Using PVC for condensing boiler venting. Will it melt? 1

[cdxx139]

Has anyone dealt with the issue of using PVC (or CPVC) for a condensing boiler flue vs AL29-4C S/S?

Almost every boiler manufacturer IOM allows PVC, CPVC or S/S flue material. I specified S/S venting and the contractor came back and wanted to install PVC, I rejected it, and it started this debate. I have done some research, and this is what I have found.

AGAINST PVC (my original position).

- PVC manufacturer material sheet states PVC is not tested for venting. The melting point of PVC is something like 160 degF. The flue of a 140 degF HWS condensing boiler is worst case 50 degF over HWST (a manufacturer gave me this rule of thumb). Im still not sure how to calulcate this, if anyones can tell me where to find the formula, it would be most appreciated.
- As the sysytems is used it will develop scale in the heat exchanger and reduce its efficiency, increasing the flue temperature higher than originally calculated.
-Just because the manufacturer says PVC can be used, does not mean it will work in my application.
- A recent article explains most of this:

http://www.plumbingengineer.com/may_11/code.php

FOR PVC (im starting to lean inthis position)

- The boiler manufacturer IOM states PVC is allowed. The boiler is 3rd party certified, which means the boilers are tested at their highest ratings (above 180 degF), and the venting allowed is acceptable to them. (If a 3rd party says its ok, shouldnt the engineer accept it?)
- From a code stand point, the inspector will allow any venting material acceptable to the manufacturer. (if the inspector is ok with it, should the engineer overrule?)
- Rumor? The article is written by a guy who makes money for expert witnessing and is drumming up business. The example in the article did not explain the problem was the incorrect vent connections. Even if S/S was installed incorrectly, there could be a carbon monoxide issue. (would make sense?)

Curious if engineers would allow PVC venting in these situations?

knowledge is power

 

[PEDARRIN2]

317069

Code used to allow for lead water pipes - until the safety issue became apparent. Now we do not use it.
Code used to allow for asbestos insulation - until the safety issue became apparent. Now we do not use it.

What was allowed or accepted in the past may not be correct. Prior to these issues, my company did allow PVC as a flue material. After the articles, we have only specified the metal product and will not specify the PVC until these concerns have been addressed. Is that a knee jerk reaction? Maybe.

So just because code allows something doesn't necessarily make it correct, especially if there is a potential safety issue. The articles stated that, in the opinion of the writer, PVC pipe should not be used until adequate testing and standards could be produced. This is not binding, this is not code, but it is an opinion of a respected engineer in the field and should be given credence

I agree that publication in a trade magazine does not replace handbooks and other published documentation. But I would assume there is a board of editors or technical reviewers that screen articles to make sure there is merit and a certain level of technical expertise. Joe, the maintenance man, does not typically get published. Respected members of the design community do.

I do work for an engineering company and sometimes the owners/clients choose to do things against our recommendations. If there is not a clear code issue, which in this case there is not, but a perceived (potential) safety issue, I can only document my recommendation and let it stand as that. The lawyers may still try to sue my company (probably will), but it will likely be less of a cost in legal fees if I supply my documentation that I recommended not doing it as opposed to not having the documentation. I can only imagine the attorney holding up the articles and asking why we did not make the owner aware of potential dangers of using PVC piping. Might as well get out the check book and start writing large checks.

PVC piping will continue to be specified as a flue material and will work satisfactory if the design professional designs the system correctly. But to give the material a blanket acceptance just because the equipment manufacturer says its ok is poor design.

 

[317069]

you are right, code requirments based on the knowldeg available at the time code has been written. I agree.
but if code today tell you flue pipe should be comply with xxxx standard or schedule, it is clear, is your material copmly withis standara then ok use it, your material does not copmly then you don't use it. all my posts I menstioned if PVC is approved for this installation , why we make it long and complicate.
if your company change its policy that is her choise I have nothing to do with it.
when you as a company have a safety issue with client decision, you don't just right it down and keep it in your drawer for lawyer inspection, you have to prevent client from doing something he can not estimate its risk ( that why he hired you), you have to talk with the city about this issue and stop project untill you agree for a solution not to wait court time,[ul]
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