[Greenbuilding] [BULK] Re: [BULK] Sprinklers-and PEX

[Keith Winston]

Pex can handle far above 120. But a solar thermal system, on a hot day, 
let's say after a power outage to let things get really hot, might be 
well over 200. PEX gets all wobbly around there. PEX-AL-PEX can work.

Once the pump is running, most flat-plate collectors won't deliver water 
outside of the PEX range, so as long as you have a lead from the 
collector (at least 6', for example, of copper) that will modulate the 
first blast from an overheated collector, and keep conduction from 
transmitting too much heat from a stalled collector. So in most cases 
the PEX will likely work fine. For evacuated tube collectors, it's 
dicier, though on smaller installations you're likely to be fine still. 
However, it depends on how many collectors, how much storage, what kind 
of pumping (PV pumps reduce stall chances!), etc etc.

Re: Sprinklers: As I noted in an earlier email, though I think I forgot 
to send it to the list, PEX fittings typically throttle the ID down, 
whereas PVC fittings don't. This would also be true of thermowelded 
fittings, i.e. those on Polyethylene like Aquatherm. I think the 
Aquatherm can handle about the same temp range as PEX.

Keith


Lawrence Lile wrote:
> Sacie sez:
>
>   
>> I learned to my distress PEX can not be used in solar water systems 
>>     
> because it can't take the heat, distressed because I embedded it in 
> my walls and to the roof in preparation for just this.  But 
> otherwise, what is bad about it?   Sacie 
>
> Uh oh, I did the same rough-in.  If PEX will take 120F for domestic hot
> water, why not solar?  Are you expecting more than 120F in a solar hot
> water heater?  
>
> A newer vacuum collector might get so hot, the older, less insulated
> collectors may not.  Any experiences?  
>
> --Lawrence
>
>
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