Pex for Webasto/Proheat

[Slow Rider]

200 degrees is the max I am seeing.


What are temperature limitations for PEX?

PEX tubing can be used up to 200° Fahrenheit for heating applications. For plumbing, PEX is limited to 180° F. Temperature limitations are always noted on the print line of the PEX tubing.. PEX systems are tested to and can be used with standard T and P relief valves that operate at 210" F and 150 psi.

taken from : http://www.ppfahome.org/pex/faqpex.html

Frank

[busing704]

I am going to start plumbing my webasto. Should it be run in a manifold or a loop (4 heads)

[Bill B /bus]

A couple of thoughts:
Minimum diameter  is 0.75" for webasto
Fittings for PEX tubing are internal fittings and are less than the required 0.75" diameter
Looked into using PEX for a buddy's install and came back to the tried and true method of 3/4" copper for the long runs between heaters and heater hose for the connections.
I use a loop system for four installs I've done. Include a "summer" loop. This circuit involves the Webasto, water heater (if  included) and surge tank.
I don't crossconnect the water systems, engine coolant and Webasto, because loss of one means loss of both. With my luck I'd lose an engine hose when the outside temperature was low. Then I'd have no motion and no heat and my bride would not be happy.
Just my $0.02
Bill

[belfert]

If you like the idea of tieing together the engine heat and Webasto heat, but don't like the risk just use a flat plate heat exchanger.  If something breaks on either side the other system will still work.

[luvrbus]

That is why you build a manifold for the system something happens to 1 zone cut it off and the others keep working. 

good luck

[Paul]

We are installing a Hydro-Hot System in the bus now.  Found the unit at a salvage store and ordered the rest as a kit from Vehicle System, now Aqua-hot.

They sent us 5/8" ID x ¾"OD TuffPEX by UPONOR    160PSI 73.4'F    /     100PSI 180'F       /      80PSI 200'f.

The system is not pressurize, so the only pressure would be from the pump and weight of the water. I do not know what pressure this would be but I think it might be 15 to 25 PSI.

The pumps are very low-pressure pumps this keeps the power demand down.

I have been told the length of the runs is critical to keep the power demand down.

Crimp fittings for PEX tubing are internal fittings and are less than the required 5/8" ID diameter.   This makes more power demand and slows the flow. I have not used these fittings.

To make sharp bends in places and in places hard to repairs later I am using ¾"OD copper and long radius sweat ells.

To couple PEX to Copper I use ¾" radiator hose and clamps. Use brass insert in the PEX