No more pvc for venting!!

Bob Gagnon plumbing and heating

Comes piped in with the first 30" in cpvc, attached to the boiler, so you can't screw up. Thanks, Bob Gagnon

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1974bobcat

No more pvc for venting!!

I went for a tour of the Viessmann building in RI and they are no longer recommending (or never did I'm not sure) the use of pvc for venting of condensing boilers.
Has any one else heard of this??? They say cpvc is the way to go!!

john_83

Some manufactors ive heard reccommend that the first five feet of the exhaust to be cpvc but thats all i ever heard

Tom Hopkins

Never!

CPVC for Vitodens 100 only

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1974bobcat

It was my understanding that this would become the norm for other mfg but has not been enforced yet

Cunner_2

PVC

I know Viessmann has never allowed PVC and Burnham is the only other manufacturer that I know of which does not allow PVC. I heard that Canada just passed a law stating that heating equipment must be vented with an approved venting system, that would certainly leave PVC out. If that were the case I believe it would have to be AL29-4-C or polypropolene. I think I see a trend forming here...........

rich pickering

Candian pvc

We can use pvc but it has to be certified. Currently, only IPEX has pipe that is stamped.

I suspect that if you dig deeper into your codes, you would find the same issue. Most pvc and abs has not been certified by the pipe manufacturers for venting.

Glen

BC requirements

Is that only pipe that is certified to the 626 "code" is acceptable and the following directive was issued re replacement of existing plastic vent systems.
http://www.safetyauthority.ca/files/D-G5 070628 5 - Plastic Venting.pdf

Kal Row

It’s because people abuse the privilege…

Had a job where the ac contractor was tasked to do the pvc venting for the boilers, and he put in cellular foam core pvc instead of the required solid schedule 40, I am praying that the inspector catches it and makes him rip it out

so maybe the manufactures are considering CPVC only as that’s not avail in foam core, at least I have never seen any

Mitch_4

System 636

The Canadian code has always had a section for special venting systems as BH vent. But it essentially fell to the manufaturers to certify venting materials in high efficiency equipment. ABS has been used here for over 20 years on Furnaces with no real problems.

Recently though power vented water heaters have had ABS, PVC and even CPVC venting systems melt. Primarily because they are not condensing equipment, and installed in laundry rooms that plug the wheels with lint reducing excedd air and velocity and the pipe overheats.

SO....CSA decided that they are FINALLY going to mandate that the plastic pipe used in a venting system meet the certification as such under the ULC S636 (hence the name of the venting system as 636 venting) rather than any ABS, PVC or CPVC...

This is now considered a SYSTEM, so you cannot mix this manufacturers pipe with anothers glue..it all comes from ONE source like SS venting.

IPEX is currently the only vendor with this product to meet the certification.

Here is a link to the 636 section of IPEX website. They make equivalent to PVC and CPVC depending on the temperature rtange of your flue gases.

http://www.ipexinc.com/Content/EN_CA/2_0_Products/2_4_Plumbing_Mechanical/2_4_9_System636.asp

This material is much denser and smoother than regular plastic pipe, you can tell it is different.

I have been using it pretty consistantly and it really is no harder than regular pipe to install, just have to do it the right way.

scrook_2

CPVC

CPVC will operate at higher temperatures than PVC, that's probably the prime reason.

Guest_8

It's GOT to be for a good reason!

Why elce would certain (high end) boiler MFGs not allow it?

PVC is not, and has never been approved for the venting of combustion equipment. I don't know why it's been allowed to be used for so long, but I'll be glad to see it go.

Not that it doesn't work! It's just fine if it's been installed properly and there is NEVER a problem with the connected fuel burning equipment. However I've seen way too many of these vents run in foam core (PVC & ABS) even though the MFG tells us we can't. Aparently, all of these systems were inspected by our friend "Hector the inspector." The foam core stuff will and does SPLIT right down the middle and I've seen it a number of times. This puts people at risk of CO poisoning.

Just say no to PVC & ABS venting.

Ross_7

PVC venting

Well, maybe if everyone read the directions, and were smart enough to know the difference between cellular core, and correct astm standard sch.40 PVC, it would be nice. But, I guess we don't live in a perfect world, so that means that we have to further idiot-proof these installs even more apparently.

rich pickering

Not approved?

Viessmann allows it as long as it is certified.

Dave Yates (GrandPAH)_2

CPVC then PVC ?

My first condensing boiler required the first ten feet be CPVC then PVC was acceptable. After running for a few minutes, there was no internal temperature difference in the flue.

Unlike PlexVent where the joint leaks resulted in a recall, I don't see the same happening with PVC. While it may be more difficult to draw an exact parallel due to the variables in how a boiler, especially a mod-con, operates as compared to a furnace or water heater where the conditions are fairly constant, PVC has a long track record.

The only failures we've seen have been when PVC was utilized where the mfgrs instructions clearly called for metal. Also when DIY'ers have replaced a direct-vent water heater with a standard atmospheric cat I water heater!

Ross_7

Exactly

I'm with you , Dave. I've yet to see any failures on PVC other than stupid installs like you say.
Ross

The Wire Nut

Perhaps...

... the issue is not what happens when a boiler is behaving normally, but what happens when a boiler is behaving abnormally. Under such circumstances, the safety margins of a material primarily intended for plumbing applications may not suffice to contain a problem. Ideally, a heating appliance will have the kinds of interlocks, inherent safety designs, etc. for the intended venting material never to become stressed in the first place.

Yet, several manufacturers never approved PVC for venting their mod-cons anyway. Rarely do companies intentionally make their products more expensive than that of the competition. Presumably, there was/is a performance problem with PVC in their mind.

How well PVC will stand up over the long term as a venting material for mod-cons may yet to be determined. My limited knowledge of venting materials seems to indicate that PVC is a US-specific material, whereas the Europeans use metals or polypropylene (PP) in their mod-con venting systems. The primary advantage of PP being that it has a significantly higher melting point than PVC.

My understanding of the plexvent problem was also that the stuff had not only leaky joints but also a nasty tendency to break and shatter without warning.

Dave Yates (GrandPAH)_2

mod-con vs furnace vs DV water heaters

My personal experience with mod-cons has been that the exhaust temp lags about 10 to 15 degrees F behind the supply water temp. Given that we can alter the supply temps and that return temps are seldom static, the PVC vents see a wide range of temps.

Furnaces, at least the older steady-state models, see a fairly static return-air temp, which renders a relatively static exhaust temp. True direct-vent models will be somewhat affected by drawing in frigid air for combustion. The newer variable speed/input "inverter" models will experience a range of flue exhaust temps that fall below existing exhaust temps.

DV water heaters use dillution to keep exhaust temps low in the flue piping. Hi-eff sealed combustion models have low exhaust temps that, again, lag behind the storage temp setting.

So, it is the boiler industry where the widest range of exhaust temps reside and the concerns raised do have a ring of truth to them. Strictly speaking, the exhaust temps do raise the issue of exceeding the max stated temp for PVC when under a given pressure. Not sure how that relates to the low pressure we see in venting and the affects flue-gas-condensation may have in keeping the interior (exposed) of the PVC cooled by virtue of wind-chill or evaporative-cooling.

Burnham's and Viessmann's explanations certainly make sense, but I'd sure like to see first-hand evidence that the PVC scare is warranted before carrying that flag.

Chris_82

not that I'm In love with this brand,...

I think regular sched. 40 on a Munchkin will last longer than the munchkin, Don't make problems where there are none. Their will always be jacklegs and skim artists who think they are making a few pennies by using foam core but it's only a matter of time till someone catches up with them. It is way past overkill to use anything like ss for these mod-con exhausts and it would almost have to be deliberate to get them to fail in any flame sort of way. On the other hand run them at half speed or jump out the air pressure switch and the co will do you in, but we have discussed this issue to death.

Unknown

Check this out

http://www.gov.mb.ca/labour/safety/pdf/me017abspvc.pdf

1974bobcat

I went to Buderus and they seem to thimk PVC is fine for venting and have not seen any evidence for concern. So I appricate all the feedback. I will watch the codes carefully. Thanks

Bob

Unknown

It is important

to remember that the max temperature for PVC is 140 degrees (F). For CPVC it is 200 degrees, that is quite a difference. There is always the possibility for flue gas temps to rise above what the prescribed operating temperature of the boiler may be. I would not be suprised in the future to see manufacturers go to Al294C only on thier flues.

Chris_82

The big concern,..

seems to be the Co that can be generated. I have seen more than enough combo jobs or bad gaskets on Al294/c to be more of a concern than switching to it for this reason, never mind the cost. The cellular stuff should be discontinued voluntarly by the pvc manufacturers. It is a vastly inferior product that does the plastic industry shame. And most of these issues are caused by the foam products never mind as most homes settele or move a little bit the foam core cracks and shifts apart.

Dave Yates (GrandPAH)_1

temp & press relationship

Check this out: http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html

If their chart is correct, the burst pressure for schedule 40 4" PVC is 142-PSI @ 140F

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Kal Row

more worried about temp deformations...

> Check this out:

> http://www.engineeringtoolbox.com/pvc-cpvc-pipes-p

> ressures-d_796.html

>

> If their chart is correct,

> the burst pressure for schedule 40 4" PVC is

> 142-PSI @ 140F

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 98&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Kal Row

am not that worried about pressure...

as combution draft is in inches instead of psi, am worried a lot about pipe deformations, in the future i intend to request that they use cpvc, have been burnt buy a sub, that put in celluar - claiming "pvc is pvc" - not goin to let that happen again!!!

Dave Yates (GrandPAH)_1

higher exhaust temps

I deliberately bumped my exhaust to 180F during domestic hot water production with my modcon. It's been a year now since I made that change. First six months since that change the modcon handled all DHW production. From Dec to now (and in the future) the modcon handles whatever the solar doesn't.

No discoloration, no deformation & it's a 3" x 28' horizontal run with 3 90-degree ells.

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Bob Gagnon plumbing and heating

Real answers

from real plumbers, thats what I like about this site. There is so much infomation out there it is hard to sift through. But I find I can usually trust another contractor to have the right answers. Thanks Dave, Bob Gagnon

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Dave Yates (GrandPAH)_1

well

Burnham and Viessmann are companies whose opinions I greatly respect. Their concerns expressed resonated with me, which caused me to seek out more information regarding PVC and its temp/press limitations.

As a contractor, I appreciate their concerns and reasons why they've chosen what they consider to be a better/safer method for venting combustion by-products. We follow their instructions to the letter when installing their products.

Other mfgrs remain convinced PVC is an acceptable and safe method for venting the by-products of combustion when installing their equipment.

For my own peace of mind, I needed to research the issue on my own. I would encourage everyone else to do exactly the same and form their own conclusions.

Venting of combustion by-products has become a mine-field over the past decade as Cat I yielded and venting began to include Cat II, III & IV. We've seen some very frightening DIY and contractor installations where death has been narrowly averted.

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Unknown

Venting over the years

Having been involved in the gas industry for over 40 years and seeing all the things people thought would work and id not I ma apprehensive about the future of plastic as a venting system. Several manufacturers are taking a god hard look at this dilema.

I just taped a seven part series for HVACTV.com this morning on Venting Today- A Complex Problem. I imagine the first one will be presented this coming Tueday the 31st of July. Some of the concerns voiced here are addressed. I have not yet found anywhere that shows PVC definitely approved for venting mid or high efficiency equipment. The codes do not directly address it and it is left up to the manufacturers and installers. To be safe go with AL294C or in the case of direct vent follow the manufacturers directions using the kits provided with the equipment.

Unknown

PVC Venting

The concerns expressed lie with several factors. The first of these being that PVC and ABS Pipe and fitting maunfacturers do not neccessary express approval for using these products for venting gas byproducts and the ASTM standards hold no mention regarding the use of venting and PVC. One or two companies that manufacture PVC pipe and fittings have put out statements to the effect that they do not recommend using it for venting gas combustion byproducts.

The second concern is that we, you or nobody else can guarantee that the pipe your distributor stocks is soild core and not foam core. Some distributors stock one or the other based on primary demand and if they did stock both that is no guarantee that they will have solid core every time you order or that what is shipped to you is solid core. There is a very strong likelyhood of foamcore pipe ending up in many of these applications due to those reasons.

The third concern is that PVC is tested and approved for 140°F temperature for "pressure applications". Mod/Con boilers can in fact exceed these temperature during high fire conditions with Domestic Hot Water or other high water temperature demands. Most mod/con manufacturers that allow PVC for venting have flue gas sensors that know this is happening and their control logic will turn down the input or modulate down to protect the pipe. Reducing the boiler input when it needs to recover the heater will lengthen that DHW recovery period. To what extent that happens is a function of boiler sizing and demand. I too have seen a couple of manufacturers that approve CPVC for the first several feet. But the real question is.... How many distributors do you deal with that actually carry 3" and 4" CPVC pipe and fittings in stock?

The fourth factor is there is more and more discussion these days about this topic and the trend of the governing agencies uses verbage referencing "Vent Systems". We see this with AL29-4C, Polypropylene and Ipex. They are indeed "vent systems" that have been tested and certified for venting applications. As mentioned, Canada has taken action to discontinue the use of PVC and ABS and that any material used for venting must be a "system" that conforms to their standards.

Our stance with our Freedom™ CM and CHG boilers is to use either AL29-4C or Polypropylene vent systems. These systems are tested and certified for venting purposes and have temperature tolerances far in excess of what you would expect with these boilers. That's my story and I'm sticking to it .....and I will be willing to bet that many other equipment manufacturers will begin to see it that way too as things progress in Canada.


Glenn Stanton

Manager of Technical Development

Burnham Hydronics

U.S. Boiler Co., Inc.

Unknown

Glenn, with your permission

may I quote you in an upcoming article I am writing for HVAC Insider and also EZINE Newsletter I write for?

Unknown

Back up for Kent (Tahoe Thermal)

Some interesting discussion for you Kent.

Unknown

Bump to

the top.

Rich Kontny_5

Same Thing

From the Veissman rep here in Milwaukee,no pvc! I am waiting for the green movement to address this also as there seems to be a controversy about pvc vapors escaping from drain lines conducting wastes and sewage. What does this mean when heat is added??? The issue from the heating side is most likely pipe failure related while the plumbing side seems to be an environmental issue.

Just when we thought we had all the answers, the trial and error process kicks in and changes the questions!


Rich K.

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