Power inverters

[SVcummins]

How do you size a power inverter ? I want to run a gasboy fuel pump and I don?t know how big of an inverter I need to run it
 

[LarrySTN]

The motor on the gasboy should have a tag with the amp draw, that figure will be the current draw after the motor is running, Starting amperage will be cosiderably higher. The inverter you choose will need to be capable of meeting the starting amperage of the motor which will be 2 - 3 times the run amps. My guess is you will need an inverter capable of starting a 1500 watt load. Many inverters are labeled with intermittent load and continuous ratings. So an inverter with a 1500 watt intermittent rating should work fine.
 

[Bob]

[Geo-TH,In]

What about buying an RV generator? I bought a Champion 3500w are around $300 a few years ago.

A 1500 w Power inverter will zap a battery.
 

[John T]

The real answer is IT DEPENDS

SHORT ANSWER: You have to know the pumps running WATTS and then size an Inverter capable of supplying that (with wiggle room) PLUS has enough short term surge capacity to start the pump...??.

Starting and running current of the pump. The initial surge current when starting may be 4 to 6 times the run current so the Inverter needs that much short term surge capacity.

BATTERY POWER TO RUN THE PUMP VIA INVERTER

For every amp the pump draws at 120 VAC, a 12 Volt battery has to supply around 11 amps to the 12 VDC to 120 VAC Inverter and the energy required to run the pump for X hours is that 11 battery amps for X hours run time IE Amp Hours of energy.

EXAMPLE to make it easy if the pump drew lets use 5 amps at 120 VAC and you ran it lets use 10 minutes. That means the battery would have to supply 55 amps for 1/6 hour or 9 Amp Hours. If it drew 10 amps for 10 minutes that's 110 x 1/6 = 18 Amp hours. As an example lets say you had a 12 volt flooded lead acid battery rated for to make it easy lets use 100 Amp Hours and you shouldn't discharge it over 50% or 50 useable amp hours before recharging. If you ran a 5 amp pump 10 minutes and consumed 9 Amp hours you would get around 5 pumpings before the battery needs recharged

Not knowing the pump power requirements its a pure guess you may need a 1000 to 1500 watt or larger (subject to pump) Inverter. It has to have the capacity to supply running current and short term surge capacity to get it started. Then you need sufficient battery and/or charging capacity. If the pump draws much less you can get by with a smaller Inverter WELL DUH

Of course if the battery was on your pickup its alternator can be supplying charging current so theres less worry with the recharge discussion above.

Its more efficient if you had a 12 VDC pump so you avoid conversion and inverter inefficiency and heat losses.

NOTE the above is an approximation and NOT intended as accurate (no pump specs here) but ONLY an example so don't anyone have a calf now

John T Long retired n rusty Electrical Engineer so noooooooooo warranty
 

[SVcummins]

That?s how it is here to bob . So I come in and buy
the junk nobody else wants 😂
 

[SVcummins]

I?ve thought about buying a generator wouldn?t be a bad investment
 

[SVcummins]

Thanks John according to the guy on tractor talk he says the gasboy pump draws 4 amps
 

[SVcummins]

Larry I will look and see what I can find on the pump . I?ve got a good hand pump it will move as much fuel as the gasboy if you got arm enough to run it but operators don?t think it?s as fun to use as I do
 

[JDEM]

You need to know the continuous rating of the inverter and if it makes a square-stepped modified sine-wave or a more correct rounded sine-wave. A "modified wave" inverter with square steps is cheap. Often $100 for a unit rated 2000 watts continuous and 4000 watts surge. It is poor for electric motor starting though. Inverters sold as "sine wave" cost more but start motors much better.

Gas pumps tend to have a start surge at 600 watts. So you need an inverter sizes around 1000 watts continuous rating.
 

[JDEM]

I am not trying to spend your money for you but . . . This is one of the best fairly low priced inverters I have used when it comes to electric motor starting. I am sure there are others but I know this one is amazing. Xantrex is one of the oldest inveter makers around. I had a mod-wave 1000/2000 running a small 120 volt refrigerator and it struggled. Got this Xantrex and MUCH better.

1000 watts continuous and 1800 watt surge rating. Your gas pump likely surges at 600 watts.

 

[buickanddeere]

All good advice so far .
As it appears that your estate could use a generator to operate the fridge, freezer, sump pump , microwave , C-pap machine etc .
This is a whisper quiet machine that will operate on either gasoline or propane . Light enough to pickup and set in the truck bed.
The general rule of thumb when purchasing an invertor or "small" generator . Is to calculate all the required loads , figure the size of the generator required and then double it .
Anyone thinking they can operate a 12.5amp load continuous on a 1500W generator is overly optimistic.
https://www.championpowerequipment.com/product/100264-3500-watt-dual-fuel-inverter/
 

[JDEM]

I am not disagreeing with you but . . . Much depends on the actual ratings of the draw and whatever is making the power.

For example, a so-called Honda 2000 watt inverter-generator is only rated to make 1600 watts continuous.

Some high-end power makers give actual output in time-frames. Some over-rate in the advertising and a few under-rate (kind of rare now
adays).

Here is one example. Xantrex 2400 watt inverter.
Rated for 9200 watts for 1 millisecond.
Rated for 6600 watts for 100 milliseconds.
Rated for 4200 watts for 5 seconds.
Rated for 2400 watts forever.
 

[Leroy]

All I know is years ago I bought a rated at 300 watt unit to try to run a dorm size refrigerator in camper that called for way less power than the invertor was rated at. would not do it so tried with a standard incandesincant light bulb of 75 Wats and that bulb would kick the unit off. Unit was rated for 4 tomes what the bulb should have taken. Think it went to scrap.
 

[JDEM]

Obviously you bought something that was misrepresented.

Many RV and marine refrigerators made my Norcold for 12 volts DC use had AC powered compressors. Norcold used a small built-in inverter to power them. I have one sitting in my shop right now. Inverter from the factory that is hard-wired is about 4" square. Pretty small unit that obviously does the job.

One of my RVs has a dorm refrigerator that is powered by a 800/1600 watt inverter. It has worked fine for many years.