluminum foil tape #2113NA specifically for flue pipes. If you have a Do It Best hardware store nearby you can order under their sku# 455598.

[Edited by MechAcc on 04-05-2005 at 05:49 AM]

[Steve Wiggins]

Why can't they make a 4" b-vent take off with a test fitting & cap already mounted? This way we won't have to drill or tape anything.

[docholiday]

B-vent should be under negative pressure, a small test hole isnt going to make a big deal. If worst comes to worst, get a 1/4 threaded bolt and cut it to 1/4" long and screw it in the hole when your done with the test.

PVC vents can handle a dollop of standard silicone over the test hole.

[Rudy]

For those wanting 'hard copy' documentation of the letters from B-Vent manufacturers allowing the drilling of their products - I finally found the files this am and finally remembered how to put them up on the website (it's been a while...).

Anyway, the link is near the bottom of this page:
http://www.bacharach-training.com/re...efercepage.htm

And by the way, docholiday is right, you really shouldn't have to seal the hole in B-Vent. However, most homeowners have heard that CO "leaks" out of a vent system.

We all know it doesn't 'leak' out - it is blown or sucked out but just to keep the concern from arising, I've always sealed the holes (except on my own equipment).

[wormy]

Thanks Rudy for posting the letters.

Much appreciated.