Running pex through existing ductwork?

NovaScotia

Looking to installing a boiler with radiators. Might seem like a dump question but is running pex tubing through existing ductwork to get heat in the rooms that I need a bad idea? I've updated boilers with existing piping but never had to run new piping. It seems like it would be a logical thing, but I'm not sure of the ramifications of doing so. Thanks for any help.

ChrisJ

NovaScotia said:

Looking to installing a boiler with radiators. Might seem like a dump question but is running pex tubing through existing ductwork to get heat in the rooms that I need a bad idea? I've updated boilers with existing piping but never had to run new piping. It seems like it would be a logical thing, but I'm not sure of the ramifications of doing so. Thanks for any help.

You need to be 100% sure there's no sharp edges or screws that will be near the pex, otherwise you'll be very sorry and it won't take long.

Other than that, the ridiculous size the ductwork is vs the pex would also be a concern of mine because the pex running through it will make it difficult to remove the ductwork later on.

Obviously I'd expect the ductwork to be disconnected and no longer in use as well.

pecmsg

How much Pex do you plan on putting in the duct work?

What does this duct supply A/C?

john_james

I know ethernet cable in plenum spaces needs to be plenum rated. I'm thinking the same concerns about toxic smoke in a fire apply to plastic pipe in a duct.

Is the ductwork still in use or are you going to seal it off and use it like a big cable/pipe raceway?

Intplm.

@NovaScotia

Im not so sure that is the best thing to do.
If you run pex in the duct work it will be laying in there, or curled in places but able to move due to water flowing through it. Im thinking you won't be able to fasten it to prevent this movement.

The inside of ductwork is not smooth, sharp seems and edges with screws sticking through.

It is not like what Bruce Willis crawled through in the movies.

Over time. And probably a shorter time than one might think. Leaks will happen.

I would get a good look at the interior of the duct work.
But even better, why not run the pex along the path of the duct work? Is that an option?

hot_rod

In commercial applications the tube would need to meet the ASTM standard, plenum rated. I'm not sure that is a residential code requirement? Some plastic tube has the listing, or wrapping it with a rated insulation works also.
here is what Rehau states.