What pipe to use for air intake?

cj5

This is a very basic question, I know, but I can't seem to find the answer anywhere.

I need to redo the air intake (not exhaust) for my high efficiency boiler.

• Is the air intake pipe regular white PVC that you can get walking into a home depot, etc?
  
• Or is it a special material and size that you need to get from some HVAC supply?
  
• If it's something special what is it called?
  
• Also just regular PVC glue or something special?
  

The only thing I can find when I look up intake pipes is the concentric intake exhaust which I don't have.

Thanks

GroundUp

That will depend on the manufacturer's specs. Typically the white schedule 40 PVC with long radius glued elbows is used, but your MFG may spec otherwise

hot_rod

I seems like the majority of the mod con boiler installation manual deals with venting requirements. Some brands have a specific supplement on venting and approved materials.

What brand and model boiler? The I&O should be available online to clear up the options.

Typically schedule 40 PVC either cellular core or pressure rated PVC is acceptable, in addition to some of the poly P plastics.

GBart

You need the manual, you cannot simply reroute your intake, there are restrictions as to the type of turns, usually wide radius and the number of turns and total length, you have to refer to the factory manual, if it doesn't meet their spec's the unit will probably not run.

cj5

It's a Navien combi NCB-240 boiler.

For the vent piping the installation manual says to use:

PVC Schedule 40 (Solid Core)
CPVC Schedule 40 or 80 (Solid Core)
Approved Polypropylene*
* Approved polypropylene systems include:
Durevent Polypro (Single Wall): 2PPS-xxx (2”), 3PPS-xxx (3”) Centrotherm Innoflue SW: ISxx02xx (2”), ISxx03xx (3”) Refer to manufacturer’s literature for detailed information.

My exhaust pipe is the higher temperature version so I think that is the schedule 80 stuff.

Intake and exhaust are both 3" diameter.

So can I just get the home depot schedule 40? Will that be exactly the right size? Or do I need a specific boiler schedule 40 version. Sorry if this is a silly question.

As far as turns and total length. I have looked into that already. My run is fairly short with 3 turns. It's just that the last guy working on it didn't aim the intake downward and located it higher than the exhaust. It is 12" higher than the exhaust and about 6" to the side but I'm not comfortable with that since I'm worried about rain and exhaust getting in. I'm going to turn the intake pipe 90 degrees so it's horizontally 12" away from the exhaust and inlet is pointing down. That will be to the installation manual intent. Ground clearance accounting for snow is adequate.

Thanks for all the input so far.
Just want to know if all types of 3" schedule 40 are all the same size.

hot_rod

Yes the PVC will be the same dimension and spec from plumbing wholesalers or box stores.
Schedule 80 is probably not common in box stores, same OD outside dimension, thicker wall and smaller ID, over kill for intake venting..

They all should have the same listing numbers stamped on the pipe regardless of the brand.

Fittings will be the same for PVC. I also prefer long sweep ells or 45° bends to make turns.

Use the primer and glue, cut the ends as even as possible for good flow, ream any inside burrs.

A 10" chop or miter saw makes a perfect cut on PVC or a large tubing cutter with a plastic cutting wheel. Proper supports also.

GBart

With the 3" you can go 150ft and 8 turns but --- Reduce the
maximum vent length accordingly for each elbow used:
Each 90° elbow equates to 5 linear feet of vent
Each 45° elbow equates to 3 linear feet of vent

so with three turns you're down to 135ft, be sure to count your downturn, still you should have plenty of length to spare

Tinman

For the intake, I've always used PVC and I don't see any reason to change that.

hot_rod

If Navian indicated solid core PVC on both intake and exhaust, that is probably what you should use. That is not so common at box stores in 3" size, go to a plbg wholesaler for a better pipe and fitting selection.

GBart

They actually indicate CPVC for the first few feet unless a temp sensor is used and enabled on the exhaust, the intake doesn't matter.

NY_Rob

Just be careful buying from Home Depot... they do have some cellular core PVC on the shelves. You need solid core PVC.

cj5

Thanks for all the feedback! So solid core schedule 40 PVC it is for the intake.