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I'm thinking about options to maintain essential power to my house during a mains power outage and when I'm not home to manage it. I wonder if a UPS connected to the main switchboard (with a "large" battery) would do the trick. Then the fridge and burglar alarms would remain active. Nothing else is important enough to require continual power. UPSs that I find with web searches seem only suited to computer server backups rather than a whole domestic house. Let's assume the house is empty for one week and there is a 24 hr or longer mains power outage during this time. I see two problems: (1) the cost of a UPS with a battery bank large enough to cope for a smallish power draw for 24 hrs, (2) how to stop the pool filter using power from the UPS ('cos it is not essential). Maybe a UPS is not the solution for problem (1). Any suggestions?
CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 1985
Posted: 10:08pm 23 May 2020
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can you run two circuits? One can be nominal mains, the other "supported" mains. I did the same thing in my workshop and I have red mains sockets for the stuff that stays on when i knock off the main power - clear indication and means I can easily isolate things without interfering with key stuff.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:12am 24 May 2020
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Your refrigerator/freezer will be the biggest problem. Running power is not going to be that high, but the initial start up surge can be a real killer.
Many UPS are typically rated for continuous fairly light duty loads, such as computer systems, alarms, emergency lighting and such. The idea is fine, but just check first, that whatever you buy has enough grunt to start up any really nasty loads that you may have repeatedly, without shortening its life.Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 08:34am 24 May 2020
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I had a UPS setup with solar panels a few years ago as a hands on learning arrangement. I ran a Fridge and a hot water urn off it. I have been running UPS setups for years with Much larger batterys and using them in the field with a generator so I didn't have to run the genny all the time.
The Ups units I have are all APC brand. They run 24 V battery power from the little 800Va units to the 3000W unit I had. I just removed the internal 12v, 7ah SLA's and hooked up some car battery cables and ran them to a couple of car batts as a a 24V setup either single or paralleled. I also got some Eaton ups units but the ones over a KW output ran 48 or 96V which is a pain in the arse when you want to get that many car batterys to power them. I like the APC units.
I would suggest you get the "Online" types rather than the Other types I forget the topology of. Basicaly one will cold boot from battery power alone. The better ones are a Battery charger and an inverter that runs all the time where the other one is direct mains fed and the battery is only switched in when there is a failure or ripple. The cheaper and more common type ( Might be "Line active" they call them) will only boot when mains power is present and then you can switch to battery power. As long as the battery is connected and not below the threshold voltage they will stay powered up but the cold boot types are a better made and more serious unit.
The online types also have a lot more surge power for starting initial high current loads but the cheaper ones will do it too, just not as much. I would suggest a UPS with at least a Kw output and don't get confused with W and Va as a lot of inverters output is specified in. 1000 Va is a lot less than 1000W so make sure you know what you are getting.
With the Fridge setup, I found the little 800Va units would start and run the normal size fridge I had no problems. I had a PWM controller running off the car batteries which allowed me to run the urn off another little UPS. Sure it took a while to boil initially as I had it set to about 400W I could see through a meter I had attached but once it was, I could keep it on the boil with only 50W. The solar controller had an output that I put on an SSR so the urn was only powered when the panels were producing power and the battery's were up to charge.
The way I would approach this is not so much with massive batteries but with just enough to get through the night which isn't going to be a lot as the fridge isn't going to use a lot of power when no one is opening it all the time but throw a load of used panels and a controller on them so the battery's only have to last the night and then will be recharged in the day.
Like everything solar, I would ( and did before) parallel a bunch of panels so even on a wet crappy day there was enough power to fully recharge the battery's and run the day loads. Wouldn't be hard to put a Monitor on your Fridge to see how much it uses a day which will be higher due to opening it or just monitor it over night and say triple that for good measure and work out your consumption from there. Do the same with whatever else you want to run and add up the total power you need. Multiply that by 5-6 and that's about the amount of panels you need to account for bad weather without over draining the batterys although you could well possibly get 2 days worth of power out of a couple of largish car battery's which will be about 1 Kwh ea. \You wouldn't want to dip below 50% though.
Most of the time it will be complete over kill but it's not the sunny days you have to worry about, it's the crappy, wet, gloomy ones. Used panels can be had for free or cheap depending where you are, a $25 Controller would keep the batterys in check and a used UPS would do the job. Panels can be a LOT cheaper than batteries and for what you are wanting, Deep Cycle marine Battery's or even large used car batteries would do the job for some time as most of the time they would be floating or minimally cycled in DOD.
I remember once as a Kid I went away with my Grandparents for a couple of weeks. Opened the front door and there was a stench like death. Somehow, while we were away a fuse blew which the deep chest freezer was attached to. The food went off and what a stink. Grandfather and a neighbour got the thing outside and grandad Dug a Huge hole up the back garden, tipped the whole lot in and filled the hole quick as he could. Some months later he dug it all up again and removed the plastic bags. He did say things grew well up there afterwards. He tried everything to get the stench out the freezer itself but nothing worked.
How serious and permanent you want to get with all this I suppose depends on how often you go away and how often you get long blackouts. You could have it anything from a lead that just plugged into the fridge and probably the power pack running the backup battery on the alarm to the separate Circuit with the Red power points as described above which is what Hospitals and other facilities do. Normal non critical power and points with fail safe backup power. Starts all getting a bit exy though unless you have a frequent need for them.
I can't imagine an alarm would take much to run and Fridge / Freezers stay pretty cold for 24 hrs plus when not opened. You can also increase this cold time by Filling them with water bottles to increase the thermal mass and stored energy.
I had an old freezer up the back I played with this and with about 26L of frozen 2L Milk bottles it was still all well frozen 2 days after it was turned off and I did Check it about 3 times a day. on the 3rd day there was some signs of melting but I dojn't think it was enough to spoil food as it was still quite cold and the water was still 90% frozen solid.
The idea would be to Fill all the space in the fridge or freezer with the water bottles to give the max cold storage and therefore the longest " Backup" time. The more cold storage you have the longer things will stay cold. This to me would be the far simpler and cheaper way of doing things.
If your backup goal is 24hours, this would be the easiest and cheapest solution of all. As alarms often run off battery and the power pack just keeps the battery topped up, just adding a 2nd 7ah, $20 Battery could give you a couple of days of backup on that or run a small panel and controller for it.
Again, I'd say you would want to do the risk Vs. cost factor first. If blackouts are infrequent and not over 24hrs in general, Saving your old Milk/ drink bottles could easy give you all the backup you need on the food side and a $20 extra battery or a larger battery in the alarm would take care of that.
Thanks for the detailed reply Davo99 and I like the idea of loading up the fridge with water bottles before I go away. The fridge only draws 200W and up to 2000W startup based on notes I made many years ago. I'd guess it would draw power only 50% of the time, perhaps less if I'm not here.
I have multiple burglar alarms (to cover shed and house on a rural property) and they are wireless with backup batteries - all powered from the main switchboard. That's why the simplest solution is probably a UPS on the main switchboard. That would be handy as well even when the family is home and we have a short power outage.
I did see the APC UPS units on one of my web searches but could not locate the full specs for them.
ryanm Senior Member Joined: 25/09/2015 Location: AustraliaPosts: 191
Posted: 11:55am 25 May 2020
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Since UPS units are a business product you're going to pay a premium on it over putting something together yourself. Depends how hands on you want to get with it.
I met an old bloke with a fishing hut that was running a fairly massive fridge on a 1500W inverter no worries.
If you went the battery route you may as well throw a small solar panel up as well and have it power the fridge during the day even when there is power to save a few bucks. That way you only need half the batteries as well so it's going to be a lot cheaper and instead of running for 24 hrs you're running for weeks/months as long as the battery can get through the night.
ryanm Senior Member Joined: 25/09/2015 Location: AustraliaPosts: 191
Posted: 12:03pm 25 May 2020
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I have an IT business, just looked it up out of curiosity. 1500W UPS came up with one unit at my supplier with 12V 27AH equivilent battery. $970
For that price you could buy;
Jaycar 1500W inverter w/ 30A solar charger - $349 130AH Eclipse AGM battery x 2 (260AH) - $538
Then you've still got enough money left over for a used 250W solar panel and a cold six pack.
noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 506
Posted: 09:58pm 25 May 2020
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Keep an eye out at dumps etc... its usually cheaper to just ditch the " old " models and replace them, have quite a few that just needed new batteries salvaged from the dump...I think it works !!
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:25pm 25 May 2020
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Nonya is right, I have repaired quite a few UPS, and often the only problem is the sealed battery has dried out. When you tell the customer how much a whole bunch of new batteries is going to cost, they say "don't bother" I will buy a new more up to date model UPS with warranty.
So a lot of old but otherwise perfectly good units end up in the dumpster, or sold for scrap value.Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 03:16am 26 May 2020
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I have bought all my UPS units this way. The batteries f rom the manufacturer are priced to kill even though they are common 7Ah or 12Ah SLA's wired and bundled together. The UPS companies charge 5-10X the price the batteries can be had for from electrical wholesalers or fleabay which makes a new unit a worthwhile proposition.
Mate of mine works for an IT company that does Data and disaster back up. They require their Clients to have equipment no more than 10 years old. A lot of perfectly good gear has to be replaced on age as after that parts can be hard to get and as the company has to have spares for their repair guarantee, the gear has to be age limited.
I have servers and UPS units off them as they just scrap or try and sell them and the UPS units don't get much.
As I don't give a damn about the batteries and was just tapping into the power feed and running car size batteries, worked out real well for me. I don't think I have paid over $40 for a ups on fleabay and my big 3Kw unit was given to me by an IT Company I bought some smaller units off because they had no interest in it. I remember the guy telling me it was too big and heavy ( weighed a ton with the batteries in it) and no company wanted old gear. From memory I got $30 For the old batteries which were well dead when I took them to the scrap yard.
For this purpose, a UPS with dead batterys and a couple of car battery's from the wreckers for 30-$40 each would be a cheap and completely practical setup. Throw on some used solar panels and you could power the fridge permanently Like I did for 6 months playing around with the setup. Think I have a YT vid on it actually.
Thanks for the replies. Need some more details it seems. The main switchboard for the whole property is in the shed, about 50m away from the house so attaching a UPS directly to the fridge in the house is not a good option. The pool circuit and burglar alarms also run directly from the shed. Assuming a 200W draw and 50% cycle for the fridge and a 50W continuous draw from the burglar alarms means I need 150W continuous draw for 24 hrs. That is: 3.6kWh. A startup power of 2000W is needed for the fridge so the UPS will need to cope with that. I guess that means a 2kW rated UPS is needed with a 3.6kWh battery bank. For 12V batteries: 12V x 300Ah / 0.8 = 450Ah if I discharge down to 20% capacity. Hope that helps. I haven't has much success with the reliability of Jaycar products so any other suggested brands for a UPS apart from the APC units mentioned by Daveo99 ? Edited 2020-05-26 14:54 by greg199
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 08:11am 26 May 2020
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Your calculation assumes the Fridge will Run 12 Hours a day..... without any one there to open it. If that is the case, buy a new fridge, the old one is either stuffed or damaged and using far too much power. I think a 25% run time would still be overkill well and truly. I can hear my old fridge run at night and it's more like 5 Min on and 2-3 Hours off.
You can buy those Plug in power meters pretty cheap. You could put one on and monitor how much it uses when you are there but I would doubt it would even run 50% of the time then. Mine sure as heck does not. Fill the empty space with water bottles and It will probably run about 5% Cycle. This means the battery capacity you are thinking is way over kill.
50W seems high for an alarm as well. Have you measured this because that's costing you a lot of money if that's actually what it's pulling.
Going on those numbers anyway, you would not need a 2 KW UPS. Like any other inverter they have a good Surge capacity and I am confident you would fire the fridge no problem with a 5-600W unit. At very worst, a 1 Kw/ 1300Va will do it without question and you'll find them a LOT cheaper than a 2Kw UPS that's for sure.
The reason I suggested solar panels was because of the batteries. 4KWH is roughly 4x 100 Ah batteries with a little margin. You could also use something like 2x N200 batteries.... which are not going to be cheap. You will need Multiple batteries because the APC units are 24V and others are Higher requiring more batteries still so I'd stick with the APC's.
The solar panels, even just 1 Kw would allow you to halve your battery capacity at very least because they could reliably supply power and recharge the batterys from the over night use which is all you would have to worry about. They would be independent of the grid and could stretch your backup to indefinite.
Again, how often and how long is your normal Blackout where you are? 24Hrs seems a long time to be backing up to start with. If it's more likely to be 6-8hrs you could get away with having a battery charger on the batterys but by the same token, if the outage is only 8 hours and the fridge is full of water bottles and no one is opening it, I think you'd walk that in without having food near spoil as well.
Measuring the actual alarm draw ( and don't go by what is printed on the thing, that will be Max possible draw not standby) You will probably find that just upgrading it's own battery would get you through 24Hrs or more without all the rest of the complication.
Powering from the main board you could get an Automatic Generator Changeover type switch Installed. Will Cost around $3-500. You could have the UPS wired into that and just have it feed the house power circuits.
I would really take into account the probability of a 24 hr outage and make sure the numbers you have for power draw are accurate because allowing for what you are going on now is NOT going to be cheap and seems rather high to me as far as the amount of power you'll need.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:31pm 26 May 2020
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A UPS is just that, zero interruption with seamless changeover from grid to battery and back again.
Do we really need that ? A momentary break supply would very likely be pefectly adequate for domestic power back up. These have a relay or a contactor that "drops out" when grid power fails, and you lose power for about half a second before power comes back on. Its much simpler with a lot less that can go wrong.Cheers, Tony.
Do you mean the alternate power supply would last 24 hrs? If so, sounds fine but where can I buy one in Australia? (Just did an internet search but yielded nothing).
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:12am 27 May 2020
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Its just an ordinary off grid inverter without all the fancy control system that a UPS must have.
Any inverter can last 24 hours if the battery is made large enough. First you need to do a power audit to determine how many Kwh storage is required. Nobody can tell you that, you need to measure what the loads actually are.Cheers, Tony.
Update after attaching my power meter to the fridge and other bits....
Fridge consumes 1.33kWh over a 15.5 hrs period (overnight), max of 1.2kW at startup and running consumes 120W. A total 24hr consumption including fridge, alarms and other bits gives less than 2.5kW. As you say Davo99, a less than 1kW UPS or equivalent should suffice. By "equivalent" I mean an inverter/charger (as maybe implied by Warpspeed).
Victron produce inverter/chargers and the Multiplus range seems suitable. Model C12/1200 (12V, 1000W continuous rating, 2400W peak) may well suffice but I see a price of around $1200. The smaller version C12/800 is about $300 cheaper.
I've not yet got a quote from an electrician to install this but I'd guess an overall cost of inverter + sparky of well over $2000 and I don't think that is worth it. Back to the drawing board.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 11:49pm 31 May 2020
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As I have said before, How often do you get blackouts and for how long? How often you go away would be a factor also.
Unless an outage is going to be over 24 Hours, I really don't think you have anything to worry about in unopened Fridges or Freezers and the alarm is easily fixed with a bigger or more batteries in Parallel.
Fill the empty space with water bottles and you are good for 24 Hours at very least. Not much point in my mind trying to protect against something that happens once every few years for 8 hours or less when in reality everything would be fine.
Depending on the probability of something happening, The peace of Mind factor may well run more to the cost of a UPS, some car batteries and Running a lead or 2 in the house to the appliances you want to protect.
Not going to be a big deal when you have the batteries in the Laundry or bathroom and just pick them up and put them away when you walk in.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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