Wrenching in L.A. [RE-wrenches]
Graham Owen
graham at solarexpert.com
Fri Jun 21 11:44:40 PDT 2002
William,
I have found Grundfoss pumps to be extremely reliable for circulating
water between solar panels and storage tanks. Since the average system
in L.A. is a pressurized open-loop type with re-circulation freeze
control a low head fractional HP pump is sufficient. A Grundfoss
UP15-42F consumes 0.74 Full Load Amps. The pump typically starts when
the water in the panels is 20 degrees higher than where the temperature
sensor is located towards the bottom of the storage tank and continues
to pump until there is only a 5 degree differential. The parasitic
power draw is insignificant when compared to the BTU's harvested off the
roof. Even closed loop systems with two pumps and a heat exchanger are
efficient. I set the "high-limit" at 180 degrees and the tempering
valve at 160. I know solar water heaters save a considerable amount of
natural gas, but. In the past 20 years I do not recall anyone calling me
to service their solar water heater because the gas bill is suddenly
higher. They typically say "we used to have an endless supply of hot
water, we could bathe 3 kids, do laundry and wash dishes without running
out of hot water, now it is gone after two showers, I think something is
wrong with the solar, can you come look at it"
Briefly regarding your spa question: To pump water up into 2 panels
(single story rise) for a spa you will most likely need at least a 1/6
HP pump, located well below the water line of the spa,(not inside the
spa) and a reliable vacuum breaker needs to be installed on the roof to
allow for drain back. I have seen some spa and almost all pool heating
systems utilizing the existing filtration pump.
I don’t know that much about DC pumping systems. I only have hands on
experience running small PV powered DC brushless pumps that circulate
water in open water loop heating systems. Freeze protection,
thermosyphoning and pump longevity can be problematic.
Graham
-----Original Message-----
From: William Miller [mailto:wrmiller at slonet.org]
Sent: Thursday, June 20, 2002 9:41 PM
To: RE-wrenches at topica.com
Subject: RE: Wrenching in L.A. [RE-wrenches]
Graham:
How about the cost of electricity to pump water to a rooftop panel? I
know little about water systems, but that won't stop me from showing my
ignorance!
I have a question about spa water heating. I was given two nice used
water panels I wanted to install on my spa. Where I live it freezes
hard in the winter. I was told I needed a system that would drain down
when not in use. Therefore, there is no siphon effect to reduce pump
energy requirements. My friend measured power draw on the higher horse
power pump I would need and it was almost as much as the heater. He
suggested I install a bigger grid tie system and forget the water
panels.
I have a potential client who wanted to install a DC water pump system.
He is on grid. I told him that when a water system is not running, your
money is not working. A grid tie system is working whenever the sun
shines. He would be foolish to invest in PV to pump water when he could
grid tie, get the rebate and tax benefits and make his investment work
every sunny day (which are plentiful in this locale).
William
At 04:26 AM 6/21/02 +0000, you wrote:
>Graham,
>
>I think your comparison is quite accurate, and it might be even more
>cost effective when replacing electric hot water systems. I've promoted
>solar hot water for years over PV in grid connected applications. Too
>bad copper pipe is so rigid compared to copper wire!
>
>Brad
>
>
>Graham Owen wrote:
>
>> I am considering adding a page to my website that hopefully convinces
>> local potential customers to have a solar water heating system
>> installed. I want to do this in such a manner that I do not make
>> disparaging remarks about PV. I find installing PV to be much more
>> fulfilling for many reasons than installing solar water heaters. I
just
>>
>> need to remain productive. Since 1982 I have installed over 700
>> residential solar water-heating systems in L.A., and when I say, I
mean
>> I. I personally drill and seal every hole in my customer’s roofs and
my
>>
>> helpers help me complete the job.
>>
>> Here is the link to the page and there is no link to it from my web
>> site
>>
>> (yet).
>>
>> http://www.solarexpert.com/solar-comparison.html
>>
>> I would truly appreciate any advice or suggestions.
>>
>> Graham Owen
>> GO Solar
>>
>>
>>
>
>
>
>Brad Bassett
>Schott Applied Power
>Tumwater, WA office
>bsbassett at earthlink.net
>
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