[Greenbuilding] Al Pex for Solar Heating System

[Bob Korves]

Automotive cooling systems typically have pressure relief at no higher than 
15 PSI.
-Bob Korves

----- Original Message ----- 
From: "Keith Winston" <keith at earthsunenergy.com>
To: "Bob Korves" <bkorves at winfirst.com>
Cc: <greenbuilding at listserv.repp.org>
Sent: Sunday, January 06, 2008 11:37 AM
Subject: Re: [Greenbuilding] Al Pex for Solar Heating System


> One challenge one runs into with radiator and other unusual (from a house 
> plumbing point of view) hoses is pressure: as long as you keep your system 
> at heating-system pressure (i.e. 12 psi or so) they can work, many of them 
> can't take higher pressures when they are hot I believe (isn't a car 
> pressure relief around 12-15 psi?). On a multi-story install that might be 
> hard for the full height of the system, though using them just at the top 
> might be made to work... I got some special high-temp plastic hose from US 
> Plastics for one stretch, it was a bit pricey (I think $3/ft). Thanks for 
> the link to Gates, I don't know them yet.
>
> Always check pressure/temp curves, when you can get 'em, for things like 
> hoses and tubing. Between silicone, teflon and all other types of 
> high-temp blah blah hose, there's some amazing things out there. It raises 
> the challenging question of bringing increasingly exotic materials into 
> the picture (with their entire manufacturing/disposal life-cycle 
> implications). Interestingly, Dupont (I think it is) has a silicone based 
> heat transfer fluid that can happily operate at 500F. It's expensive, and 
> only has 1/2 the heat capacity of water (meaning slower heat transfer, 
> sorta). I don't remember anything about the thermal conductivity, or the 
> melding of these two factors, the thermal diffusivity... I don't recall if 
> it's as low-toxicity as Polyethylene glycol...
>
> Keith
>
>
> Bob Korves wrote:
>> ----- Original Message ----- 
>> From: "Clarke Olsen" <colsen at fairpoint.net>
>> To: "Bob Korves" <bkorves at winfirst.com>
>> Cc: <greenbuilding at listserv.repp.org>
>> Sent: Sunday, January 06, 2008 7:00 AM
>> Subject: Re: [Greenbuilding] Al Pex for Solar Heating System
>>
>>
>>
>>>    Isn't it possible that automative hose will last longer in an 
>>> enclosed application
>>>    with no vibration and a narrower temp. fluctuation?
>>>    Clarke Olsen
>>>    Spencertown, NY
>>>
>>
>> Yes, it is certainly possible that the black, butyl rubber automotive 
>> hoses would last longer in a household application.  My biggest worry 
>> would be about any direct exposure to sunlight, since they are not 
>> exposed to direct, prolonged sunlight in automotive use.  Maximum 
>> temperatures would be lower, and they do not get contaminated with motor 
>> oil.  Vibration is not a problem for automotive hoses anyway -- that is 
>> their world!.  Silicone rubber hoses, which are usually red, green, or 
>> blue in color, are better in almost every respect compared to the black 
>> butyl ones, except they are softer and if they rub against things then 
>> they will rapidly wear through unless protected. Sometimes, at 500,000 or 
>> more mile engine overhauls on big trucks, when everything is renewed, the 
>> silicone hoses are re-used if they look OK. They're that good.
>>
>> In a glycol filled solar system the price of the glycol and the worry 
>> about pollution from leakage would certainly send me toward the silicone 
>> hoses, which should only be needed for short distances anyway.  There are 
>> also lots of special shapes and many sizes of these hoses made for 
>> specific applications so things like 30 or 180 degree bends with 
>> different inside diameters at each end are available.  Heater hose in 
>> standard sizes of 1/8 inch increments from 1/8 inch to 1 1/4 inch inside 
>> diameter are available. Here is a link to the Gates catalogue.  Goodyear 
>> offers a similar line. Radiator and heater hoses are what you are looking 
>> for.  Custom shapes will not be shown in the catalogue.
>>
>> http://www.gates.com/catalogs/index.cfm?site_section=catalogs&location_id=524
>>
>> -Bob Korves
>>
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