Thermal - PV and diff controller? [RE-wrenches]

[Kirk Herander]

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We made a business decision 6 months ago not to use a PV panel and DC
circulator unless we are installing off-grid SDHW. I have had very poor
luck with failing Hartell and El-sid circulators, not to mention the
snap switches. 

If you are installing an incentivized system, at least in VT, you are
required to provide a five year bumper-to-bumper warranty on the system.
Do you really want to work for free, as I have, fixing DC driven SDHW?

Last weekend I worked (for free) to change a DC system (Hartell and snap
switches to AC (Taco 008 & Goldline GL-30 controller) because the
Hartell and switches had burned out twice in a 1 1/2 year period. It is
not my only example. I can think of 3 other DC circulator failures.

No more for me. AC is cheaper and much more reliable. 

Kirk Herander
Vermont Solar Engineering
802.863.1202
fax 802.863-7908
NABCEP(tm) Certified Solar PV Installer
Xantrex Certified Dealer Charter Member
NYSERDA-eligible installer
VT Solar and Wind Partner


-----Original Message-----
From: Todd Cory, Mt. Shasta Energy Services
[mailto:toddcory at finestplanet.com] 
Sent: Wednesday, April 12, 2006 12:20 PM
To: RE-wrenches at topica.com
Subject: Re: Thermal - PV and diff controller? [RE-wrenches]

My system has two DC circulation pumps. The one on the glycol closed 
loop runs array direct with no controller.

For the pump on the potable side of the heat exchanger I  used an old 
C-30 differential controller switching the DC to the pump through a 120 
VAC relay.

I prefer to not use tanks with integral heat exchangers as they are more

expensive and it is easy to use the existing standard water heater as 
the storage tank.

Todd

Geoff Greenfield wrote:

>I like the PV direct approach for typical residential solar thermal...
nice
>20 watt panel and an el-sid and away we go.  Flow rate increases with
>sunlight (and collector temp in theory?). Usually an 80 gallon with
built in
>HE.
>
>My question - how may of you add a differential controller to the
system?  I
>didn't have a good answer for a savvy customer who asked the somewhat
>obvious question... "What keeps us from dumping heat on a sunny but
super
>cold day?"
>
>For a brighter energy future,
>
>Geoff Greenfield
>NABCEP Certified Energy Practitioner
>  
>




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