pex piping for baseboards


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Old 05-07-10, 02:44 PM
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pex piping for baseboards

can pex piping be used in a boiler application to plumb to the baseboards? Is there a particular type to use? I have read about some varios types, and to my understanding, an oxygen barrier type of pex is needed. Finally, my last concern is that the max temp rating on a lot of the stuff that I have found is 200 degrees F. This past winter when it got really cold, I was running the boiler close to 200 degrees. Is there a type of pex with a higher temp rating? If so, where is it sold? thanks for the advice.
 
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Old 05-07-10, 06:02 PM
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PEX, only with an oxygen barrier, is used for hot-water heat.

If you have to increase the boiler temp to 200 deg to stay warm, your house must be under-radiated. 200 deg water temp will reduce efficiency, etc.

What type of piping is existing?
 
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Old 05-07-10, 08:23 PM
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The current boiler system, has all copper piping, and it has baseboards in every single room, with the exception of 2 rooms, which are rather small (10'x10'), these are the two rooms in which I am going to add baseboards. Last winter, when it got extremely cold out, is when I turned up the temp to 200. Under "normal" operation, the high limit was set to 170. Now, with it getting warmer, I believe that I turned it down to about 150 or somewhere in that area. Does this answer your question?
 
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Old 05-07-10, 09:10 PM
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I don't know if it answers Mike's question, but let me rephrase it...

Did you HAVE to turn the temp up to 200? In other words, the system could not satisfy the thermostat with the high limit at 170 ? Or did turning it up to 200 just seem like the right thing to do? (you know, that psychological feeling that if the boiler is at 200, then I must feel warmer...)

I would probably use a Pex-Al-Pex tubing, or maybe Onix by Watts... the advantage to the Onix is more flexibility, won't 'kink' during install (a problem with regular PEX, especially for a DIY who won't have experience installing PEX), and the fact that you don't need any special tools to terminate the fittings.

You should be careful about turning down the temp too far... 150 is 'borderline' for a gas fired system... probably OK for oil... turn it down too low and the return water gets too cool, and makes the boiler unhappy.
 
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Old 05-08-10, 09:48 AM
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from what I recall, I turned it up to 200 to give the system a faster recovery time. Otherwise, it took quite a while for the system to satisfy the t-stat
 
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Old 05-08-10, 03:17 PM
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I ought to have explained why I wondered if your house was under-radiated.

At 200 deg, your boiler will put out less heat (Btu/hr) than at, say, 160 deg. The reason is that at a higher water temp, the boiler is less efficient due to higher stack losses.

By recovery time, are you referring to the time for the house to warm up after jacking up the thermostat in the morning? That issue could be remedied by a "smart" programmable thermostat. It keeps track of how long the heat calls are during the night, and automatically adjusts the time for thermostat's morning temp setup. I know Honeywell makes them.

The generally accepted aquastat setpoint, without outdoor reset, for conventional residential heating boilers is 180 deg, and the radiation, pump, boiler, and piping should have be sized for that.

For the coldest weather design point of your system, it would be ideal, efficiency-wise, if the boiler burner ran essentially continuously while the thermostat is just barely satisfied. That sweet-spot is seldom achieved, of course - and in your location, it wouldn't be a very conservative design point.
 

Last edited by Mike Speed 30; 05-08-10 at 03:32 PM.
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Old 05-09-10, 02:20 PM
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yes, I do have a programable t-stat. I bought it last fall. I know it is a venstar, but aside of that I cannot recall the model number. But I was unaware that it is actually more efficient for the boiler to run continious in cold weather. But when having the aquastat set to 180, this would be fine for the pex only being rated at 200?
 
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Old 05-09-10, 03:06 PM
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Originally Posted by cheinemann View Post
But when having the aquastat set to 180, this would be fine for the pex only being rated at 200?
Yes - but verify with an accurate boiler temp gauge that your aquastat setpoint is correct. Since you'll be draining your system, this would be a good time to replace the boiler gauge with a new Winters or Enfm tridicator.

Make sure you familiarize yourself with the installation instructions for PEX, including maximum spans between hangers.

Good luck!
 
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Old 05-09-10, 06:16 PM
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Yes, I am familiar with the basic installation of pex, secondly, I have a new guage, and some other misc parts sitting on the shelf, for when I plan to shut down the boiler. I am thinking that I can install baseboards, run the pex, and tie in to the existing system at a later time when its warm enough to shut the boiler down.
 
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Old 05-10-10, 04:09 PM
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when its warm enough to shut the boiler down.
I dunno about SD, but I'm wondering if I'm gonna be able to shut the system down at all this year! Frost warnings tonight in NJ! Had to bring in all the tomato plants!
 
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Old 05-10-10, 05:14 PM
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Originally Posted by NJ Trooper View Post
Frost warnings tonight in NJ! Had to bring in all the tomato plants!
Couldn't you have just covered them? Or hadn't they been planted yet?

Frost early Sunday a.m. in northern Illinois. My garden looked like a campground - with all the sheets and drop cloths spread around. One person reported ice on their birdbath.
 
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Old 05-11-10, 08:03 PM
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Sadly enough, in SD I have been going through monsoon season. Its been raining the last few days, and highs are in the low 50's and the lows are in the mid 30's. I have heard nothing of frost warnings, but I know it would not be fun to shut a boiler down right now!
 
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Old 05-11-10, 08:18 PM
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Hello,

I use Wirsbo multi-cor.. Which is pex-al-pex..Has a higher temp and pressure rating than regular pex as well as an o2 barrier..Works great for baseboard plumbing and uses compression fittings with split rings and adapter fittings to sweat back to copper pipe. I also use multi-cor in my home run piping from panel rads to my manifolds. Hope this helps

Ron
 
 

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