Plan review emergency backup

SystemSystem adminPosts: 2,511 admin
Hi All,

Been lurking for several months and have learned alot from you all. Thank you.

After a recent snow storm had us without power for 3 days I've decided to get something in place for future outages.
I won't have any solar initially but may add some in the future when funds permit.
here is my plan, could you all give me advice as to whether it will work. I haven't bought any equipment yet.
7Kw generator
Manual Transfer Switch 10 circuit.
Xantrex TR1524
Four 6 volt batteries.

If power goes out I would like to run the genset during the day which will continue to charge the batts through the xantrex. At night I want to shut the genset down and then run off the batts. I have checked my usage for what I want during an outage when running off batts:
TV&cable box 105 watts for 4-6 hours
Internet(router,wap,switch) 70 watts for 6 hours
4 cfl lamps 15 watts x 4 60 watts for 6 hours
Probably wouldn't run all of these for the full 6 hours.

I have run these through an online battery sizing calc and would need apx 110 AH battery bank at 24 volts. The four 6volts i am looking at would be 220AH

Below is a layout of the way I plan to hook things up. I have not put disconnects/fuses/breakers in the diagram, but will add them.
Generator plugs into transfer switch which power 3 or so circuits including a dedicated circuit that is running to the xantrex so it will charge the batts. One confusing thing I haven't figured out is hooking up the xantrex to the transfer switch. the circuits that I want to power will be the same ones the generator will when it is running (minus one for the fridge and the dedicated xantrex circuit). I will not be running any 220v stuff while running off genset or inverter(obviously).

Any advice/thoughts on having both the generator and the inverter hooked up to the manual transfer switch? The genset is a 4 wire connection to the transfer switch the inverter will only be 3 wires, this is confusing to me. As I said I won't be using any of the double pole circuits in the transfer switch.

Thanks for any input/suggestions.

Chris

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Comments

  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: Plan review emergency backup

    Welcome to the forum.

    The basic plan is a good one, and something I've recommended to various people many times. But the devil is in the details, as always.

    First I'd suggest you don't need a 7.5 kW generator. Sure, you can get them cheap. But they burn a lot of fuel and make a lot of noise and don't last very long. Consider spending a bit more money for an inverter-generator like the Honda or Yamaha units. Very quiet, very fuel-efficient, and very long-lasting. You may then decide you don't need the additional equipment (inverter & batteries).

    Another good thing to spend money on is a Kill-A-Watt meter. With that you can measure the actual power usage of anything you want to keep going during an outage, and under real-use conditions. No sense in buying too much or too little back-up power.

    Speaking of which, have you thought about keeping your refrigerator/freezer going for three days while the power is out? Having to toss out the frozen food can be a nasty expense - and is easily avoidable.

    Just for instance, I bought the Honda EU2000i during a power outage at the old house. I used it to run the 'frige and a chest freezer and the water pump and the TV/lights/et cetera. Part of this was accomplished by switching loads: run the freezer 'til it was cold, then plug in the 'frige. Plug in the water pump as needed, et cetera. Both refrigeration units could be left on their own overnight safely, but would not have made three days without power.

    The use of an inverter/charger can simplify things, as you can wire all "essential" circuits through it and as long as the AC is on it will keep the batteries up, switching to battery power automatically when the AC goes down. The generator should definitely have a transfer switch between it and the utility feed, but this needs only be on the "essential" circuits too; no sense trying to power the whole house from one small inverter.

    All your plan needs is a little fine-tuning.:D
  • RandomJoeRandomJoe ✭✭✭ Solar Expert Posts: 472 ✭✭✭
    Re: Plan review emergency backup

    I had a similar idea, you can see my end result in action from the link in my sig.

    Basically, I have a subpanel off my inverter that feeds the "critical" circuits, the stuff I want powered at all times. When grid power is available, or if the inverter has been plugged into a generator, those loads can be run directly while the inverter also charges the batteries. If the grid drops, the loads are instantly (and without my even noticing, usually) switched to battery backup. No need to switch loads, no loss of power. Sweet!

    It does require a little (re)wiring. I was originally going to add dedicated circuits just for the solar system, but never got around to it - the idea of dropping down walls for what are effectively "extra" outlet boxes didn't delight me. Now I think I am going to simply pull the circuits I want on backup from the main breaker panel, and wire them to my RE subpanel. (At the moment, I have "temporary" lines run to my critical loads. Good thing I'm not married, they've been there a couple years now! :roll: )

    My generator backup is manual - unplug inverter from normal grid outlet, plug into generator once it is running. But that's no biggie to me, the vast majority of my outages are short enough I never have to pull the generator out.

    I also went with an EU2000i generator. I chose it specifically for low fuel consumption. The last ice storm, many of my coworkers had trouble getting enough gas for their generators. The EU2000i is enough to run my furnace, and can recharge the battery bank while powering the fridge and some lights. Best of all, a 5-gallon gas can will run it most of a week on my expected required usage.
  • System2System2 admin Posts: 6,290 admin
    Re: Plan review emergency backup

    Thanks for the response.

    I hear you on the honda or yamaha. Just have a hard time trying to swing one of those funds wise.

    I was planning on getting one of the Tri-Fuel conversion kits for whatever generator I get and using my natural gas supply from the house.

    I do have a Kill-A-Watt, the numbers I listed came from it, so those should be pretty accurate.

    Yeah, we had to throw a few things out of the freezer so I had planned on doing as you suggest and let the generator run the fridge/freezer during the day and then should be good through the night.

    I guess i still don't understand how i would hook the inverter/charger to essential circuits without going through a manual transfer switch.

    I guess if I could eliminate the inverter/charger and the batteries I could apply that money towards a honda/yamaha. I would have to find a manual transfer switch that didn't require an l14-30 plug though right?

    thanks again.

    Chris
  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: Plan review emergency backup

    Inverter-chargers have a set of terminals labeled "AC IN" and another set labeled "AC OUT" (or equivalent). Basically, if they detect AC on the "IN" terminals that switch from inverting from the batteries to charging them, and any loads on the AC OUT are connected directly to the AC IN; essentially a built-in automatic transfer switch. When AC IN goes dead (power outage) the inverter switches from charging to inverting and powers any loads on AC OUT. Thus the AC IN can be permanently wired to your household wiring and the AC OUT can be permanently wired to a sub-panel carrying any essential loads. You just need to observe regulations for wiring and circuit protection.

    As for power off the smaller generator, you do have to do a bit of wiring. Most standard transfer switch units are designed for 240 VAC in. Obviously you wouldn't be doing that from a 120 Volt Honda! So you have to make sure you disconnect both L1 and L2 with the switch, but only connect one side. Do not try to power both sides from one source in household wiring as there may be 240 VAC loads. Then you have to be sure all your essential loads are on whichever side you energize.

    Or you can run extension cords as needed, since it is temporary. :roll:
  • solarvicsolarvic ✭✭✭✭ Solar Expert Posts: 1,053 ✭✭✭✭
    Re: Plan review emergency backup

    Mark i am installing a magnum ms-ae 4024 in my home. This inverter inverts out or passes 240 vac like you said. You can wire 120 ac to imput if you want to. and inverter outputs 240 ac. So with this inverter you could use a little honda if you wanted. Manual says if you connect 120 to imput that you will only connect the black hot to either L1 or L2, not both. Don,t know about any other brand of inverters. I plan on feeding my inverter 240 since I have a dc generator that feeds battery. :Dsolarvic:D
  • mike95490mike95490 ✭✭✭✭✭ Solar Expert Posts: 8,417 ✭✭✭✭✭
    Re: Plan review emergency backup

    Furnace / house heat ? My dad has a genset to run the furnace, to keep pipes from freezing. Summer, it's used for the fridge. But 3 days in the winter, and the pipes will start to go.

    With a big/long outage, you may loose natural gas, so don't count too heavily on it. Gas up your vehicles before the storm, and practice siphoning into your generator.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 admin Posts: 6,290 admin
    Re: Plan review emergency backup

    Thank You for all the responses.

    I think I will skip the inverter/charger and batteries for now and spend the extra money on a honda or yamaha generator. Use a 30amp 6 circuit transfer switch with an L5-30 plug.

    I did wire a temporary plug for my furnace and used the Kill-A-Watt meter on it. It runs at about 560 watts. Did see it jump to 1300 W or so when it was starting up, but I know the KAW won't give me a reliable startup reading.
    If Natural Gas does get shut off I wouldn't be able to run the furnace anyway. Figure I will get some indoor rated propane heaters, probably wouldn't keep the pipes from freezing, so shutting off water and draining will need to be in the plan. Propane heaters will keep the dogs warm anyway, which is all my wife would be concerned about. :roll:

    Thanks.

    Chris
  • mike95490mike95490 ✭✭✭✭✭ Solar Expert Posts: 8,417 ✭✭✭✭✭
    Re: Plan review emergency backup
    cfunk30 wrote: »
    .... Propane heaters will keep the dogs warm anyway, which is all my wife would be concerned about. ..
    ???

    Dogs are supposed to be portable heaters !
    I don't know if they can be zip-tied to pipes to keep them from bursting though.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • solarvicsolarvic ✭✭✭✭ Solar Expert Posts: 1,053 ✭✭✭✭
    Re: Plan review emergency backup

    Well! If you have 3 dogs you can have a 3 dog night. You would be surprised how well those space heaters work. I got a 20,000 btu one last year and it would keep my whole house warm. Put in a gas fireplace too and if I wanted to use it I shut the other one off because It was too warm with both of them running at the same time. I didn,t have any pipes freeze and it got down to about _5 f a couple times. :Dsolarvic:D
  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: Plan review emergency backup

    The only problem with space heaters is that sometimes the heat doesn't reach the pipes.

    We heat with wood mainly, but when it gets really cold it is necessary to turn on the furnace to heat up the crawl space under the house where all the pipes run because the wood stove's heat does not go through the floor that well. The furnace running in the crawlspace will keep it safely above freezing. This works much better than heat tape wrapped around the pipes.

    Of course if you don't have temps that drop to -40 you may not have this problem. :roll:
  • solarvicsolarvic ✭✭✭✭ Solar Expert Posts: 1,053 ✭✭✭✭
    Re: Plan review emergency backup

    The record I could find was -26f for my area, but it seldom goes below -10 f. But if it gets down around zero I think I will run my furnace. :Dsolarvic:D
  • vcallawayvcallaway ✭✭✭✭✭ Solar Expert Posts: 157 ✭✭✭✭✭
    Re: Plan review emergency backup

    Having been there & don that I will give you my experience.

    1st pick what your REALLY need. In our case we have the outlets in the front room, master bedroom and overhead lights.

    We chose NOT to connect the refrigerator. It did not like the MSW inverter and pulls about 1k in 24hrs.

    Next, don't buy a manual transfer box. They are over priced and a royal pain. Outages tend to happen in the middle of the night. An automatic switch means you never know the power went out. I have mine connected to a small breaker box.

    Buy an indoor rated propane heater.

    Don't buy a generator to run the whole house. Buy one to charge the batteries.

    I started off with designing the system to run off both inverter and generator. Only did that once. I have an IOTA charger for my batteries. I found it was much better just to plug that into a small generator than running everything off the genny and trying to charge at the same time.

    Buy a GOOD charger. I started with a cheap one and fried my first battery. I hooked up the IOTA w/IQ4 and after 3 yrs I've only lost minimal water.

    Frankly, if I were to start from scratch I would buy an inexpensive sinewave inverter, 30A transfer switch, IOTA charger and an small breaker box.

    I still think it is funny when we get a knock or phone call asking if our power is out. We usually don't know until we go in the kitchen and the clock on the stove is off.
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