[Greenbuilding] Simple Solar Radiant System

Wed Dec 6 09:10:31 CST 2006

well in our right coast "bay area"   (massachusetts bay) it freezes a lot. 
you might also consider that on those cold nights, the collectors will 
radiate more and go well below freezing more often. there may however be 
some forward or backward thermosyphoning at night that you may or may not 
want to eliminate with a check valve.

 i caution against using pex all the way to the collector, pex doesn't like 
uv exposure, and the 6 feet or so nearest the collector are subject to temps 
above 200-300f depending on collector style during inadvertant stagnation, 
but you could try it and see how it goes.

use propylene glycol and you probably only need a 10% solution for "slush 
protection" in your location.

----- Original Message ----- 
From: <dantonioli at earthlink.net>
To: "'Drew A. Gillett P.E.'" <deaneg at hotmail.com>
Sent: Tuesday, December 05, 2006 6:52 PM
Subject: RE: [Greenbuilding] Simple Solar Radiant System

> In your case it makes sense to go drainback. Here in the bay area, we 
> rarely
> get a freeze; actually, all we ever really get is frost, sometimes a temp 
> as
> low as 30 degrees, but that's enough to bust pipes! I have two panels, 
> will
> start with a large radiator, use 3/4" copper feeding pex tubing...or to be
> uber simple, I just might run pex all the way.
>
> No heat exchanger necessary in my case, unless glycol solutions are bad 
> for
> the inside of radiators.
>
> Dan
>
>
>
> i used drainback in part because the lift  height from tank to top of
> collector was just 6 feet and the volume of piping and fluid was large and 
> i
> didn't want to buy all that glycol and given the low temps i wanted the
> better heat capacity and viscosity of water. .   in your case the35 foot
> lift and the fact that you can minimize the piping volume and that the 
> heat
> exchanger will either be radiators or the radiant floor mean the glycol
> would be simplest.  (the lift head would be reduced to zero and the 
> pumping
> head would be small so a really low hp pump wuld work. you might consider
> the el sid 10 watt pv powered pump or remember that whatever solar water
> heater pump you are using will work. )  one way around the lift height in
> your case is put the drainback tank as high up in the envelope as 
> possible.
> (i saw one such dback tank mounted on the floor of the attic with 
> insulation
> over it.)  the htx  in the actual solar storagetank ( or in your case th
> radiant floor or radiator)  was still down in the basement now pressurized
> by the standing water in the supply and return. put the pump low to avoid
> net negative suction pressure problems at the pump inlet.
>
> either system will work, but each has different cost, design and 
> maintenance
> and efficiency issues, most installers like drainback if carefully
> engineered, installed and maintained. it is alwas advantageous efficiency
> wise to eliminate a htex if you can.
> ----- Original Message -----
> From: <dantonioli at earthlink.net>
> To: "'Drew A. Gillett P.E.'" <deaneg at hotmail.com>
> Sent: Tuesday, December 05, 2006 12:07 PM
> Subject: RE: [Greenbuilding] Simple Solar Radiant System
>
>
>> Excellend feedback, Drew!
>>
>> I'm often inclined toward simple systems and have recently been
>> frustrated by radiant folks who want me to sell me a Munchkin boiler,
>> add mass where it doesn't exist, and spend money I don't have.
>>
>> What kind of pump would you recommend? The distance from the office to
>> the roof is about thirty five feet. I'll start by pumping liquid
>> through a large radiator but might eventually add a few 55 gallon
>> drums in the shop for mass (I've got the space for them, they're
>> cheap, so why not!).
>>
>> Also, I've been wondering if I should use a drainback system or no
>> drainback and use glycol; the latter seems simpler.
>>
>> Dan
>>
>>
>>
>>
>> well dan, i installed a 7  panel 60 degree slope 4x6  used flat black
>> single cover parallel flow solar water collector system a few years
>> back to heat the basement floor of my farmhouse.  it is a drainback
>> system (used 30 gallon horizontal tank) , with used groundfos  pump
>> feeding 4 1/2 inch by 200 ft. polybutylene  loops in parallel in 1000
>> sq.ft. of  4"concrete basement floor.
>>
>> a used controller turns on the pump whenever the collector is warmer
>> than the radiant floor return (typicaly 60 on startup and 70 running
>> full out. )  the system is left on summer and winter. it ran 2000
>> sunny hours last year .  the basement of a new england farmhouse never
>> overheats even in
>> summer.   in winter, the system keeps the basement  comfortable 45-65 and
>> from freezing with no other backup heat.
>>
>> i strongly endorse your concept, use used equipment, minimize controls
>> and additional storage. and make sure the collectors are tilted
>> steeply enough to shed snow in winter and to reduce gain in summer.
>> good luck
>>
>>
>> ----- Original Message -----
>> From: <dantonioli at earthlink.net>
>> To: "'Greenbuilder list'" <greenbuilding at listserv.repp.org>
>> Sent: Monday, December 04, 2006 11:17 AM
>> Subject: [Greenbuilding] Simple Solar Radiant System
>>
>>
>>>I have a solar hot air system on my home that works only when there's
>>>enough  radiation to heat the inside of the panel to 74 degrees. The
>>>temperature  hits 74 degrees and a small, 24 watt fan turns on to
>>>brings fresh, warm  air  into the house.
>>>
>>> I want to design a simple solar radiant system that works on the same
>>> principle I have two thermal panels on my roof that will eventually
>>> be hooked up to a larger "master plan" system when time and money
>>> permit for doing everything right.
>>>
>>> In the meantime, I want to use them to heat a radiator in my cold,
>>> ground floor office that's chilly even when it's warm outside.
>>>
>>> The model is simple: one loop, filled with water/glycol, and pumped
>>> when the temperature hits a set point. When the sun shines and it's
>>> cold inside, I'll at least be able to partially heat the space with
>>> solar.
>>>
>>> Yes, I understand that a comprehensive system with storage and
>>> boilers makes sense, but that's for later.
>>>
>>> Does anyone have any experience with such a simplified system and/or
>>> know of any Homepower-type articles online?
>>>
>>> Dan Antonioli
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>>
>>
>
> 