Concerns about recent boiler installation

NY_Rob

Some of the PVC manufacturers acknowledge that their D1785/D2665 is being used in exhaust systems and offer guidelines for use....

https://www.northamericanpipe.com/sites/default/files/PL-PS-001_0117_D1785-D2665-1.pdf

Steamhead

There are better plastic venting systems that are UL approved. It's time to ban PVC for venting.

Solid_Fuel_Man

Here in Maine it is the same way. If the manufacturer states that PVC is an approved venting material then we are free to use it. That said 99% of the installs I see use PVC. The only place I don't see PVC is when the manufacturer doesn't allow for it in the I&O (Viessmann).

Our industry won't make the change until we are convinced that PVC is an actual hazard. The chloride alone running back into the boiler is enough for me to use PP, but PVC glues up nice and is always on the truck....

wklopf

KC_Jones said:

Here is a direct quote from D1785

“This standard specification for PVC pipe does not include requirements for pipe and fittings intended to be used to vent combustion gases."

I found this on the Charlotte pipe site.

"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."

The HTP installation instructions clearly state that PVC pipe meeting ASTM standard D1785 is acceptable. However, I am wondering about another thing. The HTP instructions say that a 2" 90 is equivalent to 8' of straight pipe and a 3" 90 is equivalent to 5' of straight pipe. However, the Charlotte pipe site has a table which states that a 2" 90 degree elbow has a friction loss equivalent to 5.7' of straight pipe, while for 3" pipe the number is 7.9'. Is it possible that HTP got it backwards in their directions?

KC_Jones

Your quote states plastic pipe, not PVC. There are plastic pipes that are specifically designed for use in venting that aren't made out of PVC.

If you read carefully the boiler manufacturer says to use a product that meets a standard for venting. That standard states it isn't for venting and the pipe manufacturer says follow what the boiler manufacturer says.

This is a very elaborate CYA so no one takes responsibility.

wklopf

I did a search on Google for plastic pipe for boiler exhaust and found the following piece which suggests using CPVC for the exhaust vent, due to its higher temperature resistance.

https://www.thespruce.com/vent-pipes-high-efficiency-condensing-furnaces-4119901

wklopf

After reading the piece below, I'm beginning to think that stainless steel is the only safe material for exhaust vents.

https://www.phcppros.com/articles/1911-is-pvc-an-acceptable-vent-material-for-flue-gases

Leon82

Polypropylene is also available, but it costs more.

EBEBRATT-Ed

@wklopf the difference in fitting resistance is always an issue. With plastic pipe it could be the difference between drainage or long radius elbows versus pressure or short radius elbows.

Black fittings are ridiculous , you can look up 5 different charts and get 5 different answers for the same fittings

wklopf

After studying the situation, I'm going to get the intake replaced with 3" PVC and the exhaust replaced with 3" polypropylene. That way, the effective length will be under the max of 100' for 3" pipes.