2 inverters? Low and high watts

[bbells]

Forgive me if someone has already asked this. I am at work with a Vista computer that is so slow it takes 10 minutes to search this site. Don't get me started on that since we are an internet company.
I am setting up solar in my barn. 95% of the time I will be using 100 watts or less. Less than 5% (probably less than 1%) of the time I would be using a circular saw or air compressor for short periods of time (not at the same time). Would it be beneficial to install 2 inverters, one for say 400 watts and another for 2000w? And, have the 400w on most of the time and then turn it off and turn on the 2000w inverter when I need to use more power? And, if that is a good idea, would I also need a switch on the 120vac lines out on the inverters so when one is on and the other is off AC won't backflow to the one that is off? Thanks for any help.

[jflorey2]

Forgive me if someone has already asked this. I am at work with a Vista computer that is so slow it takes 10 minutes to search this site. Don't get me started on that since we are an internet company.
I am setting up solar in my barn. 95% of the time I will be using 100 watts or less. Less than 5% (probably less than 1%) of the time I would be using a circular saw or air compressor for short periods of time (not at the same time). Would it be beneficial to install 2 inverters, one for say 400 watts and another for 2000w? And, have the 400w on most of the time and then turn it off and turn on the 2000w inverter when I need to use more power? And, if that is a good idea, would I also need a switch on the 120vac lines out on the inverters so when one is on and the other is off AC won't backflow to the one that is off? Thanks for any help.

1) The usual - solar is a mistake in that situation, running wire will be cheaper etc.
2) Good inverters have very low idle currents nowadays and can go into search modes that are even lower.
3) If you want to do this you'd almost have to run two separate circuits to the two separate inverters - one for your saw/compressor and the other for everything else. Inverters do not like seeing voltage on their outputs when they are off. And a transfer switch isn't really designed to switch every time you turn your saw on.

[bbells]

Does anyone have an actual answer to my question?

[solar pete]

Well I think more info is required before anyone can help.

Are you currently on the grid and have grid power in the barn? Are you thinking of a grid tied system or using batteries?
When you say 100watts for 95% of the time, its not that helpful, does that mean you will be running at 100watts for 23 hours a day, everyday? That would be 2300 watts or 2.3kWh (kilowatt hours per day)
What are your loads, e.g what make's up the 100wats, 2x 50watt lights ??

[Sunking]

Afraid you are not going to get any answers you like because Solar is not made to do what you want. If you want to be lied to and told what you want to hear go over to Notrhern Arizona Wind and Sun Forum. They are full of yes men. They will sell you everything you need to fail and make you feel good doing it. Here you wil just get the facts like it or not.

You cannot put large shop loads on batteries without a substantial investment in equipment you wil never recover. To run an Air Compressor say a toy sized 1 hp compressor to fill bicycle tires requires up to 5 Kw to start up and 1 Kw to run. At 12 volts will require a 1000 AH battery. A 12 volt 1000 AH weigh in around 1000 pounds and cost you every bit of $3000. It will require copper cables the size of your leg, and a minimum 1000 watt solar panel system with a high dollar 80 amp MPPT controler to feed the battery. If you run a real compressor or shop tools will require much larger equipment. Don't forget the batteries need replaced every few years.

Do yourself a favor, hire a Sparky to run a 50 amp service to your shop. Will be a lot less expensive initially and long term. Not to mention will actually work.

Otherwise dig deep down in your pockets and learn the lesson the hard way. If you insist on Solar it is going to cost you big money, and so far you have not given one bit of useful information anyone can use. Not that it matters any because when you throw large loads, you eliminate off grid solar. Off grid is for bare minimum essentials, no luxury's like shop tools, heaters, air conditioning, cooking, hot water. Just lights,enough to run a TV, and keep beer cold.

[bbells]

Just answer the question please. I don't need any of your judgements. If you cannot answer the question go to some other post. The question is simple. It isn't if I should use solar in my barn. It isn't about if I should run grid power to my barn. The question is does anyone run 2 inverters and simply switch over to a bigger one when they have more demand?

[solar pete]

No, that is not generally done, but your lack of detail makes it hard for anyone to answer this question

[SunEagle]

Just answer the question please. I don't need any of your judgements. If you cannot answer the question go to some other post. The question is simple. It isn't if I should use solar in my barn. It isn't about if I should run grid power to my barn. The question is does anyone run 2 inverters and simply switch over to a bigger one when they have more demand?

Yes it can be done that way. Since you plan on only using the larger inverter 5% of the time I would not waste any money on some type of automatic switching device but just unplug or unwire the small inverter from the battery and wire the larger inverter. Just make sure the DC wiring is big enough for the larger inverter along with the fuses on that wire to protect it.

Hope that answers your question.

As for why you chose to use solar and batteries to run your loads, well that is your choice and IMO if you feel you want to do it that way the go ahead. I won't try to stop you. Your money your choice.

[Sunking]

Sun Eagle tell him what size battery he needs to run that large inverters and panel wattage to support the batteries. Don't leave out the generator he does not know he will need. No need to bother with how dangerous a large Inverter is he intends on using.

Bells we are not trying to beat you up, but make you aware of what you are asking for. Here is what we hear you asking and has us laughing:

"I ride a bicycle most of the time to go to work and do aarons. But on weekends I need to pull a fully loaded 18-wheel tractor/trailer rig. Do I need two bicycles or just one?"

[SunEagle]

Sun Eagle tell him what size battery he needs to run that large inverters and panel wattage to support the batteries. Don't leave out the generator he does not know he will need.

Not my problem or was the question he asked. If he has sized the battery and panels too small then he will find out the hard way.

I just got back from 4 days of a peaceful beachfront mini vacation. And I realized one of the reasons I get stressed out was trying to convince people that come here they can't build a space telephone using two cans and a string or in other words use a 100 watt panel, 35Ah battery to run their 12,000 BTU AC unit.

So instead I will just try to answer their questions and not even try to stop them making purchases and possible wasting their money. It is just way TOO stressful for me. I would rather help those the really want it and ask for it. If that is not what our Admin wants me to do then I am ok taking a much longer vacation and giving up my Mod responsibilities to someone that is ok going head to head with some people that just won't listen or care about building a quality solar pv system either for on or off grid.

[solar pete]

Howdy SunEagle, man I dont want you to get stressed out at all, very happy for you to do and your say whatever you feel is OK. Please dont feel that you have to answer questions of those who are rude or dont have enough knowledge to comprehend the answer, you simply cant help some people, so its Ok to ignore some.

[bcroe]

Forgive me if someone has already asked this. I am at work with a Vista computer that is so slow it takes 10 minutes to search this site. Don't get me started on that since we are an internet company.
I am setting up solar in my barn. 95% of the time I will be using 100 watts or less. Less than 5% (probably less than 1%) of the time I would be using a circular saw or air compressor for short periods of time (not at the same time). Would it be beneficial to install 2 inverters, one for say 400 watts and another for 2000w? And, have the 400w on most of the time and then turn it off and turn on the 2000w inverter when I need to use more power? And, if that is a good idea, would I also need a switch on the 120vac lines out on the inverters so when one is on and the other is off AC won't backflow to the one that is off? Thanks for any help.

It would take a HUGE investment to build up the required equipment, then hardly be used (1%). The surge to start to a air compressor
can be huge, it must be covered. But yea, 2 different size inverters could work. A better approach might be just use a generator for the
heavy equipment. Maybe there is even a battery powered saw these days, and a portable air tank. Bruce Roe

[Mike90250]

Just answer the question please. I don't need any of your judgements. If you cannot answer the question go to some other post. The question is simple. It isn't if I should use solar in my barn. It isn't about if I should run grid power to my barn. The question is does anyone run 2 inverters and simply switch over to a bigger one when they have more demand?

I could see a scenario like that, using a morningstar SureSine 300w wired to a batch of sockets, and another 4Kw inverter wired to a couple sockets for the heavy loads.
I would NOT try switching the outputs to and fro. Just fire up the big one as needed,
at 12v there are not efficient 4kw inverters

[SunEagle]

Howdy SunEagle, man I dont want you to get stressed out at all, very happy for you to do and your say whatever you feel is OK. Please dont feel that you have to answer questions of those who are rude or dont have enough knowledge to comprehend the answer, you simply cant help some people, so its Ok to ignore some.

Thanks pete. It seemed the OP was very verbal about not wanting any help with his battery, grid tie and anything else so I felt instead of trying to beat my head against the wall helping him see the light I would just answer the question.

I will continue to help those that ask for help and try to guide anyone to make safe choices so as not to get hurt or hurt others but if I get push back on what I recommend then I will drop the rope. I would rather lose the tug of war then to get rope burns.

Now I will stand back and let this thread get back on topic.

[jflorey2]

Does anyone have an actual answer to my question?

Yes. See above. If you have trouble scrolling, see below:
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If you want to do this you'd almost have to run two separate circuits to the two separate inverters - one for your saw/compressor and the other for everything else. Inverters do not like seeing voltage on their outputs when they are off. And a transfer switch isn't really designed to switch every time you turn your saw on.