I don't want to own another gasoline powered anything...

notch · December 2013

but I do need a way to keep the heat on at my cabin when the grid is out, as temps regularly go below zero. No way can I afford or even want a giant propane genset with auto transfer switch. The cabin has a garage and is heated with a propane-fired boiler and FHW. I'm 100 miles away and can't always drop everything and drive two hours to connect up a generator to keep the FHW heating system pipes from freezing. I also can't stay there to fill the generator gas tank for as long as the grid is down. I have a electric golf cart with six 8-volt Trojan T845 batteries wired in series, and the cart isn't used in winter - it just sits on the charger, which wakes up every 15 days and tops off the charge. As I thought about my options, I started researching whether the power in the cart batteries could work and that lead me here, where I was astounded at what folks are doing off grid. I'm a city dweller, but admire what you folks are doing. Anyway, I was thinking I could connect the 48vdc cart batteries to a inverter with an auto transfer switch like this one:

http://thesolarstore.com/inverters-grid-inverters-cotek-inverters-cotek-st1000-1000w-48vdc-115vac-pure-sine-wave-inverter-free-remote-p-1269.html?utm_medium=cse&utm_source=google&k=1269&gclid=CKyg55K2wLsCFRBnOgodLlAAwQ

and when the grid goes off the cart batteries should be able to cycle the single pump in my baxi luna propane boiler for days (maybe weeks) and when the grid comes back online the charger will come on and recharge the cart batteries for the next grid outage.

It seems too easy, and so I was hoping you folks might be able to tell me what I'm missing, or what other things I need to consider. I appreciate your help and thoughts on the subject. Thanks!

Cariboocoot · December 2013

Re: I don't want to own another gasoline powered anything...

Welcome to the forum.

Before you spend any money on an inverter find out how much power your furnace equipment actually needs. You're looking at an induction motor running a circulating pump, and it could have quite a start-up demand which that inverter may not be able to supply.

Otherwise your concept is sound: the cart charger would keep the batteries up from the grid when available and power the inverter when the grid goes down to supply the critical circuits.

You will also want to know how long the outages last for, as batteries will need to be recharged sooner rather than later. If they are frequent and long-lasting adding solar charging may be in order. if they are short and infrequent I wouldn't worry about it. But the batteries would have to be able to supply the power demands for however long the grid is down.

mike95490 · December 2013

Re: I don't want to own another gasoline powered anything...

It would at least buy you time to gracefully arrange a trip to check on things.

Many things can be done with the motors, some are just way oversize, and can easily be reduced, others may have more efficient equivalents available, all of which would extend your runtime.

And most inverters with a transfer switch, have an option for auto-starting a generator. If you have propane on site, it could be used for reliably starting a small generator. (I think there are propane kits for honda and yamaha generators) if you suspect you may have outages that last beyond what your battery bank can last for.

If your boiler "plugs in" you can use a Kill-a-watt to measure how much power it draws.

FHW = ??? Forced Hot Water ???

vtmaps · December 2013

Re: I don't want to own another gasoline powered anything...

notch wrote: »

and when the grid goes off the cart batteries should be able to cycle the single pump in my baxi luna propane boiler for days (maybe weeks) and when the grid comes back online the charger will come on and recharge the cart batteries for the next grid outage.

It seems too easy, and so I was hoping you folks might be able to tell me what I'm missing, or what other things I need to consider. I appreciate your help and thoughts on the subject. Thanks!

Welcome to the forum,
What you are describing is a UPS (uninterruptible power supply). They are very common. There are small ones to use for a single computer, and there are whole house UPS systems. There are systems that use batteries for only a few minutes... just long enough for a generator to come on line. Many folks wire up a UPS to just a few critical circuits in the house (CPAP machine, computer server, furnace, etc).

btw, much of the new equipment being produced today has modern communication capabilities built in. Its not too hard to set up a system that can be monitored over the internet... some folks like to get a text message when their battery voltage goes below a certain value.

--vtMaps

waynefromnscanada · December 2013

Re: I don't want to own another gasoline powered anything...

"No way can I afford or even want a giant propane genset "

Sounds like there must be some pretty big loads there, otherwise a "giant" genset would not be required.
Also sounds like present financial situation could be a real restriction on any serious, workable UPS system.
We DEFINITELY need to know the loads and total power used per day, otherwise we're just making wild guesses as to what if anything affordable would work.

westbranch · December 2013

Re: I don't want to own another gasoline powered anything...

FHW, (forced how water?) I have to assume that this is an in floor/slab heating system..?
Is that Zero F or C?
What is the lowest average temp during winter? What is the max lowest temp?
Where are you located.
Either way, if that system was installed properly, the circulating fluid should have antifreeze in it to make sure the plumbing does NOT get damaged in the event of a power outage, and that the freezing point would be at least -10* below the average.
How long are the outages? If only a half an hour or so there should not be a problem with freezing.
hope this helps.

I don't want to own another gasoline powered anything...

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