What type of PEX for radiant heating?

belfert · June 19, 2009, 08:09:32 AM

One of my friends has offered to spend a weekend installing the Proheat heater in my bus. (I was most likely going to put it off another year.)

What type and size of PEX pipe should I use from the manifold to each heat exchanger? The heat exchangers I bought are 25,000 BTU. Do I need 3/4" or is 1/2" PEX good enough? I am going to keep this seperate from the engine cooling so I will use coolant designed for home systems. Do I need oxygen barrier PEX?

Final question is what size pipe should I use from the heater itself to the manifolds? Should I just use silicone heater hose?

Thanks in advance for any help.

gumpy · June 19, 2009, 09:36:14 AM

Depends on the size of the manifolds and the number of lines you intend to run. I would strongly recommend 3/4" between the heater and manifolds, and 1/2" for the exchanger runs.

Barrier pex should be used if your system is pressurized and has steel or cast iron in it. If it's not pressurized, it doesn't matter. By pressurized, I mean if there is a pressure cap on your reservoir.

Menard's has some nice manifolds with individual 1/4 turn valves. They are 3/4" with 1/2" valves.

craig

belfert · June 19, 2009, 09:55:31 AM

The reservoir I will probably use is just plastic with a plain cap so it seems regular PEX will be oaky.

The Proheat pump is 8 GPM. If I have four or five loops in the system will I need an auxiliary pump?

gumpy · June 19, 2009, 12:49:50 PM

8 gpm should be fine. Mine are 7.5, and I use typically only use one pump for the entire system.

How big of reservoir are you planning to use?

belfert · June 19, 2009, 05:16:43 PM

My reservoir is only maybe a gallon so it might be too small. I seem to recall that too little coolant in the system results in cycles that either too short or too long.

Nick Badame Refrig/ACC · June 19, 2009, 07:00:39 PM

Hi Brian,

I use what they call "Heat Pex" it is rated at 220 degrees and it is not sold in Lowes or HD.

It only costs pennies more then regular pex and you can easily purchace it at a local plumbing supply house.

Good Luck
Nick-

Stormcloud · June 19, 2009, 07:21:13 PM

Nick:
Does the 'heat pex' sag as much as regular pex when the heated antifreeze is circulated through it?
I am doing a similar install in my bus this summer/fall and want to do it right the first time.

Regards.

mark

Nick Badame Refrig/ACC · June 19, 2009, 07:44:17 PM

Quote from: Stormcloud on June 19, 2009, 07:21:13 PM
Nick:
Does the 'heat pex' sag as much as regular pex when the heated antifreeze is circulated through it?
I am doing a similar install in my bus this summer/fall and want to do it right the first time.

Regards.

mark

Hi Mark,

I'm pretty sure that is more flexable then regular pex and is more resistant to kinks too.

We usually use fasteners every 10" when not burrying it in concrete.

Oxygen barrier heat pex is made by a couple different mfg's and any would work just fine.

Nick-

belfert · June 19, 2009, 09:26:27 PM

Is oxygen barrier PEX the same as "heat" PEX? I know Menards carries oxygen barrier PEX locally.