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

[Kurt Nelson]

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Just to add info to my previous post.... 

I should mention that I don't do that much solar thermal, mostly doing
off-grid PV.

I can think of 7 SDHW systems that I installed in the last ten years and
all of them used PV driven Hartels.  I've never had a pump failure.
Actually I should correct that statement as I had two pumps that came in
on an order of three that didn't work right out of the box (previously
mentioned problem of manufacturer distributed defective pumps some years
back that wouldn't work PV direct).  

Also, five of these seven pumps are in systems over five years old and
only one is in operation less than four years old.  

The pumps I mentioned are brushless and in single pump,
thermal-siphoning designs.  No snap switches, which really is a weak
point in such a system and also might not be noticed by the home-owner
if it goes out (still hearing pump noise from the solar loop pump).
Maybe there is a thermostat that costs a little more than $7, but works
a lot longer.

Kurt
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Kurt Nelson
PO Box 309
Cornucopia, WI 54827
715-742-3406
sunwise at cheqnet.net


-----Original Message-----
From: Todd Cory, Mt. Shasta Energy Services
[mailto:toddcory at finestplanet.com] 
Sent: Wednesday, April 12, 2006 7:18 PM
To: RE-wrenches at topica.com
Subject: Re: Thermal - PV and diff controller? [RE-wrenches]

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Kirk,

Were you using the electronic or brush version of the Hartel pump?
Did you feed it via a LCB?
Did you monitor the max input voltage during cloud effect events?

My pump has been running flawlessly for 4+ years now. I have an old LCB 
and 5 diodes in series (.8 volt drop each) in the PV to pump circuit to 
make sure the input voltage is well below the manufacturers max 
recommendation. I think LCB's are important as I have heard these 
sometimes have a hard time starting running PV direct.

I believe Tom Lane has info on how to best match the panel to pump to 
make sure the pump does not get fried, although as I said, mine has been

fine and it is (over) powered by an ancient Arco M-55.

Todd



Kirk Herander wrote:

>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
>  
>


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