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Old 23-02-2016, 12:44   #1
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Correct tubing for hydronic heat

I'm putting an Espar hydronic heater in and wonder if the oxygen barrier pex tubing is necessary. I'm going to run an optional loop through the engine so there will be cast iron in the system.
Oxygen proof tubing seems harder to source in Canada, at least at the big box stores. Will regular tubing be a problem?
I'm using antifreeze/coolant in the system so maybe it doesn't matter.
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Old 23-02-2016, 12:56   #2
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Re: Correct tubing for hydronic heat

Simple wire reinforced hose would do just fine, no need for solid pipes.

Similar but not identical installation a friend of mine did some years ago

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Old 23-02-2016, 13:08   #3
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Re: Correct tubing for hydronic heat

The oxygen barrier is there to protect ferrous metals in the system Seems like that would include the engine block.
Flexible PEX Pipes: Radiant PEX & Reclaimed Water PEX Piping
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Old 23-02-2016, 13:18   #4
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Re: Correct tubing for hydronic heat

Oxygen barrier pex has the same physical properties as regular pex. It has a coating that prevents or rather reduces oxygen permeability a bit more then pex. I think with the small amount of pex you will use, it would be fine without the barrier. Plus as you said you'll have corrosion inhibitors in the antifreeze. That should prevent corrosion. Just keep it fresh.

If your worried you could always paint the tubing with a latex acrylic paint.

Most hydronic heating systems for homes, commercial do not have corrosion inhibitors, so a barrier coat would be required in that case. Also without a barrier coat you would get more air (O2) in the system, so a small auto-air vent would be needed too.
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Old 23-02-2016, 13:56   #5
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Re: Correct tubing for hydronic heat

BTW, your typical engine rubber hose has 10 times the oxygen permeability as basic pex. So go ahead and use regular pex.
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Old 23-02-2016, 14:16   #6
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Re: Correct tubing for hydronic heat

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Originally Posted by sailorchic34 View Post
Oxygen barrier pex has the same physical properties as regular pex. It has a coating that prevents or rather reduces oxygen permeability a bit more then pex. I think with the small amount of pex you will use, it would be fine without the barrier. Plus as you said you'll have corrosion inhibitors in the antifreeze. That should prevent corrosion. Just keep it fresh.

If your worried you could always paint the tubing with a latex acrylic paint.

Most hydronic heating systems for homes, commercial do not have corrosion inhibitors, so a barrier coat would be required in that case. Also without a barrier coat you would get more air (O2) in the system, so a small auto-air vent would be needed too.
In following your comments I notice you seem to have a great deal of knowledge re hydraulics/fluids etc.. I am thinking of designing a simple way of recovering some of the heat being lost in the exhaust stack of my diesel bulkhead heater by using copper tubing, an expansion tank and two small radiator type heater elements.
Should I start a thread at some time when I have more of the details worked out, and hope you are monitoring? I would like to get your input...
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Old 23-02-2016, 15:03   #7
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Re: Correct tubing for hydronic heat

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Originally Posted by morven55 View Post
In following your comments I notice you seem to have a great deal of knowledge re hydraulics/fluids etc.. I am thinking of designing a simple way of recovering some of the heat being lost in the exhaust stack of my diesel bulkhead heater by using copper tubing, an expansion tank and two small radiator type heater elements.
Should I start a thread at some time when I have more of the details worked out, and hope you are monitoring? I would like to get your input...
You might search on the forum for that as it's been done a time or two. Big issue is water needs to circulate when your heating with a bulkhead/ cabin heater so you don't make steam. Plus you need a pressure relief piped to a safe (non-scalding location). The problem is if no flow or low flow, you could make steam.

Another low cost method would be to make a heat pipe or two, either wrapped around the flue or embedded in it. A heat pipe is a sealed pipe with a long wick and refrigerant in it. 1/2 of the pipe is in a heated air stream the other in a cool air stream that needs heating. More then one is generally needed. No moving parts and done well it moves heat nicely. Of course that needs a vacuum pump and a bit of R34, etc.
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Old 23-02-2016, 15:04   #8
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Re: Correct tubing for hydronic heat

You can use PEX in hydronic installations. There are two things to consider that may not be evident.


The tubing is much less flexible than good quality double walled tubing. (don't use wire reinforced)
PEX give off much more heat than the rubber stuff. This may be a good or bad thing depending on your goals.


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Old 24-02-2016, 08:48   #9
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Re: Correct tubing for hydronic heat

In the states Home Depot has oxygen barrier PEX tubing.
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Old 24-02-2016, 11:00   #10
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Re: Correct tubing for hydronic heat

I used the oxygen barrier pex on my boat two years ago. I got it at Home Depot by special order. Took a few days to get it. I am not sure if it was really required but it was recommended by Sure Marine in Seattle where I got most of the parts for the job. They are an excellent resource for all things boat heater, cooling and refrigeration.
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Old 24-02-2016, 15:26   #11
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Re: Correct tubing for hydronic heat

Heating grade Pex stops oxygen loss in the heating loop, thereby not creating hydrogen in the heating loop...
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Old 24-02-2016, 16:47   #12
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Re: Correct tubing for hydronic heat

mikemenza

??????????????? I thought the oxygen went into the system and caused corrosion in any iron components.
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Old 24-02-2016, 16:50   #13
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Re: Correct tubing for hydronic heat

20+ years ago I made a ultra compact, wet base diesel fired boiler to heat our boat in New England.
I plumbed the boat with good quality automotive heater hose and ran thru great little units called "hide-a-vector" (household kick panel heaters). I did include a few auto vents in the system to rid the O ,but found that after a few weeks running very little venting occured. Charge was with anti freeze.
That unit and plumbing was still operating 6 years ago when the boat left for Texas.
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Old 24-02-2016, 17:14   #14
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Re: Correct tubing for hydronic heat

I have an oil fired boiler that gave 250° F water at 15psi. It ran thru uninsulated copper pipe to baseboard type radiators. In cold weather it burned 5+ gallons a day.
I changed the baseboards to marine forced air heaters, insulated the pipe and turned the water temp to 180° and cut the oil bill in half. Later I completely replumbed with insulated CVPC and also added plumbing so I can use engine water to heat when cruising. I also have a pellet stove with a coil that heats the boiler when running and eliminates the need for oil. Since I maintain below 180° the CVPC pipe works fine. I have pressure relief valved at the boiler and pellet stove.
The forced air heaters heat 4x as fast as the radiators. I can go from a cold boat, cold boiler to comfort in about 30 minutes. Also I can circulate the boiler water thru cold engines prior to starting. Usual water additives. Be careful of anything that could make steam. Water expands 16x going to steam and makes pressure fast.
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Old 24-02-2016, 17:46   #15
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Re: Correct tubing for hydronic heat

the heated system is under pressure as compared to atmospheric pressure.. the pex acts like an oxygen membrane.. and the oxygen moves from the higher pressure to the lower pressure...
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