PVC vs. Stainless,, are you guys buying this one?

S Ebels

A couple pluses for the concentric vents as used by Viessmann and Buderus in Europe; The incoming air which surrounds the exhaust, helps to keep things cooler during operation. The next is that the exhaust pipe is not PVC material. I think it's polypropelene which tolerates higher temps than PVC.

I have a gut feeling that this will be an issue down the road in certain higher temp applications. Thankfully, we have never used a condenser vented with PVC in a high temp application.

Ross_7

Mod/Con Boiler venting

Hey fellow wallies,

I was talking at Sid Harvey's today with the Crown Boiler rep, and this post has no bias or un- bias towards any boiler manufacturer by any means. I was looking at Crown's new Bimini Mod/con boiler which I think BTW is an ACV unit, and they were recommending the fact that to not use PVC/ABS/CPVC on any mod/con boilers. "They don't vent in plastic pipe in Europe". Their new 120 mbtuh wall hung had a polypropylene vent kit, looked very similiar to a Viessmann Vitodens concentric vent kit. What I would like to know is, if anyone on the wall has had any Mod/Con boilers of any make in the field for 5-6+ years, and if they have had any deterioration of the plastic venting. I guess I would also like to know that if there were problem with this, then how do boiler manufacturers receive a UL listing, etc. Just for grins.

Mark Hunt

I've never seen PVC fail


What about all of those hot air furnaces that have been in for 15+ years?

Power vented water heaters??

Mark H

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Ross_7

Exactly

That's what I thought also. There's some that have been in for almost 20 years. Like some the old Williamson, Lennox pulse, Carrier. I haven't seen any problems.

tom k_4

pvc/ss

are all the other boiler mfgr's that use pvc that wrong and the other guys that right?

tom k_4

pvc/ss

there are some pretty bright guys in the boiler business that I doubt would be that careless about all of us out here.........thats a pretty bold accusation.......

Unknown

Ross

The issue has to do with a couple of facts. One is that the overseeing agencies that certify usage of PVC piping for various such as PPFA (Plastic Pipe and Fittings Accoc.) have not approved it for use as a venting material for flue gasses. Sure its been out there on warm air furnaces and water heaters for several years now but there is one major difference between those types of appliances and hot water boilers......possible misapplication and possible variations in flue gas temperatures.

Warm air gas furnaces and water heaters maintain a fairly consistant flue gas temperature based on the role they play. They basicly for the most part have a pretty consistant temperature rise within. A Condensing boiler operating with high temperatures because of operating with a baseboard, toekick amd indirect heater application will have flue gas temperatures above and beyond the temperature limitations desired for PVC or in the low 200F range.

We've all lived with the PlexVent issue from the 1980's and we don't want to relive that over. Until a PVC manufacturer or controlling agency steps forward and states that it is OK to use we will be staying with an approved venting product. If the equipment manufacturer is saying you can use PVC then they will be the ones that will have to bear the liability if something goes wrong. That indeed is not a warm and fuzzy place to be when you have no backup support from the Pipe and Fitting manufacturers nor their governing agencies.

We state the use of AL294C pipe and fittings as well in our I&O manual for our new CHG Mod/Con boiler. Crown is a sister company of Burnham and the Bimini and CHG are derivitives of shared engineering initiatives. Here is a link to the CHG manual.

http://www.burnham.com/residential/CHG_51110.cfm

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

S Ebels

Think about it though..........

A F/A furnace has a whole house full of air that is ALWAYS returned at 65-70*. Exhaust vent temps that I've measured almost always fall between 110-130*. Can't say as I recall ever seeing anything over that.

Some mod con boilers however, with floating water temp via OD reset, will run approx 20-30* higher than the return water temp. At outdoor design temps and given a system that has to run medium to high water temps (BB, hydro-air or undersized panel rads) you can be looking at return temps of 140-160+. Now add the 20-30* additional in the flue and you can see exhaust temps running 180+. This is at the upper limits of regular PVC pipe and beyond the limits of Cell-core. Read any furnace manual and it will always say "do not use cellular core pipe" or "use only solid PVC pipe". Why is that? I think it's because even the furnace manufacturers are a tad leary of the limitations of PVC as a venting material.

Another way to look at it is from the plumbing code side of things and answer this question. What's the maximum WATER temperature you are allowed to discharge into a PVC drain?

I think this is a valid concern and there are shortcuts being taken in the name of keeping costs down for installation. I know for a fact that the GB is set up with a concentric pipe ala Viessmann in Europe. They don't sell it for use with PVC venting over there.

Makes you wonder........

Uni R_2

ABS

I've heard that Ontario will not be allowing the use of ABS as of January 2007. No impact on PVC/CPVC. I think it stems from from some horror stories that have arisen from using ABS on power vented water heaters.

gerry gill

is not polypropylene

a plastic?

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Uni R_2

ULC S636

I think that ULC S636 is the standard that installers should be looking to have stamped on any PVC/CPCV pipe that is being used for venting.

Thanks for the link on the CHG Glenn. I've been wondering when we'd get some info on it.

Unknown

Gerry

The Polypropylene Variant of pipe or Coaxial Polypropylene that is being used in Europe is indeed approved for gas venting but with limited distances. We will be using Polypropylene with our upcoming "Freedom" wall hung condensing boiler but will have a limited distance of around 13 equivalent feet or so. Beyond that you will have to convert to Stainless.

The Freedom will be making our website in upcoming days.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Cunner_2

Wonder it does

Steve,
I never really gave it much thought, I new that Viessmann didn't allow it, and I had heard that it was not allowed in Europe but thought that may have been a rumor. That makes a lot of sense, I'm sure that when PVC is used as intended on a Mod/Con unit it functions very well, but we also know many of the units are not utilizing the condensing fuction of the boiler when running on high temp systems, this would certainly causing flue gas temps to possibly extend beyond 200 degrees. This is a real eye opener!!! I went through the horrors of plexvent and that stuff was supposedly design for use on heating equipment. Certainly something to watch!!!!

C

Cunner_2

Careless?

Tom,
I don't think anyone is saying that the manufacturer's are careless, I would look at it from a misapplication standpoint. I'm sure when an engineer design's a Modualating High Efficiency Condensing boiler he expects it to be used as a condensing boiler not a modulating high temp boiler, if all condensing boilers were used in condensing applications such the way 90+ furnaces are, the PVC venting would be a non issue. I think most of the Mod/Con technology comes from EU where many areas have limitations of 140-160 on the supply water temp which would allow for a cooler flue gas temp, we here in the good ol' USA seem fixed on the 180 mark which would certainly put the flue gas temp over 200. I don't think anyone was careless, you don't generally plan for your product to be misapplied. I wouldn't call it a " Bold Accusation " I would call it a " Valid Point ". Definitely worth thinking about.

Just my thoughts,
C

Dave_4

Down the road

It's certainly got me thinking....

gerry gill

all these new products from burnham

where have i been? you'd think our suppliers would be keeping us posted..i'll have to check the freedom out..

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rich pickering

Interesting timing

As of Jan 1, 2007 the Canadian gas code is going to be amended.

8.9.6 Vents constructed using plastic piping shall be certified to ULC S636 - (Standard for BH gas venting - systems otherwise known as category IV venting or low temperature plastic venting).

Celcore ABS and PVC pipe is currently listed in some manufacturing manuals. Problems have been experienced in Canada with leakage and cracking of this pipe. Effective immediately Celcore pipe is not to be used for combustion venting

The above is a bulletin I just received from our gas inspections branch.

Ipex had there pvc tested a long time ago, and will have pvc stamped to ULC S636 available.

Mark Hunt

Glenn


Not on power vented water heaters. Stack temps are higher. You can only pull so much "dilution" air.

AFA forced air systems, you are assuming that the delta T across the HX is within spec. I would be willing to bet money that 99% of those systems have insufficient return air.

I tested a Triangle Tube "Prestige" the other day while it was making DHW. Highest stack temp was 150 degrees. The Prestige has an exhaust temp sensor and it read 153 degrees. That was in high fire.

Not trying to be combative here Glenn, but what is written in a book only works in the book. Testing proves everything.

If PVC is not approved for an appliance, PVC will not be used.

I may think it is BS, but the manufacturer's advice will be followed.(Other than combustion adjustments)

Mark H

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Unknown

Mark

> Not on power vented water heaters. Stack temps

> are higher. You can only pull so much "dilution"

> air.

>

> AFA forced air systems, you are assuming

> that the delta T across the HX is within spec. I

> would be willing to bet money that 99% of those

> systems have insufficient return air.

>

> I

> tested a Triangle Tube "Prestige" the other day

> while it was making DHW. Highest stack temp was

> 150 degrees. The Prestige has an exhaust temp

> sensor and it read 153 degrees. That was in high

> fire.

>

> Not trying to be combative here Glenn,

> but what is written in a book only works in the

> book. Testing proves everything.

>

> If PVC is

> not approved for an appliance, PVC will not be

> used.

>

> I may think it is BS, but the

> manufacturer's advice will be followed.(Other

> than combustion adjustments)

>

> Mark H

>

> _A

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

> 238&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_



Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Unknown

Mark

I have heard that argument time after time as well. The bottom line response to the man's question is that unless we get something in plain writing from either the Pipe and Fitting manufacturers and/or governing agencies allowing their pipe to be used for venting of gas appliances, then we will be staying with AL29-4C Stainless.

The Coaxial Polypropylene used in Europe is temperature tolerant and as a matter of fact is also very expensive. Pretty much in line with Stainless. Mark, I must say I am a bit surprised with your argument points though since you are one of the biggest proponents of Combustion Safety and possible CO emmisions around. Regardless, you know our stance on this issue and if other manufacturers in the industry want to use PVC, let it be their and your risk. Keep up the good work!

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Mark Hunt

Glenn


When I install a Burnham Mod/Con, I will use SS. Why? Because Burnahm only approves SS.

AFA combustion is concerned, the appliance cares not what it is vented with. If a burner is is wacked out it won't matter if it's PVC or SS that it is connected to. Then again, how would one know if they do not test?

I will say this. If a burner goes wild, PVC doesn't stand a snow ball's chance in hell. It will burn.

BTW, the new, FVRI, power vented water heaters push PVC to the max. I can't believe they are approved for PVC after seeing the temps I have found. How does 223 grab ya'? Then again, what about and FVRI atmospheric with a 600 degree stack temp? Vented into a b-vent chimney?

Wish you were at ISH, Chicago Glenn. I would have put a hurtin' on your company expense account!

Mark H

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Ross_7

PVC

Well,
Thanks for everyone's input. Like I said I wasn't picking on anyone, I was just curious about what everyone thought about it. Glenn, I knew that Burnham & Crown were sister companies. I know that Slant/Fin's condensing boiler is th same application, with venting recommended in stainless. Thanks again, everyone!
Ross

Jeff Lawrence_25

Steve

Just a thought.

The concentric vents we have here in the USA have about 3 feet of actual concentricity (?) then the split off to 2 separate pipes. I'd think that there really isn't any bonus from cooling off the flue gases from that.

S Ebels

Jeff

I know what you are refering to but I was talking about the concentric/coaxial venting type systems found on some appliances. These use an inner/exhaust and outer/intake pipe all the way from the appliance to the termination. It's probably the venting system with the most advantages as afar as safety, proper combustion and ease of assembly. The downside is cost and more limited length overall.

Coaxial is a better word.

Constantin

And what

> I know what you are refering to but I was talking

> about the concentric/coaxial venting type systems

> found on some appliances. These use an

> inner/exhaust and outer/intake pipe all the way

> from the appliance to the termination. It's

> probably the venting system with the most

> advantages as afar as safety, proper combustion

> and ease of assembly. The downside is cost and

> more limited length overall.

>

> Coaxial is a

> better word.

Constantin

And what's also interesting...

... is that Burnham has restricted the equivalent length of the coaxial venting much like another manufacturer that uses a presumably similar polypropylene coaxial vent approach.

As Glenn pointed out, no one should want to relive the plexvent, ultravent, etc. days so spending a bit more up front to ensure that the plastics will remain much cooler than their melting temp is a good, conservative, etc. approach. Presumably, Burnham will get beat up by the competition because coax vent or stainless is a lot more $$$ to install than PVC. But customer safety, not cost, should be the over-riding concern of installers and many condensing wall-hung boilers require less than a foot or two of venting material anyway.

Sealed combustion and coax intake/venting is a very desirable goal. Keep the CO and other combustion products out of the house, ensure no ΔP as a result of wind gusts within the combustion chamber to aid clean combustion, etc. The two pipe approach used by other manufacturers may be cheaper but I wonder to what extent clean combustion can be maintained at low fan speeds and gusty wind conditions.

Ken_40

Glenn,

Of some note, my euro-boiler is poly vented.

AND IT'S #2 FUEL OIL!

IT'S ALSO CONDENSING - BY DESIGN.

I shook my head, followed the manufacturer's caveats and used the coaxial vent kit they required. It's been a year, I just did a major teardown type annual cleaning, and it looks like the day I put it in. Instruments showed a "before" cleaning gross stack temp of 127F, and an "after cleaning of 123F.

Of course, as per the NEC, there is a Fire-o-matic temperature sensor disconnect device directly over the boiler and vent array, as well as a smoke and CO detecter with 5 feet.

I am prone to watch it like a hawk. I never walk by without looking at temps, for any leaks, sounds, or odors. So far, one year down, 50 to go...

Unknown

Thanks Ken!

If properly configured, applied and installed the Coaxial Polypropylene vent is a good product. How is life up in the mountains going? Certainly a dramatic change in life style from the rigors of New Jersey life! Truly hope you are enjoying your retirement as you well deserve it. Thanks for all you share.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Plumdog_2

High Temp Applications?

I'm not seeing the vent temps go very high even when a mod-con ramps up to 140 or beyond when Domestic HW priority kicks in. In fact the units will continue to condense. But most installation guides call for solid core PVC meeting ASTM 1785; not cellular-core. But a lot of installations done by "less attentive to detail" types are cell core; and I don't see the Inspectors catching it or having it corrected. That could be a problem.

Dale

PVC

I have seen quite a few melted pvc vents on bad running furnace and direct vent water heaters. Direct vent water heaters being more common part of the problem. I think the recent deaths at a Vermont college showed melting pvc. And, I think Dave Yates posted a failed furnace with melted/damaged pvc vent pipe. If you overfire/soot something the flue temp rises and the if it's there flue temp limit switch can always fail. I am not at all surprised that the pvc manufactures don't want to get involved in a lawsuit in an application, gas venting, that the astm rating most certainly does not cover. I think the furnace mfgs. are going to need to do their own astm work to get this fixed.

[Deleted User]

Reasons for concern???

See attached photos from a job that is approaching 5 years old. M-180 doing DHW thru 2 HTP 119 gallons DHW storage tanks.

Obvious evidence of degradation to the exhaust, and none to the combustion air. No evidence of joint failure or pipe failure other than the discoloration.

I meant to share these pics way back during the summer when I did the drive by, but got busy at the ranch and forgot.

Comments??

ME

jp_2

discoloration

looks like water rust stains?

I notice some patchiness where a clamp or tape was?

whats the inside look like?

Leo G_99

C'mon Prof

everyone knows that that yellow discolouration is from the warmth seeking Bladda bird.! Very common in higher elevations!

Leo G

[Deleted User]

jp...

The unistrut anchoring suppert had to be redone due to grown up juveniles using it as a ladder and pulling it out of the brick mounting. And yes, you can see the area where the strut clamp was and it does show less signs of discoloration. I am by no means an expert in plastic piping, but obviously the elevated temperatures, possibly compounded by elevated hydro carbons (next to the worlds longest business strip, Colfax Avenue) and regular solar exposure (N.W. corner of building, vent actually on North wall) may have something to do with it as evidenced by the fact that the ingoing combustion air pipe looks fine.

I've not had the opportunity to look inside the plastic pipe, but when we did a 2 year tear down on the combustion chamber, it had a similar colored build up on the inside of the HXer.

I will try and locate some of our older mod cons and see what conditon their vents are in.

Heres more pic's.

ME

Ross_7

cell core?

Mark,
Is that cell core piping?
Thanks!
Ross

Mark Hunt

Curious


Why no discoloration on the fittings?

Mark H

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tom_49

Are you allowed to run that much piping outside? Maybe thats part of the reason, the warm PVC against the cold outdoors.(?)

Tom

[Deleted User]

Non foam core...

is all we use, even on the combustion air, which per the manufacturer, it is OK to use foam core on the combustion air intake. We didn't want any field confusion, so we opted to use ONLY non foam core on both applications.

ME

[Deleted User]

Curiosity kills...

cat's don't it? :-)

Good ? mark, Mark!

Possibly different compound? I dunno. May tell someone can round up a plastic pipe manufacturing eggspert and have them come by and make comment.

ME

[Deleted User]

HVAC 64...

It is well within manufacturers limits as it pertains to max devloped length, and there is no limit as to % of pipe outside versus in. Its a condensing boiler, so it really doesn't care if the flue products condense in the flue.

The boiler is actually just inside the wall.

ME

Mitch_4

Ontario

The new reg will state that any ABS, PVC and CPVC that will be allowed must have the ULC rating for venting printed on it.

Water heaters I see all the time melting because they are not high efficiency, but there are furnaces here 24 years old with the original abs and it is perfectly fine.

Mitch