Condensing Boilers & PVC Exhaust

SpeyFitter

The Local Lochinvar Rep suggested that their Knight boilers don't need anything more than PVC for exhaust, that their boilers exhaust temps will never need CPVC, except for the starter piece they may include, or the 7' spec'd in their installation manual.

I find this strange as I thought condensing boilers exhaust temps were typically within 10 degrees of their supply water temps.

Does this have something to do with the intake fan diverting part of the intake air into the exhaust to cool it down? Is this a Giannoni patent/design?

CMadatMe

PVC Venting

While the attachement was put out by Viessmann and there stance on venting PVC it gives you a picture of why they don't recommend it.. I believe in the near future venting with PVC/ABS may be a thing of the past. There is some discussion going about making this a reality.

SpeyFitter

Should have clarified

If you notice in their data, it lists PVC S-636 material as being ok for certain applications in Canada. I was talking about temperature ratings specifically relative to exhaust temps and if any manufacturers have some kind of system that somehow cools the exhaust to allow you to run PVC even with higher water temps, due to some kind of vent cooling system.

In Canada any plasticexhaust  vent material (PVC, CPVC, PP-R) must now meet the S636 standard (since mid 2007) which is a big rubber stamp that makes the material way more expensive. The PVC & CPVC stuff was approved right away, the Viessmann Coaxial venting material was approved earlier this year if I'm not mistaken.

CMadatMe

Its a CPVC Pipe not a PVC Pipe

That pipe is CPVC and I-Pex is the only maker to this point that is actually marked as vent pipe that is UL rated and Canadian rated for venting a gas boiler. I have it in stock. The question I pose to potential customers that always say it's cheapier to vent PVC I say, why would you vent a high efficiency appliance with a pipe that is made to move s****? Your installing a high end piece of equip so shouldn't the vent material be of the same quality? It's funny how people say it's expensive, it's expensive compared to what? With Viessmann we are selling a heating system not just a boiler. 



In the last month I have guys that went up against other competitors wall hungs with the Vitodens 100 and that is generally the number one question from homeowners. My guys hand that vent statement to the customer and explain why. The consumer in every case wanted the Viessmann. Consumers take the safety of their famlies very seriously. I didn't know there was a price on that. In the big picture, isn't it the choice the consumers concerning what type of vent product they would choose based on the recommendations of the contractor? Shouldn't that choice be on saftey and not price?

hot_rod

overheated PVC

??

CMadatMe

Interesting Hot Rod

Have you cut is out and replaced? That would be a nice example to send out for some testing.

Mitch_6

PVC falure

I have seen PVC fail in the Heatmakers when the heat exchanger starts to plug and cannot absorb the temperature.  The pvc over heats and cracks.

I have checked the flue temperature's on allot of boilers that the exhaust side pvc is discolored.  If was a concern that I would have a potential failure however the boilers were all in line even though the exhaust pipe was darker.



Same for near boiler and silver pex, it always seems a little discolored.

CMadatMe

So there is

Some type of reaction going on. The question now becomes, What is the cause? What is this reaction and does it lead to pre-mature failure of a vent system? Can this reaction that the pipe is haviing be solved with venting with CPVC instead? If so, then why wouldn't we vent with CPVC vs PVC. The anwser to proper venting material should not be associated with the cost of the venting material but with saftey for the consumer.

TonyS

Chris Pleeeese

Plastic ratings are just there to charge more money. I dont know if you remember plexvent or ultravent. they both had a big OK stamp on them. Im not saying that GE being the resin manufacturer had anything to do with that stamp. I guess you can ask the people who died from it. As far as comparing the heat ratings with one plastic verses another, thats crap too. none of them will hold up to a worst case scenario. The only thing that will is AL294C. Im sure your customers all require that, after all safety first. But then again, smart customers might start to wonder why the only approved stainless pipe is AL294c and your boiler is made out of a much cheaper grade of stainless....316ti. I dont want to sound like a **** here but we all come here for info... not to play cheerleader for our favorite boiler. Yes Viessmann is a nice boiler, there are alot of nice boilers today. Saying things like "why use a pipe they use for sh**t is ridiculous. All three types of pipe are used for the conveyance of sh**t in industrial settings. pvc,cpvc, and pp. Comparing pvc pipe to sh**t pipe may fool a few ignorant customers but there are way to many pros here, Engineers, pipefitters,boilermakers, plumbers and welders to listen to that. Peace

CMadatMe

My Post was concerning Vent PIpe

And yes PVC and ABS are made to move s***. Ask the manufactures of that pipe. Each and every one of them have sent out statements that say PVC/ABS is not a vent material and that they do not endorese it's product as venting material. Since they make I would think that if they thought it was ok they would endorse it. Plain and simple. I would have to say atleast Viessmann has a vent statement. Can you say the same for any of the mfg that are using PVC as a vent pipe. I have never seen one.

Unknown

Curious,,,,,,

Since there is such a debate over M/C plastic vent piping,,, why do they not make-it (HX outlet) a different diameter, and employ some kind-of "adapter" for use in THAT region(available @ extra cost),,, wouldn`t that prevent any plastic vent material "mixing"?



Just curious,,,, :-) 

TonyS

We have been using pvc

for over 20 yrs now on condensing warm air units. It has an excellent track record and is approved and recomended by everyone including Trane ,ICP, Amanna. these are big companies with much to lose in a lawsuite.  Im sure they have done their own testing.

SpeyFitter

Boiler manufacturers?

Tony,

So these are all condensing boiler manufacturers you speak of?

CMadatMe

Force Hot Air

Venting systems do not see the same flue gas temps as condensing boilers. Those companies you stated are all air guys. I believe the talk of using PVC as a vent system is based on the higher flue gas temps we see in hydronic applications.

TonyS

No Scott

these are warm air manufacturers who have a longer track record using unapproved pvc  pipe for venting. But  your right, until last year I replaced 2  hydropulse boilers that were in for over 25 years, vented with pvc. They both ran 180 continuously. Arguing what plastic will hold up is ridiculous because if you really want the best, use AL29-4C. I have replaced a number of condensing furnaces already and it wasn't the pvc that gave out. Navien uses and approves the use of pvc for their tankless unit.You know why? Because it works. Can anyone here tell a horror story about pvc that could have been adverted using cpvc? Did you ever wonder why only al294c is used on the lower efficiency power vent units? Because AL294c is a patented metal from Allegheny Ludlum, not because 316 wouldn't work.It would but who is going to pay for the approvals if everyone can make it.  With all the fitters that visit this page probably represents thousands and thousands of units installed with pvc. And what do we see? a couple of discolored pieces of pipe. Spare me! Thats as convincing as the swine flue debate.

TonyS

NO , we were talking about using a material

that was not approved for venting. period

SpeyFitter

Aquatherm

It would be nice if Aquatherm offered an S636 Vent Pipe. They make excellent piping polypropolene piping for potable water/hydronics/pools, etc.

Slimpickins

PVC and Heatmakers

PVC was never approved for Heatmakers. The early models approved Hart and Cooley Hi Temp plastic for the exhaust but that was recalled and Trianco offered a replacement allowance to go to stainless. 

TonyS

exactly

just like the weil mclain golds

TonyS

The reaction is overheating

because someone didnt read the manual or stay informed on that particular boiler. Like RuffandRocky said, The HEATMAKER was not a condensing boiler.It was originally approved with plexvent or ultravent, like a few other near condensing boilers of that time. It was later replaced with AL294C. So if anyone is unfamiliar with these boilers, Trianco Heatmaker, Weil Mclain Gold and a few others. You CAN NOT use CPVC OR PVC OR PP to vent them You MUST use AL294C.



You can get all the stamps and approvals you want. It means nothing if you dont read the manual. In fact it leads to situations like this where this guy thought he should replace his heatmaker pipe with CPVC.

HDE_2

ASTM

Chris, making a blanket statement that PVC pipe manufacturers say they do not recommend PVC for venting would be incomplete or false.

Check again they merely say that the ASTM approvals do not cover appliance venting and it best left to check with the manufacturer which goes through CSA.

jalcoplumb_2

Discoloration.

I had an install that discolored like that.  The pipe had been left ouside in the sun for about 6months to a year.  I think the UV damaged the PVC.  This was the only Mod/Con that I ever had discoloration of exaust vent on.  The exaust temp was no higher that of other systems.  It has been in service for 3years now with not failure. 

jalcoplumb

Henry

Plastic vents

It amazes me when so much bs is given off by people that did not do any basic research into a subject.

Drainnage DWV PVC was not an aprooved material for venting by nearly all gas appliance manufacturers. SCH40 PVC pipe is in the US and was in Canada. There is a substantial difference between the two! SCH40 PVC is used for pressure aplication and not to moove s*****t! S636 PVC pipe is made to the exact same standards as PVC SCH40 but has different colour due to the requirements of CSA when meeting the S636 standards. It is so that one does not use regular pvc in an S636 system. Because the plastic pipe manufacturers now specify that you must use only their products for an S636 sytem, we are all taken by them. Imagine if you could not use a sch 40 PVC fitting from IPEX with a pipe from Royal? It is the same stupidity.

Now for the real shocker, ABS non-cellular is a better product for venting condensing apliances! It has higher temperature rating than PVC: 217F before is starts to deform. Anyone that has installed a PVC DWV drain for a steam humidifier knows that he will not do it again. The automatic blowdowns melt the PVC drainnage pipes and fittings. This is not the case with ABS drainnage pipe. I had blocked the S636 certification requirements for three years, since only one had the certification but NO product. It was passed at the B149.1 while I was away for that meeting. I have tested in the lab, ABS, PVC, CPVC and various metal venting systems. I have also investigated failures including one of ours. In all cases within the last 20 years, the failures were due to:

1) Improper installation by the installer, most of the time with old glue or not taking into account the expansion of the vent (BTW, ABS expands less than PVC)

2) Equipment failure that leads to higher than normal temperatures.

3) Improper quality control by the equipment manufacturer, thus the equipment is not meeting it certifed performance criteria.

There has never been a material failure under normal operating conditions of the ABS or PVC venting material.

During most of the year, we buy nearly $100K of Al29-4C per month. We have had more leaks in caps, elbows and tees with AL29-4C than any other product combined! Just because it is metal and certified to a standard, does not make it the best there is for an aplication.



The apliance manufacturer has tested his apliance under various conditions to meet its certification standards. As well, reputable manufacturers such as Lochinvar respond to what is hapenning in the field, wether good or bad. A few years ago, venting instructions were at most one page. Now, we have nearlya dozen pages of instructions. The apliance manufacturers, the utilities and us voting members of the national gas code, all want a safe industry for all users. The "Local authority having jurisdiction" has plenty of rules and regulations in our codes to be able to have a safe installation. They just need to apply it. This way they can keep the uncertified venting expert off the street and bad mouthing an apliance manufacturer or vent system.

HDE_2

What is you DWV?

Henry, why the panties in a bunch?

We are discussing PVC DWV Sch 40 Pipe & Ftgs.

(Most common sold)

Not sure what DWV PVC you are referring to???

jalcoplumb_2

Discolration.

Here is a photo of the vent that I was talking about.  Look at the spot where shipping tape was covering the pipe.  No UV damage there.  This pipe was ouside in the sun for many months before it was installed. 

jalcoplumb

SpeyFitter

ABS Solid Core

It's interesting, I cut in a tee for Flue Gas Analysis into a boiler exhaust the company I work for installed 6 1/2 years ago. It was 2" Solid core ABS, and the pipe I cut out which I replaced with a tee, was in excellent shape, and the condensing boiler it was serving was heating domestic hot water through an indirect hot water tank(165 degrees boiler supply temp) and radiant floors (115 degree max tem).



So the one thing I need to ask is why isn't ABS Soild Core not S636 approved?

Unknown

Excellent question,,,,

For our esteemed  TSSA!! Good Luck getting an answer.

ScottMP

Where are the failures ??

I have asked this question before. If Sch 40 PVC does not work for mod/cons and Canada has banned it and thousands of Mod/Cons are sold every month ...... where are the catastrophic failures ??

I have had NOT ONE of my systems have a failure of the venting system and YES we go back to at least 90% on our installs.

Scott

Henry

ABS & PVC

Sch 40 PVC and S636 PVC are one and the same, as they are manufactured to the same standards. The only difference is colour, markings and the S636 certification. ABS cannot meet the open flamme test required. The test requires a specific bunsen burner flamme for X seconds on a joint. This is repeated several times. In the S636 standards, there is NO interior temperature test! There is also a difference between the manufacturers certification procedure which is surface temperature versus B149 which is the middle of the stack. We are trying to hamonise this difference. Also, S636 is being revised. This might take quite some time!

DWV PVC is NOT SCH 40!! It is a thinner wall pipe that has no pressure rating. There is also SDR DVW PVC pipe that has even thinner walls. Neither were or are approoved for venting material.



Canada has NOT banned PVC, the B149 code states that it must be certified to S636 standards. The only failures that I have seen and that were shown to us by the provinces, were due to terrible installations not done as specified by the equipment manufacturer's certified instruction, poor workmanship (mostly using old glue) or an appliance not meeting its certified standards.

There has been a few fatalities not due to vent quality but due to improper installation whereby the vent got blocked by snow and CO seeped through poorly glued joints. The same can happen on any sidewall vent appliance with metal vents.

BTW, I worked with Aquathern at their R&D facilities in Germany two years ago testing the pipe to S636 standards. It passed. But, the Canadian market is too small for them to spend money certifying the pipe.

Kenny Greene_2

PVC Vent Failure Hotel

Sorry for the late post regarding this subject. I have attached a picture of the 4" exhaust vent 90 that failed after 8 years on a commercial water heater. Two heaters had this problem. The main issue here is the fact that the equipment room is below occupied hotel rooms. If you use pvc for venting, make sure that it is inspected annually.

TonyS

What type of commercial

water heater? Was it condensing? Was it designed for PVC?

Kenny Greene_2

The failed exhaust

The failed exhaust pipes were on A.O Smith Cyclone water heaters. The manufacturer approves pvc for the exhaust, The exhaust 90's that failed actually come with the heater when purchased. The exhaust and intake were checked for restriction.

Mark Eatherton

Looks like a stress crack to me...

But that is just an outside observation.



Was the fitting installed in such a manner that it had a significant amount of weight and or stress being applied to it?



Never seen anything like that.



ME

EricAune

Proper piping techniques are key

If undue stress is exerted on PVC, ABS or CPVC piping and fittings there is cause for failure.  Add to that stress the high operating temperatures of flue gasses and it is only amplified.  Cracks and breaks are most often a direct effect of improper installation of the piping system. 



Basic piping skills are often forgotten in order to complete the job; the venting of boiler is likely to be the last thing done before start-up.  This task is every bit as important as the hydronic piping, who cares if they have heat....if they don't wake up in the morning.



Proper piping material, fittings and hangers are always the first concern.  What about installing it correctly?