Inverter on a 24 hour timer.

Cousin Puddin Pop

Hey Guys,

I was wondering if anyone knew of a practical way of using a solid state timer to turn off a Samlex SA3000K-124 inverter during night time hours.
I don't mind opening it up for surgery.:-)

I have 12v and 24v supply rails at my disposal, no grid, no full time AC.

My load is a little freezer with enough thermal mass to go 16 hours and still remain frozen solid.

My battery bank is 230(20 amp hour rate) at 24 volts, charged with a tristar mppt, connected to 400 watts of pv panels.

The only other load is a security DVR and wireless router which draws 40 watts constantly from a Samlex SDC-23 20 Amp 24v DC to 12v DC Converter.

I do have a genset with a charger but I often go snipe hunting weeks at a time and I don't want to worry about my pudding pops.

Pointing to a actual product or product number would be appreciated, or perhaps to a inverter with a timer already built in to it.

Thanks

Cariboocoot

Re: Inverter on a 24 hour timer.

Welcome to the forum.

The power save mode isn't good enough? You want to switch it completely off?

This unit has a remote switch port; it shouldn't be difficult to connect a timer to control a relay that would operate it.

icarus

Re: Inverter on a 24 hour timer.

Bingo!

What bout something like this, maybe with a relay if you need leg current? 16 amp at 24 vdc.


http://prostores1.carrierzone.com/servlet/super-feed_com/-strse-30/DT-dsh-06-fdsh--24-VOLT-DC/Detail

Tny

inetdog

Re: Inverter on a 24 hour timer.

icarus wrote: »

Bingo!

What bout something like this, maybe with a relay if you need leg current? 16 amp at 24 vdc.


http://prostores1.carrierzone.com/servlet/super-feed_com/-strse-30/DT-dsh-06-fdsh--24-VOLT-DC/Detail

Tny

Maybe overkill, but from another thread:

BB. wrote: »

Here is one DC timer (~$75):

Flexcharge DC Timer Controller

-Bill

BB.

Re: Inverter on a 24 hour timer.

Other than using a latching relay and a digital timer--I don't know with the Samulex (I just read the data sheets like you would).

There are some (typically higher end) inverters that can take a control signal input (ground/12 volt open, etc.) or "remote inhibit" that really cut down the power usage.

Similar with inverters that have "search mode"... The inverter turns off and then sends out a 120 VAC pulse once every second or so, when it "sees" a 6+ watt load, the inverter turns on until the load "goes away"... Then back to search mode.

As an example, here is a 12 volt 300 watt (600 watt for 10 minute) TSW inverter from MorningStar. It is great inverter with both remote inhibit and search mode, but probably too small for your needs.

Specifications
User Manual

There are lots of larger inverters with a mix (or more) options that will work--But knowing more about your power needs (watts, peak watts, etc.) will probably gives a bit more direction.

Note that refrigerator/freezers are the "big/ugly" loads in off grid power land (short of microwaves, A/C, and large water pumping).

Regarding your freezer--If you can justify/find an inverter with "search mode", and your freezer is (typically) mechanical timers/thermostats and manual defrost), then "cycling" AC power is usually OK.

If they have automatic defrost, the timers typically reset on power "failure".

Also, here is an interesting link on why we use 0^oF as the "optimum" freezer temperature for long term food storage.

Question - Best Freezer Temperature

-Bill

BB.

Re: Inverter on a 24 hour timer.

Note, if you are switching the DC leg of the inverter... A freezer may need upwards of 500-1,000 watts for starting surge (and less than 150 watts running).

1,000 watts * 1/21 volts battery cutoff * 1/0.85 inverter eff = 56 Amps estimated worst case 24 VDC inverter input current

So, if you do not find an inverter with "remote inhibit", a large latching relay (latching to save ~6+ watts just to "turn on" the relay) to reliably switch such large currents (and DC current is worse than AC current when switching too).

-Bill

PS: Welcome to the forum "Cousin".

And just ignore the link spammer that thought he could post junk on a thread with three moderators answering your questions.

icarus

Re: Inverter on a 24 hour timer.

(you got to it before I could Bill!)

t

Cousin Puddin Pop

Re: Inverter on a 24 hour timer.

Bill, by large latching relay, do you mean a sealing contact? Sounds like making things more complicated with added clicky noise if I tried to sleep there.
Great idea tho I might end up going this route; call me puddin


Yeah; power save is not good enough, if it was on, the freezer would still run, drawing power for no good reason, who eats pudding pops at three AM?

The timer idea is best, there are $9 dollar versions on flea-bay(search: DC 12V Power Programmable Timer Time Relay 16A) but I can't tell if the "relay" is isolated from the 12v rail, slamming logic circuits that probably run TTL with 12 volts is a big nope in my book: perhaps a second power hungry relay if it is.


Cariboocoot, your idea about the remote switch was totally awsome, I went holy duck sticks what a great idea, just cut off the end off of a phone cord or whatever sized jack they used and start experimenting, then the cruel, cold, hammer of reality came crashing down upon my head. All the affordable timers I know of are all NC or NO: no momentary. I think the remote for the inverter uses momentary push button switches so putting one of these timers on it would be saying 1111111111111111111111111111111111111111111111111111111111111111111111111 to the inverters processor like holding your finger down on a keyboard. The thing might just freak out and start running around like a smurf with it's head on fire. There is defiantly more to this idea! It's there, I can smell it.

Any input is very welcome on my quest for higher knowledge, time for a pudding pop break

BB.

Re: Inverter on a 24 hour timer.

As I understand, a "sealing coil" is a low current/power coil that holds the contacts together once the relay has been closed by the main coil.

The latching relay I linked to only uses power to transition from on to off--not to hold on (as I understand). Saves power over a large solinoid type relay which can use 6 watts or more "on".

The "search mode" capable inverters use much less power when in "search"--but it is still a fair amount of power.

For seasonal/weekend cabins, many times it is more cost effective to use a propane fridge/freezer instead... A full blown Solar PV system with electric fridge becomes a better deal if the cabin/home is occupied something like 9 months or more per year.

A "full on" inverter running 24x7 may take 20+ watts--Or require a solar panel of:

• 20 watts * 24 hours * 1/0.52 system eff * 1/3 hours of sun = 308 watts of solar panel

~300 watts of solar panels to run the inverter 24x7 (assuming you want some winter time operation with ~3 hours per day minimum sun).

MorningStar may be coming out with some larger inverters in the near future--If they have the same features/quality of their 12 volt 300 watt--Should be worth waiting for.

Another option would be to find a 24 VDC freezer--They are out there, but typically not cheap either.

-Bill

Cousin Puddin Pop

Re: Inverter on a 24 hour timer.

Perhaps I shouldn't have said anything, a sealing contact is kind of like a high speed switch. When a 3 phase motor of high amperage is switched on it will arch at the contacts of the switch.
A sealing contact takes a signal from a lower power switch that a person manipulates, then slams shut the high amperage contacts to reduce arching. High amperage arching is plain bad for contacts, I probably did a poor job of explaining that, I haven't been in school since 2002. I have lost a lot of proper terminology, I just fix things.

I am boxed into a corner on my end so there will be no waiting for Morning Star, I'm not sure I have expressed myself clearly in my first post.
I need the 115v bus to shut down completely by means of disabling and enabling the inverter, it needs to be done without human interaction at a certain time.
I am sure I will figure out a simple solution, I just assumed this was a common problem and several people had devised some sort a genius solution to it.
Perhaps I am wrong and it is normal to baby-sit a off grid set up, I was thinking the biggest maintenance issue was going to be battery watering.

Thanks for your help.

icarus

Re: Inverter on a 24 hour timer.

I guess i am missing something. If you a simply trying to turn the inverter on and off with no human intervention, what is the matter with the timer idea? It would seem I f the issue is the worry about he full load on the inverter when the timer turns the inverter on, it would be a simple matter to install a time delay on the 120 vac side as well so that once the inverter energizes fully, the freezer could then turn on via the time delay. Am I missing something, or are we making this more complicated than we really need to?

Tony

Cariboocoot

Re: Inverter on a 24 hour timer.

Well somebody's trying to make it more complicated than it needs to be. :roll:

Disconnecting the DC in: bad idea, with or without latching relays et cetera. These lines are not really meant to be used this way and the arcing could be serious. 3kW on 24 Volts is roughly 125 Amps, and above arc point. If this is switched on/off under load (even charging the caps) it could be sparks o' plenty. I wouldn't do it.

Any inverter designed to have a "search mode" will not suffer from being powered up with a load already attached, so there is no need to put a time delay on the freezer.

Buy the remote. Hack it. Design a simple momentary pulse circuit if necessary to switch it. Connect to timer. Done.

TheBackRoads

Re: Inverter on a 24 hour timer.

2manytoyz did this with a solid state relay for work I believe, and I copied the idea. Got a solid state relay to turn on 120V AC with my charge controller (you could use a timer). My inverter is always on but the loads are controlled by the relay.