[RE-wrenches] Modules over vents

Wed Sep 24 08:04:04 PDT 2014

I have installed modules over plumbing vents many times. Some
inspectors don't seem to care, some DON'T like it. One inspector
claimed that a plumber might need to get onto the roof to snake the
drain lines through the plumbing vents on the roof. If there is
adequate air flow into and out of the vent, that is all that really
matters. They are primarily installed to allow the system to breathe,
and not create vacuums in the drain system.

Michael D. Nelson
MD Electric & Solar

On Wed, Sep 24, 2014 at 7:33 AM, Solarguy <ntrei at 1scom.net> wrote:
> I just finished installing an exhaust vent/intake pipe for a NG powered
> demand water heater in rental property I own. The manufacturers instructions
> require the vent to be a minimum of 12 inches above the roof.
>
> If you added another 6” of PV you could potentially disrupt the flow of
> exhaust and likely violate its UL listing. The ‘pipe’ trade name is “3X5”, 3
> inch diameter exhaust pipe inside a 5 inch galv pipe.
>
> If needed you could buy a 6” extension to maintain the clearance but the
> shading would still be a problem.
>
> Jim Duncan
>
>
>
> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
> Behalf Of Bill Loesch
> Sent: Wednesday, September 24, 2014 5:38 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] Modules over vents
>
>
>
>
> Bruce, August, et al,
>
> This is but one more example of confusing terminology. A plumbing vent is
> not an exhaust vent!
>
> A plumbing vent (what August calls a cold vent) is provided to allow the
> sanitary drain traps (and perhaps more) to operate properly. Without the
> properly functioning traps you would have sewer gas smell and sewer gas from
> the plumbing fixtures. This was commonplace when indoor plumbing was
> introduced to early adopters.
>
> An exhaust vent is another animal entirely. An exhaust vent carries the
> combustion products to a suitable exterior location for dilution with
> ambient air. With the advent of power vented combustion appliances, a direct
> vent (one that takes in combustion air from the outside and naturally
> exhausts combustion products to the outside) is IMHO the only responsible
> way to install any power vented appliance in a freezing climate. (Power
> vented appliances come in both condensing and non-condensing flavors-they
> can penetrate the side wall or the roof). Originally, two separate pipes
> (with two independent properly separated penetrations) was used. That
> technique is still often used today. More recently concentric vents have
> been introduced both for condensing and non-condensing applications. A
> concentric vent can simplify some installations by putting the exhaust pipe
> inside a larger air intake pipe allowing for one, albeit larger,
> penetration. As you might imagine if the exhaust flow is
> hindered/diverted/redirected by an inappropriately located solar module
> combustion gasses will be re-ingested into the intake air. Not good for
> equipment performance. My understanding is the power vented appliance
> manufacturer dictates what kind of separation/clearances are needed with
> their product. My guess is you find they want at least a foot of separation
> between the top of the " inverted cone" and the module. Probably not what
> you had in mind for an aesthetically pleasing installation.
>
> I hope this helps,
>
> Bill Loesch
>
> Solar 1 - Saint Louis Solar
>
> 314 631 1094
>
> On 23-Sep-14 6:54 PM, August Goers wrote:
>
> Bruce and All,
>
>
>
> Sorry, I hit send before I had a chance to complete my thoughts. What I
>
> meant to say was that I've found AHJs often allow us to cover cold
>
> plumbing vents but I've never tried or had any luck with covering hot
>
> vents including condensing boiler PVC vents. Once again, if in doubt you
>
> could see what the plan checker or inspector thinks.
>
>
>
> Best,
>
>
>
> August
>
>
>
> -----Original Message-----
>
> From: August Goers [mailto:august at luminalt.com]
>
> Sent: Tuesday, September 23, 2014 4:15 PM
>
> To: 'RE-wrenches'
>
> Subject: RE: [RE-wrenches] Modules over vents
>
>
>
> Bruce,
>
>
>
> I'll send you the CA plumbing code vent section offlist (attachment too
>
> large for this list). The way I read the code is that you technically
>
> can't cover any type of plumbing or hot vent. However, and I've run into
>
> little resistance from AHJs in the Bay Area by covering these. You might
>
> want to check in with your plan checker.
>
>
>
> Best,
>
>
>
> August
>
>
>
> Luminalt
>
>
>
> -----Original Message-----
>
> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
>
> Behalf Of Bruce Leininger
>
> Sent: Tuesday, September 23, 2014 3:49 PM
>
> To: RE-wrenches
>
> Subject: [RE-wrenches] Modules over vents
>
>
>
> Hi all.  We're designing a system on a roof that is literally infested
>
> with plumbing, exhaust and combustion vents.  The combustion vents are PVC
>
> and none of the vents are more than 1.5' above the roof.
>
>
>
> A racking company says that we can cover them with modules, since the
>
> modules will be at least 4' above the roof.  They have not yet provided
>
> any building code references to say that this is ok.  Do any of you know
>
> if the building code allows this?
>
>
>
> Thanks.
>
>
>
> Bruce
>
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-- 
Michael & Jessica Nelson
MD Electric & Solar Inc.
Office: 707-884-1862
Cell: 707-684-0064