Swedish real time boiler

[chuck172]

Man, he has the whole tank up over 200*

http://www.elstyrteknik.se/pannrum/

 

[DaveBP]

Not uncommon from my observations. I wonder sometimes if it's intentional or he just can't help putting "just a few more sticks" in the firebox. Hansson does the same thing sometimes.

And why not?

It's not going to overpressurize the system. Another advantage of open pressurized systems.
More heat in the tank. Longer cruise time until the next fire.
He has mixing control to keep his heat constant regardless of the tank temp.

 

[sdrobertson]

I regularly run my tanks up to 190ish so I guessing my question would be what are the actual working temps of pex. I know its allot higher than 190 but what would the long term effect be at say 210 degrees but only 25 lbs pressure? The difference is allot more BTU's stored...I know its more efficient to lower your usable temps but that is not possible this year.

 

[DaveBP]

How close to the temp/pressure limit for PEX you can run for long term use is a very good question. From the specs it looks like the temp limit is dependent on the pressure.

Anyone done any research on what those extreme limits are?

I'm going to use all metal piping until after the mixing valve to the radiant manifolds. PEX from there on.

 

[sdrobertson]

I'm going to use all metal piping until after the mixing valve to the radiant manifolds. PEX from there on.

That's a really good idea...oh well, story of my life.

 

[Gooserider]

Seems fairly common, and IMHO not a bad practice, to use black iron or copper for the near-boiler piping, just to avoid the possibility of problems with exceeding the temperature / pressure capability of PEX. I seem to recall threads in the past where people have had overheat conditions and ended up blowing out the pex they had connected directly to the boiler... I forget the exact curve, but as I recall, most pex is rated at 180*F, and it's pressure tolerance falls off fairly fast above that temperature - in an overheat, you might end up in a "race condition" as to which let go first, any near boiler PEX or the boiler PRV (30psi typical)

Doing black iron between the boiler and storage tanks seems like cheap insurance...

Gooserider