I need to replace a really old electric solar water heater in a
domestic hot water system, and I'll buy a conventional electric heater
because solar tanks cost much more but are of inferior quality.
Conventional heaters are usually modified for solar use by shortening
the dip tube in half and using it as the inlet for the solar-heated
water, and the drain opening replaces the normal dip tube for cold
water But I found this diagram:
which shows an unmodified conventional tank being used for solar
Instead of feeding the solar-heated water into the middle of the tank,
in this diagram it goes into the bottom. Will that work well?
Honestly, if your solar collector system & pump are really old you might as
well just cap the solar collector off and put a conventional water heater
in. I just did that in my home when the solar water heater went out. I spoke
to several solar water heating experts and they basically said my old solar
system (late 70's early 80's mfg. date) was useless.
Solar companies want about $750 for a 65 gal solar tank, and that's for
one without a heat exchanger (which I don't need).
I can understand a system from the early 1980s being worn out, but if
it's still in good condition, how it can be useless, provided it was
installed right in the first place (my neighbor's had some plumbing
connections wrong and a missing check valve)? I doubt that today's
solar hot water systems are much better, at least those made for
climates where freezing is rare (my freeze protection merely turns on
What I don't understand about the hookup in that diagram is that it
shows water going both in and out through the same pipe at the bottom.
It's not a misprint because I saw the same for an Australian system.
The solar collectors are as good as new (glass, copper, and aluminum),
the pump still works fine (changed impeller, shaft, and seal), and in
the warmer months the electric backup heat hardly runs at all. I have
enough valves installed to let the solar part be bypassed easily, but
that would mean spending at least $100 more in electricity.
Why did those experts say that your old system was useless?
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