What would happen if . . . .

[Titantornado]

OK, here's what I'm thinking.   I have 12 Sharp NT-175 panels that I would like to temporarily use for supplemental heating for a travel trailer. 

Panel specs are:
175 W
35.4 Vpmax
44.4 Voc

What would happen if I were to connect two strings of six directly to a 220v 2000w baseboard heater?  Seems the panel array output and heater input would be a very close match. (2100w @ 212v, and I suspect voltage would rise a bit if the heater draws under 2100 watts)

My brain thinks this would work, but it's been known to err on occasion.  Opinions?

[wpowokal]

In series volts add but watts stay the same, so each series string will give you 6 X the individual panel volts but still only 175W.

allan

[wdyasq]

Amps would remain the same .....


A X V = W

Ron

[rossw]

In series volts add but watts stay the same, so each series string will give you 6 X the individual panel volts but still only 175W.

175W with Vmp=35.4 = 4.94A.
In series, the CURRENT will remain the same.
6 * 35.4V * 4.94A = 1050 watts @ 212V

Two identical parallel strings would still be 212V, but 2100 watts.

Voltage is *slightly* less than the elements nominal voltage, so it'll take less current - panel output will increase slightly resulting in slightly more current, it'll settle somewhere close.

[Bruce S]

TitanT;
I would look at possibly the electronics of the baseboard heater.
See if you really need to have it at 220V. AND which type AC or DC. The instantaneous power may NOT be enough to get the heater heating, so to speak, since they are such a close match.
More than likely the heater will pull the panels down to voltage and dissipate the incoming power enough to just not work like you're possibly hoping.
IF they are Ni-Chrome based elements then I'm thinking there's enough electronics in there that you may be able to bypass? and go directly.
Since it is a heater even a MSW will work. Did this in the realm of 120VAC unit , oil filled heater when Natl Gas was shut off last winter due to leak at neighbor's house. Killed my standby Auto-batteries but worked 120Vac 2k watt inverter cheapo from HF.
Hope that helps address the heater portion.
Bruce S   

[mab]

Not sure what a 'baseboard' heater is but if it's low temp resistive element then it should work.

I would think carefully about switching though - the AC switches on the heater won't like it if you try to disconnect DC at full load - Voc of 264v can produce quite a long arc. The inverter route suggested by Bruce might be safer.

mab

[wpowokal]

Ross and Ron please stop trying to spoil my fun

[TomW]

I would think carefully about switching though - the AC switches on the heater won't like it if you try to disconnect DC at full load - Voc of 264v can produce quite a long arc.
mab

You could use the switches to switch suitable relays at a lower voltage on the coils. Would need a source of volts correct  for the relay coils to do it but not too tough.

More than one way to defur a feline!

Tom

[Titantornado]

Hmmm, so mixed reviews.

For those who asked, an electric baseboard heater is simply a calrod type resistive heating element with aluminum fins fitted to it to increase convection air currents across it, no electronics.  I did think about using one with a built in, bi-metal thermostat, but as mentioned, those contacts would get cooked on DC.  Really, 2000 watts, which converts to roughly 6800 BTUs isn't enough to heat the trailer, so it could be left hard-wired right to the panels. 

[rossw]

resistive heating element with aluminum fins fitted to it to increase convection air currents across it, no electronics.  I did think about using one with a built in, bi-metal thermostat, but as mentioned, those contacts would get cooked on DC.  Really, 2000 watts, which converts to roughly 6800 BTUs isn't enough to heat the trailer, so it could be left hard-wired right to the panels. 

IE, exactly what I surmised you would have/do in my original reply to you.

If you're not switching it on and off, don't have arcing problems to deal with, don't have electronics to get upset, pumping whatever power you can harness directly into the heating elements should give you a reasonably good outcome with little to no maintenance and minimal losses.

[Titantornado]

Nice!   So I guess my brain was working on par.    I think I might give this a try.  It would save quite a bit of propane.