Inverter advice needed?

netwhizkid

I need a bit of advice on this one so bear with me!

A friend who runs a small business from home is having the ESB cut off next week for several hours as they are working the area and got notification today. He works long distance and has his office in full flight all day, with a printer, fax, desktop PC and laptop going. This as you can imagine uses a nice bit of juice and he needs an alternate supply of power. He originally came asking to borrow the generator but I refused as AFAIK they produce "dirty power" unsuitable for his plethora of electronics. Anyway he needs to keep working and needs power. I have suggested an inverter and I can loan him a fully charged lorry or tractor heavy duty batter in 12 or 24v to power the inverter which should do it for the day.

He can trim down to the laptop for the day and not use the PC and will have around 2hours battery charge to begin with and about 1.5hours usage and charge before getting another 2hrs from the laptop battery. The fax will need to plugged in but will only be on standby all the time unless he needs to send off one or receive. The printer (inkjet instead of laser for the day for power saving) will consume around 60 or 70 watts while printing and his usage should be around 3 or 400 hundred watts an hour at peak capacity. We will plank a battery in the corner of the office and run a 4 way gang from the inverter to the devices and it will be completely independent of the grid or house wiring.

My plan sounds straight forward, what I want to find out about is inverters and sine wave, I know little about each and my man will spend the money no problem up to around €100 or €200 as it is important he have contact with the US always.

I have researched Maplin, Argos and Halfords and got results in each place it is only a matter of picking a good one.

Maplin Inverters
Argos Inverters
Halfords Inverters


Any suggestions?

Would a higher wattage inverter burn more power from the batteries eg. would my mates gadgets pulling 350W/hr on a 1000W inverter use more/less or the the same amount of power on as say gadgets pulling 350W/hr on a 500W inverter or would power consumption from the battery be the same regardless of the output of the Inverter? I will be giving him a large battery so I think it should hold out either way.

thanks, we have a week to get him powered up:cool:

steifanc

if your useing .3kwh of a 600w inverter or a 1000w inverter your still only using .3kwh . and the power drawn off the batt will be reflected . 300w is probly between 20/30 amps off your batt with out getting into the maths of it, and depending on your inverter.
make sure you size your batt right , an inverter will drop out when voltage gets too low to protect its self.
id be keeping an eye on the efficiency of the inverter you choose ,you dont want to be burning to much power you cant use,you batt wont last too long
what do you want to know about the sine waves ?

netwhizkid

steifanc wrote: »

if your useing .3kwh of a 600w inverter or a 1000w inverter your still only using .3kwh . and the power drawn off the batt will be reflected . 300w is probly between 20/30 amps off your batt with out getting into the maths of it, and depending on your inverter.
make sure you size your batt right , an inverter will drop out when voltage gets too low to protect its self.
id be keeping an eye on the efficiency of the inverter you choose ,you dont want to be burning to much power you cant use,you batt wont last too long
what do you want to know about the sine waves ?

Thanks for that great informative reply steifanc!:)

I don't know anything about sine waves or hertz but is it one of them that causes bog standard generator power to be dangerous to sensitive goods like computers etc?

Also secondly what advantage or disadvantage would a pure sine wave inverter like this be?

I plan to get one of these first to measure the power output required so as to get a good suitable Invertor, it will also allow me to get an idea of the costs of the Tv, Sky box etc. and general living room gadgets.

steifanc

a sine wave is the way ac power is generated .the wave pulses from + to - at a defined speed ,the speed it changes at is the frequancy .and that is measured by a si unit called herts (hz) ,so the amount of times the wave goes from + to - is the herts, 50-60 hz is normal in ireland ,50-60 cycles per second.
a pure sine wave is a clean wave ,a pure sine wave output from a inverter would take more expenctive electronics ,i would asume there slightly more expenctive. i never had need to buy one so i dont know.a pure sine wave would be what your getting from the esb is not better ,a pure sine wave would be good for equipment that would be affected by spikes and harmonics ,in your case computers , pure wave is the way to go.
the cheaper inverters would use a form of square wave , they would be fine for kettles , cookers ect.
as for the unit you were looking for to check the current ,i wouldnt bother , unless you wanted it, if you look at the devices your going to connect ,the should all have power ratings ,given in watts(w) ,just add them together and thats your load, give your self plenty of room when sizeing your inverter.
if there labels are only showing amp(a)
add the amps and multiply your total by voltage(230) you will get your watts
just be sure to size your inverter up by at least 100w to be sure,
when machines are starting they will be heavier on the juice , than when running

as for your sky box and the like,
check there spec, find the watts,
not sure what the esb charge say 30 cents a unit ?
they charge by the kwh , kilo watt hour, so one kw for one hour is 30cents
there are 1000w in a kw
if your sky box and the other units have a total of 500w, the cost to have them on for 1hr is 15cents
get the picture ?

netwhizkid

Once again great info steifanc, you are a credit to this forum. I will post back in a few days with news of our rig-up & a few photos to boot!:)

bushy...

netwhizkid wrote: »

I need a bit of advice on this one so bear with me!

A friend who runs a small business from home is having the ESB cut off next week for several hours as they are working the area and got notification today. He works long distance and has his office in full flight all day, with a printer, fax, desktop PC and laptop going. This as you can imagine uses a nice bit of juice and he needs an alternate supply of power. He originally came asking to borrow the generator but I refused as AFAIK they produce "dirty power" unsuitable for his plethora of electronics. Anyway he needs to keep working and needs power. I have suggested an inverter and I can loan him a fully charged lorry or tractor heavy duty batter in 12 or 24v to power the inverter which should do it for the day.

He can trim down to the laptop for the day and not use the PC and will have around 2hours battery charge to begin with and about 1.5hours usage and charge before getting another 2hrs from the laptop battery. The fax will need to plugged in but will only be on standby all the time unless he needs to send off one or receive. The printer (inkjet instead of laser for the day for power saving) will consume around 60 or 70 watts while printing and his usage should be around 3 or 400 hundred watts an hour at peak capacity. We will plank a battery in the corner of the office and run a 4 way gang from the inverter to the devices and it will be completely independent of the grid or house wiring.

My plan sounds straight forward, what I want to find out about is inverters and sine wave, I know little about each and my man will spend the money no problem up to around €100 or €200 as it is important he have contact with the US always.

I have researched Maplin, Argos and Halfords and got results in each place it is only a matter of picking a good one.

Maplin Inverters
Argos Inverters
Halfords Inverters


Any suggestions?

Would a higher wattage inverter burn more power from the batteries eg. would my mates gadgets pulling 350W/hr on a 1000W inverter use more/less or the the same amount of power on as say gadgets pulling 350W/hr on a 500W inverter or would power consumption from the battery be the same regardless of the output of the Inverter? I will be giving him a large battery so I think it should hold out either way.

thanks, we have a week to get him powered up:cool:

Very wise of you not to give him your genny since you weren't sure of its output, could have saved a lot of damage.

Don't put the battery inside if its a lead acid one ( truck / car battery), releases inflammable gas under load


An inverter generator might be a better solution/investment

eg

http://www.hondaireland.ie/Generator_GD_EU10i_1000_Watt_Main_Page.HTML

Stoner

Just a quick suggestion, would a generator feeding a UPS not be the trick here. The UPS will clean up the dirty supply from the generator and has the battery and electronics all in the one box.

Jonathan

If there any components that take DC you would be better off leaving out the inverter and converting from 12V or 24V directly.

steifanc

Stoner wrote: »

Just a quick suggestion, would a generator feeding a UPS not be the trick here. The UPS will clean up the dirty supply from the generator and has the battery and electronics all in the one box.

there are loads of ways to do it , ups would be ideal , if you were using a ups there wouldnt be much need to worry about a genny, cost would be a factor then,

Stoner

I'd try renting one. there are a few places out there, when i go back to the office I'll try to dig one out.

What about a small UPS that the genny powers? that would keep the cost down.

steifanc

up to the whiz kid ,i surpose if the computers are that important to the work process,for the long term buying a good ups would be the trick , you wouldnt have to worry about the esb , unless the outage was outside the conditioning of the ups.
me, id take the day off . any excuse to get out of the office !!
how do much would ups cost ,6/800 a kw ? ive no idea , them days are well gone for me !!

Umiq88

Surely things like computers laptop etc. use a DC voltage and rectify the AC supply so regardless of the quailty of the output wave a smooth DC will get to the machine from the capacitors in the power supply.

I would think this would be the case with most equipment rectifying an AC supply for a DC load. Harmonic content may be an issue though.

steifanc

psittacosis wrote: »

Surely things like computers laptop etc. use a DC voltage and rectify the AC supply so regardless of the quailty of the output wave a smooth DC will get to the machine from the capacitors in the power supply.

I would think this would be the case with most equipment rectifying an AC supply for a DC load. Harmonic content may be an issue though.

the caps will smooth the wave all right , id be worryied about busting the gates of the thyristors with uncontrolled input

Carlow52

OP: u say [We will plank a battery in the corner of the office and run a 4 way gang from the inverter to the devices and it will be completely independent of the grid or house wiring. ]

U will need to earth it

danjo

psittacosis wrote: »

Surely things like computers laptop etc. use a DC voltage and rectify the AC supply so regardless of the quailty of the output wave a smooth DC will get to the machine from the capacitors in the power supply.

I would think this would be the case with most equipment rectifying an AC supply for a DC load. Harmonic content may be an issue though.

In theory yes but practice is a different story.
Spikes can damage sensitive electronic equipment. The power supplies in laptops are fairly rudimentary due to size constraints etc. There are no big smoothing capactitors so they do require a reasonably clean supply.

enmac

Stoner wrote: »

Just a quick suggestion, would a generator feeding a UPS not be the trick here. The UPS will clean up the dirty supply from the generator and has the battery and electronics all in the one box.

I'd go along with stoner on this one
Investing in a small UPS could be very worthwhile especially if the ESB goes unexpectedly.

You could feed the UPS via the genny for the planned ESB outages and this will act as a buffer against the dirty generator waveform

I had something like this in mind:
http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR1200LCDI&tab=features&total_watts=800

FoxT

he should Contact his local Fas/IDA/local enterprise/whatever office, they might give him a free office for the day.
Or,
Move the stuff to a hotel room, probably the cheapest way out , with no worries about inverters, earthing, spikes, etc etc. If he just needs a laptop & a fax then he wont even have to bring the fax!

Note that if he is consuming 400W then the inverter will consume between 500 & 600 W. (Inverters are about 70% to 80% efficient). At 24 volts this is 20 to 25 Amps approx. At 12 volts this is 40(!) to 50(!!!) Amps.
If you want to keep him going for an 8-hour day on a 12 v supply then you will need about 50 Amps x 8 hours x 2 = 800Ah battery capacity.

Why x2 - because if you don't factor in excess capacity the likelihood is you'll whack the battery bank - Ordinary car & truck batteries are not designed to be discharged fully.

800Ah = about 7-8 ordinary car batteries.
there will be a fair amount of work in sourcing, charging, transporting, wiring, etc etc.

The hotel room is looking better & better the more i ponder it.....

FoxT

bushy...

Since the man said :

netwhizkid wrote: »

............. as it is important he have contact with the US always...........

he would/should already have a decent UPS . Just buy an inverter generator and he's sorted , no messing around , for almost ever more.

Naturally enough , an extended power cut will only happen the one extended day he has in long time.

Why an inverter generator ?

when it has a light load ( printer on standby , laptop charged etc ) its not screaming away at 1500rpm like an ordinary one.

you can chain them together easily (usually) for more power

useful for making tea ( allow this when sizing it cos someone will try it)

(should be ) nice clean power so less for the UPS to sort out

not all UPSs filter that well

Pete67

If you do have to use a non-invertor generator, a good tip is to put a resistive load on it of about 30% - so for a 1kVA generator make sure there are three or four hundred watt bulbs plugged in and switched on before you plug in any electronics. The constant load enables the generators voltage regulator to control better and helps avoid damaging high voltage spikes. Also use an extension cable with built in surge regulation for the electronics.