My problem is that even within the same office of the local authority, different people state different requirements.

 

Water heater vent status as of this moment:


I think I've felt aluminum pie plates that were thicker than z-flex. In this particular case, real-world safety does not enter the equation, IMEO. The most important thing is that I'm complying with our Overlords' wishes (at least I think I am).

Does anyone know what the official name is for the cross-brace/support beneath the round duct pictured below, or are they something the duct-installers fabricate as they go along?

The reason that I ask is that Goodman states in the furnace installation manual that:

"Piping must be adequately secured and supported to prohibit sagging, joint separation, and/or detachment from the furnace. Horizontal runs of vent/flue piping must be supported every three to five feet and must maintain a 1/4 inch per foot downward slope, back towards the furnace, to properly return condensate to the furnace’s drain system."

I'm thinking that those metal supports above would be a very easy way to prevent/support the 4 plastic pipes, as a group, from sagging within the joist space, rather than hang down a metal support-ribbon for each pipe. I could simply place the supports 1 inch lower within the joist space every 4 feet and rest the pipes on them. (If the center-lines of the pipes are not absolutely horizontal, I'll build up a bit on top of the support under those pipes that are a bit higher than the others.) At the joist space opening into the furnace room, I'd simply rest the pipes on the horizontal wall stud at the top of the wall beneath the joists. I might adhere a piece of felt to the top of the metal supports so the pipes resting on it could rest on something "comforatble".

Again, what is that metal support called? If they're available commercially, I'll buy three of them. They'd instally very easily and quickly. Otherwise, I'll either fabricate them or do the same job with some wood 1x2s or even some scraps of 2x4s that are kicking around.

Thanks.

BTW, two Alpine reps have told me that Goodman has told them that sloping the comustion-air pipes is not necessary, but it will be practically impossible to get something in writing from Goodman to that effect. The second rep. gave me the Goodman techinical services telephone number to give to the inspector, should he/her have any concerns about my installation of the combustion-air pipes. I guess Goodman tech. serv. reps actually talk to regulatory enforcers like inspectors, as opposed to ordinary Joes like homeowner-customers.

 

That support metal looks like filter channel which has been cut down.
I, most certainly, would slope the combustion air pipes. I've seen condensation trapped in the intake air pipes as well as the exhaust.

 

I finally found the quote icon!

I guess I'm going to have to go the wood route for the supports. I'll just fire a couple of nails in each end and that will be that.

The Rinnai furnace pictured in my first post has a concentric vent. The combustion air pipe looks like a rather thick vacuum cleaner hose. That thing goes into a big P-trap-like shape before it enters the wall behind the furnace. It's been that way for the length of time we've had the furnace. (The inspector of the installation said I did a great job.) I take it and the exhaust pipe apart every year for examination and there's never been one drop of water in either. This is not surprising because during Edmonton's very cold winters the outside air is unbelievably dry. As that air enters a building and heats up a bit, it get's even drier. Therefore, I'm not worried one iota about moisture/condensation building up in the combustion air pipes. (But what does worry me is our local Overlords, and that is why I'm going to keep that Goodman number handy.)

 

My experience tells me if I deviate from either the National Fuel Gas Code, International Mechanical Code, or the manufacturer's installation manual, I'm in for a ration of crap from the inspector & I'd best be prepared to show him documentation as to why I did what I did. In general, if you follow the I&O manual, you are OK unless a code is more restrictive. As long as you follow the most restrictive reference you can't go too far wrong. I've never had an inspector reject a job because I went beyond what was required.

 

My two-furnace project is finished.

Working backwards:












I arranged the plastic pipes so that they would be as short as possible. The longest of the plastic pipes is the combustion air line on the left furnace. It is 23.5 feet long, including its length inside the concentric vent.

Rather than deal with a possible rejection by an inspector due to using Gastite, as you can see, I caved in and fabricated a 3/4" black iron header arrangement that is as solid as a rock.

I have performed temperature rise tests on both the basement (LEFT) and main-level furnaces in their default, from the factory, condition. Surprisingly to me, they were 39 and 40 F, respectively, in both low and high stage operation. Typically, return air was 69 F and hot-air-out was 109 F at about two feet from hot air plenum. Fantastic!

This was a very interesting and challanging project that forced me to learn various skills from sheet metal work to black iron pipe joinery to plastic pipe arrangement. If I had to do this again, it would take me 1/3 the time.

I have a question about furnace filters. Obviously, there are literally dozens of filters available in a wide price range. Our furnace takes 25 x 16 x 1" filters. What's the best bang for the buck for a good filter that does not restrict air flow very much?

Thanks.

 

Installation looks good. Good move on using the steel instead of CSST for the gas piping.
Regarding the filters: I prefer a good, full thickness, glass fiber filter.
The only thing I saw in the installation was, in the fourth picture, where there is foam(?) sealant around the pipes. Here, we are required to use a fire stop sealant which is red or orange in color. Don't know if codes are the same there or not.

 

Our Overlords' inspection takes place tomorrow between 8 AM and noon. I'm sure the foam issue will be pointed out if it is indeed an issue. It wouldn't be too difficult to swap foams if it were required.

If it were required, I'd probably remove the silcone caulk and foam surrounding the concentric vent from outside the house working in, rather than try to work in that cramped space from inside. Then I'd use whatever foam is required and cap/seal it to the siding using the same pure silicone sealant that you see in the photos of the rain caps.

If there were ever a fire at this location, it would mean that a gas fire is making its way through both heat exchangers, through the induced draft fan and down the vent line to the concentric vent and then across the combustion air space and, finally, through the outer wall of the concentric vent to the foam. This is a near impossiblity, if not an absolute impossibility. The plastic exhaust pipe at the furnace would be up in flames long before the above journey were made to the foam.

FWIW, beyond the requirement for a securing strap, the concentric vent installation manual makes no mention of installing either sealant on the outside of the house (to seal the vent to the siding, which is a must-do, IMO) or any sealing/insulating material to surround/seal/insulate and make air-tight the 1/4" space between the edge of the drilled hole and outer body of the vent. The Alpine tech. rep. with whom I've been communicating said foam was typical for the latter purpose, but he never mentioned any particular type or color of foam which I am almost certain he would have done, if necessary.

After all, the combustion air is drawn into the combustion air space that surrounds the inner vent/exhaust pipe and this situation remains the same for probably at least 24 inches of the 30 inch-length of the vent. I put my hand into the exhaust gas yesterday and that gas isn't much warmer than my exhaled breath.

The outer body of the vent, the part inside the house, is essentially the temperature of the air being drawn into the system. When it's -30 C outside, that vent is going to be very cold to the touch.

 

Our installation was deemed acceptable by two inspectors -- one gas, one HVAC-- today, thank goodness. These events mark the end of our two-furnace, one water-heater-vent project.

Should we haven any problems with our furnaces in the future, I'll either resurrect this thread or start a new one with linked reference to it.

Thanks for all the advice and the opportunity to post.

 

Congrats on a job well done. Rare is the homeowner who will take the time to do things as they should be. We're glad to have had the chance to help in some small way.