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Old 19th February 2009, 10:47   #61
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Originally Posted by kalpeshc View Post
I am looking to get myself an inverter for my house in Surat. We have regular load shedding for around 2-3 hours (not more). I require some kind of power backup which can run at least 3 fans, 3 tube lights ... for around 2 hours max.
Kalpesh, there is an important aspect that you must keep in mind. Is your house wired up for fitting an inverter to supply selected loads only?
If not, you need to buy an inverter of large capacity. The batteries need NOT be 'matched' to the inverter capacity. The batteries can be of just sufficient capacity to run your desired loads for the required time.

So why the big inverter?
So that you do not have a blackout each time that there is a power outage. This can be very irritating and defeats the inherent strength of an inverter.

An example will make it clear: Suppose you plan to run only 1000 watts of lights/fans during the outage, but normally you have 1500 watts worth of stuff on in the house.
The moment power fails, a 1000 watts inverter will trip on overload. You'll have to reduce the load to 1000 watts before you manually turn on the inverter again.

Now suppose you buy a 1500 watts inverter. It will carry on uninterrupted. You should then manually turn off the unwanted load to bring it to the planned level so that you can achieve the planned backup time.

Also, please remember that batteries gradually lose storage capacity with age. Much before you need to replace them, their capacity will have reduced to nearly half of new ones.
Keep this in mind while selecting your system.
You can run a small fridge but costs for the system will go up dis-proportionately, as Sir Alec has already mentioned.

You'll almost certainly have to increase your budget or cut down on the outage load!
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Old 19th February 2009, 10:51   #62
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Thanks Anup

I'd rather cut down on my requirements than budget in these times. I think i can live with a temporary blackout for a few minutes instead of spending more money for a higher capacity inverter. Otherwise if I'd have to factor in my TV, fridge, making this an expensive exercise.

What brands are recommended? Are separate brands for batteries recommended too?
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Old 19th February 2009, 11:06   #63
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Originally Posted by anupmathur View Post
Kalpesh, there is an important aspect that you must keep in mind. Is your house wired up for fitting an inverter to supply selected loads only?
In most houses, all the 15 A & 5 A connections are separated.
Other than that there are other separations also.
I have had an inverter fitted in 3 different places I have stayed at.
In 2 of them, I was able to connect the invertor on for just the fans
& lights in one room. In my current place, other than 5A & 15 A separation,
the kitchen & bathroom are also separate from the rest of the rooms.
So my current invertor is wired to all the 5A lines except kitchen &
bathroom.

Quote:
Originally Posted by anupmathur View Post
An example will make it clear: Suppose you plan to run only 1000 watts of lights/fans during the outage, but normally you have 1500 watts worth of stuff on in the house.
The moment power fails, a 1000 watts inverter will trip on overload. You'll have to reduce the load to 1000 watts before you manually turn on the inverter again.

Now suppose you buy a 1500 watts inverter. It will carry on uninterrupted. You should then manually turn off the unwanted load to bring it to the planned level so that you can achieve the planned backup time.
It may not be so simple. For eg. the Fridge load isn't very high. A small
invertor would be able to take the load easily, but the problem is that
the fridge's startup load is very high. So when the power goes, the
fridge's get switched off - now the invertor cuts in & it's not able
take the fridge's startup load - if there was a way to prevent the fridge
from cutting off, then the load wouldn't be high.
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Old 19th February 2009, 11:13   #64
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Originally Posted by carboy View Post
It may not be so simple. For eg. the Fridge load isn't very high. A small
invertor would be able to take the load easily, but the problem is that
the fridge's startup load is very high. So when the power goes, the
fridge's get switched off - now the invertor cuts in & it's not able
take the fridge's startup load - if there was a way to prevent the fridge
from cutting off, then the load wouldn't be high.
Carboy, sorry, I am unable to quite understand what you are saying here.

What is not so simple?

If the inverter is on and the fridge cuts in, there will be an overload trip of the inverter, if the rating of the inverter is not large enough to handle that surge.
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Old 19th February 2009, 11:49   #65
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Quote:
Originally Posted by anupmathur View Post
Carboy, sorry, I am unable to quite understand what you are saying here.

What is not so simple?

If the inverter is on and the fridge cuts in, there will be an overload trip of the inverter, if the rating of the inverter is not large enough to handle that surge.
Lol... what he is trying to say IMO, is that a fridge can also run in a small inverter setup provided you figure out a way to keep the compressor running all through the outage, as the surge comes only when the compressor tries to switch on.

In other words what he is saying is that if the fridge's compressor never switches off (as it normally does every few while) then a continuously running fridge can also be supported with a small capacity inverter. Basically a hypothetical scenario.
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Old 19th February 2009, 12:13   #66
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APC sells its 800 va model through Metro for about 13,000 inclusive of the stand & battery. You need to call the support center and installation is done within 2 days for an extra 200-350 bucks. Depending on who you talk to :-)
Its the cheapest deal, even dealer are quoting atleast 2k more than this. (Jan 2009 prices)
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Old 19th February 2009, 12:37   #67
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Quote:
Originally Posted by Zappo View Post
In other words what he is saying is that if the fridge's compressor never switches off (as it normally does every few while) then a continuously running fridge can also be supported with a small capacity inverter. Basically a hypothetical scenario.
Yes - that was what I was trying to say - not contradicting anupmathur, but taking his point further.


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Originally Posted by ak916 View Post
APC sells its 800 va model through Metro for about 13,000 inclusive of the stand & battery.
So what capacity battery is this?

Last edited by carboy : 19th February 2009 at 12:43.
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Old 19th February 2009, 13:07   #68
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Originally Posted by carboy View Post

So what capacity battery is this?
120 AH, Prestolite and Amco are available
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Old 19th February 2009, 13:58   #69
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Quote:
Originally Posted by Zappo View Post
Lol... what he is trying to say IMO, is that a fridge can also run in a small inverter setup provided you figure out a way to keep the compressor running all through the outage, as the surge comes only when the compressor tries to switch on.
Thanks, Zappo.

Quite so. If the compressor can be prevented from cutting off!
One method of doing this would be to set the thermostat for max cooling. And keep draining the inside cold air by opening the fridge door frequently. LOL!

There do seem to be inverters claiming to have the ability to handle large surge loads, specifically meant for running small fridges.

Unrelated but nice to know is that the good old direct cool fridges are better at lasting out through a power outage than the frost free ones.
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Old 19th February 2009, 14:18   #70
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Another sort of inverter related question. We have a setup running in the village but the batteries are a pain in the rear. We spend a few weeks in India every year but by then the batteries have had it and need replacing.

I know that people in the UK leave their motorbike batteries on a trickle charge throughout the winter when they are not using their bikes. This keeps the batteries topped up and they encounter no battery problems in the summer when using their bikes.

We did try leaving a low wattage bulb on so the batteries on the inverter would drain and recharge (hoping this would prolong the life of the batteries) but this little experiment failed as the inverter started to whistle and this annoyed the neighbours.

So could we just put two trickle chargers on the batteries and leave throughout the year till we need them ? Has anyone tried this ?
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Old 19th February 2009, 15:13   #71
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Originally Posted by anupmathur View Post

Quite so. If the compressor can be prevented from cutting off!
One method of doing this would be to set the thermostat for max cooling. And keep draining the inside cold air by opening the fridge door frequently. LOL!
The cutoff would still happen when the powercut happens.
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Old 19th February 2009, 15:18   #72
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The cutoff would still happen when the powercut happens.
Turn off all loads and start the fridge. If this does not work the inverter is far too small!
If it does, wait for a minute and then turn on other loads.

I don;t see why it is so crucial to have the fridge running through a few hours outage!
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Old 19th February 2009, 15:42   #73
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There are high chances that the life of a fridge will be affected if it keeps on restarting 4-5 times a day because of power cuts
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Old 19th February 2009, 15:46   #74
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Quote:
Originally Posted by Zappo View Post
Lol... what he is trying to say IMO, is that a fridge can also run in a small inverter setup provided you figure out a way to keep the compressor running all through the outage, as the surge comes only when the compressor tries to switch on.

In other words what he is saying is that if the fridge's compressor never switches off (as it normally does every few while) then a continuously running fridge can also be supported with a small capacity inverter. Basically a hypothetical scenario.
Fridge will definitely trip the inverter because inverter has switching delay time even more than that of lineinteractive ups forget online UPS. In simple words even if the fridge is running (compressor on) and power goes off, it will cut in the compressor before it switches to inverter

So fridge is a definite no unless you have huge 3kva inverter with room full of battery.
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Old 19th February 2009, 16:13   #75
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Quote:
Originally Posted by kalpeshc View Post
There are high chances that the life of a fridge will be affected if it keeps on restarting 4-5 times a day because of power cuts
Kalpesh, a fridge cuts off many more times a day than that! That is not a reason to worry.


As for running a fridge on an inverter, I just found out that a 2500VA, Sine Wave inverter, 4 batteries based (48 volts DC input) is required for successful operation! This for a 165 ltrs fridge!!

Last edited by anupmathur : 19th February 2009 at 16:19.
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