ideas/suggestion on setup - transfer switch

mshen11

lets assume i have a generator and/or a battery bank w/ the prosine 3.0 (note: the prosine has a transfer switch built in). my goal is to use both grid and battery, but not have grid tied inverter/machineary

right now by doing NOTHING i can sastisfy my goal awkwardly - run extension cords all of the house; a next step up would be to install separate wiring system throughout the house (that would be very painful according to an electrician who has seen the inside the walls).

my proposal to the electrician is that in my main breaker box i have identified 10 out of 16 or 20 so circuits. i would have him pull them out and put it in a subpanel. the master panel would have a switch to control the subpanel. then i would have him install a plug-in socket next to the prosine/generator and run wire to the subpanel. if i want 100% grid power, i do nothing. if i want to use battery/generator on the subpanel, i would turn off the subpanel breaker in the main panel and attach into the plug.

his comment was creating a subpanel is a lot of work (pulling things out and putting it in new panel). instead he proposes an automatic transfer switch w/ 10 relays instead of the subpanel. that way it is less work and cleaner. however the difference is $500 in the cost of the transfer switch. i would have to install the plug-in socket next to the prosine and then wire it to the transfer switch. according to him this setup would satisfy my goal of running both w/ and w/out grid power.

can someone comment or give new insight for me? or an alternative (cheaper) solution?

Cariboocoot

Re: ideas/suggestion on setup - transfer switch

Let's see if I understand this right, to begin with.

You want to take ten circuits and make it possible to run them either from the inverter or from the grid?

The first thing I would point out is that your Prosine 3.0 is a 3kW inverter, and therefor not capable of handling 10 circuits because that would be roughly 18,000 Watts (15A * 120 VAC = 1800 W per circuit). I doubt that the NEC would allow that, even though we all know the likelihood of all those circuits being run anyplace near capacity at the same time is nearly nil. (I run 3 15A circuits & 1 20A off my 3.5kW inverter, but the power usage is very carefully monitored. Rarely is there ever more than 1kW total actually being drawn.)

The safest way is to pick one circuit and use it as a feed for the AC in on the Prosine, then run the inverter output to the circuit the breaker used to feed. This is the kind of thing that is done for 'critical' devices, such as refrigerators, in case the power goes down.

As for the cost comparison of your stated choices, the electrician should give you estimates: do it this way, it will cost $X; do it that way, it will cost $Y. The functionality of the end result would be the same.

BB.

Re: ideas/suggestion on setup - transfer switch

I did something similar with a manual transfer switch (cheap 6 circuit one designed for a genset)... Picked the circuits that gave me lights, ran the fridge, freezer, sump pump, and a couple outlets. All to run off a small 2 watt genset.

But like Marc says--doing this with the Prosine in the middle would be very limiting for most homes...

If you wire up the Prosine behind a second, larger transfer switch (use the Prosine like a "generator" input to the second transfer switch)--at least 99% of the time, your circuits will all be just like a normal household setup... Only reduce power usage during emergencies (powering 10 circuits with one 3kW prosine would still need some serious energy management if you want this to be automated).

-Bill

GreenPowerManiac

Re: ideas/suggestion on setup - transfer switch

The easiest way I would recommend is to wire what you need to a completely separate load center. No Grid ties what-so-ever. Transfer switches are expensive like noted. More wiring and confusing it gets. One incorrect breaker or mistake could cause your inverter to blow or worse your battery bank. Not having a transfer switch you're playing with fire and can literally burn the house down. Are you willing to risk it ?

I'd leave the Grid out of the Renewable energy system.

Wire up some loads you're sure will work consistently with your RE system and leave it at that.

Your electrician can easily transfer the lines to the separate box right next to your Main load center.

mshen11

Re: ideas/suggestion on setup - transfer switch

Cariboocoot wrote: »

You want to take ten circuits and make it possible to run them either from the inverter or from the grid?

The first thing I would point out is that your Prosine 3.0 is a 3kW inverter, and therefor not capable of handling 10 circuits because that would be roughly 18,000 Watts (15A * 120 VAC = 1800 W per circuit). I doubt that the NEC would allow that, even though we all know the likelihood of all those circuits being run anyplace near capacity at the same time is nearly nil. (I run 3 15A circuits & 1 20A off my 3.5kW inverter, but the power usage is very carefully monitored. Rarely is there ever more than 1kW total actually being drawn.)

The safest way is to pick one circuit and use it as a feed for the AC in on the Prosine, then run the inverter output to the circuit the breaker used to feed. This is the kind of thing that is done for 'critical' devices, such as refrigerators, in case the power goes down.

As for the cost comparison of your stated choices, the electrician should give you estimates: do it this way, it will cost $X; do it that way, it will cost $Y. The functionality of the end result would be the same.

correct 10 circuits and make it possible to run them either from the inverter or from the grid.

but partly incorrect on the next statement "not capable of handling 10 circuits because that would be roughly 18,000 Watts (15A * 120 VAC = 1800 W per circuit)" - here is the explanation: those 10 circuits would include things like bedroom 1, 2, 3, kitchen lights, dining, living room, etc... out of all those areas, we are only in at most 2 rooms at any one time. since we've already conserved the heck out of the place, there is not little to no parasitic loads or anything in there that uses electricity (with exception of 1 fridge and 2 alarm clocks).

marc - are you saying even though i may be right (that my usage would be below 3000 and it is possible), this setup is against code?

also have a small yahama generator (2800i). i can only use either or (prosine), not both at the same time right?


i would like to use both grid and battery - i can wire up a separate independent wire system but it would be a hassle to move the plug from grid to off-grid plug (plus as electrician note, very difficult to run wires in the house).


edit: in the 10 circuits below are what is drawing power as we speak
* main fridge
* dorm fridge
* kitchen radio clock
* bedroom radio clock
* whatever parasitic load the washer has (i dont think there is any)... washer is the GE washer 2manytoyz has

and if it is night time, you add
* tv (600watts)
* computer (50watts)
* no more than 5 low wattage CFL (normally 3)



whats in the other 4 or 6 circuits (left in the main breaker)?
- dryer
- HVAC/AC
- dishwasher
- stove/oven

mshen11

Re: ideas/suggestion on setup - transfer switch

BB. wrote: »

I did something similar with a manual transfer switch (cheap 6 circuit one designed for a genset)... Picked the circuits that gave me lights, ran the fridge, freezer, sump pump, and a couple outlets. All to run off a small 2 watt genset.

But like Marc says--doing this with the Prosine in the middle would be very limiting for most homes...

If you wire up the Prosine behind a second, larger transfer switch (use the Prosine like a "generator" input to the second transfer switch)--at least 99% of the time, your circuits will all be just like a normal household setup... Only reduce power usage during emergencies (powering 10 circuits with one 3kW prosine would still need some serious energy management if you want this to be automated).

-Bill

pretty much exactly what i want to do... but in my case 10 circuits will be under 3000 watts. like i said, we have the conservation down pat - that is how we can choose so many circuits.

Cariboocoot

Re: ideas/suggestion on setup - transfer switch

The tricky bit is (as I understand it) once you 'hardwire' an inverter into your home's electrical system it becomes a part of that system and is therefor subject to NEC. In that case, the Prosine's "two outlet" capacity could not be legally connected to ten outlets rated at 15A each. The Code doesn't reference what you plug in to an outlet - a 100 Watt bulb or a 1500 Watt heater - it is concerned with the rating of the outlet. Even though, as we all know, several outlets are routinely fed from one 15 A breaker because it is highly unlikely they'll all be at maximum capacity. Let's face it; most things use less than 200 Watts.

I am not by any means up to date on the National Electric Code, so I can't say this is 100% certain. And no two inspectors are alike either, so they may interpret things differently as well.

The problem for you would be that the first thing to be over-loaded would not be the 10 15A breakers fed from the inverter, but the inverter itself. Measure the actual Wattage of all the things you want to run, and add them up. Then you'll know what the total could be if everything is on at once. Some of the things you listed are big power users (refrigerators, washing machines, dishwashers, TV, clothes dryer, and especially HVAC).

mshen11

Re: ideas/suggestion on setup - transfer switch

well i dont want to hardwire the prosine to anything. i am thinking of giving the output of the prosine a wire and a plug which will plug into a plug in the wall that goes to the transfer switch. likewise i can choose to plug in the generator instead of the prosine. basically the prosine will be equivalent to a generator.

or are we talking about the same thing?

<quote>Then you'll know what the total could be if everything is on at once. Some of the things you listed are big power users (refrigerators, washing machines, dishwashers, TV, clothes dryer, and especially HVAC). </quote>

not quite... no hvac and no clothes dryer (those are excluded).
but yes clothe washer would be on the list - but we would never use it. if we do, we would make sure we have 1000watts available. but i understand what you mean by load calculation.

so the only question is - is it legal? note im not hardwiring the prosine. i will plug in the prosine (or generator) into the outlet made for the automatic transfer switch.

VERY worst case in case t here is no electricity and i am bumping up against the 3000watts. i just go to the subpanel and turn off a few breakers... until i am not in danger of overloading.

Cariboocoot

Re: ideas/suggestion on setup - transfer switch

mshen11 wrote: »

well i dont want to hardwire the prosine to anything. i am thinking of giving the output of the prosine a wire and a plug which will plug into a plug in the wall that goes to the transfer switch. likewise i can choose to plug in the generator instead of the prosine. basically the prosine will be equivalent to a generator.

This is why there should be a transfer switch; so that at no time would grid power be connected to this other "input". From that respect, there's no reason you couldn't treat the Prosine as a "generator". As long as the "emergency generator power input" meets code, there should be no issue. The "power in" outlet should be labeled as such, even though there would be no chance of it being live 'as is'.

not quite... no hvac and no clothes dryer (those are excluded).
but yes clothe washer would be on the list - but we would never use it. if we do, we would make sure we have 1000watts available. but i understand what you mean by load calculation.

Remember it's much easier to overload an inverter than a circuit breaker! The inverter will react almost instantly to too much current, whereas a breaker has to carry 'over current' for a minimum amount of time before it trips.

so the only question is - is it legal? note im not hardwiring the prosine. i will plug in the prosine (or generator) into the outlet made for the automatic transfer switch.

VERY worst case in case t here is no electricity and i am bumping up against the 3000watts. i just go to the subpanel and turn off a few breakers... until i am not in danger of overloading.

If the install meets code for an emergency generator power hook-up, there shouldn't be an issue. Inspectors get 'funny' about things they don't understand - like inverters. Not hardwiring the Prosine is the big difference, in my opinion.

CVN-71

Re: ideas/suggestion on setup - transfer switch

What you're proposing is very similar to what I'm trying to set up as well. I do not want to be hooked to grid. When my power goes out, I want to be able to run a few key circuits, not all at the same time. I'm also looking for ideas for set up. Basically, I want to be able to run fridge and oil furnace blower (at intervals), a TV, and a few lights during power outages. Also run the well pump for a few minutes at a time to fill the pressure tank.

I plan to use extension cords to the fridge and TV, as they will only be a few feet from the inverter. For the Furnace and Well pump, I want to hard wire, with a manual transfer switch at each one to select between shore power and the inverter power. I have a Magnum 4000w inverter. I was thinking of having a panel with 6 circuits, one each hard wired to the well/furnace transfer switches, and one to a wall outlet for TV, one to outlet for refer, and one to another outlet for lighting/misc loads, and one to 220V outlet if I need to run dryer or stove. I'm figuring I can kill the circuits I'm not using, and rotate them based on power need at the time so as not to exceed inverter capacity. Where am I going wrong with this thinking? Thanks

Cariboocoot

Re: ideas/suggestion on setup - transfer switch

CVN-71 wrote: »

What you're proposing is very similar to what I'm trying to set up as well. I do not want to be hooked to grid. When my power goes out, I want to be able to run a few key circuits, not all at the same time. I'm also looking for ideas for set up. Basically, I want to be able to run fridge and oil furnace blower (at intervals), a TV, and a few lights during power outages. Also run the well pump for a few minutes at a time to fill the pressure tank.

I plan to use extension cords to the fridge and TV, as they will only be a few feet from the inverter. For the Furnace and Well pump, I want to hard wire, with a manual transfer switch at each one to select between shore power and the inverter power. I have a Magnum 4000w inverter. I was thinking of having a panel with 6 circuits, one each hard wired to the well/furnace transfer switches, and one to a wall outlet for TV, one to outlet for refer, and one to another outlet for lighting/misc loads, and one to 220V outlet if I need to run dryer or stove. I'm figuring I can kill the circuits I'm not using, and rotate them based on power need at the time so as not to exceed inverter capacity. Where am I going wrong with this thinking? Thanks

You have a 4 kW inverter.
Now go back and start adding up all those things you want to be able to run in the event of a power outage. Here's a shortcut on two: electric dryer plugs into a 30A 240 VAC outlet, electric range into a 50A 240 VAC outlet. These are definitely not going to run off 4 kW. Got electric hot water? Another 'not much chance' unit (some have 3500 Watt elements, some 4500 Watts). Well pump probably will run okay, if it's shallow well. It will use a lot of battery power in short order though. Furnace blower is a 'probably will work'.

For power outages, better to keep the refrigerator/freezer running so you're not throwing out food. Furnace could probably be run as well, so you don't freeze. Pump water as needed (big pressure tank is a good idea). For cooking ... got a microwave?

It's just amazing how much electricity we use when we have it readily, and cheaply, available. Everyone should have to try to live off 1 kW hour a day for a month, just to become more aware!

mshen11

Re: ideas/suggestion on setup - transfer switch

CVN-71 wrote: »

What you're proposing is very similar to what I'm trying to set up as well. I do not want to be hooked to grid. When my power goes out, I want to be able to run a few key circuits, not all at the same time. I'm also looking for ideas for set up. Basically, I want to be able to run fridge and oil furnace blower (at intervals), a TV, and a few lights during power outages. Also run the well pump for a few minutes at a time to fill the pressure tank.

I plan to use extension cords to the fridge and TV, as they will only be a few feet from the inverter. For the Furnace and Well pump, I want to hard wire, with a manual transfer switch at each one to select between shore power and the inverter power. I have a Magnum 4000w inverter. I was thinking of having a panel with 6 circuits, one each hard wired to the well/furnace transfer switches, and one to a wall outlet for TV, one to outlet for refer, and one to another outlet for lighting/misc loads, and one to 220V outlet if I need to run dryer or stove. I'm figuring I can kill the circuits I'm not using, and rotate them based on power need at the time so as not to exceed inverter capacity. Where am I going wrong with this thinking? Thanks

fundamentally we want to do the same thing but we are totally different. i want to run ALL the small power consumption items, as often as possible. you want to run all (what seems like) all your power hungry critical items only in outages.

the key for both of us is to count the wattage carefully and size them correctly. i beleive i have - even if i am wrong, i can cut the items out one at a time. you on the other hand need to be careful... you dont have a lot of items to cut

CVN-71

Re: ideas/suggestion on setup - transfer switch

I have counted/measured the loads. I do not intend to run anything continuous except for perhaps the TV for a few hours and a CFL or 2 for a couple of hours. Kids are gone, we both work till 7:30pm so only use power for a few hours per nite and 20min in the morning. Only running the fridge is critical. If the house gets too cold during an outage, we will want the option to run furnace just to take the extreme chill out. I do not intend to run the furnace or water pump or anything else with a big load at the same time. I will rotate them on and off as necessary. I survived the last 7-day outage on a 1000w generator (my 6500w would not start), the only real power I needed over that was a 1200w coffee pot and enough to run the water pump for a few minutes to fill the pressure tank. I think if I choose loads wisely and rotate as necessary, I'll be OK. We always have the 6500 generator as a backup and another backup 5500w generator (purchased during the big storm on the 6th day) to supplement as needed. The 1000w generator seized after shutdown after running continuously for 168hrs.

Cariboocoot

Re: ideas/suggestion on setup - transfer switch

This begs the question: if you've already got back-up power from generators, why do you want to buy solar?
The usual answer is that it's quieter, of course!
Or possibly your just considering recharging the inverter batteries from the generator so it will be quiet at night. That's often done too.

It isn't just a matter of individual load sizes as in the 4 kW inverter simply won't run 12 kW of stove (which doesn't draw all of that all the time anyway). The other issue is the cumulative Watt hours; that determines the size of your battery bank.

The basic math (without efficiency losses):
100 Watts @ 120 VAC = 0.83 Amps.
100 Watts @ 12 VDC = 8.3 Amps. In other words, every 100 Watts of power will require 8.3 Amp/hrs to run it for an hour.
At the ridiculously extreme end of the spectrum you'd have 4 kW @ 12 VDC = 333 Amps * 24 hours = 7992 Amp/hrs (times two for a depth of discharge maximum of 50% capacity).

But of course you already know you don't need that much! Just me being silly, really.:p

Just take a look at my sig and you'll see a more practical set-up, although I'll have more battery than that and more panels next year - heavier use when you're off-grid all the time. It's very similar to your requirements. With it I run the 'frige 24 hrs a day, plus lights, water pump as needed, septic pump (big draw/short time) and the office computer equipment & satellite Internet/phone connection (biggest continuous power user).

Yes, a 'self-contained solar-recharged inverter back-up system' instead of a noisy, smelly, gas-burning generator is doable. Could plug in to a standard 'whole house' back-up power connector usually used by generators. You're both already well aware of the need to manage the loads, and that's the biggest issue.

Good luck with it!