PV timer

Hello freinds, I'm triying to build a PV pump array that will pump ground water 1 hour per day. I have 290 volts of panels in series DC. I can find many charge controllers but I can't seem to find any solar timers that will allow me to do this. Any ideas?

I guess I'm asking. Am I gonna fry my system and cook myset if I use a timer that is built for AC current?? Or are there high voltage DC timers made for this??

 

More questions than answers:

1. What kind (brand/model) of pump are you using that will handle 290v DC ?

2. How many panels of what size (rated voltage and amperage) have you strung together to get 290v ?

3. WHY have you strung those panels together for that high a voltage ?

4. What is the amperage output of that string ?

 

290v sounds like grid tie string inverter voltage.
why is the voltage so high?
Last time I checked the was only one charge controller that went over 150v and it was expensive. That particular charge controller appears to be marked as an add on or to convert grid tie panels for off grid use.

 

Any batteries, or are you powering the pump directly? Without a battery it's hard to keep a timer running when the sun doesn't shine.

That said, if you are battery less you could tap off of a couple of panels to charge a cheap pair of UPS gel cell type batteries (24volt), and then run a regular lawn genie irrigation timer (24volts), and control a 24 volt coil in a contactor relay that would turn on your pump for an hour, or for 2 half hours or.... whatever you might want.

Rancher

 

You can do that (although I question the voltage)...suns shines, pump pumps into a storage tank, tank gravity feeds the end use (ideally), or a small DC pump can be used to supply the end use.

 

You can buy all kinds of digital DC timers that have their own internal battery. Amp rating isn't the highest on the output contact (10-16amp)...and they are for 12v, not 290.

 

It is a grundfos deep well pump rated 30v to 300vdc. There are 4 250 watt panels at about 70 open volts each wired in series. It is in a single string because they are a distance from the pump would require a bigger cable than I currently have. I believe the string is 4 amps.

 

Yes

 

They are grid tie type panels being used off grid. I have an mppt charge controllers for charging my battery bank. These panels go directly to the pump.

 

The issue is I don't want to wear out my deep well pump buy pumping the entire time the sun is shining. I only need an hour of pumping per day at noon. Has anyone ever done this at high voltage DC? Can an AC timer be used?

 

The timer could be set up to run on 24vdc or 110vac that activates a solenoid for the higher voltage DC.

 

You would be very well advised to check the pump curves and see what they'll do under your operating conditions of head and flow. You also need to check the power curve and compare it to the pump characteristics.
(If you haven't already of course - -)

 

Assuming you're pumping into storage, a simple float switch will do what you want....tank full, switch cuts power to pump.

 

Check your panels again....most likely they are mid 30 range voltage, not 70. A 60 cell panel is around 30v, a 72 cell panel mid 30 range.....1/2v per cell approximately.

 

This is a 320 watt version of the same panel. They are 65 open volts and 55 load volts. I figure high to be safe

 

I'm running the same Grundfos pump off of 180 VDC. Been doing it for about 5 years. The Grundfos pump has built-in MPPT. It always works. My well is 580 feet. At 290 Volts, you're nearing the max input voltage of the pump. On a cold day, solar panel voltage output will increase. I wouldn't run it that close.

I fill a 330 gallon IBC tote used as a storage tank and I use a float switch to keep it full. I then use a 12 Vdc RV pump to pump water from the tank and pressurize it, (has a separate solar panel, 12 volt battery and charge controller).

The float switch switches 12 VDC control voltage which in turn operated a high voltage Solid State Relay (takes about 20mA). The SSR does the actual switching of the high DC voltage from the solar panels to operate the pump.

If you had a timer that operates on 12 VDC or thereabouts and has a low voltage output, you could use a Solid State Relay to turn the pump on and off. I use a Crydom D4D12 SSR, rated at 400 VDC, 12 Amps. It's quite reliable since there are no contacts to weld shut or burn out. It has a wide input range of 3.5 to 32 Vdc for the "coil". It's difficult to find an electromechanical relay rated for such high DC voltage, and those rated for AC may arc and burn the contacts when used for DC.

I also keep a spare at the BOL, but have never had one burn out. Be sure to observe your polarities. Reverse polarity will destroy the SSR in such a way that once turned on, it will never turn off. Yeah, I learned it the hard way.

Best prices I've found on the D4D12 SSR is on eBay.

 

How many of these panels ?
4 then Series/Parallel them , same power , but not close to hypeVOC
100Vdc or so 15 amps that way & the pump and controls like less force
Sloth

 

Thanks Altoid. This is the type of information I was looking for. I'll check it out.