Will heat from hydronic heating hoses melt PVC pipe?

belfert · September 16, 2011, 06:56:29 PM

My coach has a 2" thinwall PVC pipe running front to back that used to have copper lines for the A/C running through it.

If I run two 3/4" heater hoses for my hydronic heat through that pipe will I melt the pipe? The hoses are going to be a tight fit.

luvrbus · September 16, 2011, 07:00:24 PM

No but why use hose use CPVC or Pex it flexible enough

good luck

desi arnaz · September 16, 2011, 08:12:29 PM

Pex is much better

belfert · September 17, 2011, 05:51:15 AM

Using PEX or CPVC versus heater hose doesn't solve the problem of heat being transferred to the thinwall PVC pipe. It sounds like you guys think there isn't going to be enough heat transfer to cause the PVC pipe to deform? I know that PVC can't be used for hot water.

Will 3/4" PEX be large enough for the main trunk line between my Proheat heater and the manifold? PEX has a smaller ID than other 3/4" pipe because the wall is thicker. I already purchased the 3/4" heater hose a year or two ago, but I think PEX might be better.

Sean · September 17, 2011, 05:58:33 AM

PVC, including schedule 30, is rated for use up to 140°F. Your hydronic fluid can get much hotter than that, up to 180°F or so if it comes from the main engine loop, and around 165°F from a diesel boiler like a Webasto. While the hose itself will provide some insulation, you should figure that the temperature on the outside of the hose can approach the fluid temperature during some periods of operation.

I don't think the pipe will melt at that temperature, but it can get soft and then deform. FWIW.

-Sean
http://OurOdyssey.BlogSpot.com

luvrbus · September 17, 2011, 06:36:40 AM

Brian, what Sean is telling is the 140 degrees is operating temp under pressure,it takes 225 to 275 degree to get pvc hot enough to bend depending on the sch and size they make heaters for that,
I see a lot of people using the stuff for generator stacks you should find a flow chart on Pex and rubber I am sure Pex will flow more rubber

good luck

edroelle · September 17, 2011, 06:46:14 AM

I don't know about the Proheat pump, but the Webasto circulating pump is limited to 110' of circulation loop. More than that, and you may not get enough flow to the coils.

Ed Roelle
Flint, MI

Oonrahnjay · September 17, 2011, 06:52:32 AM

Quote from: edroelle on September 17, 2011, 06:46:14 AMI don't know about the Proheat pump, but the Webasto circulating pump is limited to 110' of circulation loop. More than that, and you may not get enough flow to the coils.

Ed, do you use the circulating pump internal in your Webasto unit or do you have an external circulating pump (or more than one) as well? Thanks.

belfert · September 17, 2011, 07:45:41 AM

I believe I should be within the pumping capacity of the Proheat pump. I had checked this a year or two back when I first started planning this project.

luvrbus · September 17, 2011, 08:37:53 AM

Brian, one thing is to be real careful when installing the Webasto make sure there is no where to create a air pocket, those things will put you in the poor house buying the over temp fuse at $ 35.00 a pop you get a air pocket they will blow the fuse just another little item people don't tell you about lol.
You can buy one that resets but they are pricey I am sure other places sell those other than Aqua Hot they charged me over $300.00 for one then went it bad in about 4 years

good luck