will this work

big D · July 2009

Hi Guys..
This is my 2nd post about my RV solar project and thought I would run it by the experts here at NAW.

Here's my parts list.

2- SUN_HS_120 pv"s
1- Samlex pure sine 600w inverter
1-Rogue mppt 30a charger/controller
2- T105 trojan batteries 225Ah ea
2 unirac 990014 tilt rack mounts

This will be installed as a stand alone system to power my tv center (HD dvr, 30in flat screen lcd, surround sound,dvd player and tv lift,) which when all powered up and in use, only draws 245 watts and about 3.05amps) per Kill-a-watt meter.Also my 1 1/4 hp cistern water pump on demand (unknown wattage).

The inverter and controller are rite next to battery box and about 15ft from PV's

Which would be best-PV's at 24v and small wire to controller or 12v and large wire (#4 or #6) to controller?.

Also these pV's from Sunelect. may be positive ground. How can I tell if that is true and will they work in this application? I just ordered them so not in my hot little hands yet. Any input would be greatfully appreciated

n3qik · July 2009

Re: will this work

Since you got a MPPT controller, go 24v from panels to controller.

1 1/4 HP motor with a 600 watt inverter is not going to work. It will need some where around 15 amps or 1800 watts.

mikeo · July 2009

Re: will this work

Also my 1 1/4 hp cistern water pump on demand (unknown wattage).

Why do you need a 1 1/4 hp cistern pump. I only have a 1/2 hp submersible in a 50 ft well. Can you pump the water you need with a small Flojet 4325-343 24 volt pump or similar.

big D · July 2009

Re: will this work

Good morning Mike.

That water pump is what is commonly used in Baja(from what I'm told). I just looked at the paperwork for it and it's either 1hp or 1 1/4 hp. at 110v.

This will be used to fill my rv water tank when needed. Usually just turn on my Gen set to fill.

My biggest issue is 2 t105 in series for the 12v I need or 4 t105 in series/parallel so 12v at 450ah. space is limited and possible positive ground on the PV's.

any thoughts?

icarus · July 2009

Re: will this work

You are missing a significant element. While you have listed our loads,, you haven't given any component. For example, if you are running all your stuff for 1 hour, is very different than running them for 12 hours.

Sit down and "do the math". Figure out how long every unit is going to be used on a daily/weekly basis and come up with a gross total. Then factor in net system efficiencies and only then can you get a handle on whether or not you need 2 T105's or 4. Or whether or not your panel configuration is big enough.

As I have suggested before, as a quick calculation, if you take the name plate rating of your Pv, divide it in 1/2 to account for ALL system efficiencies, multiply this number by the hours of GOOD sun exposure and that tells you about how much you can expect to get out of a Pv system per day. Remember, if this is a Rv installation the ability of having the Pv properly aimed very often is quite small, so further de-rating would be suggested.

So in your example 240 watts of Pv MIGHT yield: 240/2*4=480 watt hours available.

That 480 would run your 245 watts of load for ~2 hours.

Just for the record,, our system is ~ 300 watts. Our total consumption for all uses during a 24 hour day is ~4-600 what hours. This is with a system that is ideally aimed for it's location, and we get ~close to 7 hours of good sun in the summer. 5 in the winter,, but we get huge reflection off of snow and ice as well as cold Pv temps adding to our harvest.

Good luck.

Tony

Cariboocoot · July 2009

Re: will this work

big D wrote: »

Good morning Mike.

That water pump is what is commonly used in Baja(from what I'm told). I just looked at the paperwork for it and it's either 1hp or 1 1/4 hp. at 110v.

This will be used to fill my rv water tank when needed. Usually just turn on my Gen set to fill.

My biggest issue is 2 t105 in series for the 12v I need or 4 t105 in series/parallel so 12v at 450ah. space is limited and possible positive ground on the PV's.

any thoughts?

Either 1 or 1 1/4 HP is way over the limit for a 600 Watt inverter. 1 HP running will draw approximately 1000 Watts, +/- depending on how much work it's actually doing (pump motors are not a straight forward draw). Start-up can be five times that. I'm quite certain you don't need that much pump just to fill a tank, no matter what the source. Are you sure that's not a digester pump on the holding tank for pumping the sludge out?

I've never heard of a PV being "positive ground" or negative for that matter: they have two wires or connectors on them; one (+) and one (-), neither connected to the array frame. There might be something different out there, but I've never come across it.

As Tony said, you really need to know at least approximate running times to determine how many Watt/hours you use, which in turn determines how many Amp/hrs of battery you'll need. That is then the major factor in picking an array that will provide sufficient recharging for the system.

Alternately, if you can only put 'so many' panels on the roof (this being an RV), that sets the limits the other way 'round for how much power you can use before having to start the generator to re-charge.

icarus · July 2009

Re: will this work

Marc,

There are issue with certain Sun Panels regarding a positive ground bias:http://forum.solar-electric.com/showthread.php?t=4718&highlight=sun+panel+positive+ground

There seems to be conflicting conclusions as to whether or not the issue has been resolved. I run my system without reference to ground,, which doesn't solve the issue.

Tony

PS As the OP suggest,, use the genny to fill the water,, the pump is way to big for the inverter as well a too big a draw on the battery bank. A little bit of gasoline will be cheap by comparison.

big D · July 2009

Re: will this work

Thanks Tony for your input. I'm still trying to figure this stuff out.

here is my total wattage. as best as I can figure based on the Kill-a-watt meter.

231w at 3hrs daily for 693w per day x 7 for 4851 weekly use.

PV's at 240/2*4=480 * 7= 3360WH weekly. hope this is conservative as I think I get good long winter days of sun. with tilted pv"s to 75 degree tilt possible.

The use totals are maxed with all on which should be high.

battery's = 4 t105's wired series/parallel for 2 banks of 6v 225AH for 12v at 450AH should be a minimum starting amount.(space permitting)

Been rv'ing for a long time now and know how to live a conservative life style.
Also have a onboard 5kw genset which I'm trying not to use daily.

Does this make sense to or am I way off still?

Cariboocoot · July 2009

Re: will this work

Tony;

All I can say is: "Good grief!"

And thanks!

walt66 · March 2012

Re: will this work

big D wrote: »

Good morning Mike.

That water pump is what is commonly used in Baja(from what I'm told). I just looked at the paperwork for it and it's either 1hp or 1 1/4 hp. at 110v.

This will be used to fill my rv water tank when needed. Usually just turn on my Gen set to fill.

My biggest issue is 2 t105 in series for the 12v I need or 4 t105 in series/parallel so 12v at 450ah. space is limited and possible positive ground on the PV's.

any thoughts?

is your water from a pila or a well? I have an 1100 gallon pila in the ground and use a 12 volt pump hooked into my motorhome to fill the tank in the motorhome, I live in Campo Los Compadres in San Felipe, Baja, Norte.

Walt, 2002 HR Endeavor, fulltiming for 10 years.:D

BB. · March 2012

Re: will this work

Welcome to the forum Walt.

regarding BigD, he has not logged on for 2.5 years. You can try sending him a pm If you would like to contact him.

Bill

will this work

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