Inverter Loading

[Brian Graham]

I have a question about inverters and circuit planning.

The Xantrex 1850 is a 15A inverter. IE, good enough for 1 full 15A circuit. But clearly you don't load it with only 1 circuit, especially lighting.

So lets say it runs my upstairs lighting, furnace fan and either the microwave OR washer OR dishwasher. But if someone inadvertantly runs the washer & dishwasher at the same time its going to blow the fuse to the inverter.

So would you actually get as many inverters as necessary so there was a max 15A draw on it at any point in time? But it wouldn't make sense to have an inverter dedicated to the washer alone, most of the time sitting there doing nothing. And then how do you plan circuits with receptacles, where all of a sudden a large temporary load is added - such as a vacuum - which now overloads the circuit? I can't imagine you'd buy an extra inverter to handle a circuit of receptacles which are normally unused.

What I'm trying to get at is how much is load balancing, knowing enough not to run certain items together, and how much is done in balancing inverters loads? (So hard to write this clearly and succinctly..)

The answer can't be to just get a larger inverter. The same concept can occur with a larger one too..

 

[George Ghio]

I have a question about inverters and circuit planning.

The Xantrex 1850 is a 15A inverter. IE, good enough for 1 full 15A circuit. But clearly you don't load it with only 1 circuit, especially lighting.

So lets say it runs my upstairs lighting, furnace fan and either the microwave OR washer OR dishwasher. But if someone inadvertantly runs the washer & dishwasher at the same time its going to blow the fuse to the inverter.

So would you actually get as many inverters as necessary so there was a max 15A draw on it at any point in time? But it wouldn't make sense to have an inverter dedicated to the washer alone, most of the time sitting there doing nothing. And then how do you plan circuits with receptacles, where all of a sudden a large temporary load is added - such as a vacuum - which now overloads the circuit? I can't imagine you'd buy an extra inverter to handle a circuit of receptacles which are normally unused.

What I'm trying to get at is how much is load balancing, knowing enough not to run certain items together, and how much is done in balancing inverters loads? (So hard to write this clearly and succinctly..)

The answer can't be to just get a larger inverter. The same concept can occur with a larger one too..

Generally the ROT is that your inverter should be able to provide 60% of
your total possible load continuously. The reason being is that you are
not likely to run at more than 60% for more than short periods and the
max output for short periods will meet the excess needs.

This said; Unless you know what your loads really are there is no point
guessing.

There is no substitute for correct system sizing.

 

[[email protected]]

you basically have a balancing act; anything with an ac motor
can draw a high surge, approximatley 6 times draw at start up.
on my 12 volt system, the clothes washing machine during rinse cycle
takes 40 amps, and it surges to about 150 amps when starting for
about 1 second; on the dishwasher, the surge is so fast that the
inverter handles it with ease; the microwave oven takes 170 amps
continious, with no measurable surge; i do not have any measurements
for heating systems; if two ac motors surge in the above example
surge at the same, your on the edge; if three surge at the same
instant, the fuse will probably go. the odds of all three, even
two surging at the same time is small. get yourself a couple of
extra fuses and test if it works for you. it is a lot cheaper
than multiple inverters; perhaps you may wish to purchase
a very small true sine wave inverter to handle the known loads of
lights, as well as other small loads, and leave the large inverter
for the known large loads.

Paul

 

[daestrom]

So the little load controller micro would know the amps and duration of
surge on each requested load... I guess instead of a bunch of solid
state relays near the breaker box, it would have to be a x10 type of
distributed system.... when you try to 'turn on' the washer, it sends a
request for washer on, the computer thinks.... "Hmm... need 10 amp
surge for 3 sec.... let me turn off these two ceiling fans for 3 sec...
the carbon based units wont even notice" So every outlet would have a
20A SSR on it and an 'on off' or 'start' button near the applicance
that was plugged in there to alert the controller that it was being
used. Every motor would have a priority, like a task. Your pool would
turn green if the pool pump never got to run because the washer was
always running. You'd need a set of rules for when to run what. Is this
what they invented fuzzy logic for? "He wants me to run the coffee pot,
the TV, the microwave, and the washing machine at the same time, but
the fridge needs 10 minutes, so I'll put those other things on a chrom
for 10 minutes from now..."

Not so much 'fuzzy logic' as an 'expert system'. A wide variety of 'rules'
to follow, with the 'goal' of not exceeding capacity nor accumulating a
backlog of requests. Such a system could also be 'adaptive' in that it
could trend usage of each load and anticipate some of the demands.

Some various constraints could be included, like: 1)Don't cycle power to
computer loads (i.e. don't commit a self-lobotomy) 2)lighting loads cannot
be interrupted for more than 10 seconds (otherwise the carbon-based units
will reprogram you!!) 3) refrigerator, pool-pump and washing machine may be
delayed/staggered up to 30 minutes. 4) A/C, furnace or ceiling fans may be
delayed/staggered a variable amount of time depending on outside temperature
5) Lack of occupancy/motion detection may turn off lighting in some rooms
but not others.

All in all, this could be a fun project for the hobbiest/hacker.

daestrom

 

[wmbjk]

So the little load controller micro would know the amps and duration of
surge on each requested load... I guess instead of a bunch of solid
state relays near the breaker box, it would have to be a x10 type of
distributed system.... when you try to 'turn on' the washer, it sends a
request for washer on, the computer thinks.... "Hmm... need 10 amp
surge for 3 sec.... let me turn off these two ceiling fans for 3 sec...
the carbon based units wont even notice" So every outlet would have a
20A SSR on it and an 'on off' or 'start' button near the applicance
that was plugged in there to alert the controller that it was being
used. Every motor would have a priority, like a task. Your pool would
turn green if the pool pump never got to run because the washer was
always running. You'd need a set of rules for when to run what. Is this
what they invented fuzzy logic for? "He wants me to run the coffee pot,
the TV, the microwave, and the washing machine at the same time, but
the fridge needs 10 minutes, so I'll put those other things on a chrom
for 10 minutes from now..."

For a whole-house system, one can use multiple Outback inverters.
They'll come on-line as needed. See page 25,
http://www.outbackpower.com/pdfs_manuals/Americas and Mobile manual rev 72.pdf
Wayne