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Is PVC an acceptable vent material for flue gases?
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Comments
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You'd have to ask them....
While you're at it, ask them why they are the only manufacturer who requires 1" of clearance around all venting and water piping...
I don't know for a fact, but I suspect that their lawyers had something to do with it. I am sure they maintain a regular staff of legal beagles to handle the day to day threat of lawsuits, and after they read the I&O manual for the Knight, being used to the old cat 1 B vent venting, they decided that it would be a good direction to go with the 1" minimum clearance when everyone else sees fit to go zero clearance...
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PVC
I think the US needs a standard, similar to the ULC S628 certifying vent material as to suitability and temp limits.
Appliance manufacturers should be required to have manual reset limit switches on their vent outlets consistent with the vent standard. I don't think software based, or auto resetting limits are suitable. Resetting the whole boiler or simply waiting clears the fault and leaves owners and poorly trained service staff thinking they have an electronics glitch.
There's no reason why appliance manufacturers couldn't make the vent switch part of the vent transition adapter, so if you installed a unit with stainless vent, the switch in the transition part has a higher setting.
The only issues I've seen in the field with PVC have been joint separation issues, usually from primer not being used on initial assembly.There was an error rendering this rich post.
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speaking of cement and primer
was it ever intended for exhaust venting ?
With all the expansion/contraction of the pipe and fittings.
I always try to use the heavy bodied formula glue. Comes out like snot, and is expensive but rarely do I get a leak, (when I test PVC for plumbing). The regular bodied stuff is just too watery for me, and it seems like your holding the fitting together forever before it sets.
I would prefer a mechanical joint instead. But that would probably mean the vent materials would cost just as much as the mod/con boiler.0 -
Ron George's Reply.
I appreciate all the comments. I read the article as pasted above and I see there were several paragraphs that were copied in twice. But the message is there. I understand there many different dynamics in this issue. The piping manufacturers, the condensing equipment manufacturers, the contractors etc. The contractors have the fear that if they use something other than the cheapest material they may not be the low bidder. PVC material is only a choice because the manufacturers have offered it as a choice. PVC may not melt or sag in most installations, if the flue gas temperatures are kept close to the 140 degree limit and as long as the exposure time and the temperature difference are minimal. Currently if a system is undersized and there is a hard water situation the flue gas temperature can rise significantly over time. The piping will eventually fail in extreme situations. As I explained the University staff removed and replaced the PVC flue piping in extreme cases without notifyng the manufacturer or calling an outside contractor. Not all cases get reported. Even if they did report them, the manufacturers would not be willing to share these failures. The University does not even want the noteriety.
I want to just point out a few facts that if these were presented to a jury it might not bode well for manufacturer's selling equipment and recommending PVC venting or contractors installing PVC venting which clearly violates the codes and the standard for the product.
Here are a few points to note:
1. The code requires all flues to be listed and labeled for the intended purpose. There is no such listing for PVC pipe used as combustion gas flues in the US:
2. the piping manufacturers have the following temperature limits for the following plastic piping systems:
ABS Schedule 40 160 ° F
PVC Schedule 40 140° F
CPVC Copper Tube Size 180° F
CPVC Scheule 80 200° F
3. For those of you that do not have a copy of the ASTM Standard, ASTM D1785 standard applicable to PVC plastic pipe and fittings includes: the following note:"This standard specification for PVC pipe does not include requirements for pipe and fittings intended to be used to vent combustion gases".
4. To those of you who wondered if I understand the difference between high efficiency and condensing, They are the same in this case high efficiency boilers and water heaters are condensing appliances. Thus they must use stainless steel (s/s) flues to prevent corrosion from condensing flue gasses. Manufacturers have are now recommending PVC as a less expensive alternative to S/S yet PVC is not listed for this application.
5. To the person who wondered if this is only a water heater problem; In a closed boiler system you always have a make-up water connection. In some cases if you have a leaky seal on a circulator or any other leak in the system make-up water is introduced. If the water is neutral PH there is not much scaling, but if the water is hard (full of minerals) the minerals will preciptate out on the heating surface of the boiler causing a loss in efficiency. The loss in efficiency = a rise in flue gas temperature. This is when there can be problems. I have seen many well maintained and properly installed systems work fine. It is usually only when there is a design problem or installation problem that the high temperature flue gas is an issue. A design problem is having a boiler water temperature of 200 degrees Fahrenheit. The flue gas must be hotter than the water temperature! In this case the flue gas temperature at best would be about 220 F. Heating and hydronic system do not work as well when the heat transfer fluid temperature is lowered to 120 to 140 degrees F. Many tmes the heating coils are designed for higher temperatures. This is a common problem. I am not sure if it is much of a problem for a gas fired furnace unless the filters are not cleaned regularly and the airflow drops off. In that case it could also be a problem.
6. I am seeing a proliferation of water heaters with a heating coil for heating hot water supplied to a fan coil unit in a residential unit. I have also seen water heaters used without heat exchangers providing domestic hot water into heating coils. A water heater is an open system and is a disaster waiting to happen in this situation with a PVC vent. In the University installation mentioned above, there were 4 bedroom apartments with four students assigned to each apartment with a 48 gallon water heater with a heating coil in and a small circulator serving a fan coil unit. It was serving four college students on cold winter mornings with showers, shaving, breakfast, dishwashing , clotheswashing and the heating load for the fan coil unit. The burner in the water heater was working overtime without the winter temperature in the northern climate near zero for weeks at a time. We found that the worst case flues were on units that were on top floors where there was a greater heating load. I do not recommend combined heating hot water and domestic hot water heating systems for many reasons that are worthy of a full magzine article.
7. As for using an infrared thermometer on the outside of the plastic flue pipe. That will not give you the actual flue gas temperatures. In the test it was mentioned the heat was not on for long. In a newer installation or an installation with good water quality the temperature may not get too high. When the burner is overworked because of being undersizing or overloaded, coupled with scale on the water side of the heating surface it causes the burner to stay on much longer and there is a loss of heat transfer into the water which causes the flue gas temperatures to rise. This condition causes long cyles of high temperature flue gasses.
8.F.Y.I. I have recently, since writing the article, and before the publication, I applied for a patent (pending) for a temperature sensor in the flue outlet of a boiler or water heater to sense excess temperatures and shut off the burner to prevent damage to PVC flue pipes. The controls allow intermittent operation to prevent freze-ups and it sounds an alarm to alert the homeowner of a problem. With this technology, Boiler and water heater manufacturers can utilize plastic vent pipes without worries of overheating.
9. It goes without saying that installing a water softener in hard water areas is vitally important.
10. As contractors and manufacturers you have an obligation to follow the code which as I read it does not permit plastic flues because they are not listed for that purpose. If a manufacturer utilizes a temperature sensor to sense the outlet flue temperature they can propose a code change to allow an exception for plastic piping meeting a standard if they have a temperature sensor and burner controls to limit flue gas temperatuers. There is an obligation to provide a safe system for the customer. Even if the custmer elects to choose someone else to try and install it consider yourself off the hook if there is a problem. I suspect it won't be long before the inspector organizations become aware of this issue and stop allowing PVC plastic flue pipes. Stainless steel flue pipes are available and other types of high temperature plastic materials are available (ABS, CPVC & Polypropylene) but there is not a product standard developed specifically for plastic flue gas pipe applications yet.
Cheers0 -
Code Conflicts
As the former chairman of a mechanical and plumbing code committee for one of the model codes, I would have the following intrepretation if I was asked. When there is a code conflict such as the code conflict where the code requires all flue venting products to be listed and labeled for that application vs the manufacturer recommending PVC flues, The code must be followed. There is an exception in the code that allows the manufacturers' instructions to be followed if the manufacturers' instruction are more stringent. The manufaccturers instructions allowing PVC flue pipes is LESS stringent that the requirement for listed and labeled flue pipe materials. Therefore, in my opinion PVC flue pipes are not allowed by code.0 -
Thanks Ron for
coming to the Forum here and answering the questions posed. I will take some time tomorrow to digest all this and I am sure some who typically post here will have some questions.
We welcome you here by the way as there are often code questions that arise so if your valuable time permits stop by and visit us anytime.0 -
Am I the only one who see's a potential conflict of interest here...
It looks to me like he (Mr. George) has a BIG dog in this fight.
(8.F.Y.I. I have a patent pending for a temperature sensor in the flue outlet of a boiler or water heater to sense excess temperatures and shut off the burner to prevent damage to PVC flue pipes. The controls allow intermittent operation to prevent freze-ups and it sounds an alarm to alert the homeowner of a problem. With this technology, Boiler and water heater manufacturers can utilize plastic vent pipes without worries of overheating. It goes without saying that installing a water softener in hard water areas is vitally important.)
Thank you for full disclosure Mr George, but you use an article as a lightning rod, and then stand by and offer to sell early lightning strike detection equipment?
I agree that this is an issue that needs to be addressed, and it appears that the codes are making some effort in that direction. It just appears to me to be a conflict of interests unless the author completely dis-associates himself from the code writing authority.
Please feel free to correct me if I am wrong...
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Ron's Reply
The article was written before there was a patent. I realized the opportunity to file for a patent after the article was written. The article was based on facts. I simply realized the problem and report about it. After reporting about it I filed for a patent for the technology to correct the problem. Feel free to check the date on the application. That is the American Way. When I recognized a problem I reported on it and then thought about it. while thinking about it, I came up with a solution for it. My patent application did not change anything.
The codes do not allow PVC flue pipes and never have. The manufacturers publish in their literature that you can use PVC instead of Stainless steel to make their condensing equipment more competitive with non-condensing equipment.
I have come up with a way to allow you to use PVC if the manufacturers’s want to add the safety controls to their equipment. There should also be an industry standard developed to test the controls. Currently we do not have that option. We can always use stainless steel flues. That has always been the only code approved method of venting gas fired appliances. Even is an inspector allowes PVC Venting because he is not fully aware of the issue, that does not make it legal as far as the code is concerned. You cannot point to an installation and say the inspector approved this one so they must all be acceptable.
The PVC standard referenced in many manufacturers product standard listing contains language stating the the PVC pipe in this standard is not intended for venting combustion gasses" Other manufacturers have language that simply allows PVC venting materials without any references to a standard. There is no way for a manufacturer to prevent flue gasses from rising if there is hard water supplied to a system or is a filter is not cleaned properly.
If you read the codes and the standards, they clearly do not allow PVC for venting combustion gasses.
Please don't throw stones at me because I found many failed systems, reported on this and then had an Idea to make it better.0 -
Fair enough then...
I will give you the benefit of time and assume the patent idea was after the fact.
So, what would YOU do if you were the king?
It's too late to close the gate, the cattle are already out roaming around the country side, legal or not.
There was not a lot of response in regards to my asking for how many completely failed systems people have come across in the field.
If I were a plastic PVC pipe manufacturer, how far would I have to go to get my pipe certified for applications including the handling of flue products?
Sorry about casting stones, but you must admit, there does appear to be some potential conflicts of interest on the outside. I'm not one to cast stones unless I see a need to.
So, one of my previous questions that I'd really like you to address is "Why are installers not required to perform a combustion analysis on EVERY piece of fired equipment to help eliminate the production of Carbon Monoxide?"
They should be required to leave a copy of the analysis attached to the equipment, and it should also be mandatory to have the appliances checked every 2 years with the obligatory report again left on site.
Carbon monoxide is THE most preventable means of inadvertent poisoning in the world today. Why have the codes not addressed this?
Dave Yates and myself went through the process of trying to get combination DHW/space heating systems outlawed, and it appeared to me that the codes were quite strongly influenced by money (water heater industry) and backed up by the HBA (What's it going to cost, and what are the perceived benefits to the home builder?) with little to no regards to the end user. Personally, I was not impressed with the reaction of the code officials in regards to our attempts to eliminate inadvertent exposure to large quantities of Legionaires Disease. They seemed quite lackadaisical in their efforts, and also seemed highly influenced by the water heater manufacturers wishes want's and needs and disregarded the health concerns we raised, which have been documented by a major recognized authority (CDC).
After having been through this process, I probably would not waste my time and effort to go through it again... regardless of how many lives we could save.
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Mark. stop garbaging this thread up
with the FACTS!!. They are on a Snipe hunt and by God they are going to find one!!!0 -
Not a new idea
What about all the gas fired condensing appliances that already have a flue temp limit device? I keep hearing 140 degrees, but sch 40 DWV PVC has a max temp rating of 158.
For instance my Navien Tankless has a 149 degree flue overtemp sensor. I know there are other appliances that have them also. CSA approves this safety to allow PVC venting.0 -
Ron's Reply
To answer your question, "Why are installers not required to perform a combustion analysis on EVERY piece of fired equipment to help eliminate the production of Carbon Monoxide?"
The issue of carbon monoxide is important, but not in this case. ALL combustion creates Carbon Monoxide. The issue here is the flue gas temperatures exceed the temperature limits of the flue materials (PVC). In most cases the excess is not too bad and discoloration occurs. As time passes in hard water areas, the heat exchangers scale up on the water side of the combustion flues and then the combustion gasses cannot transfer heat into the water. When this happens, the flue gas temperatures rise. If the temperatures rise high enough the pipes sag and melt. At that point, carbon monoxide becomes an issue.
I agree the appliances should be checked at regular intervals with documentation left on site. We do this with backflow preventers. I also feel there should be deliming connections on all hydronic heating equipment in case they are needed.
The code does address flue venting options. you can use non condensing equipment or if you use condensing equipment the correct category vent must be installed. PVC is not listed to any category. A few manufacturers appear to be the ones giving out misinformation about he use of PVC as a flue vent for combustion gasses.
I agree with you and Dave on the elimination of combination units for DHW/space heating systems. I have seen many scald injuries associated with combined systems that were too hot because they were undersized and the temperatures were cranked up to compensate. The two systems typically operate at different temperature ranges. Either the building will have poor heating or there is a risk of scalding. The proper system design requires knowlegeable maintenace personnel. I find these days not many companies keep good maintenance personnel on staff for such sophisticated systems. I also agree with your observations of the lobbying efforts and strength of the WH manufacturers and the HBA.
I also agree many code officials are not up to date on the Legionella issue. F.Y.I. I developed a website and formed an organization aimed at educating the industry about how to prevent Legionella bacteria growth in building water systems. www.legionellaprevention.org
I have served on a few hot water design and product standard committees that had manufacturer participants that spoke up and said they did not want to use the "L" word because then they would be acknowlwdging there is a problem.
The CDC seems to have taken a reactionary verses preventative approach in their Legionella efforts.
Cheers0 -
Re: CO prevention
Good point Mark about CO poisoning.
The sad fact is most of it goes undetected as low level poisoning that make people sick but don't make the news. It is almost always misdiagnosed by the Doctor.
If there was a standard you talk of that required all combustion appliances to be tested, it would prevent more poisonings than current codes ever can.0 -
At a minimum...
the codes SHOULD require the installation of a CO alarm, which they currently don't in most states.
Then there is the problem of time weighted CO values... Obviously no concensus there.
And then there is the issue of battery maintenance on the detector. I've seen statistics somewhere regarding the fact that dead batteries were found in smoke detectors, and had they been replaced, lives would have been saved. It's a sobering statistic.
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PVC Temperature limits.
The maximum temperature limits for PVC Piping is 140 degrees according to the technical manual for the PVC piping manufacturers.
Check your facts.
The temperature limit of 158 is not for PVC pipe.
How does PVC pipe behave at different temperatures?
PVC pipe exhibits decreasing pressure rating and stiffness with increasing temperature. As with dimensions, the pressure ratings and published pipe stiffness figures for PVC pipe are listed at an operating temperature of 73F. To determine the pressure ratings and stiffness of PVC pipe at higher temperatures, multiply the pressure rating or pressure class and the stiffness / deflection by the pipes de-rating factors at that temperature. An example of a table of PVC pipe de-rating factors is shown below. Consult with the manufacturer of your pipe for specific data. The typical upper limit for continuous use of PVC pipe is 140 F.
The following are the primary applications for PVC pipe folloed by the standards.
1. Water Pipe:- ASTM D1785, Sch 40 and 80 pipe (1/8" to 24" sizes)
- ASTM D2241, SDR pipe (SDR 13/5 to 64 - 1/8" to 36" sizes)
- AWWA C900, Water mains 4" through 36"
- AWWA C905, Water transmission pipe 14" through 36"
- AWWA C909, Molecularly Oriented Polyvinyl Chloride (PVCO) Pressure Pipe, 4" to 24" for Water Distribution
- ASTM D2665, Sch 40 (Can be dual marked D1785)
- ASTM F891, Cellular core Sch 40, 1 1/4" through 12"
- ASTM D1785 & D2241, Iron Pipe Size OD pressure pipe
- ASTM D3034, SDR pipe, 4" through 15"
- ASTM F891, Cellular core sewer pipe ODs, 2" through 18"
- ASTM D2729 (2" through 6") or D3034
- ASTM F1504 - special product for relining of underground pipes, 4" through 15"
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Facts?
Mr. George,
PVC venting had a pressure during operation of what? Not even close to 1 PSI, so I don't understand your plumbing rating argument there.
Arguing temperature derating meaning stress and pressure operating failure will occur when there is no significant measurable pressure?
At 140 degrees 3" still has a burst pressure rating of over 100 psi, but who cares were not talking about fluids in the pipes.
Is this the case of a plumbing engineer straying into HVAC waters?0 -
Facts?
What PVC pipe and fitting manufacturer approves and recommends their PVC pipe and fittings for appliance exhaust?
Just because the equipment manufacturer "allows" it doesn't mean the manufacturer approves it being used in that application.0 -
What It Boils Down To
Is very simple. Show the testing data. Mfgs that allow PVC venting should via the Freedom of Information Act via the DOE pr the Consumer Protection Agency have to show the public the testing data that PVC is a safe product for the removal of flue gases. We have statements from the mfgs of the product itself that clearly states it has not been tested. So show us the data.
Whether you have used it for 100 yrs with no problems has no bearing. Trial and error to justify its use is not in the best interest of public saftey. For me that is the issue I have a problem with. If you have the data proving it is a safe means of removal of flue gases then lay it on the table for all to view.
If it's safe then so be it. The reluctance of mfgs to show or anwser questions concerning this subject itself raises questions. Plex Vent was caught with somewhere in the 250K installation range divided up between numerous mfgs. Thus the liability cost to them was a micro dot compared to what the cost would be if they were held liable with PVC vent issues.
With M&G and Centrotherm daily getting the PPs products approved for equipment I can see this issue slowly and quitely going away over the next couple of yrs. PPs will keep the vent cost in a reasonable price range.There was an error rendering this rich post.
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What it really boils down to
Is very simple, the 140F degree ASTM specification that keeps getting referred tp here clearly states 'this specification is for pressure systems using PVC pipe and fittings'. ' This system is intended for pressure applications where operating temperatures will not exceed 140F.'
So once again, an ASTM needs to be added for PVC in a non pressure/temperature rating.
I suspect testing agencies are on it but would take years to test and approve. Then this issue will go away, and PVC pipe manufacturers will line up along side furnace and boiler manufactures for there use.
Until then, the code I read clearly approves of this as long as equipment manufacturer instructions are followed.
There is no code forbidding its use.0 -
You guys worry too much!
I know for a fact that PVC can be used for ANYTHING! I just ran across an expansion tank (on a 1,257,000 btu snowmelt boiler) that was made out of a piece of 6"cell core PVC pipe. It even had a clever little "sight glass" made of pex so you could tell how much air was in the top. Also the support stands were made of 3" PVC with nice little cradles sawn in to spread out the load. PVC can be used for lawn funiture, chicken coops, pontoon boats, and most anything where costly materials are not an option.0 -
Solutions to the problems....
Regarding DHW system sliming up, how about the REQUIRED use of an electronic water conditioner. No chance of lime scale accumulation with these devices, and hence, no excessive flue gas temperatures.
As for the control to watch the flue gas temperatures, the SIT controllers that are on many modcon appliances already have a flame suppression circuit if the flue gasses get too hot.
As for closed loop heating systems, to the best of my knowledge, there are NO "requirements" for a solid connection to the potable water system. A good tight system should not require continuous make up. No leak is a good leak, and all leaks need to be taken care of immediately. I have not made a solid connection to the make up water on my heating system (except commercial applications) for the last 10 years. I cover this fact with a low water cut off wired in series with a low pressure cut off. If there is a leak on one of my systems, my insurance company (and ME) want to know about sooner, rather then never or too late. Numerous mechanical inspectors have reviewed my methodology (do a site search here for the term PIG) and have approved it, and have stated that it should be a code requirement.
As for the use of non approved PVC for venting, or any plastic for that matter (ABS, PVC, CPVC) why not require full and complete support for all horizontal lengths (angle iron) of plastic tubing exposed to temperatures in excess of 140 degrees F. Remember also, as others have pointed out, that the initial testing and approval of PVC was with the weight of water and pressure being inside o the pipe. In the field application of the plastic products as venting products, they are NOT filled with water, and they are NOT being exposed to internal pressure of more than hundredths of an inch WC.
This is America. We CAN figure it out. We need to establish a standard for plastic flue pipes, and we need to do it YESTERDAY...
EDIT: One last thing that I've mentioned before that NEEDS to be instituted NOW, the required combustion flue gas analysis, and a follow up test every year or two. This will not only save energy, but will also save LIVES, at a minimal cost to the end user.
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Good Points Mark
One solution as you pointed out would be to requiring water treatment, but probably only in cases where there is hard water. The threshold of hard water needs to be defined. However the water in some areas may change in quality at different times of the year.
As for the high temp limit on the boilers, water heaters, I'm not sure if all equipment has that technology. In fact most of the tempeature sensors cut out at much higher temperatures. The temperature limit for each flue material would need to be mandatory then various types of plastic flue pipe materials could possibly be used with corresponding standard for the flue pipes. I would be worried that PVC with a temp limit of 140 F would mean the operating temperature of the system would be about 120 F (about 20 degrees below the max temperature limit of the piping. At 120 F the heating capacity of the system is less. Most hydronic systems work better with temperatures closer to 200 F. Many heat exchangers/coils are designed for heating hot water temperatures well in excess of 120 F.
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The codes requires all products to be listed for their intended application
The code requires all products to be listed for their intended application.
The standard for PVC pipe does not include venting combustion flue gasses. In fact the ASTM standard specifically mentiones the PVC pipes are not intended for venting combustion flue gasses.
Therefore The code does not allow PVC for venting flue gasses even if the manufacturer says you can. There is a section in the code that addresses conflicts that mentions. When the manufacturers' instructions conflict with the code language, the more stringent language applies. The more stringent language is the listing requirement.
Therefore the way I read it, the code DOES NOT allow PVC for venting flue gasses.0 -
PVC is not currently approved as a venting material.
PVC is not currently approved as a venting material for combustion gasses. I see where some have used examples where they have seen PVC used somewhere else. That is a "Monkey see, monkey do" syndrome.
The manufacturers are wrong when they reccomend PVC for use as a venting material because it is not listed for that purpose. The code addresses that and overides the manufacturers instructions if they are less stringent than the code requirement for all products to be listed and labeled for their intended application.
The ASTM D1785 standard clearly states PVC is not for use for venting combustion gasses.
Many Inspectors are unaware of this also.
I would not want to be a defendant in a trial and use the defense strategy of "I saw someone else do it wrong so I did it wrong" Two wrongs don't make a right. A thousand wrongs don't make it right. We should make a habit of reading the codes and reading the product standard.0 -
PVC has many uses - compressed gasses is not one of them.
PVC pipe is not intended to be used with any compressed air or gasses. This is what an expansion tank is doing. PVC pipe will explode with vilent force if it is subjected to compressed gasses and it is exposed to physical damage. Most PVC pipe technical manuals are full of these warnings.
As for other uses of PVC pipe. I used 4 inch PVC Pipe to make a Goal post in my backyard so my son could practice kicking field goals. But I would never use it for venting combustion gasses or for compressed gasses. I tried to attach a video of a test that shows a piece of 6 inch PVC pipe with 100 PSI exploding when put under stress. It looks like a bomb going off. The video is apparently too big for the blog.
Reminder: Do not use PVC pipe for compressed air or gasses and do not pressure test PVC pipe with compressed air. The storred energy of the compressed gasses propels pipe shards like shrapnel from a hand grenade when it explodes.0 -
PRessure vs Temperature ratings for Plastic piping
PVC pipe is rated at 100 PSI at 73 degrees F
At 100 degrees F PVC is rated at 60 PSI
At 120 degrees F PVC is rated at 40 PSI
At 140 degrees F PVC is rated at 20 PSI
At temperatures near and above 140 F the PVC pipe starts to become soft and pliable. If there are any stresses of forces acting on the pipe it could melt and collapse blocking off the flue and causing a carbon monoxide leak in the building.
See the link below for temperature pressure ratings for PVC pipe:
P.S.
The standard for PVC pipe specifically states it is not for venting combustion flue gasses.
http://www.engineeringtoolbox.com/thermoplastic-pipes-temperature-strength-d_794.html0 -
ULC is a Candian Standard
ULC is a Canadian UL Standard and is not referenced in the codes in the United States. Therefore, it does not apply in the United States.0 -
Ipex
The answer would be IPEX, it's the same material with approval stickers now costing more. A requirement in Canada0 -
Yes
Definitely in agreement on that subject0 -
Where is the code?
Please show me the code that specifically say a furnace or boiler or water heater can not be venting any combustion exhausts using PVC schedule 40 pipe.
Any code in the U.S. (ICC, Uniform, Any state code) . Please post it for all, thanks.
ASTM is not a code, its a testing standard . The way you read it is incorrect, otherwise building inspectors across the nation would have also come to the same interpetation. And local codes always supercede any minimum national codes or standards.
This polypropylene pipe that is mentioned here as a replacement to PVC is still only rated up to 180F. IMO, not much better than PVC.0 -
Ron what is your
take on:
Anyone using InnoFlue?This is a product from Centrotherm Eco Systems. It is a polypropylene vent system. It is based on ULC S636. It can be used up to 230°F or (110° C). it is zero clearance to combustibles. It can be used with oil, propane and gas fired appliances.
They claim cost comparison on 3" diameter 24 foot long system with 4 elbows. Estimated labor rate of $40 per hour PVC material cost $167, labor $120 total $287. For CPVC material $520 labor $120 total $640. Compared to InnoFlue material $172 labor $60 total $232. Very interesting.
To check it out go to www.centrotherm.us.com0 -
Violent PVC:
Ron is correct on the volatility of PVC under pressure. Especially when cold. Where I work, the water department started using PVC water mains on new expansions. They went to make a service tap on a 10" PVC main in February a few years ago and when they started to drill, the pipe fractured and exploded. It almost drowned the person in the trench. These problems continued. There are now very precise procedures to be followed when tapping PVC water mains. The company now uses only ductile iron for water mains.
I have seen a few strange failures of PVC that no explanation could ever be found.
But I ask again, does Charlotte Pipe list their PVC for anything but water, drainage or sewerage?0 -
Kinda a joke, Ron
I'm aware of the test procedures for plastic pipe, and danger of using compressed air for that purpose. I also insisted that the makeshift expansion tank be removed and replaced with an approved tank before I ever put pressure in that system. I also have vented many, many furnaces and boilers with PVC. As with anything in this Field of Endeavor, the craftsman can make or break the whole deal. I have seen my share of stainless systems that fell apart due to faulty workmanship.0 -
As far as I can tell
there also is no difference in IPEX system 636 listed PVC pipe or CPVC pipe. It's just PVC that was tested to 230F degrees , under no pressure, it also has orange stickers listing its use for combustion flue gas.0 -
It looks like a good alternative to PVC
Polypropylene plastic pipe material can take higher temperatures than Polyvinyl Chloride pipe materials. I think Polypropylene is the way to go for condensing equipment if a consensus standard can be developed in the U.S. It appears from a few posts that some people don't understand there is a clear difference in pipe materials and the materials ability to handle different temperatures. PVC can only handle temperatures up to 140 degrees F and should not be used for venting combustion gasses because most heating hot water and domestic hot water systems operate at or above 140 F and the flue gas temperature is always above the system operating temperature. If a furnace is not maintained and the filter is dirty, you can have reduced airflow which leads to increased flue gas temps. According to the manufacturers: the various pipe materials can handle the following temperatures:
PVC (Polyvinyl Chloride) Schedule 40 = (White) 140 F
ABS (Acrylonitrile butadiene styrene) (Black) Schedule 40 = 160 F
PVC (Chlorinated Polyvinyl Chloride) (tan) Copper Tube Size = 180 F
CPVC (Chlorinated Polyvinyl Chloride) (Gray) Schedule 80 = 200 F
PP (Polypropylene) Schedule 40 = 230 F
As you can see there is a type of Polypropylene that is clearly the best choice of the plastic materials listed above. Although there are some virgin polypropylene pipe materials that are intended for use in lab waste and pure water systems that are very soft and they would be less resistant to heat than the materials listed to ULC S636. Additives are added to the polypropylene to increase its resistance to heat. The wall thickness and the additive will affect the materials ability to withstand heat. Not all Polypropylene can take 230 F Additives were included with various types of polypropylene lab waste fittings to reduce the flame spread and smoke development ratings in order to get approval for plenum spaces. I believe the adative in that case was silica sand. The same or different additives may or may not be used in the ULC S636 listed pipes to increase the heat resistance of the piping.
We quickly need to get an industry standard started through the ASTM or ASME standard writing organization for plastic flue pipe materials. The standard working group needs to have a consensus of installers, manufacturers, engineers and other experts. When the standard is complete, then the testing labs can test the materials to the industry standards and then list and label or mark the products as meeting the standard. The listing and labeling portion is important for inspectors to be able to know which products meet the standard for flue gas venting, After the standard is developed, then the Model codes in the US can accept the plastic flue gas materials. I suspect the PVC and ABS would not pass the test otherwise this would probably have already happened. Until then, there is nothing allowing PVCs use in the codes. PVC is clearly not allowed by code because it is not a listed and labeled system, unless it is utilized under an engineered system in which the engineer has to provide a testing report and inspect the installation. Until there is a standard referenced in the code and the products are listed to that standard, they are not allowed. Even Polypropylene systems at 230F can experience problems if the flue gas temperatures exceed 350 degrees F which is very possible in cases where there is poor water quality and/or poor maintenance.
I think it is important to require either annual inspections of boilers and water heaters utilizing plastic flue pipes for problems or require water softeners and temperature sensors on the flue gas outlet.
Until then, listed and labeled Stainless Steel flues are available and approved by the code for condensing equipment.
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Reply to Icesailor
Ice man,
I have talked to Charlotte pipe reps and they indicated Plastic pipe can be used for many things so that is why they have a free "Plastic Pipe Technical and Installation Manual" available for downloading from their website. The manual has engineering data and performance limitations for ABS, PVC and PVC pipe. PVC DWV pipe is non-pressure applications. See page 40 for temperature ratings for PVC pipe. See pages 109 - 115 for other warnings. Pay particular attention to Page 115. which has the following text:
Using Plastics for Combustion Gas Venting
Charlotte Pipe recommends that inquiries about the suitability of plastic piping systems for venting combustion gasses should be directed to the manufacturer of the water or space heating equipment being installed. As stated in the International Code Council’s International Fuel Gas Code 503.4.1.1:
Plastic Pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer’s installation instructions.
Furthermore, several of the ASTM standards applicable to plastic pipe and fittings that Charlotte Pipe manufactures include the following note:This standard specification does not include requirements for pipe and fittings intended to be used to vent combustion gases. This standard specification does not include requirements for pipe and fittings intended to be used to vent combustion gases.
They are basically saying if a manufacturer of a fuel burning appliance recommends the use of plastic pipe, there is no standard that they list to for venting combustion gasses and the manufacturer or the appliance is responsible for making sure there is a standard that will cover the perfomance of the product under the most extreme conditions the product will potentially see with their equipment. Again, a product test in a standard should address the most extreme conditions for heat and other stresses not the most ideal conditions. The conditions or maximum/minimum temperature and stresses for each material should be listed in a standard which should be titled something like "Plastic piping for venting combustion gasses".
The link the the Charlotte Pipe Technicaal and Installation data manual is below:
http://www.charlottepipe.com/Documents/PL_Tech_Man/Charlotte_Plastics_Tech_Manual.pdf0 -
correction
I posted above about IPEX ULC 636 PVC approved pipe for flue gas venting being reted for 230F.
I stand corrected, the pipe is only rated to 65C or 148F.
But it is approved, same PVC just with orange stickers. So the way I see it, Charlotte pipe manufacturer has yet to get their pipe ULC 636 labeled. And others are taking advantage by saying their PP pipe is better, basically this entire thread is just one big advertisment .0 -
PVC Venting:
In other words (as I have been informed), if there is a problem with the PVC pipe and fittings when used to vent gas appliances, and there is a lawsuit, PVC is off the hook, they have no responsibility, and it is you and the appliance manufacturer and their "approval" for the product.
Kind of like condoms. They are supposed to work but if they don't, you are on your own.
I was told that in litigation gases, where there is litigation over PVC vent failures, the defense table has no Representative from the PVC pipe and fittings table. That tells me something. There is no responsibility from the manufacturers of the product. The manufacturers of the appliance are assuming the responsibility and you are responsible for the install.0 -
What I'm getting from all this
is that in a lot of cases, PVC venting has worked fine for years, as long as nothing has gone wrong with the unit being vented.
But, if something does go wrong that boosts the flue gas temperature, it may not hold up. Then the lawyers come in, the manufacturer of the PVC argues that the PVC was not installed for its intended purpose, and we're left holding the bag.
ME, I recall that when you intentionally deferred maintenance on your own mod-con to see what would happen, it dropped to something like 68% efficiency over a period of time. Do you recall if that resulted in elevated flue-gas temperatures?All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting0 -
Frank...
My little Munchkin has the SIT control with the flame suppression circuit on it. It will idle the burner back, regardless of the load, based on an increase in flue gas temperature. The low burner/heat exchanger thermal efficiency was evident with cold start up on high burn. I have enough flow meters and sensors on this boiler that I can tell you its thermal efficiency by the minute.
Without the flame suppression circuit, I may have very well exposed the PVC to higher temperatures, but that is the reason the manufacturer uses the flame suppression feature.
METhere was an error rendering this rich post.
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