1234 said:
I have one of those 300 watt @ 110 volt floor heaters in my bathroom.
what kind of amps would it draw if I put (solar) dc directly into it or
would that be a bad idea. I am just thinking it would be more efficient
than converting my dc to ac first
It would work, and it would be more efficient, but it is still a bad idea.
You would need to arrange your panels in series (I am assuming you plan to use
five (10) of the common 120W @ 24 VDC panels wired in series) to get an
approximate 120 VDC output @ 5 Amps, similar in voltage to what the floor
heaters require. NOTE: this also gives you a total of 600 Watts (so you would
need 2 heaters to absorb your output)
Next, if you want any heat at any time other than the 4-8 hours midday when
you will produce PV power, you will have to store the output of the panels in a
set of batteries. You could arrange a set of (10) 12 VDC batteries in series to
do this, but you still need a charge controller to correctly maintain the set of
batteries Oh, by the way you will need to add another PV panel to account for
your systems additional voltage needed to charge the 12 VDC batteries (they need
13+ VDC to charge) By the way don't use car batteries, they will quickly fail,
you need deep cycle batteries like RV batteries.
Two other problem areas, that are related to each other. Circuit protection
devices, circuit breakers or fuses, for a 120 VDC circuit must be rated for
600VAC / 120VDC. The same 600VAC / 120VDC ratings are also required on any
switches in your system, which means that you can't use the original heater
switches, since I am sure they don't have this large of an rating. These
problems occur because AC circuits are self quenching for the arc created when a
loaded circuit is interrupted, but the DC arcs are only quenched by larger
distances. (the cyclic reversal of current flow puts the arc out)
I am sorry to be a wet blanket on such a neat sounding idea.
--
to avoid having to make supply
Jim Baber
www.baber.org
1350 W Mesa Ave.
Fresno CA, 93711
(559) 435-9068
(559) 905-2204 cell
Email
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